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REVIEWS
UDC 579.841: 577.114 https://doi.org/10.15407/biotech11.04.005
NON-TRADITIONAL PRODUCERS OF MICROBIAL EXOPOLYSACCHARIDES
T. P. PIROG, A. A. VORONENKO, M. O. IVAKHNIUK National University of Food Technologies, Kyiv, Ukraine E-mail: [email protected]
Received 12.03.2018
Data on exopolysaccharides synthesis by psychrophilic fungi and bacteriae, halo- and thermophilic archaea and bacteriae, including those isolated from deep-sea hydrothermal vents — sources — were provided. Physiologic significance, physico-chemical properties and possible practical applications of exopolysaccharides from unusual sources were analyzed. Most of them have immunomodulating, antiviral, anticoagulant, antitumor, antioxidant activities promising for medical and pharmaceutical applications.
Meanwhile, based on the literature date, the conclusion follows about the urgent necessity to develop efficient technologies for synthesis of these exopolysaccharides by nontraditional producers, which currently lags far behind common techniques.
Key words: exopolysaccharides, thermophiles, psychrophiles, halophiles, hydrothermal vents.
Microbial exopolysaccharides (EPS) are high molecular hydrocarbonic exogenous products of microbial metabolism [1-3]. They are widely used in industry (food production, chemistry, oil production, etc.) due to their ability to gel, emulsify, flocculate, form suspensions and to change rheological parameters of aqueous systems [3-5].
Most of currently known microbial EPS have similar functional properties that determine their practical significance [2, 4]. Thus, it is not surprising that only a few of many isolated, described and studied polysaccharides of microbial origin (xanthan, gellan, alginate, dextran) are produced industrially [1, 4].
A polysaccharide must now have unique properties to enter the free niches of rapidly developing fields like medicine, pharmacy, cosmetics, and nature conservation.
Since late XX century, scientists actively study microorganisms living in habitats previously overlooked in the search for bioactive compounds-producing microorganisms (permafrost, hot springs, oceanic depths, salt marshes, etc.). Quite possibly, they survive in such places due to specific adaptive mechanisms and synthesis of protective compounds [5], including EPS with new properties.
Such organisms are known as extremo-philes, or microorganisms isolated from extreme habitats [6, 7]. We argue that the terms "extremophile" and "extreme" are not quite applicable, since microbiology considers "extreme" conditions in which only specialized microorganisms survive and many other taxa perish. Therefore this review refers to them simply as "nontraditional".
To date, a number of reviews have been published about synthesis of EPS by non-traditional producers [6-17]. However, the reviewers mostly paid attention to habitat description, physico-chemical properties and environmental significance of the synthesized polysaccharides and almost ignored the possibility of practical applications [13]. In addition, the reviews were devoted to a specific group of microorganisms (thermophilic [15], halophylic bacteriae [14, 16] and archaea [18], cryophilic yeast [19], sea microbes [9, 10, 17], and microorganisms isolated from hydrothermal vents [8]). Only a few papers reviewed several unusual producers at once [6, 7, 12]. The listed studies were published in 2010-2012 and include mostly summaries of specifics of EPS biosynthesis and their physico-chemical properties. A recent paper [11] discusses practical applications of several polysaccharides, synthesized by bacteriae isolated from hydrothermal sources.
This review aimed to summarize the available information on EPS synthesis by non-traditional producers (thermo-, cryo, halophilic microorganisms and bacteriae isolated from deep-sea hydrothermal vents), and properties of polysaccharides that support their potential practical application in medicine, pharmaceutical, food industries and nature conservation.
Thermophiles
The studies of thermophilic microorganisms started approximately in 1967 [20]. The paper briefly summarized the available knowledge about the microorganisms. In those days, attention was mostly paid to their environmental niche and the mechanisms enabling their survival at high temperatures.
One of those adaptive mechanisms is synthesis of microbial EPS. It should be noted that, unlike industrial mesophilic producers, using thermophils for the preparation of polysaccharides has a number of technological advantages, in particular, at elevated temperatures, the viscosity of the culture fluid and the possibility of the process infection are reduced, as well as mass exchange processes increase, etc. [21-25].
Archaea. The first reports of EPS synthesis by thermophilic archaea began to appear at the end of XX century [26-29]. In 1993, Nicolaus et al. [26] found out that the thermoacidophilic archaea Sulfolobus solfataricus MT4 and MT3, isolated from a hot acidic spring (Agnano volcanic crater, Italy) produced EPS at 75-88 °C.
The main disadvantage of those archaea as well as almost all other thermophilic producers of EPS is the low concentration of the target product (Table 1). This can be caused by low concentrations of the carbon and energy source (2-9 g/l) in the cultivation medium. Special attention was paid to the polysaccharide effect on physiology. Thus, several papers [27, 28, 30] presented data on synthesis of EPS by archaea linked to biofilm formation. Rinker et al. [27, 28] studied the growth of hyperthermophilic anaerobic organism Thermococcus litoralis DSM 5473. They established that biofilms formed on hydrophilic surfaces (polycarbonate filters) followed by accumulation of sulfated mannan (over 0.3 g/l EPS). Other researchers [30] studied the biofilm structure in thermoacidophilic archaea of the genus Sulfolobus.
Polysaccharides can perform other vital functions other than the formation of biofilms which protect the microorganisms from unfavorable factors and toxins. Thus,
a hypothesis was formulated [29] that EPS of thermophilic methanogenic archaea Methanosarcina thermophila TM-1 can be an osmoprotectant.
Notably, researchers [26-30] did not try to intensify EPS synthesis by thermophilic archaea. Due to the low concentration of the target product, this microorganisms are hardly going to be industrially important in the near future. Another complication is the difficulty of culturing most thermophilic archaea that require complex media with a lot of vitamins, amino acids, etc. [27, 28].
Bacteriae. Simultaneously with studying EPS-synthesizing archaea, researchers turned to thermophilic bacteriae. Almost all of them belong to the family Bacillaceae (the genera Bacillus [31-33], Geobacillus [22, 3436], Anoxybacillus [37], Aeribacillus [24]) and Paenibacillaceae (the genus Brevibacillus [23, 25]) with optimal growth temperature of 45-65 °C (Table 1). Notably, the first reports of EPS synthesis by thermophilic bacteriae also included representatives of these families. Thus, Manca et al. [35] in 1996 reported isolation of extremely thermophilic bacteriae Geobacillus thermoantarcticus, which at 65 °C synthesized up to 400 mg/l sulfated EPS from soil near the crater of Melbourne volcano (Antarctica).
Besides representatives of Bacillaceae and Paenibacillaceae, synthesis of polysaccharides is known for hyperthermophilic bacteriae of the genus Thermotoga (optimal temperatures 80-85 °C) [27] and thermophiles of the genus Thermus (optimal temperature 60 °C) [38].
All thermophilic bacteriae in the literature produce less than 1 g/l EPS [22-25, 32, 33, 35, 36, 38]. Recently, bacteriae Anoxybacillus sp. R4-33, able to produce 1.1 g/l polysaccharide and tolerant of high temperature and radiation were isolated from geothermal radon springs (China) [37].
Thermophilic obligate methanotroph Methylococcus thermophilus 111n synthesizes up to 5 g/l EPS [2] and thus is a much better choice. Those amounts were achieved after a complex investigation of pH, temperature, diluted oxygen concentration, gaseous methane to oxygen ratio conditions, and the pre-treatment of the inoculum. The exogenous addition of 0.5 g/l aspartic acid (obtained by transferring amino group to oxaloacetic acid) to the culture medium of strain 111n was followed by an almost two-fold increase in the polysaccharide biosynthesis rate [2].
The EPS of several thermophilic and thermotolerant bacteriae were observed to
have antiviral [31, 34, 39] and immuno-modulating [38] activities and to inhibit biofilm formation [40].
Treatment of mononuclear cells of human peripheral blood with polysaccharide solutions (300 pg/ml) of strains Geobacillus thermodenitrificans B3-72, Bacillus licheniformis B3-15 and T14 stimulated the production of IFN-y, IFN-a, TFN-a, IL-12 and IL-18 and inhibited the replication of herpes simplex virus type 2 [31, 34, 39]. In the presence of EPS of strains B3-72, T14 and B3-15 the virus was inhibited by 67, 77 and 85%, respectively [39]. Notably, antiviral activity is usually seen in sulfated polysaccharides [41], and the compounds described in [31, 34, 39] did not contain sulfate groups.
Lin et al. [38] isolated from the biofilm of Thermus aquaticus YT-1 a polysaccharide that heightened immune response. That EPS was observed to act as an agonist of TLR2 receptor and helped induce synthesis of cytokines IL-6, TNF-a, and nitrogen monoxide (NO) by murine macrophages and human monocytes. That immunoregulatory activity supposedly was caused by galactofuranose in its structure [38].
Several thermophilic representatives of the genus Bacillus were also observed to synthesize polysaccharides with anticytostatic activity [22, 33]. Fraction 1 EPS B. licheniformis T14, consisting of fructose, fucose and glucose (1:0.75:0.28), at 500 ppm raised LD50 of avarol (a cytostatic agent) from 0.18 to 0.99 mg/ml [33], and EPS of Geobacillus tepidamans V264 raised it to 2.24 mg/ml [22].
Recently Spano et al. [40] found that EPS of B. licheniformis T14 at 400 pg/ml inhibited biofilm formation by multiresistant strains Escherichia coli 463, Klebsiella pneumoniae 2659, Pseudomonas aeruginosa 445 and Staphylococcus aureus 210 by 74, 56, 54 and 60%, respectively. The researchers suggested that due to the emulsifying properties of the polysaccharide it is able to impact the hydrophobicity of bacterial cells and so prevent their primary adhesion to surfaces [40].
A summary of EPS biosynthesis by thermophilic and thermotolerant microbes is given in Table 1. Currently, the microbes are not considered promising due to low EPS synthesis ability. Meanwhile such polysaccharides have properties important for medicine and pharmacy (antiviral, immunomodulating, anticytostatic, etc.),
which can stimulate work on intensifying their synthesis.
EPS-producing microbes from deep-sea hydrothermal vents. Deep-sea hydrothermal vents, characterized by high concentrations of toxic compounds (sulfides and heavy metals), sharp changes in temperature and pressure, are habitats of thermophilic bacteriae with various properties [8, 21, 42-44].
Since the first such vent was discovered in 1977 near the Galapagos, a great many other hydrothermal vents with various unique microorganisms were found [43, 44]. Thus, from the East-Pacific Rise (2600 m deep), EPS-synthesizing strains of bacteriae from the generaAlteromonas [45-48] and Vibrio [49] were isolated; at Mid-Atlantic Ridge (3500 m deep), bacteriae Alteromonas macleodidi subsp. fijiensis var. medioatlantica were found [50]; at Guaymas Basin and North Fiji Basin (2000 m deep), strains A. macleodii [43] and Alteromonas infernus [44] were isolated, respectively.
Despite the fact that these EPS-producing bacteriae were isolated from extreme habitats, most of them turned out to be mesophilic neutrophils with optimal growth temperature 25-35 °C and pH 6-8 [43-45, 46-50], and only a few of them were thermophiles (40-45 °C) [49].
The EPS-producing bacteriae isolated from deep-sea hydrothermal vents became a subject of active research in 1990s [4244, 47-49]. In 1994, Guezennec et al. [42] published results of screening EPS-producing bacteriae isolated from hydrothermal vents. Almost all polysaccharides except for neutral monosaccharides contained sulfate moieties (to 21.5%) and glucuronic acids (to 7.9%), several had amino sugars (to 2.5%).
Interestingly, EPS-producing bacteriae are isolated not only from soil or water near hydrothermal vents [42], but from the surfaces of various organisms living there (shrimps, worms, etc. [45, 46, 4850]). The strain Alteromonas macleodii subsp. fijiensis var. medioatlantica MS907, producing 9 g/l EPS after 72 hours of culturing was found on carapax of the shrimp Rimicaris exoculata [50].
The outer shell of a sea polychaete Alvinella pompejana (at the depth of 2600 m) yielded EPS-synthesizing bacteriae Alteromonas sp. HYD1545 and A. macleodii subsp. fijiensis biovar deepsane HYD657 [45, 48]. The strain HYD1545 after 120 hours of culturing produced 11 g/l of polysaccharide [48], and strain HYD657 produced 7 g/l EPS after
00
Table 1. Synthesis of exopolysaccharides by thermophilic and thermotolerant microorganisms
Microorganism Culture temperature Carbon source, g/1 EPS concentration, g/1 Physico-chemical properties of EPS Physiological role, functional properties and prospects of EPS application References
content Molecular mass, kDa
EPS of thermophilic archaea
Methanosarcina thermophila TM-1 45-55°C Trimethyl-amine, 4.8 - Glucuronic acid (over 40% ) - Osmo-protectant [29]
Sulfolobus acidocaldarius 76 °C - - Glucose, galactose, mannose, iV-acetylglucosamine - Biofilm formation [30]
Sulfolobus solfataricus MT3 75 °C Glucose, 3 7.0 mg/1 Glucose, mannose, glucosamine, galactose (1.2:1.0:0.77:0.73). Sulfates 5-12% - - [26]
Sulfolobus solfataricus MT4 88 °C Glucose,3 8.4 mg/1 Glucose, mannose, glucosamine, galactose (1.2:1.0:0.18:0.13). Sulfates 5-12% - - [26]
Sulfolobus tokodaii 76 °C - - Glucose, galactose, mannose, iV-acetylglucosamine - Biofilm formation [30]
Thermococcus lit oralis DSM 5473 88 °C Maltose, 2 0.18-0.32 Mannan, sulfates 1-2% 41 Biofilm formation [27, 28]
EPS of thermophilic and thermotolerant bacteriae
Aeribacillus pallidus 418 55 °C Maltose, 9 0.17 Fraction 1: mannose, glucose, galactosamine, glucosamine, galactose, ribose (1:0.16:0.1:0.09:0.07:0.06:0.04) Fraction 2: mannose, galactose, glucose, galactosamine, glucosamine, ribose, arabinose (1:0.5:0.46:0.35:0.24:0.16:0.14) Fraction 1: 700; Fraction 2: 1000 Emulgent [24]
Anoxybacillus sp. R4-33 55 °C Glucose, 10 1.1 Fraction 2: mannose, glucose (1:0.45) 1000 Adsorbs heavy metals [37]
Bacillus licheniformis B3-15 45 °C Glucose, 6 0.165 Fraction 1: mannose, glucose (1:0.3); Fraction 2: mannose; Fraction 3: glucose 600 Antiviral and immunomodulatory [31, 32]
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Microorganism Culture temperature Carbon source, g/1 EPS concentration, g/1 Physico-chemical properties of EPS Physiological role, functional properties and prospects of EPS application References
Bacillus licheniformis T14 50 °C Sucrose, 50 0.366 Fraction 1: fructose, fucose, glucose and traces of galactosamine, mannose (1:0.75:0.28:traces:traces) 1000 Antiviral, immunomodulatory and anticy-totoxic. Inhibits biofilm formation [33, 39, 40]
Brevibacillus thermoruber 423 55 °C Maltose, 18 0.897 Glucose, galactose, galactosamine, mannose, mannosamine (1:0.3:0.25:0.16:0.04) - - [25]
Brevibacillus thermoruber 438 55 °C Maltose, 18 78.1 mg/1 - - - [23]
Geobacillus tepidamans V264 60 °C Maltose, 30 111.4 mg/1 Glucose, galactose, fucose, fructose (1:0.07:0.04:0.02) >1000 Anticytotoxic [22]
Geobacillus thermoantarcticus 65 °C Mannose, 6 0.4 Fraction 1: mannose, glucose (1:0.7); Fraction 2: mannose and traces of glucose Sulfated Fraction 1: 300; Fraction 2: 300 Emulgent [35]
Geobacillus thermodenitrificans B3-72 65 °C Sucrose, 6 70 mg/1 Fraction 1: glucose, mannose (1:0.3); Fraction 2: mannose, glucose (1:0.2) Fraction 2: 400 Fraction 2: antiviral and immu-nomodulating [34, 36]
Methylococcus thermophilus 11 In 40 °C Methan 5 Fraction 1: mannose, galactose, glucose, fucose, xylose, rhamnose, glucuronic acid. Fraction 2: mannose, glucose, xylose, rhamnose - Intensification of oil production [2]
Thermotoga maritima DSM 3109 88 °C Maltose, 2 0.120 Glucose, ribose, mannose (1:0.06:0.03) - Flocculant [27]
Thermus aquaticus YT-1 60 °c - - Galactofuranose, galactopyranose, iV-acetylglucosamine (1:1:2) 500 Immunomodulatory activity; adjuvant to vaccines [38]
Note: «-» — no data available.
52 hours of culture [45]. Further research [51] of EPS of strain HYD657 established that they efficiently protect keratinocytes from inflammation agents. The protective effect was also found towards Langerhans cells, which are sensitive to the ultraviolet and play an important role in the system of human skin immune protection. Nowadays, cosmetic preparation Abyssine® was developed based on the polysaccharide (deepsane). It is recommended for soothing and protection against irritation of sensitive skin [52].
Notably, the polysaccharide of strain HYD657 has an unusual component, a residue of 3-0-(1-carboxyethyl)-D-glucuronic acid [45]. Currently, the compound was also found in EPS of the strain Alteromonas sp. HYD1644, isolated from the epidermis of the polychaete Alvinella caudata [46], and in drought-resistant cyanobacteriae Nostoc commune DRH-1 [53]. Helm et al. [53] suggested that this and other uronic acids with carboxyethyl moieties play a key part in providing survival in unfavorable conditions. For example, such functional groups can help EPS attach to adjacent chains of the polymer, organic (biofilms) or inorganic surfaces, etc.
The strain Vibrio diabolicus HE800T was isolated from polychaete Alvinella pompejana. The strain produces a polysaccharide similar to hyaluronic acid [49]. The EPS is made up equally from glucuronic acid and hexosamines (N-acetylglucosamine and N-acetylgalactosamine) [54]. Treating damaged skullcap skin of Wistar rats with the EPS made the wound close sooner, while the trabecular and cortical anatomic structure of the defect fully recovered [55]. Zanchetta et al. [55, 56] suppose that the effect is caused by the ability of EPS to form extracellular matrix that helps direct adhesion of osteoblasts and pericytes, generally protect the damaged site while it heals, and to bind calcium.
Senni et al. [57] suggested that glycoso-aminoglycan polysaccharide of strain HE800T is a promising agent for various derivatives (heparan sulfate, chondroitin sulfate, etc.). Such depolymerization of native polysaccharide to molecular mass of 22 kDa with further deacetylation and sulfation (sulfate content 34%) resulted in a polymer similar to heparan sulfate. Those derivatives were observed to stimulate proliferation of dermal and gingival fibroblasts and inhibit secretion of matrix metalloproteinases [57].
The EPS of Alteromonas infernus GY785 after sulfation (sulfate content 40%) and controlled depolymerization by free radicals to molecular mass of 24 kDa substantially raised APTT (activated partial thromboplastine time) [58, 59]. The anticoagulant activity of the polysaccharide was on the level of calcium pentosan polysulfate though 2.5-6.5 times lower compared to heparin [58]. Notably, due to the low sulfate content in the native polysaccharide (5.5-10%) it did not have anticoagulant activity [58].
Recently the effect of depolymerized EPS of strains V. diabolicus HE800T and A. infernus GY785 on the complement system was studies [60]. The low molecular (2.9 kDa) derivative of the polysaccharide of strain HE800T to a large extent activated the system (60% activation at 50 pg EPS), while the depolymerized (molecular mass 23 kDa) and sulfated (sulfate content 37-42%) EPS of strain GY785, conversely, caused its significant inhibition (78% inhibition at 10 pg EPS). Due to those properties, the polysaccharides are promising for treating diseases caused by deregulation of immune system and over activation of the complement system.
Therefore, EPS of bacteriae isolated from hydrothermal vents can become widely accepted into medical, pharmaceutical and cosmetic industries due to anticoagulant, pro-tectant, immunomodulatory and regenerative activities. Notably, such microorganisms can synthesize up to 11 g/l of the product, and some polysaccharides from hydrothermal-dwelling bacteriae are already mass-produced. For example, EPS of A. macleodii subsp. fijiensis biovar deepsane HYD657 is used for cosmetics (Abyssine®).
Data on EPS of bacteriae isolated from hydroterms are summarized in Table 2.
Psychrophiles
Cold environments are found from deep seas to snow-laden mountaintops, from Arctic to Antarctica. Temperature of almost 75-80% of the Earth surface is below 5 °C [60-62]. Cold habitats are characterized by frequent sharp changes in temperature (cycles of freezing and thawing, etc.), UV-radiation, nutrient concentration [63, 64]. Oceanic and sea waters also have pressure and salinity oscillations [21]. Evidently, microorganisms would not survive in such conditions without relevant adaptive mechanisms [62, 65, 66].
EPS play a large role in it. Exopolymers, including polysaccharides, take part in
Microbial source* Carbon source, g/1 EPS content, g/1 Physico-chemical properties of EPS Physiological effect, functional properties and possible implementations of the EPS References
Chemical composition Molecular mass, kDa
Alteromonas infernus GY785 Glucose, 30 Fraction 1: 5.5 Fraction 2: 4.3 Fraction 1 (water-soluble): glucose, galactose, glucuronic and galacturonic acid (1.0:0.9:0.7:0.4). Sulfates 5.5-11% Fraction 1: 1000 Anticoagulant, adsorbent [44, 58, 59]
Alteromonas macleodii subsp. fijiensis ST716 Glucose, 30 6 Galactose, glucose, mannose, glucuronic and galacturonic acid (1.0:0.95:0.4:1.1:0.57). Sulfates 5% 330 Thickener [43]
Alteromonas macleodii subsp. fijiensis biovar deepsane HYD657 Glucose, 30 7 Galactose, glucose, rhamnose, fucose, man-nose, glucuronic, galacturonic and 3-0-(l-carboxyethyl)-D-glucuronic acids (1.0:0.43:0.8 6:0.5:0.43:0.5:0.5:0.5). Sulfates 7.5% 1100-1600 Protects keratinocytes and Langerhans cells from inflammation agents [45, 51]
Alteromonas macleodii subsp. fijiensis var. medioatlantica MS907 Glucose, 30 9 Galactose, glucose, glucuronic and galacturonic acids (1.0:0.5:0.7:0.26) 1500 Thickener [50]
Alteromonas sp. HYD1545 Glucose, 30 11 Glucose, galactose, mannose, glucuronic and galacturonic acids (1.0:0.55:0.04:0.24:0.14) 1800 - [48]
Alteromonas sp. HYD1644 Fructose, 40 Fraction 1: 7.5 Fraction 2: 5.0 Fraction 1 (water-soluble): galactose, glucose, rhamnose, mannose, glucuronic, galacturonic and 3-0-(l-carboxyethyl)-D-glucuronic acids (1.0:0.74:0.7:0.13:0.4:0.19:0.23) Fraction 1: 5000 Thickener [46, 47]
Vibrio diabolicus HE800T Glucose, 40 2.5 Glucuronic acid, iV-acetylglucosamine, iV-acetylgalactosamine (1:0.5:0.5) 800-850 Raw material to obtain glycosaminoglycan derivatives. Fastens bone fusion [49, 54-57]
aggregation, adhesion to surfaces and other microorganisms, biofilm formation, nutrient storage, etc. in marine bacterial communities [66-68]. Often aggregates of salty drops remain unfrozen after the sea water freezes, and the microbes are trapped in salt canals [63, 66]. Then, EPS are cryoprotectants and protectants from high salinity [62, 65, 66].
The majority of microorganisms, able to survive at low temperature, are yeasts and bacteriae [8]. Notably, phylogenetic research also registers a lot of representatives of Archaea [61], although they have not been cultured.
Fungi. EPS synthesis by fungi at relatively low temperatures is a novel approach. The first report of polysaccharide production by cryotolerant mycelial fungi appeared only at the beginning of XXI century. In 2002, Selbmann et al. [69] established the ability of Phoma herbarum CCFEE 5080 cultured on medium containing sorbitol (60 g/l) to produce 13.4 g/l 7412 kDa glucan. Due to cryoprotectant properties of the polysaccharide, strain CCFEE 5080 is able to grow at 0-5 °C (optimal temperature 28 °C) [70].
Another glucan-producing fungus is strain Thelebolus sp. IITKGP-BT12 [68]. Unlike the strain CCFEE 5080, at 18 °C it synthesizes only 1.94 g/l EPS. Experiments have shown that the glucan has significant antiproliferative effect on cells of skin cancer in B16-F0 mice. IC50 (the concentration at which maximal inhibition occurred) of the EPS was 275.4 pg/ml. The polysaccharide had almost no effect on normal fibroblasts of the L929 line (at the concentration of 187.5-1500 pg/ml cytotoxicity was almost absent) [67].
Recently, isolation of EPS-synthesizing cryotolerant yeasts of the genera Sporo-bolomyces [71] and Cryptococcus [72-74] was reported from Livingstone Island. Cultivation in medium with sucrose (40-50 g/l) and ammonium sulfate (0.25%) at 22-24 °C resulted in 4.6-6.4 g/l of poly-saccharides (Table 3).
Research of economically valuable properties of EPS of yeasts from the Livingstone Island confirmed their possible use in cosmetics, food industry [73, 75, 76] and medicine [78]. EPS of strain Cryptococcus laurentii AL100 exhibited high emulgent activity, significantly enhanced by other polysaccharides (xanthan, guar gum, cellulose, etc.) [73].
Other researchers showed that cosmetic emulsions with 2% EPS Sporobolomyces salmonicolor AL1 remained stable for a month at -10 °C and for 3 months at 22 and 45 °C [75, 76]. To achieve similar results, concentration of synthetic emulgent Arlacel 165 or Rofetan N/NS was 5% [75]. Besides that, EPS of S. salmonicolor AL1 has anticytostatic activity. At 5 ppm it changed LD50 of (cytostatic) avarol from 0.18 to 0.10 ppm [77].
EPS of cryotolerant fungi can be used as emulgents and thickeners in food and cosmetic practices at low temperatures. They are promising for medicine and pharmacy due to antitumor and anticytostatic activities.
Bacteriae. Reports of EPS synthesis by cryophilic and cryotolerant bacteriae started shortly after the first study about polysaccharides of cryotolerant fungi [69].
Polysaccharides of cryotolerant bacteriae isolated from free ice and marine aggregates in the Antarctic ocean, with in situ temperature of 4 °C were described in 2005 [78]. Six of the studied isolates belonged to the genus Pseudoalteromonas, three to the genera Shewanella, Polaribacter, and Flavobacterium. A strain CAM030T represented the family Flavobacteriaceae, later it became a new taxon Olleya marilimosa [79]. Most cryophilic bacterial producers isolated after 2005 belong to the genera Pseudoalteromonas, Polaribacter and Flavobacterium (Table 3).
By their monosaccharide content, the polysaccharides of cryophilic bacteriae are similar to EPS of marine bacteriae (Table 2).
Lowering the growth temperature from 20 to 10, or to -2 °C caused an almost 30fold rise in EPS-producing ability of strain Pseudoalteromonas sp. CAM025 (up to 99.9 and 97.2 mg EPS/g biomass, respectively), and a changed monosaccharide ratio [80].
Cryoprotectant properties of EPS of Pseudoaltermonas sp. SM20310 were studied in [63]. At 30 mg/ml EPS the number of living cells of strain SM20310 and E. coli DH5a was 7 to 18 times as high as in the control group (without EPS) after three cycles of freezing-thawing. Other researchers [68] report that adding the polysaccharide of cryotolerant bacteriae Flavobacterium sp. ASB 3-3 at 50 mg/ml led to a four times increase in the number of living cells of strains ASB 3-3 and E. coli DH5a after two cycles of freezing-thawing compared to the cultures without EPS.
Cryotolerant bacteriae Pseudoalteromonas elyakovii ArcPo 15 isolated from Chukchi Sea were observed to synthesize 1.7 MDa EPS with high cryoprotectant activity [81]. Adding the
EPS (0.5%) to a suspension of E. coli DH5a resulted in 94.2% survival of the cells after five cycles of freezing-thawing. Adding 20% glycerin resulted in 54.1% survival of the cells.
Due to the cryoprotectant ability of bacterial EPS we suggest using them as alternative cryoprotectant agents for long-term storage of suspended cultures [82, 83].
According to Carrion et al. at 10% EPS of Pseudomonas sp. ID1, survival of E. coli ATCC 10536 after freezing and storing for seven days at -20 and -80 °C was 36 and 64%, respectively [82]. Cell survival decreased at lower EPS concentrations. After similar freezing of EPS-synthesizing strain ID1, the cell survival rates were 75 and 94%, respectively. Another study [84] showed that EPS of cryophilic Colwellia psychrerythraea 34H are a better cryoprotectant agent for freezing cells at -80 °C than 10% glycerin solution.
Notably, cryoprotectant properties of polysaccharides are not limited to merely the protection of microbial cells. Sun et al. [84] reported that, survival rate of human dermal fibroblasts after 20 hours at 4 °C reached 76.1% with 500 pg/mg EPS of Polaribacter sp. SM1127, while without the polysaccharide it was only 44.2%.
In the native environment, other physico-chemical factors besides temperature can induce EPS synthesis, such as pressure and salinity [63, 83]. For example, culturing C. psychrerythraea 34H at high hydrostatic pressure (up to 400 atm) resulted in EPS content increasing 4.5-7.5 times.
Polysaccharides of cryophilic and cryotolerant bacteriae can also hold moisture [84, 85], emulsify [82, 68, 86], flocculate [68, 86] and adsorb metal [86, 87].
Research of EPS of bacterial strains Polaribacter sp. SM1127 and Zunongwangia profunda SM-A87 [84, 85] showed that after 72 hours of incubation with silica gel (relative humidity 43%) the polysaccharide of strain SM1127 retained 76% moisture, which is higher than for hyaluronic acid, glycerin, sodium alginate. This is possibly due to not only a lot of glucuronic acid and N-acetylglucosamine (components of hyaluronic acid), but also fucose, which has moisturizing properties, in EPS [84]. The polysaccharides also have antioxidant activity [84, 85]. Thus, the level of neutralization of 2,2-diphenyl-1-picrylhydrazyl radical radical (DPPH), hydroxyl radical (OH) and superoxide anion
(02) at 10 mg/ml of EPS of SM1127 and SM-A87 10, was 27.2-55.4%. Further research
[87] established the ability of EPS of strain SM-A87 to adsorb Cu2+ and Cd2+ (48 and 39.75 mg/g EPS, respectively).
After optimization of the culture medium
[88] in the fed-batch culture [85], the concentration of EPS of strain Z. profunda SM-A87 increased to 17 g/l, which is 1.93 times higher compared to the initial.
Recently Sathiyanarayanan et al. [68, 86] isolated cryotolerant Flavobacterium sp. ASB 3-3 and Pseudomonas sp. PAMC 28620 (AS-06/29) from the soil of Svalbard Arctic glacier fore-field. The optimal carbon and energy source for those bacteriae, unlike other microbial sources of EPS (Table 3) is glycerin. At the medium with 30 g/l of this substrate, the bacteriae produced 7.25 g/l EPS with flocculant and emulgent properties.
In kaolinite suspension (0.5%), flocculant activity of 40 mg/l EPS for strains PAMC 28620 and ASB 3-3 70 was 71.2 and 91.3%, respectively [68, 86]. The polysaccharide of strain ASB 3-3 emulsified n-hexane (emulsification index 66.3%) and n-hexadecane (64.3%) just as efficiently as sodium dodecyl sulfate [68]. EPS of strain PAMC 28620 efficiently emulsified toluene (67.2%) and methyl octanoate (66.7%) [86]. Besides that, polysaccharide of strain PAMC 28620 expediently adsorbed Fe2+, Cu2+, Mg2+, Zn2+ (approximately 99%), and Mn2+, Ca2+ (92%) [86].
Unlike thermophilic and thermotolerant sources (Table 1 and Table 2), cryophilic and cryotolerant microorganisms synthesize more EPS (up to 17 g/l; Table 3), and their polysaccharides have cryoprotectant, emulsifying properties, retain moisture and adsorb heavy metals. That, consequently, makes the polysaccharides potentially attractive for various fields from food industry (foodstuffs storage) and cosmetics (production of protective cosmetics) to environment-friendly technology (purification of waste waters).
Halophiles
Halophiles are organisms able to survive in briny habitats, whose development requires salt. The salt in question is generally NaCl, while many researchers in their experiments on halophilic cultures use sea salt which contains not only NaCl but also comparatively small amounts of other salts of two- and monovalent metals
[89].
Table 3. EPS synthesis by cryophilic and cryotolerant microorganisms
Microbial source Incubation temperature Carbon source, g/1 EPS concentration, g/1 Physico-chemical properties of EPS Physiological effect, functional properties and possible avenues of implementation of EPS References
Chemical composition Molecular mass, kDa
EPS of cryotolerant fungi
Cryptococcus flavus al51 24 °C Sucrose, 50 5.75 Mannose, glucose, xylose, galactose (1:0.47:0.17:0.03:0.08) 1010 - [72]
Cryptococcus laurentii al62 22 °C Sucrose, 40/50 4.73/4.6 Xylose, mannose, glucose (1:0.74:0.41) 8 - [74]
Cryptococcus laurentii al100 22 °C Sucrose, 40 6.4 Arabinose, mannose, glucose, galactose, rhamnose (1:0.25:0.2:0.1:0.05) 4.2 Emulgent [73]
Phoma herbarum CCFEE 5080 28 °C Sorbitol, 60 13.4 Glucan (glucose 100%) 7412 Cryoprotectant [69]
Sporobolomyces salmonicolor al^ 22 °C Sucrose, 50 5.2-5.6 Mannose, glucose, galactose (1:0.1:0.08) >1000 Thickener, emulgent [71, 75-77]
Thelebolus sp. IITKGP-BT12 18 °C Glucose, 50 1.94 Glucan (glucose 100%) 500 Antiproliferative activity [67]
EPS of cryophilic and cryotolerant bacteriae
Flavobacterium sp. ASB 3-3 25 °C Glycerin, 30 7.25 Glucose, galactose (1:0.43). Sulfates were found - Emulgent, floc-culant, cryoprotectant [68]
Polaribacter sp. SM1127 15 °C Glucose, 30 2.11 iV-acetylglucosamine, mannose, glucuronic acid, galactose, fucose, glucose, rhamnose (1:0.84:0.76:0.62:0.26:0.06:0.03) 220 Cryoprotectant, moisture-retention agent, antioxidant [84]
Pseudoalteromonas elyakovii ArcPo 15 15 °C Glucose, 20 1.64 Mannose, galacturonic acid (3.3:1.0) 17000 Cryoprotectant [81]
Pseudoalteromonas sp. CAM025 10 °C Glucose, 30 99.9 mg/ g biomass Glucose, galactose, rhamnose, mannose, fucose, arabinose, ribose, glucuronic acid (1:0.64:0.61:0.31:0.25:0.12:0.05: 0.26). Sulfates 5% 5700 Cryoprotectant [80]
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As to salinity, halophiles can be halotolerant (upper salinity limit 15%), weak (NaCl content of 2-5%), moderate (5-5%) and extreme halophiles (20-30%) [16].
Usually, they can be found in various saline habitats such as salt lakes, salt evaporation ponds, saline soils, mines, food products, etc. [21, 90]. Traditional halophilic sources are salterns, which usually have high salt content, intensive sunlight and low oxygen levels [90-95].
Archaea. Main papers on polysaccharide synthesis by halophilic archaea include research on isolation of new producers [94, 96], EPS structure [97-99], and the possibilities of their practical application [96].
In 1988, Antón et al. [96] established that extremely halophilic archaea Haloferax mediterranei ATCC 33500 cultured on a medium with 1% glucose and 25% sea salt produced 3 g/l of sulfated high molecular polysaccharide. Viscosity of EPS solutions was stable in wide ranges of pH, temperature and salinity. Hence EPS of strain ATCC 33500 can be utilized in increasing oil production from wells with high salt content. Later, researchers established the structure of repeating sequences of EPS strain ATCC 33500 [98] and other EPS-synthesizing archaea, in particular Haloferax gibbonsii ATCC 33959 [97] and Haloferax denitrificans ATCC 35960 [99].
At the end of the twentieth century, for new producers of polyhydroxyalkanoates and EPS, Nicolaus et al. [94] isolated three obligate halophilic strains T5, T6 and T7, which synthesized 35-370 mg/l EPS, from the salt works of Tunisia. The isolates belonged to the genus Haloarcula. Among halophilic EPS-synthesizing archaea is strain Halobacterium volcanii 1539, which produces 300 mg/l sulfated polysaccharide [100].
There have been no new studies on EPS synthesis by halophilic archaea after that, until a recent
report of EPS-synthesizing archaea Haloterrigena turkmenica DSM-5511, isolated from briny soil (Turkmenistan) [101]. The polysaccharide has high emulsifying (emulsification index of sunflower and olive oils are 62.2 and 59.6%, respectively) and antioxidant activity (68.2% neutralization of DPPH- at 10 mg/ml EPS). The EPS also better than hyaluronic acid and sodium alginate retained moisture.
Similar properties were found in certain polysaccharides of cryophilic bacteriae [85, 86] (Table 3). However, the level of target product is too low (at least now) in strain H. turkmenica DSM-5511 to consider it a marketable EPS source.
Bacteriae. Polysaccharides of halophilic bacteriae induced scientific interest almost simultaneously with the first reports of EPS synthesis by halophilic archaea. The most studied bacteriae belonged to the genera Halomonas [90-92, 95, 102-110], Idiomarina [111], Alteromonas [111], Salipiger [93] and Halobacillus [112].
Those bacteriae are moderately halophilic, their optimum salt content is 2.5-13%, usually 7.5% (Table 6). Most of them survive increased salinity (up to 20-25%) [64, 91, 113], and therefore are halotolerant microorganisms.
In early 1990s, reports were published on the synthesis of sulfated polysaccharide (2.8 g/l) by moderately halophilic bacteriae Volcaniella eurihalina F2-7 [104, 109] (now Halomonas eurihalina [114]).
Soon, wide-scale screening of possibly halophilic producers isolated from solar salterns in Morocco was published [92]. Thirty two isolates of the genus Halomonas were selected for a more detailed analysis out of more than 500 isolates. Only four of them accumulated over 2 g/l polysaccharide, and the highest amount (2.8 g/l) was produced by strain S-30. According to phylogenetic analysis, the strain and isolates S-7, S-31T and S-36 were combined into a new species Halomonas maura [115]. Further optimization of the cultivation medium (reducing sea salt concentration, instead adding 2.5% NaCl and 0.05% MgCl26H2O) increased EPS production of strain S-30 to 3.8 g/l [103].
Strain Halomonas xianhensis SUR308, isolated from soil of a solar saltern (India) [90, 91], on a medium with glucose (1%) and NaCl (10%) produced 2.56 g/l EPS [91]. Further increase of glucose content to 3% and decrease of NaCl to 2.5% was followed by increased EPS production to 7.87 g/l [90]. The polysaccharide was not toxic for Huh7 human hepatocytes.
Also, the polymer had high antioxidant activity: the level of neutralization of DPPH-was 72% at 1 mg/ml EPS 72% [91].
Poli et al. [95] reported isolating a moderately halophilic bacteria Halomonas sp. AAD6T from Turkish salterns. Later it was identified as the typical strain of a new species Halomonas smyrnensis [113]. It produced levan (a fructose homopolysaccharide). Adding 50 mM boric acid, 0.8 mg/l thiamine and trace quantities of salts of Mn, Zn, Fe and Cu to the culture medium resulted in a five times increase in levan concentration (up to 8.84 g/l) compared with the initial medium [116].
Further studies aimed to lower the production cost of the target product by using various molasses instead of sucrose in the EPS biosynthesis medium [105]. EPS concentration reached 7.56 g/l (12.4 g/l after 210 hours of cultivation) in culture medium with beet pre-treated with calcium phosphate, sulfate acid and activated carbon. In culture medium with likewise pre-treated starch molasses (a side product of manufacturing dextrose from starchy materials) it was 4.38 g/l. Using starch molasses as a substrate resulted in levan with high emulgent activity [117]. Levan of strain AAD6T was shown to be useful in targeted delivery of drugs, in particular, of antibiotic vancomicyn [118]. It also increased LD50 of avarol from 0.18 ppm to 10 ppm [95]. Anticoagulant activity of artificially sulfated derivatives of that EPS was studied in [119].
Ruiz-Ruiz et al. [110] studied antitumor properties of polysaccharides of halophilic bacteriae Halomonas stenophila B100 and N12T. Artificially sulfated EPS (sEPS) of strains B100 and N12T (sulfate content 23 and 17%, respectively) efficiently decreased proliferation of T-cells of acute lymphoblast leukemia line Jurkat (500 pg/ml sEPS of strain B100 resulted in 100% inhibition of cell proliferation). Only sEPS of strain B100 induced apoptosis of tumour cells (lines CEM, MOLT-4, HPB-ALL, etc.), while healthy T-cells resisted the apoptosis induction [111]. Authors considered that antitumor effect to directly depend on the concentration of sulfates. It was suggested that sulfates change the charge of polymer molecule to negative and affect its structure, increasing the interaction between EPS and the target cell surface [110].
Bacteriae of the genus Halomonas are not only moderately halophilic producers of polysaccharides. A strain isolated from the hypersaline soil of solar saltern (Spain), Salipiger mucosus A3T (sEST 5855T) cultured
for 72 hours in a medium with 1% glucose and 7.5% sea salt produced 1.35 g/l EPS [93]. Approximately the same amount of EPS (1-1.5 g/l) was obtained from strains Idiomarina fontislapidosi F23T, Idiomarina ramblicola R22T and Alteromonas hispanica F32T isolated similarly from hypersaline habitats [111]. Unlike these bacteriae, strain
Halobacillus trueperi AJSK produced almost 13 g/l EPS on an optimized medium [112].
Many polysaccharides of moderate halophilic organisms can adsorb cations of various metals [93, 103, 106, 111, 117] (Table 4), emulsify carbohydrates, vegetable and mineral oils [91, 93, 102, 103, 106, 111, 117] (Table 5). Besides that, EPS of Halomonas
Table 4. Adsorption of metal cations by polysaccharides of halophilic bacteriae
EPS-producing microbe Adsorption rate, mg/g EPS References
Cu2+ Pb2+ Co2+
Alteromonas hispanica F32T 6.95 30 4 [111]
Halomonas almeriensis M8T 19.2 24.5 10 [106]
Halomonas anticariensis FP35T 26.6 26.3 10.5 [117]
Halomonas anticariensis FP36 28.1 25.15 10.5 [117]
Halomonas maura S-30 4.24 46.4 0.72 [103]
Halomonas ventosae A112T 12 24.8 2.5 [117]
Halomonas ventosae A116 27.6 25.7 10 [117]
Idiomarina fontislapidosi F23T 16.3 40 8 [111]
Idiomarina ramblicola R22T 26.25 44.65 10 [111]
Salipiger mucosus A3T 15.7 43.5 8.7 [93]
EPS-producing microbe Emulsifying index,% References
Oil Tetra-decane Octane Kerosene
sunflower olive mineral
Alteromonas hispanica F32T 55 40 50 50 55 67.5 [111]
Halomonas almeriensis M8T 65 67.5 67.5 62.5 65 65 [106]
Halomonas anticariensis FP35T 47.5 40 47.5 45 45 - [117]
Halomonas anticariensis FP36 37.5 42.5 50 55 42.5 - [117]
Halomonas stenophila HK30 70 85 55.8 41 56.7 80 [102]
Halomonas ventosae A112T 51 42.8 35.5 57.5 57.5 - [117]
Halomonas ventosae A116 60 55 62.5 60 60 - [117]
Halomonas xianhensis SUR308 - 71.3 - 80.3 76.3 - [91]
Idiomarina fontislapidosi F23T 65 60 62.5 45 60 55 [111]
Idiomarina ramblicola R22T 60 65 62.5 55 60 62.5 [111]
Salipiger mucosus A3T 70 60.3 71 75 70 70 [93]
Control
Triton X-100 62.5-67.5 60-62.5 60-67.5 62.5-65 60-62.5 60-62.2
Tween 80 62 61.562.5 60-70 60-62.5 60 60 [91, 93, 102, 106, 111, 117]
Table 5. Emulsifying properties of polysaccharides of halophilic bacteriae
Table 6. Synthesis of exopolysaccharides by halophilic and moderately halophilic microbes
Microbial source Salt content Carbon source, g/1 Physico-chemical properties of EPS Physiological effect, functional properties, possible avenues of implementation of EPS References
EPS content g/1 Chemical composition Molecular mass, kDa
EPS of halophilic archaea
Haloarcula sp. T6 NaCl, 200 g/1 Glucose, 6 0.045 Mannose, galactose and glucose (1:0.2:0.2) - - [94]
Haloarcula sp. T7 NaCl, 200 g/1 Glucose, 6 0.035 Mannose, galactose and glucose (1:0.2:0.2) - - [94]
Haloarcula japónica T5 NaCl, 200 g/1 Glucose, 6 0.37 Glucuronic acid, mannose and galactose (3:2:1) - - [94]
Halobacterium volcanii 1539 NaCl, 156 g/1 Galactose, 10 0.3 Mannose. Hexuronic acids present. Sulfates 0.6% - - [100]
Haloferax mediterranei ATCC 33500 Sea salt, 25% Glucose, 10 3 Mannose, glucose, galactose. Sulfates 6% >100 Thickener, intensification of oil production [96]
Haloterrigena turkmenica DSM-5511 NaCl, 200 g/1 Glucose, 10 0.207 Glucose, glucosamine, glucuronic acid, galactose, galactosamine (1:0.65:0.24:0.22:0.02). Sulfates 2.8% Fractions 1-3: 801.7; 206; 37.6 Emulgent, antioxidant, moisture retention agent [101]
EPS of moderately halophilic bacteriae
Alteromonas hi.spani.ca F32T Sea salt (7.5%) Galactose, 10 1.25 Mannose, glucose, xylose (1:0.29:0.11). Sulfates 0.25% 19000 Biofilm formation. Emulgent, adsorbent [111]
Halobacillus trueperi. AJSK NaCl (61.56 g/1) Glucose, 22,2 12.93 - - - [112]
Halomonas alkali.antarcti.ca CRSS NaCl (100 g/1) Sodium citrate, 3 2.9 g EPS/g biomass Mannose, xylose, glucose, galactosamine, fructose, rhamnose, not indentified component (1:0.7:0.3:0.2:traces:traces:0.3) - Thickener [64, 108]
Halomonas almeriensis T M8 Sea salt (7.5%) Glucose, 10 1.7 Fraction 1: mannose, glucose, rhamnose (1:0.38:0.01); Fraction 2: mannose, glucose (1:0.97). Sulfates 1.4% Fraction 1: 6300; Fraction 2: 15 Emulgent, adsorbent [106]
Halomonas anticariensis FP35T Sea salt (7.5%) Glucose, 10 345.5 mg/1 Mannose, galacturonic acid, glucose (1:0.82:0.33). Sulfates 0.73% 20 Biofilm formation. Emulgent, adsorbent [117]
Halomonas anticariensis FP36 Sea salt (7.5%) Glucose, 10 0.386 Mannose, galacturonic acid, glucose (1:0.87:0.4). Sulfates 1.16% 46 Biofilm formation. Emulgent, adsorbent [117]
Halomonas euri.hali.na F2-7 Sea salt (7.5%) Glucose, 10 2.8 Glucose, mannose, rhamnose (molar ratio 2.9:1.5:1). Sulfates 2.7% - Thickener, emulgent, intensification of oil production [104, 109]
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EPS content g/l Chemical composition Molecular mass, kDa
Halomonas maura S-30 Sea salt / NaCl (2.5%) Glucose, 10 3.8 Mannose, galactose, glucose, glucuronic acid (1:0.4:0.84:0.63). Sulfates 6.5% 4700 Emulgent, thickener; adsorbent [92, 103]
Halomonas smyrnensis AAD6 NaCl (137.2 g/l) Sucrose, 50 1.84-8.84 Fructose (levan) >1000 Flocculant [118]; targeted drug delivery [119], anticoagulant [120]; anticytotoxic activity [95, 116]
NaCl (137.2 g/l) Processed beet molasses (30 g/l carbohydrates) 12.4 Fructose, glucose(traces) >1000 [105]
Halomonas stenophila B100 Sea salt (7.5%) - - Glucose, galactose, mannose (1:0.91:0.34). Sulfates 7.9% 375 Antitumor activity [110]
Halomonas stenophila HK30 Sea salt (5% ) Glucose, 10 3.89 Glucose, glucuronic acid, mannose, fucose, galactose, rhamnose (1:0.3:5.5:0.23:0.19:0.0 5:0.002) Fraction 1: 1400; Fraction 2: 82 Biofilm formation. Thickener, emulgent; flocculant [102]
Halomonas stenophila N12T Sea salt (7.5%) - - Glucose, mannose, fucose (1:0.52:0.53). Sulfates 2.45% 250 Antitumor activity [110]
T Halomonas ventosae Al 12 Sea salt (7.5%) Glucose, 10 283.5 mg/1 Mannose, glucose, galactose (1:0.43:0.25). Sulfates 1.09% 53 Biofilm formation. Emulgent, adsorbent [117]
Halomonas ventosae'Al 16 Sea salt (7.5%) Glucose, 10 289.5 mg/1 Mannose, glucose, galactose (1:0.42:0.22). Sulfates 0.71% 52 Biofilm formation. Emulgent, adsorbent [117]
Halomonas xianhensis SUR308 NaCl (10% / 2.5%) Glucose, 10/ 30 2.56 / 7.87 Glucose, galactose, mannose, xylose, ribose (1:0.74:0.39:0.04:0.02) - Thickener, emulgent, antioxidant [90, 91]
Idiomarina fon ti.slapi.dosi F23T Sea salt (7.5%) Glucose, 10 1.45 Fraction 1: mannose, glucose, galactose, xylose (1:0.61:0.32) Fraction 2: mannose, glucose, galactose, xylose (1:1:0.5:traces). Sulfates 0.65% Fraction 1: 1500; Fraction 2: 15 Biofilm formation, emulgent, adsorbent [111]
Idiomarina ramblicola T R22 Sea salt (7.5%) Glucose, 10 1.5 Fraction 1: mannose, glucose, rhamnose (1:0.37:0.1); Fraction 2: mannose, glucose, galacturonic acid, rhamnose, xylose (1:0.35:0.47: traces: traces). Sulfates 0.5% Fraction 1: 550; Fraction 2: 20 Biofilm formation. Emulgent, adsorbent [111]
T Salipiger mucosus A3 Sea salt (2.5-7.5%) Glucose, 10 1.35 Mannose, galactose, glucose, fucose (1:0.97:0.58:0.39). Sulfates 0.9% 250 Emulgent, adsorbent [93]
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stenophila HK30 have high flocculant activity: 72.06% EPS in a suspension of kaolinite (0.5%) at 20 mg/l EPS [102].
Table 6 summarizes information on EPS synthesis by halophilic archaea and moderately halophilic bacteriae.
Thus, studies of EPS from non-traditional sources (cryophilic fungi and bacteriae, halo-and thermophilic archaea and bacteriae, including those from deep-sea hydrothermal vents) is a novel field which began to develop rapidly at the end of the twentieth century. Many of those isolated microorganisms produce polysaccharides. The physiological effect, physico-chemical properties and possibilities of industrial application of those EPS are studied. Those substances due to their immunomodulating, antiviral, anticoagulant, antitumor, antioxidant activities can be widely employed, in medicine and pharmacy, etc.
Meanwhile the practical implementation of polysaccharides is limited by the low efficiency
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of production. Non-traditional sources produce EPS in much lower concentrations than the traditional ones. In our opinion, solving this problem is only a question of time, because various approaches to metabolic and gene engineering for microbial synthesis intensification are already developed [88, 112, 120-122].
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НЕТРАДИЦ1ЙН1 ПРОДУЦЕНТИ М1КРОБНИХ ЕКЗОПОЛ1САХАРИД1В
Т. П. Пирог А. А. Вороненке М. 0.1вахнюк
Нащональний ушверситет харчових технологш, Кшв, Украша
E-mail: [email protected]
Наведено даш л^ератури щодо синтезу екзополiсахаридiв психроф^ьними грибами, гало- i термоф^ьними археями та бак-терiями, зокрема й вид^еними з глибоко-водних пдротермальних венив — джерел. Проаналiзовано фiзiологiчну роль, фiзико-хiмiчнi властивост та можливi галузi практичного використання екзопол^аха-ридiв, синтезованих нетрадищйними продуцентами. Бiльшостi з них притаманна iмуномодулювальна, противiрусна, антико-агулянтна, протипухлинна, антиоксидантна актившсть, що робить 1х перспективними для застосовування у медицин та фармаце-втицi.
Водночас аналiз лiтератури засвщчив не-обхiднiсть розроблення ефективних техноло-гiй одержання таких полiсахаридiв, осшль-ки показники 1х синтезу нетрадищйними продуцентами е значно нижчими порiвняно з традицiйними.
Ключовi слова: екзопол^ахариди, термофiли, психрофiли, галофiли, гiдротермальнi венти.
НЕТРАДИЦИОННЫЕ ПРОДУЦЕНТЫ МИКРОБНЫХ ЭКЗОПОЛИСАХАРИДОВ
Т. П. Пирог А. А. Вороненке Н. А. Ивахнюк
Национальный университет пищевых технологий, Киев, Украина
E-mail: [email protected]
Представлены данные литературы о синтезе экзополисахаридов психрофильными грибами, гало- и термофильными археями и бактериями, в частности выделенными с глубоководных гидротермальных вентов — источников. Проанализированы физиологическая роль, физико-химические свойства и возможные отрасли практического использования экзо-полисахаридов, синтезированных нетрадиционными продуцентами. Большинство из них обладает иммуностимулирующей, противовирусной, антикоагулянтной, противоопухолевой, антиоксидантной активностью, что делает их перспективными для применения в медицине и фармацевтике.
В то же время анализ литературы показал необходимость разработки эффективных технологий получения таких полисахаридов, поскольку показатели их синтеза нетрадиционными продуцентами значительно ниже по сравнению с традиционными.
Ключевые слова: экзополисахариды, термофилы, психрофилы, галофилы, гидротермальные венты.
