The invention describes a process for the production of ethanol from a composition comprising glucose and between 50 μM and 100 mM acetic acid, said process comprising fermenting said composition in the presence of a recombinant yeast which is capable to convert acetic acid anaerobically; maintaining the amount of undissociated acetic acid at a value of at least 50 μM; and recovering the ethanol. Said process is useful for both starch and cellulosic based, acetic acid containing hydrolysates and advantageously results in a greater consumption of acetic acid and thus higher ethanol yields.

The invention relates to a recombinant cell, preferably a yeast cell comprising: a) one or more heterologous genes encoding a glycerol dehydrogenase activity; b) one or more genes encoding a dihydroxyacetone kinase (E.C. 2.7.1.28 and/or E.C. 2.7.1.29); c) one or more heterologous genes encoding a ribulose-1,5-biphosphate carboxylase oxygenase (EC 4.1.1.39, RuBisCO); and d) one or more heterologous genes encoding a phosphoribulokinase (EC 2.7.1.19, PRK); and optionally e) one or more heterologous genes encoding for a glycerol transporter, wherein the recombinant yeast comprises overexpression of one or more PPP-genes. This cell can be used for the production of ethanol and advantageously produces little or no glycerol.

The present invention relates to a yeast cell that is genetically modified comprising: a) a disruption of one or more aldehyde dehydrogenase (E.C: 1.2.1.4) native to the yeast; b) one or more nucleotide sequence encoding a heterologous NAD+-dependent acetylating acetaldehyde dehydrogenase (E.C. 1.2.1.10); c) one or more nucleotide sequence encoding a homologous or heterologous acetyl-CoA synthetase (E.C. 6.2.1.1); and d) a modification that leads to reduction of glycerol 3-phosphate phosphohydrolase (E.C. 3.1.3.21) and/or glycerol 3-phosphate dehydrogenase (E.C. 1.1.1.8 or E.C. 1.1.5.3) activity, native to the yeast.

The invention relates to a recombinant cell, preferably a yeast cell comprising: a) one or more heterologous genes encoding a glycerol dehydrogenase activity; b) one or more genes encoding a dihydroxyacetone kinase (E.C. 2.7.1.28 and/or E.C. 2.7.1.29); c) one or more heterologous genes encoding a ribulose-1,5-biphosphate carboxylase oxygenase (EC 4.1.1.39, RuBisCO); and d) one or more heterologous genes encoding a phosphoribulokinase (EC 2.7.1.19, PRK); and optionally e) one or more heterologous genes encoding for a glycerol transporter. This cell can be used for the production of ethanol and advantageously produces little or no glycerol.

The invention relates to a process for producing a fermentation product that comprises fermentation of a carbon source in a reactor with a cell, capable of converting sugar, glycerol and acetic acid, wherein the carbon source comprises sugar and acetic acid, comprising the following steps: a) Inoculating a optionally diluted carbon source with the cell; b) optionally fermenting the reactor in batch mode; c) adding carbon source comprising glycerol and optionally sugar gradually to the reactor; d) after sufficient fermentation time, isolation of fermentation product from the reactor, e) optionally keeping the remaining fraction after isolation of step d) as spent broth; and f) optionally using the spent broth in step a) to dilute the carbon source.

The present invention relates to genetically modified microorganisms comprising one or more heterologous nucleic acid molecules together encoding at least three different proteins, each protein comprising an enzymatic domain and a bacterial microcompartment-targeting signal polypeptide, wherein said enzymatic domains each catalyse a different substrate to product conversion in the same metabolic pathway, and wherein said microorganisms are essentially free of bacterial microcompartments (BMCs); and to cell free systems comprising aggregates comprising at least three different proteins, each protein comprising an enzymatic domain and a bacterial microcompartment-targeting signal polypeptide, wherein said enzymatic domains each catalyse a different substrate to product conversion in the same metabolic pathway, and wherein said system does not comprise bacterial microcompartments; and to methods for the production of said microorganisms and cell free systems and their use in methods of producing a product of interest.

The invention relates to a process for producing a fermentation product that comprises fermentation of a carbon source in a reactor with a cell, capable of converting sugar, glycerol and acetic acid, wherein the carbon source comprises sugar and acetic acid, comprising the following steps: a) Inoculating a optionally diluted carbon source with the cell; b) optionally fermenting the reactor in batch mode; c) adding carbon source comprising glycerol and optionally sugar gradually to the reactor; d) after sufficient fermentation time, isolation of fermentation product from the reactor, e) optionally keeping the remaining fraction after isolation of step d) as spent broth; and f) optionally using the spent broth in step a) to dilute the carbon source.

The invention describes a process for the production of ethanol from a composition comprising glucose and between 50 M and 100 mM acetic acid, said process comprising fermenting said composition in the presence of a recombinant yeast which is capable to convert acetic acid anaerobically; maintaining the amount of undissociated acetic acid at a value of at least 50 M; and recovering the ethanol. Said process is useful for both starch and cellulosic based, acetic acid containing hydrolysates and advantageously results in a greater consumption of acetic acid and thus higher ethanol yields.

The invention relates to a recombinant cell, preferably a yeast cell comprising one or more genes coding for an enzyme having glycerol dehydrogenase activity, one or more genes coding dihydroxyacetone kinase (E.C. 2.7.1.28 and/or E.C. 2.7.1.29); one or more genes coding for an enzyme in an acetyl-CoA-production pathway and one or more genes coding for an enzyme having at least NAD.sup.+ dependent acetylating acetaldehyde dehydrogenase activity (EC 1.2.1.10 or EC 1.1.1.2), and optionally one or more genes coding for a glycerol transporter. This cell can be used for the production of ethanol and advantageously produces little or no glycerol.

Cell that is genetically modified comprising: a) one or more nucleotide sequence encoding a NAD.sub.+-dependent acetylating acetaldehyde dehydrogenase (E.C. 1.2.1.10); b) one or more nucleotide sequence encoding a acetyl-CoA synthetase (E.C. 6.2.1.1); c) one or more nucleotide sequence encoding a glycerol dehydrogenase (E.C. 1.1.1.6); and d) one or more nucleotide sequence encoding a dihydroxyacetone kinase (E.C. 2.7.1.28 or E.C. 2.7.1.29).