Background: The use of the enzymatic hydrolysis of lignocellulose with subsequent fermentation to ethanol provides a green alternative for the production of transportation fuels. Because of its recalcitrant nature, the lignocellulosic biomass must be pretreated before enzymatic hydrolysis. However, the pretreatment often results in the formation of compounds that are inhibitory for the enzymes or fermenting organism. Although well recognized, little quantitative information on the inhibition of individual cellulase components by identified inhibitors is available.
Results: Strong cellulase inhibitors were separated from the liquid fraction of the hydrothermal pretreatment of wheat straw. HPLC and mass-spectroscopy analyses confirmed that the inhibitors were oligosaccharides (inhibitory oligosaccharides, IOS) with a degree of polymerization from 7 to 16. The IOS are composed of a mixture of xylo- (XOS) and gluco-oligosaccharides (GOS). We propose that XOS and GOS are the fragments of the xylan backbone and mixed-linkage β-glucans, respectively. The IOS were approximately 100 times stronger inhibitors for Trichoderma reesei cellobiohydrolases (CBHs) than cellobiose, which is one of the strongest inhibitors of these enzymes reported to date. Inhibition of endoglucanases (EGs) by IOS was weaker than that of CBHs. Most of the tested cellulases and hemicellulases were able to slowly degrade IOS and reduce the inhibitory power of the liquid fraction to some extent. The most efficient single enzyme component here was T. reesei EG TrCel7B. Although reduced by the enzyme treatment, the residual inhibitory power of IOS and the liquid fraction was strong enough to silence the major component of the T. reesei cellulase system, CBH TrCel7A.
Conclusions: The cellulase inhibitors described here may be responsible for the poor yields from the enzymatic conversion of the whole slurries from lignocellulose pretreatment under conditions that do not favor complete degradation of hemicellulose. Identification of the inhibitory compounds helps to design better enzyme mixtures for their degradation and to optimize the pretreatment regimes to minimize their formation.
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http://dx.doi.org/10.1186/1754-6834-6-135 | DOI Listing |
Prep Biochem Biotechnol
January 2025
Department of Biotechnology, Kalasalingam Academy of Research and Education, Krishnankovil, Tamil Nadu, India.
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January 2025
School of Food Science and Pharmaceutical Engineering, Nanjing Normal University, No. 2 Xuelin Road, Nanjing 210097, China. Electronic address:
Lignocellulosic biomass is the most abundant form of biomass available for fuel production, serving as the fourth leading energy source globally. However, inhibitors generated during pretreatment processes often hinder fermentation performance and conversion efficiency. In this study, we developed an enhanced computer-assisted enzyme cocktail strategy (ComEC 2.
View Article and Find Full Text PDFPlants (Basel)
December 2024
Department of Molecular and Translational Medicine, University of Brescia, Viale Europa 11, 25123 Brescia, Italy.
Agro-industrial residues have transitions from being an environmental problem to being a cost-effective source of biopolymers and value-added chemicals. However, the efficient extraction of the desired products from these residues requires pretreatments. Fungal biorefinery is a fascinating approach for the biotransformation of raw materials into multiple products in a single batch.
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November 2024
School of Food Science and Engineering, Shaanxi University of Science & Technology, Xi'an 710021, China.
The kiwifruit () is an important nutritional and economic fruit crop. However, the short edible window period of kiwifruit has seriously affected its market value. 1-Methylcyclopropene (1-MCP), as a novel ethylene inhibitor, is widely applied to delay fruit ripening and senescence.
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December 2024
Department of Agroindustrial Technology, Faculty of Agricultural Engineering and Technology, IPB University, Bogor 16680, Indonesia; Department of Chemical Engineering, Faculty of Engineering, University of Indonesia, Depok 16424, Indonesia.
Food loss and waste caused by oxidation result in environmental and economic losses and health threats. Lignin is an abundant aromatic polymer with varied antioxidant capacity, which can reduce food oxidation caused by radical species exposure. The lignin antioxidant strength can be influenced by source, type, structure, processing, degradation products, chemical modifications, and particle size.
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