Poster Presentation 2-35

Study of Relevant Naturally Pentose-assimilating Yeasts Tolerance to Brewery’s Spent Grain Hydrolysate

Luís C. Duarte*, Florbela Carvalheiro, Inês Neves and Francisco M. Gírio

INETI, Departamento de Biotecnologia

Estrada do Paço do Lumiar 22,

1649-038, Lisboa, Portugal

Phone: +351-217165141

Fax: +351-217163636

E-mail: luis.duarte@ineti.pt

Previously, it has been shown that the yeast Debaryomyces hansenii can readily use brewery’s spent grain (BSG) hydrolysates without any previous detoxification step. In order to further exploit this raw material, other potential yeast cell factories (namely, Pichia stipitis and Kluyveromyces marxianus) were also grown in this hydrolysate.

All yeasts were cultivated in shake flasks using BSG hydrolyzates at the initial pH of 5.5, in detoxified and non-detoxified hydrolysates both supplemented with mineral nutrients. To elucidate the differential yeast tolerance, all yeasts were also grown in complete chemically defined media containing glucose, xylose and arabinose, supplemented with inhibitor(s) as required.

The yeasts exhibited slight differences in terms of specific growth rate, biomass productivity and yield, with D. hansenii being the one that presented the best performance. In chemically defined medium acetic acid (1.5 g/L) was the least severe inhibitor and in D. hansenii it even increased biomass productivity, probably due to a buffering effect. Furfural (1 g/L) and 4-methylcatechol (0.5 g/l) diminished biomass productivity and increased lag phase in all yeasts. These effects were enhanced when a mixture of the three inhibitors was assayed.