Bioethanol production by heterologous expression of Pdc and AdhII in Streptomyces lividans

Two genes from Zymomonas mobilis that are responsible for ethanol production, pyruvate decarboxylase (pdc) and alcohol dehydrogenase II (adhII), were heterologously expressed in the Gram-positive bacterium Streptomyces lividans TK24. An examination of carbon distribution revealed that a significant portion of carbon metabolism was switched from biomass and organic acid biosynthesis to ethanol production upon the expression of pdc and adhII. The recombinant S. lividans TK24 produced ethanol from glucose with a yield of 23.7 % based on the carbohydrate consumed. The recombinant was able to produce ethanol from xylose, l-arabinose, mannose, l-rhamnose, galactose, ribose, and cellobiose with yields of 16.0, 25.6, 21.5, 33.6, 30.6, 14.6, and 33.3 %, respectively. Polymeric substances such as starch and xylan were directly converted to ethanol by the recombinant with ethanol yields of 18.9 and 8.8 %, respectively. The recombinant S. lividans TK24/Tpet developed in this study is potentially a useful microbial resource for ethanol production from various sources of biomasses, especially microalgae.