Enzymatic biomass utilization and modification
September 24-28, 2017
Environmental concerns, the requirements for energy and carbon efficiency as well as the need to reduce dependency on fossil feedstocks lead to a necessity to develop new bio-based processes and products that support sustainable development and create novel possibilities to boost Bioeconomy. Lignocellulosic biomass mainly composed of cellulose, hemicellulose and lignin is a renewable, abundant non-food starting material for various applications. Cellulases and related enzymes have for decades attracted substantial interest in various industrial applications. For the total hydrolysis of biomass to produce biofuels and other chemicals, mixtures of different (hemi)cellulolytic enzymes have been used, composed of cellobiohydrolases, endoglucanases, β-glucosidases, hemicellulases and helper activities that act in a synergistic manner. On the other hand, for the fibre-based applications usually tailored, or monocomponent enzyme preparations have been applied. The exact composition and proportions of the different enzymes depends in each case on the raw material used, and also on the biorefinery concept to be applied.
Despite of the vast development of the lignocellulolytic enzymes, more efficient enzymes and enzyme cocktails are still needed. At VTT, novel cellulolytic enzymes have been discovered from environmental samples, culture collections, metagenomic libraries and genomic databases. Enzyme properties have also been improved by protein engineering. We have also analyzed the limiting factors in the hydrolysis, especially the role of hemicellulose and lignin. Molecular level mechanistic studies have paved way for development of more efficient enzymes. Besides biomass degradation, enzymes have been applied for fibre modification. Furthermore, protease deletion strains and strains with modified cellulase regulation pathways have made it possible to substantially increase protein production in Trichoderma reesei, the industrial production host.
- Igarashi K., Uchihashi, T., Koivula A., Wada, M., Kimura, S., Okamoto, T., Penttilä M., Ando, T. and Samejima, M. (2011) Traffic jams reduce hydrolytic efficiency of cellulase on cellulose surface. Science, 33, 1279-1282.
- Ilmén M., den Haan R, Brevnova E, McBride J, Wiswall E, Froehlich A, Koivula A, Voutilainen S.P, Siika-aho M, la Grange D.C., Thorngren N, Ahlgren S, Mellon M, Deleault K, Rajgarhia V, van Zyl W.H, Penttilä M (2011) High level secretion of cellobiohydrolases in Saccharomyces cerevisiae. Biotechnology for Biofuels 4, 30-45.
- Viikari, L., Vehmaanperä, J. and Koivula, A (2012) Lignocellulosic ethanol: from science to industry. Biomass and Bioenergy 46, 13-24.
- Nakamura, A., Tsukada, T., Auer,S., Furuta, T., Wada, M., Koivula,A., Igarashi, K., and Samejima M. (2013) Tryptophan residue at active-site tunnel entrance of Trichoderma reesei cellobiohydrolase Cel7A is important to initiate degradation of crystalline cellulose. J.Biol.Chem. 288, 13503-13510.
- Rahikainen, J. L., Moilanen, U., Nurmi-Rantala, S., Lappas, A., Koivula, A., Viikari, L., & Kruus, K. (2013). Effect of temperature on lignin-derived inhibition studied with three structurally different cellobiohydrolases. Bioresource Technology, 146, 118–25.
- Voutilainen S.P., Nurmi-Rantala, S., Penttilä M., and Koivula A. (2013) Engineering chimeric thermostable GH7 cellobiohydrolases in Saccharomyces cerevisiae. Appl. Microbiol. Biotechnol. 98, 2991-3001.
- Colabardini, A.C., Valkonen M; Huuskonen A; Siika-aho M; Koivula A; Goldman G.H; Saloheimo M (2016) Expression of two novel β-glucosidases from Chaetomium atrobrunneum in Trichoderma reesei and characterization of the heterologous protein products. Mol. Biotechnology. 58, 821-831.
Anu Koivula, "Enzymatic biomass utilization and modification" in "Enzyme Engineering XXIV", Pierre Monsan, Toulouse White Biotechnology, France Magali Remaud-Simeon, LISBP-INSA, University of Toulouse, France Eds, ECI Symposium Series, (2017). http://dc.engconfintl.org/enzyme_xxiv/120