Research

Laboratory-scale method for enzymatic saccharification of lignocellulosic biomass at high-solids loadings

Christine M Roche^1,2 , Clare J Dibble¹ and Jonathan J Stickel¹

¹  National Renewable Energy Laboratory, National Bioenergy Center, 1617 Cole Boulevard, Golden, CO 80401-3393, USA

²  Current address: University of California-Berkeley, Department of Chemical Engineering, 201 Gilman Hall, Berkeley, CA 94720-1462, USA

author email corresponding author email

Biotechnology for Biofuels 2009, 2:28doi:10.1186/1754-6834-2-28

Published:	4 November 2009

Abstract

Background

Screening new lignocellulosic biomass pretreatments and advanced enzyme systems at process relevant conditions is a key factor in the development of economically viable lignocellulosic ethanol. Shake flasks, the reaction vessel commonly used for screening enzymatic saccharifications of cellulosic biomass, do not provide adequate mixing at high-solids concentrations when shaking is not supplemented with hand mixing.

Results

We identified roller bottle reactors (RBRs) as laboratory-scale reaction vessels that can provide adequate mixing for enzymatic saccharifications at high-solids biomass loadings without any additional hand mixing. Using the RBRs, we developed a method for screening both pretreated biomass and enzyme systems at process-relevant conditions. RBRs were shown to be scalable between 125 mL and 2 L. Results from enzymatic saccharifications of five biomass pretreatments of different severities and two enzyme preparations suggest that this system will work well for a variety of biomass substrates and enzyme systems. A study of intermittent mixing regimes suggests that mass transfer limitations of enzymatic saccharifications at high-solids loadings are significant but can be mitigated with a relatively low amount of mixing input.

Conclusion

Effective initial mixing to promote good enzyme distribution and continued, but not necessarily continuous, mixing is necessary in order to facilitate high biomass conversion rates. The simplicity and robustness of the bench-scale RBR system, combined with its ability to accommodate numerous reaction vessels, will be useful in screening new biomass pretreatments and advanced enzyme systems at high-solids loadings.