The physiological role of gamma-aminobutyric acid in relieving the effect of furfural inhibitor for improvement the production of lipid in D. intermedius Z.

In order to improve the production and quality of lipid of D. intermedius Z under the furfural stress environment, different exogenous γ-aminobutyric acid (GABA) addition strategies and their reasons for improving the fermentation performance were investigated. For this purpose, the effect of different concentrations of furfural on the production of biomass and lipid in D. intermedius Z was researched. The result shows that the growth of D. intermedius Z nearly stopped when 1.0 g/L furfural was adopted. However, when 1.5 mmol/L GABA was used, the highest biomass and lipid production of 4.56 g/L and 1.83 g/L were obtained, respectively, which were 36.53 % and 61.95 % higher compared to the control group (the normal development BG11 medium). Additionally, the changes in microalgal cell morphology were analyzed using the scanning electron microscope (SEM) technology, and the results suggest that GABA addition could significantly mitigate the toxic effects of excessive furfural by maintaining the integrity of the cell. Simultaneously, the activities of key enzymes involved in fatty acid synthesis, such as nitrate reductase (NR), phosphatidic acid phosphatase (PAP), acetyl CoA carboxylase (ACC), and fatty acid synthase (FAS), were enhanced under the optimal condition, and thus improving lipid production. According to the results in this study, the exogenous GABA addition strategy is a simple and effective approach to improve microbial tolerance and enhance its fermentation performance.