Study of Different Parameters Affecting Production and Productivity of Polyunsaturated Fatty Acids (PUFAs) and γ-Linolenic Acid (GLA) by Cunninghamella elegans Through Glycerol Conversion in Shake Flasks and Bioreactors

• Published in: Microorganisms (Basel) 2024-10, Vol.12 (10), p.2097
• Main Authors: Vasilakis, Gabriel, Roidouli, Christina, Karayannis, Dimitris, Giannakis, Nikos, Rondags, Emmanuel, Chevalot, Isabelle, Papanikolaou, Seraphim
• Format: Article
• Language: English
• Subjects: bioconversion; Biodiesel fuels; Biomass; Bioreactors; Carbon; Carbon/nitrogen ratio; Cell culture; Cultivation; Cunninghamella elegans; Engineering Sciences; Enzymes; Experiments; Fatty acids; filamentous fungi; Flasks; Fungi; Fungiculture; g-linolenic acid; Glycerol; Linolenic acid; Lipid metabolism; Lipids; Metabolites; Microorganisms; Nitrogen; Pharmaceuticals; Physiology; poly-unsaturated fatty acids (PUFAs); Polyunsaturated fatty acids; Productivity; Sustainable use; Temperature
• ISSN: 2076-2607; 2076-2607
• DOI: 10.3390/microorganisms12102097

Microbial cultures repurposing organic industrial residues for value-added metabolite production is pivotal for sustainable resource use. Highlighting polyunsaturated fatty acids (PUFAs), particularly gamma-linolenic acid (GLA), renowned for their nutritional and therapeutic value. Notably, Zygomycetes' filamentous fungi harbor abundant GLA-rich lipid content, furthering their relevance in this approach. In this study, the strain NRRL Y-1392 was evaluated for its capability to metabolize glycerol and produce lipids rich in GLA under different culture conditions. Various carbon-to-nitrogen ratios (C/N = 11.0, 110.0, and 220.0 mol/mol) were tested in batch-flask cultivations. The highest GLA production of 224.0 mg/L (productivity equal to 2.0 mg/L/h) was observed under nitrogen excess conditions, while low nitrogen content promoted lipid accumulation (0.59 g of lipids per g of dry biomass) without yielding more PUFAs and GLA. After improving the C/N ratio at 18.3 mol/mol, even higher PUFA (600 mg/L) and GLA (243 mg/L) production values were recorded. GLA content increased when the fungus was cultivated at 12 °C (15.5% / compared to 12.8% / at 28 °C), but productivity values decreased significantly due to prolonged cultivation duration. An attempt to improve productivity by increasing the initial spore population did not yield the expected results. The successful scale-up of fungal cultivations is evidenced by achieving consistent results (compared to flask experiments under corresponding conditions) in both laboratory-scale (Working Volume-Vw = 1.8 L; C/N = 18.3 mol/mol) and semi-pilot-scale (Vw = 15.0 L; C/N = 110.0 mol/mol) bioreactor experiments. To the best of our knowledge, cultivation of the fungus in glycerol-based substrates, especially in 20 L bioreactor experiments, has never been previously reported in the international literature. The successful scale-up of the process in a semi-pilot-scale bioreactor illustrates the potential for industrializing the bioprocess.