Kinetic and Stoichiometric Modeling-Based Analysis of Docosahexaenoic Acid (DHA) Production Potential by Crypthecodinium cohnii from Glycerol, Glucose and Ethanol

Abstract

Docosahexaenoic acid (DHA) is one of the most important long-chain polyunsaturated fatty acids (LC-PUFAs), with numerous health benefits. Crypthecodinium cohnii, a marine heterotrophic dinoflagellate, is successfully used for the industrial production of DHA because it can accumulate DHA at high concentrations within the cells. Glycerol is an interesting renewable substrate for DHA production since it is a by-product of biodiesel production and other industries, and is globally generated in large quantities. The DHA production potential from glycerol, ethanol and glucose is compared by combining fermentation experiments with the pathway-scale kinetic modeling and constraint-based stoichiometric modeling of C. cohnii metabolism. Glycerol has the slowest biomass growth rate among the tested substrates. This is partially compensated by the highest PUFAs fraction, where DHA is dominant. Mathematical modeling reveals that glycerol has the best experimentally observed carbon transformation rate into biomass, reaching the closest values to the theoretical upper limit. In addition to our observations, the published experimental evidence indicates that crude glycerol is readily consumed by C. cohnii, making glycerol an attractive substrate for DHA production.

The Biorefinery of the Marine Microalga Crypthecodinium cohnii as a Strategy to Valorize Microalgal Oil Fractions

“…Therefore, the specific growth rate reported in this work was higher than that reported by Berzins et al (2022) [38] for glycerol. This difference might be due to the different systems used to grow the microalga, since cells grown in shake flasks [38] are usually exposed to adverse conditions, such as oxygen limitation and/or uncontrolled medium pH, which are overcome in a bioreactor (as used in this work), due to a higher mass transference (as a result of a better aeration, agitation and mixing) and medium pH control. Biomass productivity (g/L h) was calculated as follows: X t − X 0 /(t t − t 0 ), where X t is the biomass concentration at the instant t, X 0 is the biomass concentration at t 0 (inoculation time); the same formula was used to calculate TFA and DHA productivities.…”

“…Cui et al (2018) [37] also reported a specific growth rate of 0.05/h for C. cohnii growth on glucose, in 250 mL shake flasks. However, Berzins et al (2022) [38] reported C. cohnii specific growth rates of 0.05 0.02 and 0.05/h when the microalga was grown on glucose, glycerol and ethanol, respectively, in 1 L shake flasks. Therefore, the specific growth rate reported in this work was higher than that reported by Berzins et al (2022) [38] for glycerol.…”

“…However, Berzins et al (2022) [38] reported C. cohnii specific growth rates of 0.05 0.02 and 0.05/h when the microalga was grown on glucose, glycerol and ethanol, respectively, in 1 L shake flasks. Therefore, the specific growth rate reported in this work was higher than that reported by Berzins et al (2022) [38] for glycerol. This difference might be due to the different systems used to grow the microalga, since cells grown in shake flasks [38] are usually exposed to adverse conditions, such as oxygen limitation and/or uncontrolled medium pH, which are overcome in a bioreactor (as used in this work), due to a higher mass transference (as a result of a better aeration, agitation and mixing) and medium pH control.…”

“…Hosoglu and Elibol (2017) [43] concluded that the highest C. cohnii CCMP 316 biomass and lipid content (7.3 g/L and 36.5% (w/w), respectively) were attained when pure glycerol was used as carbon source, when compared to glucose. Berzins et al [38] studied C. cohnii CCMP 316 growth and DHA production using glucose, ethanol and glycerol as carbon sources, and showed mathematical modeling results which demonstrated that glycerol had the best experimentally observed carbon transformation rate into biomass, reaching the closest values to the theoretical upper limit. The authors concluded that crude glycerol was readily consumed by C. cohnii, making this feedstock an attractive substrate for DHA production from this microalga, which corroborated the results reported in the present work.…”

Metabolic modeling ofHermetia illucenslarvae resource allocation for high-value fatty acid production

“…One of the major focal points in biology are processes which impact and shape organisms, giving rise to an enormous variation in different phenotypes including metabolism and even biomass composition in different growth and dietary conditions (1), (2), (3). In recent years, a consensus has been reached that resource allocation strategies and mechanisms are key points in determining an organism's phenotype specificities (4), (5) Hermetia illucens (Balck soldier fly, BSF) is widely recognized in the industry due to its ability to rapidly recycle organic waste and decompose the material into high-value lipids and proteins (6).…”