Rhodotorula mucilaginosa R2: A potent oleaginous yeast isolated from traditional fermented food, as a promising platform for the production of lipid-based biofuels, bioactive compounds and other value added products

Abstract

Oleaginous yeasts may provide an alternative platform for the sustainable production of microbial lipids-derived biodiesel and other health promoting bioactive metabolites such as natural pigments. In this regard, traditional fermented foods are unique and untapped habitats for the isolation and characterization of oleaginous yeasts with beneficial properties. In this study, we analysed the yeast diversity from selected traditional fermented foods of Manipur and Mizoram, India and studied their oleaginous attributes for biodiesel production. 14 potential oleaginous yeasts were isolated using culture-dependent techniques. The isolates were identified by 5.8S internal transcribed spacer (ITS) rRNA gene sequencing. Intracellular triacylglycerides (TAG) accumulation by yeast cells were confirmed by Nile red fluorescence microscopy. Fatty acid methyl esters (FAME) profile of the yeast strains were analysed by GC-MS. The identified yeast isolates belonged to seven different genera viz. Rhodotorula, Pichia, Candida, Saturnispora, Wickerhamomyces, Zygoascus and Saccharomyces. Rhodotorula mucilaginosa R2 exhibited the maximum lipid content (% lipid/g dry cell weight) of (21.63 %) after 96 h of growth in nitrogen-limited medium. R. mucilaginosa R2 single cell oil (RMSCO) was transesterified into biodiesel with a conversion efficiency of 96.6 % using a heterogeneous potassium hydroxide catalyst (K-RAC) supported on R. mucilaginosa R2 deoiled cake activated carbon. The physico-chemical properties of the biodiesel derived from R. mucilaginosa R2 single cell oil were within the limits of ASTM and EN standards. FAME analysis of the transesterified lipid extract suggested the potential use of yeast derived oil as an alternative to vegetable oil for biodiesel production. Furthermore, carotenoids obtained from the pink yeast R. mucilaginosa R2 was composed of torularhodin, torulene and β-carotene and exhibited strong antioxidant activity. Keywords: Oleaginous yeast, Triacylglycerides, Fermented food, Rhodotorula mucilaginosa