Efficient bioconversion of high-content volatile fatty acids into microbial lipids by Cryptococcus curvatus ATCC 20509

- High-content VFAs were efficiently converted into microbial lipids.
- Increasing inoculation concentration was beneficial for yeast growth.
- Nitrogen to carbon ratio was crucial for the utilization of high-content VFAs.
- Alkaline initial pH lessened the inhibition of high-content VFAs on yeast cells.

The lower utilization ratios of high-content VFAs resulted in less lipid yield by the oleaginous yeast Cryptococcus curvatus ATCC 20509. In this work, increasing the inoculation concentration to OD600 = 5.1 improved the acetic acid utilization ratio (99.8%) and lipids production (4.63 g/L) in mediums with 30 g/L of acetic acid. For the higher acetic acid concentration (40 g/L), increasing the nitrogen to carbon ratio (0.033) and raising the initial pH (pH = 8) was superior over improvement in the inoculate, with the lipid production increased from 1.08 g/L to 6.49 g/L. Subsequently, mixed VFAs at concentrations of 30 g/L and 40 g/L were used as the carbon source to simulate waste-derived VFAs. High lipid production (4.82 and 7.45 g/L, respectively) was correspondingly achieved with similar high lipid yield (0.187 g/g). This study provides an effective strategy to enhance the bioconversion of high-content VFAs into microbial lipids.