High lipid accumulating bacteria isolated from dairy effluent scum grown on dairy wastewater as potential biodiesel feedstock

Abstract

The study evaluated the lipid accumulation potential of bacteria isolated from dairy effluent scum by the valorization of dairy wastewater as a renewable feedstock for biodiesel production. Three oleaginous bacteria (i.e. DS-1, DS-6, and DS-7) were screened on the basis of their lipid accumulation (>20% lipid content) and productivity on a glucose-based medium. The effect of different carbon sources (i.e. lactose, sucrose, starch, glucose, and xylose) on lipid accumulation capacity of the bacterial isolates was evaluated. The rod-shaped oleaginous bacterium DS-7 could accumulate 90% lipid with 1.2 g/l·d lipid productivity using lactose as a sole source of carbon. The bacteria could efficiently utilize dairy wastewater (~50% reduction in BOD) with reasonably high lipid accumulation (72.78%), biomass production (4.29 g/l) and lipid productivity (0.727 g/l·d). The lipids accumulated by bacterium DS-7 were mostly neutral lipids and contained fatty acids of chain length C14:0-C18:0, as confirmed by nile red staining and nuclear magnetic resonance (NMR) spectroscopy. Fourier-transform infrared (FTIR) spectroscopy and gas chromatography (GC) analysis of fatty acid methyl esters (FAME) revealed that transesterified bacterial lipids from the isolated bacteria DS-7 are suitable for biodiesel applications.