The main drawback for ethanol production from lignocellulosics is the generation of toxic compounds (i.e. 2-furaldehyde and acetic acid) from the acid hydrolysis required to release fermentable sugars from this biomass. In this work, twenty three respiratory deficient (RD) strains were obtained by treating Pichia stipitis NRRL Y-7124 with acriflavine, rhodamine and acrylamide. The ethanol yield on these strains was not improved, but one of the mutants, P. stipitis ACL 2-1 RD (lacking cytochrome c) obtained from the treatment with acrylamide, showed the highest specific ethanol production rate (1.82 gg-1h-1). Otherwise, ACF8-3 RD strain, obtained from the treatment with acriflavine, tolerated the highest acetic acid concentration (7.80 gL-1), estimated using a Levenspiel model, while the RHO2-3 RD strain was able to stand up to 1.5 gL-1 2-furaldehyde with a growth and ethanol production inhibition of 23 and 22% respectively. Results from this work indicate that the Respiratory Deficient phenotype conferred to these strains interesting attributes for the ethanol production using lignocellulosic residues, because it increased the tolerance to toxic compounds (i.e. acetic acid and 2-furaldehyde) found not only in sugar cane bagasse hydrolysates but also from other lignocellulosic residues. Hence, the respiratory deficient phenotype might be a strategy for improvement of the ethanol production and further studies should be done in order to understand all the phenomena involved in this process.

Ethanol production by <i>Pichia stipitis</i> with altered respiration and tolerance to toxic compounds from lignocellulosic hydrolysis

247th National Meeting (2014)

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Ethanol production by Pichia stipitis with altered respiration and tolerance to toxic compounds from lignocellulosic hydrolysis