Sunday, April 29, 2007

Effect of different amounts of cellulase preparation on Kluyveromyces marxianus CECT 10875 growth and ethanol production

E. Tomás-Pejó, M.J. Negro, J.M. Oliva, and M. Ballesteros. Renewable Energies Department, CIEMAT, Research Centre for Energy, Environment and Technology, Avda. Complutense, 22, Madrid, Spain

Lignocellulosic biomass such as wood, crop residues or herbaceous material is a plentiful and low cost resource that can be used for ethanol production.

            Processes to obtain ethanol from lignocellulose based on enzymatic hydrolysis consist basically in three steps: pretreatment, enzymatic hydrolysis and fermentation. High ethanol yields can be achieved in a Simultaneous Sacharification and Fermentation (SSF) process where the enzymatic hydrolysis and fermentation are run in the same vessel.

            SSF optimization would require higher solids content in order to obtain final ethanol concentration as high as possible and decrease distillation cost. Ethanol concentration in fermentation broth of 4% (v/v) could be considered as a bench marck for an economycally viable distillation. Higher matter content implies, higher amounts of enzyme preparation in the SSF media.

            Since commercial cellulases obtained from Trichoderma reseii are expected to contain preservatives added to increase the product’s self-life, higher amounts of cellulases preparation in the SSF could act as potencially inhibitory compounds for microorganism growth. The aim of this research is to study the effect of commercial cellulases on Kluyveromyces marxianus CECT 10875, a thermotolerant yeast capable of fermenting glucose at temperatures above 40ºC with good ethanol yields.

            Fermentation tests to study the effect of different amounts of cellulases on fermentation parameters of K.marxianus have been performed. Assays have been carried using medium with glucose.

In order to study the effect of cellulase preparation on K.marxianus growth and ethanol production in an SSF process, tests have been performed at different substrate concentrations (Sigmacell crystalline cellulose).