Rhodococcus opacus PD630 Bioconversion of Molasses Desugarized Solubles for Fatty Acid Production

Abstract

The oleaginous bacterium Rhodococcus opacus PD630 accumulates triacylglycerides (TAGs), from which the fatty acid components can be converted to biodiesel. In this work, we demonstrate the simple, robust bioconversion of the agricultural byproduct molasses desugarized solubles (MDS), a co-product of the second and final extraction of sugar from sugar beets, to fatty acids suitable for biodiesel production. In 48 hours of batch culture, R. opacus PD630 grown in dilute MDS accumulates 3.01 g/L dry biomass that is 43% fatty acids, with simultaneous growth and lipid accumulation. Palmitic (C16:0), cis-10-heptadecanoic (C17:1), and oleic (C18:1n9) acids are most abundant, representing 30%, 19%, and 18% of total fatty acids, respectively. Lowering the growth temperature causes a shift toward saturated fatty acids, as palmitic (C16:0), stearic (C18:0), and margaric (C17:0) are most prevalent. Analysis of MDS, rich in organic acids, revealed that aspartic and glutamic acids were preferentially consumed, leaving some sucrose, lactic acid, and malic acid in solution. This simple bioconversion process of an agricultural byproduct, which requires no added nutrients or buffers, could provide a robust platform for larger scale production of biodiesel precursors.