1 Microbial Engineering, Biosystems Division, Risø National Laboratory for Sustainable Energy, Technical University of Denmark2 Biosystems Division, Risø National Laboratory for Sustainable Energy, Technical University of Denmark3 Risø National Laboratory for Sustainable Energy, Technical University of Denmark4 BioGasol ApS5 Department of Systems Biology, Technical University of Denmark
TECHNOLOGY FOCUS - BIOTECHNOLOGY - Preparation (claimed): Producing recombinant bacterium having enhanced ethanol production characteristics when cultivated in growth medium comprising glycerol comprises: (a) transforming a parental bacterium by (i) the insertion of a heterologous gene encoding glycerol dehydrogenase; and/or (ii) up-regulating a native gene encoding glycerol dehydrogenase; and (b) obtaining the recombinant bacterium. Preferred Bacterium: In the recombinant bacterium above, the inserted heterologous gene and/or the up-regulated native gene is encoding a glycerol dehydrogenase selected from glycerol dehydrogenase (E.C 220.127.116.11); glycerol dehydrogenase (NADP(+)) (E.C. 18.104.22.168); glycerol 2-dehydrogenase (NADP(+)) (E.C. 22.214.171.124); and glycerol dehydrogenase (acceptor) (E.C. 126.96.36.199). The heterologous gene encoding a glycerol dehydrogenase is derived from Thermotoga or is derived from Geobacillus. It is selected from SEQ ID NO. 1-17. Sequences not defined here may be found at ftp://ftp.wipo.int/pub/publishedpctsequences/publication. The heterologous gene encoding glycerol dehydrogenase has been incorporated into the chromosome of the bacterium, or is inserted into a lactate dehydrogenase encoding region of the bacterium, or is inserted into a phosphotransacetylase encoding region of the bacterium, or is inserted into an acetate kinase encoding region of the bacterium. It is operably linked to an inducible, a regulated or a constitutive promoter. The up-regulated glycerol dehydrogenase gene is over-expressed on a multicopy plasmid. The bacterium is a thermophilic bacterium. It is derived from the genus of Thermoanaerobacter. The bacterium is a Thermoanaerobacter mathranii strain selected from BG1 (DSMZ Accession number 18280) and its mutants. Specifically, the bacterium is the Thermoanaerobacter mathranii strain BG1G1 (DSMZ Accession number 19229). Preferred Method: In the method above, the carbohydrate source is a polysaccharide selected from starch, glucose, lignocellulose, cellulose, hemicellulose, glycogen, xylan, glucuronoxylan, arabinoxylan, arabinogalactan, glucomannan, xyloglucan, and galactomannan. The method is a fermentation process performed under strict anaerobic conditions.