método de identificar um polipeptídeo heterólogo tendo atividade enzimática para converter piruvato, acetaldeído ou acetato em acetil-coa no citosol de uma célula de levedura, vetor para a expressão de polipeptídeos heterólogos em levedura, célula de levedura recombinante e método de produzir um produto de fermentação

The present invention relates to a method of identifying a heterologous polypeptide having enzymatic activity for converting pyruvate, acetaldehyde or acetate into acetyl-CoA in (the cytosol of) of a yeast cell comprising: a) providing a mutated yeast cell comprising a deletion of at least one gene of the (PDH) by-pass, selected from the genes encoding the enzymes pyruvate decarboxylase (PDC), acetaldehyde dehydrogenase (ALD), and acetyl-CoA synthetase (ACS); b) transforming said mutated yeast cell with an expression vector comprising a heterologous nucleotide sequence encoding a candidate polypeptide having potential enzymatic activity for converting pyruvate, acetaldehyde or acetate into acetyl-CoA; c) testing said recombinant mutated yeast cell for its ability to grown on minimal medium containing glucose as sole carbon source, and d) identifying said candidate polypeptide as a heterologous polypeptide having enzymatic activity for converting pyruvate, acetaldehyde or acetate into acetyl-CoA in (the cytosol of) said yeast cell when growth of said cell is observed. The invention further relates to a method of producing a fermentation production such as butanol.