초록
<P><B>ABSTRACT</B><P> The two metabolically versatile actinobacteria Rhodococcus opacus PD630 and R. jostii RHA1 can efficiently convert diverse organic substrates into neutral lipids mainly consisting of triacylglycerol (TAG), the precursor of energy-rich hydrocarbon. Neither, however, is able to utilize xylose, the important component present in lignocellulosic biomass, as the carbon source for growth and lipid accumulation. In order to broaden their substrate utilization range, the metabolic pathway of d -xylose utilization was introduced into these two strains. This was accomplished by heterogenous expression of two well-selected genes, <I>xylA</I> , encoding xylose isomerase, and <I>xylB</I> , encoding xylulokinase from Streptomyces lividans TK23, under the control of the <I>tac</I> promoter with an Escherichia coli-Rhodococcus shuttle vector. The recombinant R. jostii RHA1 bearing <I>xylA</I> could grow on xylose as the sole carbon source, and additional expression of <I>xylB</I> further improved the biomass yield. The recombinant could consume both glucose and xylose in the sugar mixture, although xylose metabolism was still affected by the presence of glucose. The xylose metabolic pathway was also introduced into the high-lipid-producing strain R. opacus PD630 by expression of <I>xylA</I> and <I>xylB</I> . Under nitrogen-limited conditions, the fatty acid composition was determined, and lipid produced from xylose by recombinants of R. jostii RHA1 and R. opacus PD630 carrying <I>xylA</I> and <I>xylB</I> represented up to 52.5% and 68.3% of the cell dry weight (CDW), respectively. This work demonstrates that it is feasible to produce lipid from the sugars, including xylose, derived from renewable feedstock by genetic modification of rhodococcus strains. </P></P>