Научная статья на тему 'Illumination influence on Chlorella sorokiniana biomass synthesis'

Illumination influence on Chlorella sorokiniana biomass synthesis Текст научной статьи по специальности «Химические науки»

CC BY
79
19
i Надоели баннеры? Вы всегда можете отключить рекламу.
Журнал
Biotechnologia Acta
CAS
Область наук
Ключевые слова
CHLORELLA SOROKINIANA / BIOMASS GROWTH / CULTIVATION CONDITIONS / KINETIC REGULARITIES / ЗРОСТАННЯ БіОМАСИ / УМОВИ КУЛЬТИВУВАННЯ / КіНЕТИЧНі ЗАКОНОМіРНОСТі / РОСТ БИОМАССЫ / УСЛОВИЯ КУЛЬТИВИРОВАНИЯ / КИНЕТИЧЕСКИЕ ЗАКОНОМЕРНОСТИ

Аннотация научной статьи по химическим наукам, автор научной работы — Bazarnova Y., Lyskova N., Kuznetsova T., Trukhina E.

The aim of the work was to estimate the influence of illumination on the rate of Chlorella sorokiniana alga biomass synthesis; kinetic dependencies of the synthesis and unit rate of biomass growth at different illumination conditions. Verification of adequacy of kinetic dependencies has been implemented. The kinetic equations and values of the unit rate of biomass growth derived in studied illumination modes made it possible to calculate the time needed for the synthesis of the set amount of biomass and related growth medium consumption required for a set of cultivation conditions.

i Надоели баннеры? Вы всегда можете отключить рекламу.
iНе можете найти то, что вам нужно? Попробуйте сервис подбора литературы.
i Надоели баннеры? Вы всегда можете отключить рекламу.

ВЛИЯНИЕ ОСВЕЩЕННОСТИ НА СИНТЕЗ БИОМАССЫ МИКРОВОДОРОСЛЕЙ Сhlorella sorokiniana

Целью работы было оценить влияние освещенности на скорость синтеза биомассы микроводоросли Chlorella sorokiniana , кинетическую зависимость синтеза и удельную скорость роста биомассы в различных условиях освещенности. Установлено, что наибольшее значение удельной скорости роста клеток биомассы достигается в режиме освещенности 2200-2800 Лк; Т(К) 400 (дневной свет). Проведена проверка адекватности полученных кинетических зависимостей. Кинетические уравнения и значения удельной скорости роста биомассы в изученных режимах освещенности позволят рассчитать время, необходимое для синтеза заданного количества биомассы и связанного с ней расхода питательной среды в заданных условиях культивирования.

Текст научной работы на тему «Illumination influence on Chlorella sorokiniana biomass synthesis»

UDC 577.115.083:608.2 https://doi.org/10.15407/biotech12.03.050

ILLUMINATION INFLUENCE ON Chlorella sorokiniana BIOMASS SYNTHESIS

Y. Bazarnova

N. Lyskova Peter the Great St. Petersburg Polytechnic University, Russia

T. Kuznetsova E. Trukhina

E-mail: jbazarnova@spbstu.ru

Received 02.02.2019 Revised 23.04.2019 Accepted 05.07.2019

The aim of the work was to estimate the influence of illumination on the rate of Chlorella sorokiniana alga biomass synthesis; kinetic dependencies of the synthesis and unit rate of biomass growth at different illumination conditions. Verification of adequacy of kinetic dependencies has been implemented. The kinetic equations and values of the unit rate of biomass growth derived in studied illumination modes made it possible to calculate the time needed for the synthesis of the set amount of biomass and related growth medium consumption required for a set of cultivation conditions.

Key words: Chlorella sorokiniana, biomass growth, cultivation conditions, kinetic regularities.

Technologies employing vegetation biomass as a source of energy and valuable food components are currently considered as biotechnologies being implemented on a large scale. The search for productive types of biomass puts forward phototrophic organisms as a perspective source of energy and raw material for extracting phytocomponents [1-3]. When developing the processes of extracting the valuable phytocomponents from the biomass of phototrophic organisms it is important not only to consider the possibility of obtaining diverse target products from the biomass but also to organize a safe production with a minimal strain on environment [4-8].

These requirements are fairly fulfilled in the case of Chlorella alga biomass, which finds its vast scope of application as the source of biofuel of the third generation and raw material for obtaining valuable food components, including lipids and carotenoids.

In this regard, an urgent task is to select optimal biomass cultivation conditions that would not demand substantial energy-related and financial expenditures [9-13].

This work is focused on the studying of kinetic regularities of synthesis of alga Chlorella sorokiniana biomass in different

illumination modes and deriving kinetic dependencies that characterize the influence of spectral structure of luminous flux on the biomass accumulation speed.

Materials and Methods

The initial concentration of Chlorella sorokiniana alga cells in suspension amounted to 4.2 mln cells per ml; temperature of the mixture is (23±1) °C; intensity of mixture aeration is 1.5 l per min (liters per minute); mixing mode is periodic (15 min once per day); mixing speed is 500 rps (revolutions per second).

Illumination conditions for the biomass suspension are the following:

• Mode 1. Fluorescent lamp, illumination intensity is 2200-2800 lx, T = 400 K, daylight (later referred as DFL);

• Mode 2. Infrared incandescent lamp, spectral area of the luminous flux — 3.5-5.0 pm, illumination is 14100 lx (later referred as IR);

• Mode 3. UV-radiation with a mercury gas-discharge lamp with a spectral area of the luminous flux of 320-400 nm during 3 hours on the first day of cultivation (later

referred as UV-A) and further illumination with a fluorescent lamp, illumination intensity 2200-2800 lx, T = 400 K, daylight (later as UV+DFL).

Dimensional parameters of the photobioreactor (Fig. 1) are the following: height — 380 mm, diameter — 50 mm, volume — 500 ml.

air

4

Fig. 1. Laboratory photobioreactor for Chloralla sorokiniana microalga cultivation:

1 — pump-aerator; 2 — source of radiation (IR or UV); 3 — daylight lamp; 4 — magnetic agitator; 5 — anchor of magnetic agitator; 6 — aeration tube

The concentration of the cell suspension of microalgae in the culture medium was determined using a calibration graph of dependence of the optical density of the suspension on cell concentration. The optical density of the suspension was determined at a wavelength of 750 nm. Culture medium was used as a reference solution. Sampling for spectrophotometry was carried out after mixing the suspension. The measurements were carried out in the range of optical density of 0.2-0.6, which corresponds to the linearity of the Beer-Lambert law. The cells were counted in in the hemocytometer in 5 large squares [14] in the absence of signs of cell flocculation. Dilution of the suspension was carried out at its high concentration. Dilution was taken into account when calculating the concentration.

Concentration of alga cells in the suspension was identified by measuring the optical density using a spectrophotometer with 750 nm wavelength and with a subsequent

conversion to the quantity of cells in 1 ml of suspension in the hemocytometer . The values of optical density of the series of solutions were used for calibration graph construction.

Cultivation was implemented with the use of tap-water based growth medium containing a range of macro- and microelements shown in the table 1 below [15].

Regression analysis was used for mathematical processing of experimental data. Graphic dependences are presented after statistical processing using the least squares method implemented in Microsoft Excel. The degree of reliability of the experimental results is confirmed by their threefold repetition and reproducibility of data.

Results and Discussion

The derived calibration dependency is, as follows: y = 26.729x — 0.591 (R" = 0.9883). It was used for identification of C. sorokiniana alga cells quantity at the wavelength X = 750 nm.

Fig. 2 illustrates dynamics of C. sorokiniana cells' biomass synthesis in accordance with illumination conditions.

Analysis of experimental dependency of alga cells' biomass concentration on duration of the process demonstrated compliance between the curve manner and Verhulst logistic equation (1) [16]:

f),

(1)

where x is concentration of cells' biomass, mln cells/ml at the current moment; K is population capacity, mln cells/ml; p is unit speed of growth, days -1.

Equation (2) is used to identify the unit speed of growth:

lnX = lnX0 + |t,

(2)

where X0 and X are concentrations of cells' biomass, mln cells/ml at the initial and current moment, correspondingly.

It was established that the speed of alga biomass accumulation reaches its maximum at the concentration of cells of 21 mln cells/ml with a further decrease. Fig. 3 illustrates the relation between cell growth speed and their concentration.

Exponential phase of growth on the graph with vertical lnX and horizontal t axes represents a line with a tangent of inclination angle equal to the value of p (Fig. 4).

Equation (3) is likewise appropriate to be used for calculation of the unit speed of growth:

2

3

3

Table 1. The composition of the culture medium for microalgae for a laboratory reactor volume of 10 liters

Culture medium A

Substance Molecular weight, g/mol Concentration in stock solution, mg/l Concentration in culture medium, ^g/l Amount of substance per reactor, ml

ZnSO4-7H2O 287.53 0.1 100 10.0

CuSO4-5H2O 249.66 0.1 10 1.0

CoSO4-7H2O 281.06 0.1 100 10.0

MnCl2-4H2O 197.91 0.1 500 50.0

H3BO3WF 61.83 0.1 50 5.0

Na2MoO4-2H2O 241.96 0.1 100 1.0

Culture medium B

Substance Molecular weight, g/mol Concentration in stock solution, mg/l Concentration in culture medium, №/l Amount of substance per reactor, ml

FeCl3-6H2O 270.21 1.0 4,000 40.0

Na2EDTA-2H2O 372.24 1.0 6,000 60.0

Culture medium C

Substance Molecular weight, g/mol Concentration in culture medium, mg/l Amount of substance per reactor, g

KNO3 101.1 1,000 3,03

KH2PO4 136.07 100 0,32

MgSO4-7H2O 246.48 240 2,4

Fig. 2. Dynamics of C. sorokiniana cells' biomass synthesis in different illumination modes: *P < 0.05 compared with the concentration of cells in the variant with the DFL lighting mode on the same day

of cultivation

1,

1 1

,1, '0.80

60 40 20 00

60 40 20 00

0.00 10.00 20.00 30.00 40.00 mln cells/ml

0.00

10.00 20.00 30.00 mln ce Ils/m I

40.00

mln ce I Is/m I

Fig. 3. Dependency of growth speed of alga C. sorokiniana cells on their concentration (equation 1):

a — DFL; b — IR; c — UV+DFL

Fig. 4. Exponential phase of growth of C. sorokiniana alga cells under various illumination condition modes

in semi-log coordinates:

the points represent experimental data; lines - calculated kinetic model

M =

Infx./xo

(3)

With X1 and X2 as concentrations of cells' biomass, mln cells/ml at time i1 and t2, correspondingly.

Table 2 shows kinetic equations characterizing the speed of C. sorokiniana alga cells' biomass synthesis and unit speed of growth.

Thus, the maximum value of unit speed of growth of cells' biomass is reached at DFL illumination mode.

Table 2. Kinetic equations of C. sorokiniana alga cells' biomass synthesis

Cultivation conditions Verhulst model and unit speed of growth, p, days-1

DFL, illumination intensity is 2200-2800 lx, T = 400 K (daylight) ^ = 0.26x fl -XI dt y 41 ) p = 0.26±0.01

IR, spectral area of luminous flux is 3.5-5.0 pm illumination intensity is 14100 lx dX = 0.l5xfl - XI dt y 38 ) p = 0.15±0.01

UV-radiation during 3 hours of the first day of cultivation using a mercury gas-discharge lamp with a spectral area of luminous flux 320-400 nm. DFL, illumination intensity 2200-2800 lx, T = 400 K (daylight) dx „ i x ^ — = 0.25x1 1--I dt y 39 ) p = 0.25±0.01

4 6 S Time, davs

6 9 12 Time, days

6 8 Time, days

Fig. 5. Kinetic dependencies of C. sorokiniana alga cells' biomass synthesis in various illumination modes: a — DFL; b — IR; c — UV+DFL

b

a

c

iНе можете найти то, что вам нужно? Попробуйте сервис подбора литературы.

Fig. 5 comprises results of adequacy verification for derived kinetic dependencies. The results of modelling of synthesis kinetics for Chlorella alga biomass complies with data obtained by the authors [17].

This way, the following observation has been established: the peak K population capacity in the set temperature conditions (23±1) °C amounts to 41 mln cells/ml during DFL illumination mode, 2200-2800 lx, (daylight) which is 1.7 times bigger than during IR illumination mode with radiation intensity of 14100 lux. It was identified that a short-time radiation during the initial stage of alga cells' biomass synthesis in a spectral diapason of 320-400 nm does not results in a significant increase of the synthesis speed.

REFERENCES

1. Zheng Y, Chi Z, Lucker B, Chen S. Two-stage heterotrophic and phototrophic culture strategy for algal biomass and lipid production. Bioresour. Technol. 2012, 103 (1), 484-488. https://doi. org/10.1016/j.biortech.2011.09.122

2. Roeselers G, Van Loosdrecht M. C. M, Muyzer G. Phototrophic biofilms and their potential applications. J. Appl. Phycol. 2008, 20 (3), 227235. https://doi.org/10.1007/s10811-007-9223-2

3. Overmann J., Garcia-Pichel F. The phototrophic way of life. In The Prokaryotes: Prokaryotic Communities and Ecophysiology (V. 9783642301230, P. 203-257). SpringerVerlag Berlin Heidelberg. https://doi. org/10.1007/978-3-642-30123-0_51

4. Halim R, Danquah M. K., Webley P. A. Extraction of oil from microalgae for biodiesel production: A review. Biotechnol. Adv. 2012, V. 30, P. 709-732.

5. Vonshak A. Laboratory techniques for the cultivation of microalgae. In book: Handbook of Microalgal Culture: Biotechnology and Applied Phycology. John Wiley & Sons. 2004, P. 577.

6. Christenson L., Sims R. Production and harvesting of microalgae for wastewater treatment, biofuels, and bioproducts. Biotechnol.Adv. 2011, 29 (6), 686-702. https:// doi.org/10.1016/j.biotechadv.2011.05.015

7. Politaeva N, Bazarnova Y, Smyatskaya Y., Slugin V., Prokhorov V. Impact of carbon dopants on sorption properties of chitosan-based materials. J. Ind. Pollut. Control. 2017, V. 33, P. 1617-1621.

8. Abdelaziz A. E. M, Leite G. B., Hallenbeck P. C. Addressing the challenges for sustainable production of algal biofuels: I. Algal strains and nutrient supply. Environ. Technol. (United Kingdom). 2013, V. 34, P. 1783-1805.

The kinetic equations and values of unit speed of growth derived in the studied illumination modes provide the method of calculation of time required for the synthesis of a set amount of biomass and related growth medium consumption in the set cultivation conditions.

Acknowledgements

This work was performed within the implementation of Federal Targeted Programme for Research and Development in Priority Areas of Development of the Russian Scientific and Technological Complex for 2014-2020, the project "Development and implementation of innovative biotechnologies for treatment of microalgae Chlorella Sorokiniana and duckweed Lemna minor" (Agreement № 14.587.21.0038) ), the unique project identifier is RFMEFI58717X0038.

9. Stepanov S. S., Zolotareva E. K. Influence of methanol on the content of NAD(P)H, free amino acids and protein in the cells of Chlamydomonas reinhartdii. Ukr. Biochem. J. 2013,N 85, P.82-89.

10.Audzhanova V. K. Morphological and systematic characteristics of Chlorella. Its production and implementation. Naychnyy Vestn. 2014, N 1, P. 113-126. (In Russian).

11. Moiseev I., Tarasov V., Trusov L. Evolution of bioenergetics. Time of algae. Chem. J. 2009, N 12, P. 24-29. (In Russian).

12. Franco M. C. Batch cultivation of microalgae in the Labfors 5 Lux Photobioreactor with LED Flat Panel Option. InforsHT Application note. 2014, P. 1-6.

13. Westerhoff P., Hu Q., Esparza-Soto M., Vermaas W. Growth parameters of microalgae tolerant to high levels of carbon dioxide in batch and continuous-flow photobioreactors. Environ. Technol. 2010, V. 31, P. 523-532.

14. Meledina T. V., Ivanova V. A., Fedorov A. V. Instrumental and methodological base of experiments in the field of food biotechnology products from plant materials. Tutorial. St. Petersburg: ITMO University. 2017. (In Russian).

15. Crofcheck C. L., Xinyi E., Shea A., Monst-ross M., Crocker M., Andrews R. Influence of media composition on the growth rate of Chlorella vulgaris and Scenedesmus acutus utilized for CO2 mitigation. J. Biochem. Tech. 2012, V. 4, P. 589-594.

16. Kingsland S. E. Modeling nature: episodes in the history of population ecology. Chicago: University of Chicago Press. 1995.

17. Dvoreckij D. S., Dvoreckij S. I., Temnov M. S., Peshkova E. V., Akulinin E. I. Technology of lipids obtaining from microalgae. Tambov: FGBOU VPO "TGTU". 2015. (In Russian).

ВПЛИВ ОСВ1ТЛЕНОСТ1 НА СИНТЕЗ Б1ОМАСИ М1КРОВОДОРОСТЕЙ Chlorella sorokiniana

Ю. Г. Базарнова Н. С. Лискова Т. А. Кузнецова Е. В. ТрухЬна

Санкт-Петербурзький полггехшчний ушверситет Петра Великого, РФ

E-mails: jbazarnova@spbstu.ru

Метою роботи було ощнити вплив осв^ле-носм на швидшсть синтезу б^маси мшроводо-ростi Chlorella sorokiniana, кшетичну залеж-нiсть синтезу i питому швидкiсть росту бмма-си за рiзних умов освiтленостi. Встановлено, що найбiльше значення питомоï швидкост росту клiтин бiомаси досягаеться в режим1 освiтленостi 2200-2800 Лк; Т (К) 400 (денне св^ло). Проведено перевiрку адекватност отриманих кiнетичних залежностей. Кше-тичнi рiвняння i значення питомоï швидкост росту бiомаси у вивчених режимах осв^лено-стi дадуть змогу розрахувати час, необхщний для синтезу заданоï кiлькостi бiомаси i пов'я-заних з нею витрат живильного середовища в заданих умовах культивування.

Ключовi слова: Chlorella sorokiniana, зростан-ня бммаси, умови культивування, кшетичш закономiрностi.

ВЛИЯНИЕ ОСВЕЩЕННОСТИ НА СИНТЕЗ БИОМАССЫ МИКРОВОДОРОСЛЕЙ Chlorella sorokiniana

Ю. Г. Базарнова Н. С. Лыскова Т. А. Кузнецова Е. В. Трухина

Санкт-Петербургский политехнический университет Петра Великого, РФ

E-mails: jbazarnova@spbstu.ru

Целью работы было оценить влияние освещенности на скорость синтеза биомассы микроводоросли Chlorella sorokiniana, кинетическую зависимость синтеза и удельную скорость роста биомассы в различных условиях освещенности. Установлено, что наибольшее значение удельной скорости роста клеток биомассы достигается в режиме освещенности 2200-2800 Лк; Т(К) 400 (дневной свет). Проведена проверка адекватности полученных кинетических зависимостей. Кинетические уравнения и значения удельной скорости роста биомассы в изученных режимах освещенности позволят рассчитать время, необходимое для синтеза заданного количества биомассы и связанного с ней расхода питательной среды в заданных условиях культивирования.

Ключевые слова: Chlorella sorokiniana, рост биомассы, условия культивирования, кинетические закономерности.

i Надоели баннеры? Вы всегда можете отключить рекламу.