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 provides a non-naturally occurring bacterium having decreased or eliminated activity of an enzyme that catalyzes the reaction defined by EC 1.2.7.5, such as aldehyde:ferredoxin oxidoreductase (AOR). Optionally, the bacterium also has decreased or eliminated activity of an enzyme that catalyzes the reaction defined by EC 1.2.1.10 and/or EC 1.1.1.1, such as aldehyde dehydrogenase, alcohol dehydrogenase, or bifunctional aldehyde/alcohol dehydrogenase. The invention further provides methods of producing products by culturing the bacterium in the presence of a gaseous substrate containing one or more of CO, CO.sub.2, and H.sub.2.

Provided are a recombinant yeast producing 3-hydroxypropionic acid (3-HP) and a method for producing 3-HP using the same, more particularly, a recombinant yeast producing 3-HP, comprising an exogenous AADH gene; an endogenous or exogenous ACC gene; an exogenous MCR gene; and an exogenous HPDH gene, and producing 3-HP through [Pyruvate Acetaldehyde.fwdarw.Acetyl-CoA Malonyl-CoA Malonate semialdehyde 3-HP] biosynthesis pathway, and a method for producing 3-HP using the same.

The present invention provides for novel metabolic pathways to reduce or eliminate glycerol production and increase product formation. More specifically, the invention provides for a recombinant microorganism comprising a deletion of one or more native enzymes that function to produce glycerol and/or regulate glycerol synthesis and one or more native and/or heterologous enzymes that function in one or more engineered metabolic pathways to convert a carbohydrate source, such as lignocellulose, to a product, such as ethanol, wherein the one or more native and/or heterologous enzymes is activated, upregulated, or downregulated. The invention also provides for a recombinant microorganism comprising one or more heterologous enzymes that function to regulate glycerol synthesis and one or more native and/or heterologous enzymes that function in one or more engineered metabolic pathways to convert a carbohydrate source to ethanol, wherein said one or more native and/or heterologous enzymes is activated, upregulated or downregulated.

The present invention provides for a mechanism to reduce glycerol production and increase nitrogen utilization and ethanol production of recombinant microorganisms. One aspect of this invention relates to strains of S. cerevisiae with reduced glycerol productivity that get a kinetic benefit from higher nitrogen concentration without sacrificing ethanol yield. A second aspect of the invention relates to metabolic modifications resulting in altered transport and/or intracellular metabolism of nitrogen sources present in corn mash.

The present invention relates to a yeast cell, in particular a recombinant yeast cell, the cell lacking enzymatic activity needed for the NADH-dependent glycerol synthesis or the cell having a reduced enzymatic activity with respect to the NADH-dependent glycerol synthesis compared to its corresponding wild-type yeast cell, the cell comprising one or more heterologous nucleic acid sequences encoding an NAD.sup.+-dependent acetylating acetaldehyde dehydrogenase (EC 1.2.1.10) activity. The invention further relates to the use of a cell according to the invention in the preparation of ethanol.

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.sub.+-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 present invention relates to a yeast cell, in particular a recombinant yeast cell, the cell lacking enzymatic activity needed for the NADH-dependent glycerol synthesis or the cell having a reduced enzymatic activity with respect to the NADH-dependent glycerol synthesis compared to its corresponding wild-type yeast cell, the cell comprising one or more heterologous nucleic acid sequences encoding an NAD.sup.+-dependent acetylating acetaldehyde dehydrogenase (EC 1.2.1.10) activity. The invention further relates to the use of a cell according to the invention in the preparation of ethanol.

There is provided an acetogenic microbial cell which is capable of producing at least one higher alcohol from a carbon source, wherein the acetogenic microbial cell is genetically modified to comprise an increased expression relative to its wild type cell of at least one enzyme, E.sub.8, a butyryl-CoA:acetate CoA transferase (cat3). There is also provided a method and use of the cell to produce higher alcohols.

The disclosure discloses construction and application of an engineered strain of E. coli for producing malic acid by fixing CO.sub.2, and belongs to the field of fermentation. The engineered strain is obtained by performing genetic engineering transformation on Escherichia coli MG1655; the genetic engineering transformation includes knocking out a fumarate reductase gene, a fumarase gene, a lactate dehydrogenase gene and an alcohol dehydrogenase gene and freely overexpressing a formate dehydrogenase, an acetyl coenzyme A synthetase, an acylated acetaldehyde dehydrogenase, a formaldehyde lyase, a dihydroxyacetone kinase, a malic enzyme and a phosphite oxidoreductase to obtain a strain GH0407. The strain is used for producing malic acid by fermentation, anaerobic fermentation is performed for 72 hours with CO.sub.2 and glucose as a co-substrate, the production of malic acid reaches 39 g/L, the yield is 1.53 mol/mol, and accumulation of malic acid in the original strain is not achieved.