The invention provides a genetically modified bacterium for production of thiamine; where the bacterium is characterized by a transgene encoding a thiamine monophosphate phosphatase (TMP phosphatase having EC 3.1.3.-) as well as transgenes encoding polypeptides that catalyze steps in the thiamine pathway. The genetically modified bacterium is characterized by enhanced synthesis and release of thiamine into the extracellular environment. The invention further provides a method for producing thiamine using the genetically modified bacterium of the invention; as well as the use of the genetically modified bacterium for extracellular thiamine production.

Disclosed are methods for producing from a gaseous substrate comprising CO, CO.sub.2, and optionally H.sub.2 at least one oxygenated product. Also provided are methods of using a broth deficient in thiamine or thiazole-containing thiamine precursors as a screening tool for suitable ethanol producing acetogenic carboxydotrophic bacteria strains, operating a syngas fermentation without the addition of thiamine or thiazole-containing thiamine precursors, controlling bacterial contamination in a bioreactor, and methods for preparing animal feed and fertilizer.

The present disclosure relates to a genetically modified host cell having improved production of thiamine, wherein the host cell expresses one or more heterologous ThiO enzymes converting glycine into dehydroglycine (DHG) in the host cell and/or one or more heterologous ThiI enzymes catalyzing the transfer of sulfur from IscS to the sulfur carrier protein ThiS in the host cell, whereby the production of the thiamine in the genetically modified host cell is improved compared to an unmodified parent host cell.