Biodegradation of phenolic derivatives by Rhodosporidium toruloides: Effect on growth, cell morphology, lipid and biodiesel production

Phenol derivatives are considered one of the most hazardous pollutants, posing a significant risk to the ecosystem. The present study investigates the ability of the Rhodosporidium toruloides 9564T to degrade the selected phenol derivatives, i.e., catechol, 4-chlorophenol (4-CP), and 4-nitrophenol (4-NP), and simultaneously produce lipids. The experiments were performed using minimal salt media with varying ranges of catechol (0.25 g/L-1.5 g/L), 4-CP (0.25-1.5 g/L), and 4-NP (0.1-1 g/L) with a 10 % inoculum size. Results showed that R. toruloides 9564T completely degraded 1 g/L catechol, 0.5 g/L 4-CP, and 0.1 g/L 4-NP. In comparison with the two phenol derivatives, the maximum biomass (2.096 +/- 0.093 g/L), total lipid (0.774 +/- 0.031 g/L), and lipid content (36.92 +/- 0.147 %.) produced during catechol degradation. The GC analysis revealed the percentages of saturated fatty acids in lipids were 66.21, 86.43, and 81.39 % for catechol, 4-CP, and 4-NP. Catechol, 4-CP, and 4-NP biodiesel qualities (cetane number, cloud point, pour point, viscosity, etc.) matched ASTM-D6751 and EN 14214. To assess the potential environmental impact, the degraded samples by yeast were analyzed for phytotoxicity, which exhibited reduced toxicity. Consequently, R. toruloides proves to be a promising agent for valorizing wastewater treatment for biodiesel production.