Yield-determining factors in high-solids enzymatic hydrolysis of lignocellulose
By J. Kristensen, C. Felby, H. Jørgensen. Biotechnology for Biofuels, 2009
656 citations recorded by the source corpus.
BackgroundWorking at high solids (substrate) concentrations is advantageous in enzymatic conversion of lignocellulosic biomass as it increases product concentrations and plant productivity while lowering energy and water input. However, for a number of lignocellulosic substrates it has been shown that at increasing substrate concentration, the corresponding yield decreases in a fashion which can not be explained by current models and knowledge of enzyme-substrate interactions. This decrease in yield is undesirable as it offsets the advantages of working at high solids levels. The cause of the 'solids effect' has so far remained unknown.ResultsThe decreasing conversion at increasing solids concentrations was found to be a generic or intrinsic effect, describing a linear correlation from 5 to 30% initial total solids content (w/w). Insufficient mixing has previously been shown not to be involved in the effect. Hydrolysis experiments with filter paper showed that neither lignin content nor hemicellulose-derived inhibitors appear to be responsible for the decrease in yields. Product inhibition by glucose and in particular cellobiose (and ethanol in simultaneous saccharification and fermentation) at the increased concentrations at high solids loading plays a role but could not completely account for the decreasing conversion. Adsorption of cellulases was found to decrease at increasing solids concentrations. There was a strong correlation between the decreasing adsorption and conversion, indicating that the inhibition of cellulase adsorption to cellulose is causing the decrease in yield.ConclusionInhibition of enzyme adsorption by hydrolysis products appear to be the main cause of the decreasing yields at increasing substrate concentrations in the enzymatic decomposition of cellulosic biomass. In order to facilitate high conversions at high solids concentrations, understanding of the mechanisms involved in high-solids product inhibition and adsorption inhibition must be improved.
Subfields: Biomedical Engineering, Biotechnology, Plant Science
View Paper: https://www.semanticscholar.org/paper/b773c4b1964422e5f604494cbbad3f2b426f681d
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Citations in the corpus
- Pretreatment of lignocellulose: Formation of inhibitory by-products and strategies for minimizing their effects. (2016, neutral): “The use of hardwood and agricultural residues with high acetyl content as feedstocks as well as the development of high-solid processes (Kristensen et al., 2009) contribute to making inhibition by aliphatic carboxylic acids more important.”
- Fungal enzyme sets for plant polysaccharide degradation (2011, background): “reesei are highly sensitive to product inhibition, in particular by cellobiose, which might explain the need for a high amount of CBHs in an effective fungal cellulase enzyme mix (Bezerra and Dias 2005; Holtzapple et al. 1990; Kristensen et al. 2009).”
- The challenge of enzyme cost in the production of lignocellulosic biofuels. (2012, background): “It must be noted that the optimal value of enzyme loading varies depending on feedstock, solids loading, and pretreatment technology, among other variables (Kazi et al., 2010; Kristensen et al., 2009;Wyman et al., 1992).”