Construction and parameters modulation of a novel variant Rhodococcus opacus BM985 to achieve enhanced triacylglycerol-a biodiesel precursor, using synthetic dairy wastewater

Abstract

Abstract Biofuel from bacterial lipids like triacylglycerol (TAG) is known to alleviate difficulties encountered in production of first (1 G), second (2 G) and third generation (3 G) biofuels. Rhodococcus opacus converts glucose into TAG, a biodiesel precursor, by using intermediates in the Kennedy pathway and specific PAP2 enzymes. The elucidation of genes involved, their functions and operational parameters is incomplete. Consequently, we have constructed a PAP2 over-expressing improved variant Rhodococcus opacus BM985 (BM985), optimized and evaluated its parameters for maximizing biodiesel production using synthetic dairy wastewater (SDWW) as the primary medium. Post application of optimization tools, we witnessed an impressive spike in TAG from 34.5% to 68% TAG/dry cell weight (DCW) content in BM985 cells at reactor level – a 1.98-fold increment compared to WT together with a lower BM985 biomass yield (0.76 g/g) but significant biomass concentration (3.7 g/L DCW). BM985 was effective in treating synthetic dairy wastewater with a chemical oxygen demand (COD) removal of ˜88% as compared to 65% by wild-type (WT). The fatty acid compositions obtained and thus the biodiesel properties such as cetane number, iodine number, osmotic stability etc. from BM985 strongly support the potential of BM985 as an alternative source for biofuel production and for DWW treatment.