Monday, May 4, 2009
5-14
Cellulase production, enzymatic hydrolysis and ethanol production on steam-pretreated spruce using Trichoderma atroviride mutants
Krisztina Kovacs1, George Szakacs2, and Guido Zacchi1. (1) Department of Chemical Engineering, Lund University, P.O. Box 124, Lund, 22100, Sweden, (2) Department of Applied Biotechnology and Food Science, Budapest University of Technology and Economics, Gellert ter 4, Budapest, 1111, Hungary
The production cost of enzymes represents a significant part in the overall cost of the biomass-to-ethanol process. Therefore, development of more effective cellulase secreting microorganisms and improvement of the hydrolytic properties of the enzyme mixtures are of great importance. Trichoderma reesei has been chosen by many researchers and industrial companies to produce commercial cellulases, even though this species practically does not secrete β-glucosidase, which is a key enzyme for the complete hydrolysis of cellulose.
We developed new Trichoderma atroviride mutants, which produced high levels of cellulases and β-glucosidases on steam-pretreated spruce (SPS). Due to extracellular β-glucosidases, the Trichoderma atroviride supernatants hydrolyzed the SPS more efficiently than the Trichoderma reesei supernatants. On the other hand, when the whole fermentation broths were used, i.e. bound enzymes were also present, the hydrolytic capacity of Trichoderma reesei was significantly enhanced.
The in-house produced enzyme supernatants and whole fermentation broths were compared with commercial enzymes in the simultaneous saccharification and fermentation (SSF) process to produce ethanol from SPS. The Trichoderma atroviride enzyme preparations and the whole broth of Trichoderma reesei proved to be as efficient in the SSF as the commercial cellulase mixtures (ethanol yields of 60-75%), while low ethanol yields (< 40%) were obtained with the β-glucosidase deficient Trichoderma reesei supernatant.
We presume that the use of new enzymes produced on SPS by a Trichoderma strain with good extracellular β-glucosidase level will lead to more cost effective production of bioethanol from pretreated lignocelluloses.
We developed new Trichoderma atroviride mutants, which produced high levels of cellulases and β-glucosidases on steam-pretreated spruce (SPS). Due to extracellular β-glucosidases, the Trichoderma atroviride supernatants hydrolyzed the SPS more efficiently than the Trichoderma reesei supernatants. On the other hand, when the whole fermentation broths were used, i.e. bound enzymes were also present, the hydrolytic capacity of Trichoderma reesei was significantly enhanced.
The in-house produced enzyme supernatants and whole fermentation broths were compared with commercial enzymes in the simultaneous saccharification and fermentation (SSF) process to produce ethanol from SPS. The Trichoderma atroviride enzyme preparations and the whole broth of Trichoderma reesei proved to be as efficient in the SSF as the commercial cellulase mixtures (ethanol yields of 60-75%), while low ethanol yields (< 40%) were obtained with the β-glucosidase deficient Trichoderma reesei supernatant.
We presume that the use of new enzymes produced on SPS by a Trichoderma strain with good extracellular β-glucosidase level will lead to more cost effective production of bioethanol from pretreated lignocelluloses.