Simultaneous Microbial Oil Synthesis and Recovery from Oleaginous Yeast Cultivation for Biolubricant Conversion

Abstract

This study aimed to: 1) select the effective oleaginous yeast strain for enhancing yeast oil (YO) production and secretion, 2) monitor the expression of key lipogenic genes, 3) investigate in-situ and ex-situ oil recovery using oil capturing agents (OCAs), and 4) study the feasibility of biolubricant production using YO as the primary feedstock. Seven yeast candidates for YO production were evaluated. NIS was added during cultivation to enhance intracellular oil secretion. Oil recovery was conducted through both in-situ and ex-situ methods using different OCAs. YO was utilized to synthesize biolubricants via trimethylolpropane (TMP) esterification. Rhodosporidium toruloides TISTR 5186 exhibited the highest efficacy in YO production in a glycerol-based medium. The highest total YO (TO) formation and oil content were at 4.0 g/L and 78.38% (w/w), respectively, with 0.7% (w/v) Tween 20. Under this condition, the expression of ACC and DGA genes significantly increased by 3.4 and 3.6-fold, respectively. SP70 OCA effectively adsorbed extracellular oil (EO), providing 90.49% (w/w) ex-situ EO recovery within 1 day. A TO quantity of 53.37 g was achieved through online ex-situ oil recovery and fed-batch fermentation in a 5-L bioreactor. The conversion of YO into TMP-fatty acid esters as biolubricants on a laboratory scale was successful. Simultaneous YO production and recovery present a promising process to enhance TO production without cell disruption.