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