Retargeting of heterologous enzymes results in improved β-carotene synthesis in Saccharomyces cerevisiae.

Aims: Carotenoids are a class of hydrophobic substances that are important as food and feed colorants and as antioxidants. The pathway for β-carotene synthesis has been expressed in various yeast species, albeit with rather low yields and titers. The inefficient conversion of phytoene to lycopene is often regarded as a bottleneck in the pathway.

Enhanced fed-batch fermentation of 2,3-butanediol by Paenibacillus polymyxa DSM 365.

Fed-batch fermentations for the production of 2,3-butanediol (BDL) with Paenibacillus polymyxa DSM 365 were investigated in 2-L-fermenters. A suitable micro-aerobic set-up enabled high product selectivity of up to 98% R,R-BDL towards meso-BDL and acetoin. Up to 111 g L(-1)R,R-BDL within 54 h could be achieved with sufficient supply of complex medium (yeast extract).

Continuous asymmetric ketone reduction processes with recombinant Escherichia coli.

The reduction of methyl acetoacetate was carried out in continuously operated biotransformation processes catalyzed by recombinant Escherichia coli cells expressing an alcohol dehydrogenase from Lactobacillus brevis. Three different cell types were applied as biocatalysts in three different cofactor regeneration approaches. Both processes with enzyme-coupled cofactor regeneration catalyzed by formate dehydrogenase or glucose dehydrogenase are characterized by a rapid deactivation of the biocatalyst.