Characterization and statistical lipid optimization of an oleaginous soil fungus, Gongronella butleri HMA-10: a promising novel source for sustainable lipid production.

Oleaginous fungi, as a vital part of the microbiota in naturally diverse ecosystems, represent a reservoir for biomass-based lipid production. The challenge is the selection of promising strains with cost-effective operation for multiple applications. In the current study, 12 fungal strains were isolated and screened for their oleaginicity. All strains were fermented and accumulated over 20% lipids in their cell dry weight (CDW). After the preliminary screening, one strain was genetically identified as Gongronella butleri HMA-10 due to its maximum biomass (15.8 ± 0.8 g/L) and lipid (40.6 ± 1.7%) yields. Moreover, the HMA-10 was subjected to optimization of various parameters with the help of response surface methodology (RSM) for maximum lipid accumulation. The selected strain was fermented on fructose associated with a combination of sodium nitrite and yeast extract, exhibiting optimum nutritional conditions with a C/N ratio of (40:1). Cultivation conditions (4 days, 27.5 ℃, and pH of 7.0) resulted in the highest CDW and lipid content. Scaling up of HMA-10 in bioreactor fermentation under optimized conditions significantly induced biomass and lipid content (19.5 g/L and 53%), compared with shake flask fermentation (15.8 ± 0.8 g/L and 40.6 ± 1.7%), respectively. Fatty acid (FA) profile was confirmed by gas chromatography (GC) analysis, and the results revealed that oleic acid (OA) was the predominant (46.91%), while palmitic acid (PA), linoleic acid (LA), and γ-linolenic acid (GLA) were found in significant quantities (21.13, 9.67, and 8.06%), respectively. This study employed for the first time G. butleri HMA-10 as a promising candidate for high lipid accumulation with a potential second-generation biodiesel production in large-scale industrialization.