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 18.104.22.168); glycerol dehydrogenase (NADP(+)) (E.C. 22.214.171.124); glycerol 2-dehydrogenase (NADP(+)) (E.C. 126.96.36.199); and glycerol dehydrogenase (acceptor) (E.C. 188.8.131.52). 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.