Valorization of durian peel as a carbon feedstock for a sustainable production of heterogeneous base catalyst, single cell oil and yeast-based biodiesel

The present study reports a successful attempt to produce single cell oil (SCO), heterogeneous base catalyst and yeast-based biodiesel from durian peel as a promising carbon feedstock by means of the waste-to-energy concept. For this purpose, first, durian peel (DP) was hydrolyzed by dilute sulfuric acid to obtain xylose-rich DP hydrolysate (XDPH) and post-hydrolysis DP solid residue (DPS). Candida viswanathii PSY8, a newly isolated oleaginous yeast, showed high SCO accumulation (5.1 ± 0.1 g/L) and SCO content (35.3 ± 0.13 %) on undetoxified XDPH medium. A novel heterogeneous base catalyst (DPS-K) prepared from DPS by wet impregnation technique with KOH, exhibited considerable catalytic activity to convert SCO-rich wet yeast of C. viswanathii PSY8 into yeast-based biodiesel (FAME) via direct transesterification with a maximum FAME yield of 94.3 % under optimal conditions (6 wt% catalyst, 10:1 methanol to wet yeast ratio, 75 °C, and 2 h). Moreover, most of the yeast-based biodiesel properties obtained from the FAME profiles were correlated well with the biodiesel standards limit of Thai, ASTM D6751 and EN 14214. Additionally, the energy output of FAME produced about 37.5 MJ/kg was estimated. Thus, this present finding demonstrated the favorable strategy for sustainable and eco-friendly production of new generation biodiesel.