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Научни трудове на Съюза на учените в България-Пловдив, серия Б. Естествени и хуманитарни науки, т. XVIII, ISSN 1311-9192 (Print), ISSN 2534-9376 (On-line), 2018. Scientific researches of the Union of Scientists in Bulgaria-Plovdiv, series B. Natural Sciences and the Humanities, Vol. XVIII, ISSN 1311-9192 (Print), ISSN 2534-9376 (On-line), 2018.
ИЗСЛЕДВАНЕ НА ДИСПЕРСНИЯТ СЪСТАВ НА МОДЕЛНИ ЕМУЛСИИ, СЪДЪРЖАЩИ БИОПОЛИМЕР, СИНТЕЗИРАН ОТ ХАЛОФИЛНИ МИКРООРГАНИЗМИ ОТ ЩАМ CHROMOHALBACTRE CANANDESYS Хр. Кисов1, М. Кунчева2,И. Панчев2, М. Камбурова3, Н.Радченкова3 Институт по оптични материали и технологии "Академик Йордан Малиновски", БАН, (София 2Университет по хранителни технологии, Пловдив 3Институт по микробиология "Стефан Ангелов", БАН, София
STUDY ON THE DISPERSIVE COMPOSITION ON MODEL EMULSIONS CONTAINING BIOPOLYMER SYNTHESIZED FROM HALOPHILIC MICROORGANISMS OF THE CHROMOHALBACTRE
CANANDESYS S TRAIN Hr. Kisov1, M. Kuncheva2, I.Panchev2, M. Kamburova3, N. Radchenkova3 'Institute of Optical Materials and Technologies (IOMT) "Academician Jordan Malinovski" - BAS, Sofia, Bulgaria 2University oTFoao Techuolagies, Plovdiv, Bulgaria 3Institute of Microbiology "Stephan AngelsflO' - BAS, Safia, Bulgaria
Abstract
In this work are presented experimental data from the study of the dispersion composition of model emulsions containing biopolymer synthesized from halophilic microorganisms of the strain Chromohalbactre canandesys isolated from the Bulgarian salt niches (the Atanasovsko lake). The optimum temperature of the synthesis of the biopolymer is 30° C and pH 7.3 at a concentration of 15% NaCl. A model oil/water emulsion contains sunflower oil and biopolymer of various concentrations. The stability of the emulsions is determined by conventional methods (centrifugation and spectrophotometry). Dispersion characteristics of the emulsion (size distribution and average size) were examined by the instrument for measurement the size of particles contained within a sample.
Keywords: biopolymer, Chromohalbactre canandesys, emulsion, particle size distribution. Iatroduetioa
There is a number of microorganisms synthesize polysaccharides which are wide applied as emulsifiers, stabilizers, foaming agent, thickeners, linking and gelling agent in cosmetics, medicine and other fields (1). A research group comprising scientists at IMB-BAS, Sofia, have focused their attention on finding new and biotechnologically unused saline niches as a source of isolating and studying microorganisms (halophilic bacterial strains) that are interesting from a biotechnological perspective in terms of synthesis of biopolymers as for physicochemical properties and functional characteristics. One of the most prospective applications of biopolymers
is their use as stabilizers and foaming agents for cosmetic and food industries. Their full water solubility is prominent feature of their surface active properties. Surfactants are adsorbed at the interface between the dispersed and continuous phase to stabilize the dispersed particles by means of their functional groups, spatial interactions, hydrophobic and hydrogen bonds. In this work we present experimental data from the study of the stability and the particle size distribution of model emulsions containing a new biopolymer (EPS) synthesized from halophilic microorganisms of the strain Chromohalobacter canadensys strain isolated from the Bulgarian salt niches (the Atanasovsko lake) and some polysaccharides, which have an effect of a synergism. Materials and methods
Diversity and biosynthetic ability for exopolysaccharide production of heterotrophic moderately halophilic and halotolerant bacteria isolated from the Bulgarian salt niches (the Atanasovsko lake) were investigated. The Chromohalbactre canandesys strain was observed as a perspective biopolymer producer. The optimal pH was 7.3 and the optimal concentration of NaCl was 15 %. The biosynthesis and emulsifying capacity of EPS was evaluated following the methods described in our works (2. 3). The sunflower oil used was a commercially available product. For the emulsion preparation biopolymers were dissolved using a magnetic stirrer at a temperature of 45-50 0 C. The IKA ULTRA - TURAX T1 disperser at 50 s-1. Emulsion stability was evaluated by centrifugation at 3000 x g for 10 min as describe in (3).
The particle size distribution of the emulsion and the average size of particles are based on method of Dynamic Light Scattering. The Dynamic Light Scattering (DLS) measures Brownian motion and relates this to the size of the particles. It does it by illuminating the particles with a laser and analyzing the intensity fluctuations in the scattered light by Zetasizer Nano particle characterization system of Malvern.
The samples tested diluted with distilled water to concentrations of samples 1,2,3,5 and 6 are 1: 200 and samples 4, 7 are 1:300 respectively. This is due to the fact that at higher concentrations it becomes cloudy and unsuitable for research.
Results and discussions
Maintaining an emulsion requires an emulsifying agent which lowers the surface tension of the droplets and forms a barrier to help prevent coalescence of the droplets. EPS has shown to be an excellent emulsifying agent.
The synergistic effect of the synthesized microbial polysaccharide in relation to the emulsion stabilizing properties was studied in mixtures with xanthan gum, guar gum, cellulose gum. Tabl. 1 presents polysaccharides concentration (w/v) of % of water medium and results of the emulsifying stability of the model emulsion systems at centrifugation and the average size of particles in emulsions. In all experiments the percentage of the separated oil was zero.
Tab.1 Average size of particles for all emulsions
№ Concentration of biopolymers (in %) to the water medium Stability at centrifugation (% non-destroyed emulsion) Average size, d (nm)
1 0,5 % EPS 70 5295
2 0,5 % EPS +0,5 % guar gum 100 326
3 0,5 % EPS +0,5 % cellulose gum 94 491
4 0,5 % EPS +0,5 % xanthan gum 76 Peak 1-5821, Peak 2- 360
5 2 % EPS + 0,5 % guar gum 100 610
6 2 % EPS + 0,5 % cellulose gum 100 879
7 2 % EPS + 0,5 % xanthan gum 80 4717 (three very close peaks)
In the figures below are shown graphs of the distribution of the partial size in the emulsions for all samples.
Fig.1.1
Size Distribution by Intensity
10 100 Size (d.nm)
Record 1: exo sample7 1|
Fig. 1.2
Fig. 1.3
Size (d.nm) Record 2: exo_sample5_5~2]
Fig. 1.4
Size Distribution by In!
10 100 Size (d.nm)
Record 1: exo sample7 1
Record 2: exo sample7 2
Record 3: exo sample7 3|
The studied dispersion characteristic shows the particle size distribution and average size in the samples which is correlated with stability on the emulsion systems. From the results presented in Table 1 and the graphs in Fig. 1, we can see that the best dispersion characteristic is the emulsion, obtained with EPS + guar gum (experiments 2 and 5) and EPS + cellulose gum (experiments 3 and 6). These emulsion systems are with smaller size of oil droplets and homogeneous in size distribution (they have only one peak). The emulsions obtained with EPS + xanthan gum (experiments 4 and 7) have the largest size of oil droplets and have two peaks.
Fig. 1.6_
Size stribution by Intens.
- 1 1
Size (d.nm) cord 3: exo sample2 200 3| 1000 10000
Size Distribution by Inten
Record 3: exo_sample4 3|
Fig. 1.7
100.....
n 80.....
; 60.....
f 40.....
; 20.....
Size Distribution by Inte
10 100 Size (d.nm)
Record 1: exo sample8_2 1
Record 2: exo sample8_2 2
Record 3: exo sample8_2 3|
Fig1. Graphs of the distribution of the partial size in the emulsions
80
0.1
1000
10000
0.1
3<-0.1
1000
10000
0.1
size (d
Conclusion
Best synergistic effect to stabilize and increase dispersion of emulsion systems is achieved with hydrocolloids guar gum and cellulose gum.
Acknowledgements
The authors wish to thank the National Science Fund of the Ministry of Education for the Funds provided for research project DTK 02/26 from 01.05.2015 under which this work was carried out. Special thanks for the leadership of the Institute of Optical Materials and Technologies (IOMT) "Academician Jordan Malinovski" - BAS. References
1) Dickinson E. (1992) An Introduction to Food Colloids, Oxford University Press, Oxford
2) Radchenkova N., S. Vassilev, I. Panchev, G. Anzelto, I. Tomova, P. Nocolaus, M. Kuncheva, K. Petrov, M. Kamburova, (2013), Production and Properties of Two Novel Exopolisaccharides synthesized by thermophilic Bacterium Aeribacillus pallidus 418, App. Biochem. Vol. 171m pp. 31-43
3) Kuncheva M. I. Panchev, K. Pavlova, S. Russinova-Videva, K. Georgieva, S. Dimitrova, (2013), Functional characteristies of an Exopolysaccharide by Antarctic Yeast Strain Criptococus Laurentii AL 62. Biotechnology & Biotechnological EQ, 27,5 pp. 40984102.
Correspond author Dr. Hr. Kisov, e-mail: hristokisov@iomt.bas.bg christokissov@yahoo.com
