Comparison of N and P requirements of Isochrysis galbana under phototrophic and mixotrophic conditions

Euglena gracilis produces paramylon, which is a feedstock for high-value functional foods and nutritional supplements. The enhancement of paramylon productivity is a critical challenge. Microalgae growth-promoting bacteria (MGPB) can improve microalgal productivity; however, the MGPB for E. gracilis remain unclear. This study isolated bacteria capable of enhancing E. gracilis growth and paramylon production under mixotrophic conditions. Enterobacter sp. CA3 and Emticicia sp. CN5 were isolated from E. gracilis grown with sewage-effluent bacteria under mixotrophic conditions at pH 4.5 or 7.5, respectively. In a 7-day E. gracilis mixotrophic culture with glucose, CA3 increased E. gracilis biomass and paramylon production 1.8-fold and 3.5-fold, respectively (at pH 4.5), or 1.9-fold and 3.5-fold, respectively (at pH 7.5). CN5 increased E. gracilis biomass and paramylon production 2.0-fold and 4.1-fold, respectively (at pH 7.5). However, the strains did not show such effects on E. gracilis under autotrophic conditions without glucose. The results suggest that CA3 and CN5 promoted both E. gracilis growth and paramylon production under mixotrophic conditions with glucose at pH 4.5 and 7.5 (CA3) or pH 7.5 (CN5). This study also provides an isolation method for E. gracilis MGPB that enables the construction of an effective E. gracilis–MGPB-association system for increasing the paramylon yield of E. gracilis.

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Regulation of Phagotrophy by Prey, Low Nutrients, and Low Light in the Mixotrophic Haptophyte Isochrysis galbana

Microbial Ecology ◽

10.1007/s00248-021-01723-w ◽

2021 ◽

Author(s):

Juan Manuel González-Olalla ◽

Juan Manuel Medina-Sánchez ◽

Alessandra Norici ◽

Presentación Carrillo

Keyword(s):

Isochrysis Galbana ◽

Low Light

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Effect of growth rate on the eicosapentaenoic acid and docosahexaenoic acid content of Isochrysis galbana in chemostat culture

Applied Microbiology and Biotechnology ◽

10.1007/bf00166076 ◽

1994 ◽

Vol 41 (1) ◽

pp. 23-27 ◽

Cited By ~ 38

Author(s):

E. Molina Grima ◽

J. A. S�nchez P�rez ◽

F. Garc�a Camacho ◽

J. M. Fern�ndez Sevilla ◽

F. G. Aci�n Fern�ndez

Keyword(s):

Growth Rate ◽

Docosahexaenoic Acid ◽

Eicosapentaenoic Acid ◽

Acid Content ◽

Chemostat Culture ◽

Isochrysis Galbana

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Insights into the physiology of Chlorella vulgaris cultivated in sweet sorghum bagasse hydrolysate for sustainable algal biomass and lipid production

Scientific Reports ◽

10.1038/s41598-021-86372-2 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Neha Arora ◽

George P. Philippidis

Keyword(s):

Sweet Sorghum ◽

Lipid Production ◽

Scale Up ◽

Cellular Growth ◽

Sweet Sorghum Bagasse ◽

Triacylglycerol Synthesis ◽

Sugar Addition ◽

Dry Cell Weight ◽

Sorghum Bagasse ◽

Mixotrophic Conditions

AbstractSupplementing cultivation media with exogenous carbon sources enhances biomass and lipid production in microalgae. Utilization of renewable organic carbon from agricultural residues can potentially reduce the cost of algae cultivation, while enhancing sustainability. In the present investigation a medium was developed from sweet sorghum bagasse for cultivation of Chlorella under mixotrophic conditions. Using response surface methodology, the optimal values of critical process parameters were determined, namely inoculum cell density (O.D.750) of 0.786, SSB hydrolysate content of the medium 25% v/v, and zero medium salinity, to achieve maximum lipid productivity of 120 mg/L/d. Enhanced biomass (3.44 g/L) and lipid content (40% of dry cell weight) were observed when the alga was cultivated in SSB hydrolysate under mixotrophic conditions compared to heterotrophic and photoautotrophic conditions. A time course investigation revealed distinct physiological responses in terms of cellular growth and biochemical composition of C. vulgaris cultivated in the various trophic modes. The determined carbohydrate and lipid profiles indicate that sugar addition to the cultivation medium boosts neutral lipid synthesis compared to structural lipids, suggesting that carbon flux is channeled towards triacylglycerol synthesis in the cells. Furthermore, the fatty acid profile of lipids extracted from mixotrophically grown cultures contained more saturated and monosaturated fatty acids, which are suitable for biofuel manufacturing. Scale-up studies in a photobioreactor using SSB hydrolysate achieved a biomass concentration of 2.83 g/L consisting of 34% lipids and 26% carbohydrates. These results confirmed that SSB hydrolysate is a promising feedstock for mixotrophic cultivation of Chlorella and synthesis of algal bioproducts and biofuels.

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Extracellular carbohydrate liberation in the flagellates Isochrysis galbana and Prymnesium parvum

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s002531540001657x ◽

1965 ◽

Vol 45 (3) ◽

pp. 755-772 ◽

Cited By ~ 51

Author(s):

A. F. H. Marker

Keyword(s):

Organic Matter ◽

Light Intensity ◽

Nitrogen Starvation ◽

Axenic Culture ◽

Isochrysis Galbana ◽

Prymnesium Parvum ◽

Extracellular Production ◽

Low Light ◽

Passive Release ◽

Dying Cells

The production of extracellular carbohydrate has been studied in Isochrysis galbana and Prymnesium parvum in axenic culture. Increased extracellular production of carbohydrate occurred at reduced and increased salinity, low light intensity and under conditions of nitrogen starvation in Isochrysis, and in some cases appeared to be associated with the sedimentation of the cells from stagnant culture. Extracellular carbohydrate production was found to be greatest during the early and later stages in growth and dropped to a minimum during the mid-growth phase. Experiments indicated that the cells were not being damaged during harvesting of the cultures. A close similarity was found between the monosaccharide components of the intra- and extracellular carbohydrate after acid hydrolysis; both contained glucose, galactose, arabinose, xylose and ribose. It is suggested that the production of most of the extracellular carbohydrate is due to the passive release of organic matter from dead or dying cells.

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Control of nitrogen assimilation in Stichococcus bacillaris by growth conditions

Canadian Journal of Botany ◽

10.1139/b87-052 ◽

1987 ◽

Vol 65 (3) ◽

pp. 432-437 ◽

Cited By ~ 2

Author(s):

Iftikhar Ahmad ◽

Johan A. Hellebust

Keyword(s):

Glutamine Synthetase ◽

Nitrogen Assimilation ◽

Continuous Light ◽

Synthetase Activity ◽

Glutamine Synthetase Activity ◽

Dark Cycle ◽

Continuous Darkness ◽

Cell Carbon ◽

Stichococcus Bacillaris ◽

Mixotrophic Conditions

Stichococcus bacillaris Naeg. (Chlorophyceae) grown on a 12 h light: 12 h dark cycle divides synchronously under photoautotrophic conditions and essentially nonsynchronously under mixotrophic conditions. Photoassimilation of carbon under photoautotrophic conditions was followed by a decline in cell carbon content during the dark period, whereas under mixotrophic conditions cell carbon increased throughout the light–dark cycle. The rates of nitrogen assimilation by cultures grown on either nitrate or ammonium declined sharply during the dark, and these declines were most pronounced under photoautotrophic conditions. Photoautotrophic cells synthesized glutamine synthetase and NADPH – glutamate dehydrogenase (GDH) exclusively in the light, whereas in mixotrophic cells about 20% of the total synthesis of these enzymes during one light–dark cycle occurred in the dark. NADH–GDH was synthesized almost continuously over the entire light–dark cycle. In the dark, both under photoautotrophic and mixotrophic conditions, the alga contained more than 50% of glutamine synthetase in an inactive form, which was reactivated in vitro in the presence of mercaptoethanol and in vivo after returning the cultures to the light. The thermal stability of glutamine synthetase activity was less in light-harvested cells than in dark-harvested cells. The inactivation of glutamine synthetase did not occur in cultures growing either heterotrophically in continuous darkness or photoautotrophically in continuous light. This enzyme appears to be under thiol control only in cells grown under alternating light–dark conditions, irrespective of whether this light regime results in synchronous cell division or not.

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