Submitted to: Applied Microbiology and Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/11/2004
Publication Date: 4/1/2005
Citation: Weimer, P.J., Dien, B.S., Springer, T.L., Vogel, K.P. 2005. In vitro gas production as a surrogate measurement of the fermentability of cellulosic biomass. Applied Microbiology Biotechnology. 67:52-58. Interpretive Summary: Measuring the potential of crops or crop residues to serve as sources of ethanol by yeast fermentation is a relatively tedious procedure. Bacterial contamination reduces ethanol yield, making it necessary to conduct experiments under conditions that prevent the entry of bacteria. In addition, analysis of ethanol requires expensive instrumentation. We have adapted a simple gas pressure device to measure the amount of gases produced during fermentation, which is closely related to the amount of ethanol produced in an enzyme/yeast bioconversion system. We also observed that biomass materials can be evaluated for fermentability using a simple lab assay with microorganisms from a cow's digestive tract, and that gas produced in this fermentation is well-correlated with the amount of ethanol that can be produced from the same material in an enzyme/yeast bioconversion system. These methods simplify measurement of biomass fermentability, permitting rapid screening of large numbers of biomass samples. This method should be useful to breeders of biomass energy crops for evaluating the quality of newly-developed lines, or the effect of growth environment on quality.
Technical Abstract: Gas production during simultaneous saccharification and fermentation (SSF) measured in sealed, volume-calibrated serum vials using a digital pressure gauge, was strongly correlated with ethanol production (r2 > 0.9) at both early (24h) and late (7d) time points. Good correlations (r2~0.68 to 0.84) were also observed between ethanol production during SSF and gas production in a parallel in vitro ruminal fermentation. Because the in vitro ruminal fermentation assay can be performed without sterilization of the medium or without the use of aseptic conditions, this assay may be useful as a rapid primary screen of the fermentability of biomass materials.