Abstract

PENA SERNA, Carolina; ARANGO ISAZA, Rafael  and  RESTREPO BETANCUR, Luis Fernando. The effect of adding iron and zinc ions to ethanol production from two recombinant Saccharomyces cerevisiae strains. Rev. colomb. biotecnol [online]. 2010, vol.12, n.1, pp.158-168. ISSN 0123-3475.

Ethanol production by fermentation is influenced by the presence of metallic ions such as iron and zinc because these are alcohol dehydrogenase enzyme cofactors. Studying this effect leads to identifying the behaviour of microorganisms in industrial substrates containing high concentrations of these kinds of ions. This work therefore evaluated biomass production, residual sugars and ethanol production by fermenting three S. cerevisiae strains (CBS8066, recombinants GG570-CIBI and GG570-CIBII) under the effect of adding ferrous ion at 0, 50 and 150 µM and zinc ion at 0 and 50 µM. The strains had inhibited biomass and ethanol production when zinc and ferrous ions were added; such inhibition was greater in the presence of zinc or iron having higher concentrations. GG570-CIBI had 4 g/L reduction in biomass production and ethanol production dropped by 40% in the 150 µM iron-50 µM zinc treatment (compared to base treatment). GG570-CIBII was the less affected, having less than 11% inhibition of ethanol production at 20 h fermentation. GG570-CIBII presented the greatest ethanol production when 150 µM iron was added to the culture medium with or without adding zinc; in this case, production was 9% and 14% greater than CBS8066 and GG570-CIBI ethanol production, respectively, in the same conditions. GG570-CIBII will be evaluated later on using industrial substrates due to its lower ethanol production inhibition, thereby leading to better yields being obtained.

Keywords : pdc gene; adhII gene; Zymomonas mobilis; ferrous ion; zinc ion.

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