Described herein are recombinant host organisms expressing a sugar transporter and an active pentose fermentation pathway. Also described are processes for producing a fermentation product, such as ethanol, from starch or cellulosic-containing material with the recombinant host organisms.

Provided herein are Metschnikowia species that produce xylitol from xylose when cultured, as well as methods to make and use these Metschnikowia species.

The present disclosure is related to genetically engineered microbial strains and related bioprocesses for the production of xylitol. Specifically, the use of dynamically controlled synthetic metabolic valves to reduce the activity of certain enzymes, leads to increased xylitol production in a two-stage process.

The present invention concerns novel Saccharomyces cerevisiae yeast strains capable of multiplying on a substrate comprising at least one C5 sugar with a speed and rate of multiplication compatible with the industrial production of yeast. It also concerns novel strains which, when cultured, make it possible to obtain yeasts having an application efficiency, i.e. an efficiency that is satisfactory in applications and uses of interest in industries such as breadmaking, biomass production, flavour production, the production of secondary metabolites, protein production, ethanol production, brewing, winemaking or the production of yeast extract.

The invention relates to a method for preparing a yeast which is capable of simultaneously fermenting a pentose and a hexose sugar, the method comprising providing a yeast which comprises: one or more heterologous genes encoding an enzyme of a pentose metabolic pathway, a disruption of a gene encoding a ribulose-phosphate 3-epimerase and a disruption of a gene encoding a glucose-6-phosphate isomerase, and one or more overexpressed endogenous genes encoding an enzyme of the pentose phosphate pathway; and subjecting the yeast to evolutionary engineering on a medium comprising a hexose sugar and at least one pentose sugar, selecting for a yeast with improved growth rate when grown on a media comprising a hexose and at least one pentose sugar, so as to obtain an evolved yeast.

Provided herein are Metschnikowia species that produce xylitol from xylose when cultured, as well as methods to make and use these Metschnikowia species.

The present invention discloses a construction method and a recombinant yeast stain Yarrowia lipolytica for xylitol synthesis; Adopting Yarrowia lipolytica as the host, introducing genes into the host through metabolic engineering to enable the recombinant yeast to synthesize xylitol from glucose, fructose, glycerol and starch as carbon sources, block the synthesis pathway of by-products, so that it can synthesize xylitol from the aforesaid carbon sources by fermentation, thus obtain the engineered Yarrowia lipolytica strain to synthesize xylitol from glucose and other carbon sources. After fermentation, xylitol crystal is obtained by ion exchange, decolorization, concentration and crystallization of the clear and transparent fermentation liquor after isolation of the strains from the fermentation. This construction method of engineered Yarrowia lipolytica described in the invention, and the Yarrowia lipolytica strain obtained by this method can simplify the existing method for chemical synthesis of xylitol and have good application.

The present invention provides for novel metabolic pathways to detoxify biomass-derived acetate via metabolic conversion to ethanol, acetone, or isopropanol. More specifically, the invention provides for a recombinant microorganism comprising one or more native and/or heterologous enzymes that function in one or more first engineered metabolic pathways to achieve: (1) conversion of acetate to ethanol; (2) conversion of acetate to acetone; or (3) conversion of acetate to isopropanol; and one or more native and/or heterologous enzymes that function in one or more second engineered metabolic pathways to produce an electron donor used in the conversion of acetate to less inhibitory compounds; wherein the one or more native and/or heterologous enzymes is activated, upregulated, or downregulated.

A method for preparing a yeast capable of simultaneously fermenting a pentose and a hexose sugar, comprising: (a) providing a yeast comprising: one or more heterologous genes encoding an enzyme of a pentose metabolic pathway; disruptions of a gene encoding a ribulose-phosphate 3-epimerase and of a gene encoding a glucose-6-phosphate isomerase; one or more overexpressed endogenous genes encoding an enzyme of the pentose phosphate pathway; and a disruption of one or more genes encoding an NADPH dependent 6-phosphogluconate dehydrogenase, (b) subjecting said yeast to evolutionary engineering on a medium comprising a hexose sugar and at least one pentose sugar, selecting for a yeast with improved growth rate obtain an evolved yeast; (d) restoring, in the evolved yeast, one or more of the disrupted genes, or: (d) identifying genetic permutations in at least part of the genome of the evolved yeast by genome sequencing; (e) constructing an improved pentose and hexose-fermenting yeast comprising one or more said genetic permutations. Also described is a recombinant yeast comprising one or more heterologous genes of a pentose metabolic pathway, and a gene encoding a variant of a parent polypeptide, the variant comprising an amino acid sequence comprising at least one mutation, when aligned with the amino acid sequence in SEQ ID NO: 6.

The present invention relates to a method of preparing a strain of sugar fermenting Saccharomyces cerevisiae with capability to ferment xylose, wherein said method comprises different procedural steps. The method comprises mating a first sporulated Saccharomyces cerevisiae strain with a second Saccharomyces cerevisiae haploid strain. Thereafter, screening for mated cells is performed, growing such mated cells, and verifying that mated cells exhibit basic morphology by microscopic inspection. Thereafter, creation of a mixture of the mated cells is performed, subjecting the mixture to continuous chemostat lignocellulose cultivation and obtaining the sugar fermenting Saccharomyces cerevisiae cells with capability to ferment xylose is performed. The invention also comprises strains obtained by said method.