Sustainable arabitol production by a newly isolated Debaryomyces prosopidis strain cultivated on biodiesel-derived glycerol

The purpose of this research was the bioconversion of biodiesel-derived glycerol to arabitol through the adoption of sustainable bioprocessing. Arabitol production by Debaryomyces prosopidis FMCC Y69 was significantly affected by initial glycerol concentrations. The highest arabitol concentration of 45.5 g/L was achieved in the case of 120 g/L initial glycerol combined with the highest yield (0.379 g arabitol/g initial glycerol). The yeast strain showed a non-typical oleaginous behavior with low accumulation of lipids (up to 20.9% w/w) despite nitrogen-limited condition that prevailed in the fermentation media. Endopolysaccharides (IPs) were considerably high with a yield on the produced dry cell weight (Y-IPs/X) (=40.9% w/w) when 85 g/L of glycerol was utilized as the starting material. The fermentation efficiency was further improved when the optimal carbon to nitrogen (C/N) ratio was applied. More specifically, arabitol production was maximized (reaching 56.5 g/L) at a C/N ratio of 158 moles/moles while yield and productivity were also enhanced with respective values of 0.48 g arabitol/g consumed glycerol and 0.112 g/L.h. The increase in C/N ratios led to a decrease in cell dry weight (DCW) concentrations, which is rationally associated with decreased nitrogen availability in the growth medium. Y-IPs/X values were remarkably high (23.1-26.1% w/w) at the end of each fermentation with the highest concentration in absolute values of 7.3 g/L achieved at the lowest C/N ratio employed (i.e., 79 moles/moles). This study demonstrated the efficient arabitol production along with other value-added metabolites, such as IPs and cellular lipids, implementing biotechnology and renewable resources and thus contributing to the development of circular economy technologies.