Presented herein are oleaginous strains of yeast such as Saccharomyces cerevisiae that have been modified to allow for xylose utilization. Such strains are also modified to allow for higher lipid accumulation utilizing a broad range of sugar monomers such as those released during pretreatment and enzymatic saccharification of lignocellulosic biomass. Methods of producing lipids and ethanol using these yeast strains are also disclosed.

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.

Described herein are recombinant yeast cells expressing a xylulose kinase (XK) which are suitable for fermentation of pentoses. Also described are recombinant yeast cells with higher tolerance to formic and/or acetic acid and suitable for fermentation of pentoses. Also described are recombinant yeast cells expressing an enolase, a phosphofructokinase beta subunit, a 6-phosphofructo-2-kinase, a glucose-6-phosphate isomerase, a phosphoglycerate mutase and/or a triose-phosphate isomerase, and suitable for fermentation of pentoses. Also described are recombinant yeast cells expressing a phosphoglucomutase and/or phosphoribomutase which are suitable for fermentation of pentoses. Further described are methods of using or producing such recombinant yeast cells and related materials.

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.

The present invention relates to polypeptides which are Gal2 variants comprising at least one amino acid substitution at a position corresponding to M435, and optionally further amino acid substitution(s). The present invention further relates to nucleic acid molecules encoding the polypeptides and to host cells containing said nucleic acid molecules. The present invention further relates to a method for the production of bioethanol and/or other bio-based compounds, comprising the expression of said nucleic acid molecules, preferably in said host cells. The present invention also relates to the use of the polypeptides, nucleic acids molecule or host cells for the production of bioethanol and/or other bio-based compounds, and/or for the recombinant fermentation of biomaterial containing pentose(s), preferably D-xylose and/or L-arabinose.

The present invention relates to a method for obtaining a strain capable of efficiently propagating in a low nutritive potential medium, capable of metabolizing pentoses and of resisting fermentation inhibitors, comprising the following steps; a) growth of a strain of recombinant yeast with a strain of wild yeast lacking any impairments, the recombinant yeast strain comprising at least one copy of an exogenous gene of xylose isomerase and at least one additional copy of a gene of D-xylulokinase included in the genome and linked to a single sexual characteristic of the strain, b) at least two cycles of genome shuffling by sporulation and or random hybridization, c) selection of the population obtained in step b) according to a suitability criterion of the strains to metabolize xylose, d) selection of the population obtained in step c) according to a suitability criterion of the strains to grow in a Pref type medium, a medium with low nutritive value. The invention also relates to a cell, a yeast or a strain of recombinant yeast obtained according to the method, and to the use of such a cell for the production of bioethanol.

The invention relates to a cell capable of converting one or more pentose sugar and one or more hexose sugar into fermentation product constitutively expressing one or more heterologous or homologous polypeptide having the amino acid sequence set out in SEQ ID NO: 20, or a variant polypeptide thereof having at least 45% identity to SEQ ID NO 20. In an embodiment the heterologous polypeptide has glyoxalase activity.

This invention is aimed at improving an ethanol fermentation ability of a recombinant yeast strain having an ability of assimilating pentose, such as xylose or arabinose. The recombinant yeast strain haying an ability of assimilating pentose is obtained by lowering activity of a gene involved in upstream of glyceraldehyde-3-phosphate in the Embden-Meyerhof pathway.

The present invention relates to polypeptides which are Gal2 variants comprising at least one amino acid substitution at a position corresponding to T354, and optionally further amino acid substitution(s). The present invention further relates to nucleic acid molecules encoding the polypeptides and to host cells containing said nucleic acid molecules. The present invention further relates to a method for the production of bioethanol and/or other bio-based compounds, comprising the expression of said nucleic acid molecules, preferably in said host cells. The present invention also relates to the use of the polypeptides, nucleic acids molecule or host cells for the production of bioethanol and/or other bio-based compounds, and/or for the recombinant fermentation of biomaterial containing pentose(s), preferably D-xylose and/or L-arabinose.

An engineered yeast strain capable of efficient fermentation of xylose to ethanol, and methods of making and using the strain, are provided.