The present invention provides for a mechanism to completely replace the electron accepting function of glycerol formation with an alternative pathway to ethanol formation, thereby reducing glycerol production and increasing ethanol production. In some embodiments, the invention provides for a recombinant microorganism comprising a down-regulation in one or more native enzymes in the glycerol-production pathway. In some embodiments, the invention provides for a recombinant microorganism comprising an up-regulation in one or more enzymes in the ethanol-production pathway.

The present invention provides for a mechanism to completely replace the electron accepting function of glycerol formation with an alternative pathway to ethanol formation, thereby reducing glycerol production and increasing ethanol production. In some embodiments, the invention provides for a recombinant microorganism comprising a down-regulation in one or more native enzymes in the glycerol-production pathway. In some embodiments, the invention provides for a recombinant microorganism comprising an up-regulation in one or more enzymes in the ethanol-production pathway.

A process for the production of ethanol. comprising: fermentation of a feed. under anaerobic conditions. wherein the feed contains a di-saccharide. oligo-saccharide and/or poly-saccharide and wherein the fermentation is carried out in the presence of a recombinant yeast cell. which recombinant yeast produces a combination of proteins having glucosidase activity: and recovery of ethanol. and a recombinant yeast cell for use therein.

A recombinant yeast cell comprising a nucleotide sequence encoding a protein, which protein comprises an amino acid sequence of SEQ ID NO: 01 or an amino acid sequence which has at least 90% sequence identity, preferably at least 95%, 98%, or 99% sequence identity with the amino acid sequence of SEQ ID NO: 01.

A recombinant yeast cell functionally expressing: a nucleic acid sequence encoding a native protein having transketolase activity (EC 2.2.1.1); and a nucleic acid sequence encoding a heterologous protein having transketolase activity (EC 2.2.1.1).

A recombinant yeast cell functionally expressing: a) a nucleic acid sequence encoding a protein comprising phospho-ketolase (PKL) activity (EC 4.1.2.9 or EC 4.1.2.22) and/or a nucleic acid sequence encoding a protein having phosphotransacetylase (PTA) activity (EC 2.3.1.8) and/or a nucleic acid sequence encoding a protein having acetate kinase (ACK) activity (EC 2.7.2.12); and/or) a nucleic acid sequence encoding a protein having transketolase activity (EC 2.2.1.1), wherein the expression of the nucleic acid sequence encoding the protein having transketolase activity is under control of a promoter (the TKL promoter), which TKL promoter has an anaerobic/aerobic expression ratio for the transketolase of (2) or more.