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 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 disclosure relates to microorganisms capable of producing poly(hydroxyisobutyric acid) (poly(HIBA)) from feedstocks and methods of producing poly(HIBA), methacrylic acid (MAA), and methacrylate esters (MAE) from feedstocks.

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 processes for producing ethanol from lignocellulosic hydrolysates comprising, hexoses, pentoses and acetic acid, whereby genetically modified yeast cells are use that comprise an exogenous gene encoding an acetaldehyde dehydrogenase and a bacterial gene encoding an enzyme with NAD.sup.+-linked glycerol dehydrogenase activity. The process is further characterised in that glycerol is present in or fed into the culture medium, whereby the modified yeast cell ferments the hexoses, pentoses, acetic acid and glycerol to ethanol. The invention further relates to yeast cells for use in such processes. The yeast cells advantageously comprise genetic modifications that improve glycerol utilization such as modifications that increase one or more of dihydroxyacetone kinase activity and transport of glycerol into the cell. The yeast cell further preferably comprises a functional exogenous xylose isomerase gene and/or functional exogenous genes which confer to the cell the ability to convert L-arabinose into D-xylulose 5-phosphate and they may comprise a genetic modification that increase acetyl-CoA synthetase activity.

This invention relates to a recombinant cell, preferably a recombinant yeast cell comprising: a) a gene coding for an enzyme having glycerol-3-phosphate dehydrogenase activity, wherein said enzyme has a cofactor dependency for at least NADP.sup.+ and/or for NADPH; b) a gene encoding an enzyme having at least NAD.sub.+ dependent acetylating acetaldehyde dehydrogenase activity (EC 1.2.1.10); and c) a mutation or disruption in at least one gene selected from the group of GPD1 and GPD2. Said cell is suitable for ethanol production, has a reduced glycerol production at high ethanol yield.

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 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.

A combination of an electrochemical device for delivering reducing equivalents to a cell, and engineered metabolic pathways within the cell capable of utilizing the electrochemically provided reducing equivalents is disclosed. Such a combination allows the production of commodity chemicals by fermentation to proceed with increased carbon efficiency.

The use of microorganisms to make alpha-functionalized chemicals and fuels, (e.g. alpha-functionalized carboxylic acids, alcohols, hydrocarbons, amines, and their beta-, and omega-functionalized derivatives), by utilizing an iterative carbon chain elongation pathway that uses functionalized extender units. The core enzymes in the pathway include thiolase, dehydrogenase, dehydratase and reductase. Native or engineered thiolases catalyze the condensation of either unsubstituted or functionalized acyl-CoA primers with an alpha-functionalized acetyl-CoA as the extender unit to generate alpha-functionalized -keto acyl-CoA. Dehydrogenase converts alpha-functionalized -keto acyl-CoA to alpha-functionalized -hydroxy acyl-CoA. Dehydratase converts alpha-functionalized -hydroxy acyl-CoA to alpha-functionalized enoyl-CoA. Reductase converts alpha-functionalized enoyl-CoA to alpha-functionalized acyl-CoA. The platform can be operated in an iterative manner (i.e. multiple turns) by using the resulting alpha-functionalized acyl-CoA as primer and the aforementioned alpha-functionalized extender unit in subsequent turns of the cycle. Termination pathways acting on any of the four alpha-functionalized CoA thioester intermediates terminate the platform and generate various alpha-functionalized carboxylic acids, alcohols and amines with different -reduction degree.