Oleaginous yeast Meyerozyma guilliermondii shows fermentative metabolism of sugars in the biosynthesis of ethanol and converts raw glycerol and cheese whey permeate into polyunsaturated fatty acids

Abstract

We studied the biotechnological potential of the recently isolated yeast Meyerozyma guilliermondii BI281A to produce polyunsaturated fatty acids and ethanol, comparing products yields using glucose, raw glycerol from biodiesel synthesis, or whey permeate as substrates. The yeast metabolism was evaluated for different C/N ratios (100:1 and 50:1). Results found that M. guilliermondii BI281A was able to assimilate all tested substrates, and the most efficient conversion obtained was observed using raw glycerol as carbon source (C/N ratio 50:1), concerning biomass formation (5.67 g·L−1) and lipid production (1.04 g·L−1), representing 18% of dry cell weight. Bioreactors experiments under pH and aeration‐controlled conditions were conducted. Obtained fatty acids were composed of ~67% of unsaturated fatty acids, distributed as palmitoleic acid (C16:1, 9.4%), oleic acid (C18:1, 47.2%), linoleic acid (C18:2 n−6, 9.6%), and linolenic acid (C18:3 n−3, 1.3%). Showing fermentative metabolism, which is unusual for oleaginous yeasts, M. guilliermondii produced 13.7 g·L−1 of ethanol (yields of 0.27) when growing on glucose medium. These results suggest the promising use of this uncommonly studied yeast to produce unsaturated fatty acids and ethanol using cheap agro‐industrial residues as substrates in bioprocess.

Self-produced hydrogen sulfide improves ethanol fermentation by Saccharomyces cerevisiae and other yeast species

“…Treatment with the H 2 S donor in K. marxianus increased ethanol synthesis as in S. cerevisiae (Figure 8a). In M. guilliermondii , it was noted that ethanol synthesis took longer than 24 h when glucose was the carbon source [33]; for this reason, the exponential-phase cells were treated with NaHS and treated again 24 h later. As observed in K. marxianus , ethanol synthesis increased after the H 2 S donor treatment on M. guilliermondii (Figure 8b) confirming that there is an effect of H 2 S on the fermentation activity of these two species of yeast.…”