Background: The selection of new yeast strains could lead to improvements in bioethanol production. Here, we
have studied the fermentative capacity of different auxotrophic mutants of
Saccharomyces cerevisiae
, which are
routinely used as hosts for the production of heterologous proteins. It has recently been found that these
strains exhibit physiological alterations and peculiar sensitivities with respect to the parental prototrophic
strains from which they derive. In this work the performance of auxotrophic S. cerevisiae CEN.PK strains was
compared to the corresponding prototrophic strain, to
S. cerevisiae T5bV, a strain isolated from grape must and
to another auxotrophic strain,
S. cerevisiae BY4741.
Results: The results indicate that the fermentative capacity of strains grown in 2% glucose was similar in all the
strains tested. However, in 15% initial glucose, the auxotrophic strains exhibited a more than doubled ethanol
yield on biomass (10 g g
-1dw) compared to the prototrophic strains (less than 5 g g
-1dw). Other tests have also
evidenced that in medium depletion conditions, ethanol production continues after growth arrest.
Conclusions: The results highlight the capacity of auxotrophic yeast strains to produce ethanol per mass unit, in a
higher amount with respect to the prototrophic ones. This leads to potential applications for auxotrophic strains
of
S. cerevisiae in the production of ethanol in both homogeneous and heterogeneous phases (immobilized
systems). The higher ethanol yield on biomass would be advantageous in immobilized cell systems, as a
reduced yeast biomass could greatly reduce the mass transfer limitations through the immobilization matrix.
