COMBINED EXPRESSION OF TREHALOSE PRODUCING AND TREHALOSE DEGRADING ENZYMES

1 . A recombinant yeast host cell having:

a first genetic modification for expressing an heterologous trehalase; and

a second genetic modification for increasing trehalose production.

2 . The recombinant yeast host cell of claim 1 , wherein the heterologous trehalase is a cell-associated trehalase.

3 . The recombinant yeast host cell of claim 1 , wherein the heterolgous trehalase is a secreted trehalase.

4 . The recombinant yeast host cell of claim 1 , wherein the heterologous trehalase:

(a) has the amino acid sequence of SEQ ID NO.: 26, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 28, 30, 32, 34, 36 or 38;

(b) is a variant of the amino acid sequence of (a) exhibiting trehalase activity; or

(c) is a fragment of the amino acid sequence of (a) or (b) exhibiting trehalase activity.

5 . The recombinant yeast host cell of claim 1 , wherein the heterologous trehalase is from Neurospora sp., Achlya sp., Ashbya sp., Aspergillus sp., Escovopsis sp., Fusarium sp., Kluyveromyces sp., Komagataella sp., Metarhizium sp., Microsporum sp., Neosartorya sp., Ogataea sp., Rhizoctonia sp., Schizopora sp., or Thielavia sp.

6 . The recombinant yeast host cell of claim 5 , wherein the heterologous trehalase is from Neurospora crassa, Achlya hypogyna, Ashbya gossypii, Aspergillus clavatus, Aspergillus flavus, Aspergillus fumigatus, Aspergillus lentulus, Aspergillus ochraceoroseus, Escovopsis weberi, Fusarium oxysporum, Kluyveromyces marxianus, Komagataella phaffii, Metarhizium anisopliae, Microsporum gypseum, Neosartorya udagawae, Ogataea parapolymorpha, Rhizoctonia solani, Schizopora paradoxa, or Thielavia terrestris.

7 .- 57 . (canceled)

58 . The recombinant yeast host cell of claim 1 , wherein the second genetic modification allows (i) expression of a second heterologous enzyme involved in producing trehalose and/or a second heterologous regulatory polypeptide involved in regulating trehalose production and/or (ii) overexpression of a second native enzyme involved in producing trehalose and/or a second native regulatory polypeptide involved in regulating trehalose production.

59 . (canceled)

60 . The recombinant yeast host cell of claim 58 , wherein the second genetic modification allows the expression of at least one of TPS1, TPS2, TPS3 or TSL1.

61 .- 64 . (canceled)

65 . The recombinant yeast host cell of claim 1 which exhibit increased robustness when a stressor is present, compared to a corresponding recombinant yeast host cell having the first genetic modification and lacking the second genetic modification.

66 . The recombinant yeast host cell of claim 1 further comprising at least one of:

a third genetic modification allowing or increasing expression of at least one heterologous saccharolytic enzyme;

a fourth genetic modification allowing or increasing production of formate;

a fifth genetic modification allowing or increasing utilization of acetyl-CoA;

a sixth genetic modification limiting production of glycerol; and/or a seventh genetic modification facilitating transport of glycerol in the recombinant yeast host cell.

67 . The recombinant yeast host cell of claim 1 which belongs to a species from genus Saccharomyces sp.

68 . The recombinant yeast host cell of claim 67 wherein the species is Saccharomyces cerevisiae.

69 . A process for converting a biomass into a fermentation product, the process comprising contacting the biomass with the recombinant yeast host cell defined in claim 1 under conditions to allow conversion of at least a part of the biomass into the fermentation product.

70 . The process of claim 69 , wherein the biomass comprises corn.

71 . The process of claim 70 , wherein the corn is provided as a mash.

72 . The process of claim 69 , wherein the fermentation product is ethanol.

73 . The process of claim 69 being conducted, at least in part, with a stressor present.