Dataset Information

Characterization of Rice Straw Prehydrolyzates and Their Effect on the Hydrolysis of Model Substrates Using a Commercial endo-Cellulase, β-Glucosidase and Cellulase Cocktail.

ABSTRACT: Pretreatment and enzymatic saccharification are two major upstream processes that affect the economic feasibility and sustainability of lignocellulosic biofuel production. Cellulase-inhibiting degradation products, generated during dilute acid pretreatment, increase enzyme usage, and therefore, it is essential to mitigate their production. In an attempt to elucidate the most deleterious degradation product to enzymatic hydrolysis, hydrolyzates were generated from rice straw, and their effect on enzyme activity was determined. Ground rice straw was subjected to the following pretreatments having a combined severity factor of 1.75: T1-160 °C, pH 1.7; T2-180 °C, pH 2.25; and T3-220 °C, pH 7.0. The liquid prehydrolyzates were freeze-dried, and their inhibitory effects on the activities of a commercial cellulase cocktail, endo-cellulase, and β-glucosidase were determined using filter paper, carboxymethyl cellulose, and cellobiose, respectively. Addition of 15 g L(-1) of T1, T2, or T3 freeze-dried prehydrolyzates resulted in 67%, 57%, and 77% reduction in CMC-ase activity of endo-cellulase, respectively. In the presence of 35 g L(-1) of T1, T2, or T3 prehydrolyzates, the filter paper activity of the cellulase cocktail was reduced by 64%, 68%, and 82%, respectively. Characterization of the freeze-dried prehydrolyzates showed that T3 had significantly higher xylo-oligosaccharides and total phenolic content than T2 and T1.

SUBMITTER: Rajan K

PROVIDER: S-EPMC4165551 | biostudies-other | 2014 Sep

REPOSITORIES: biostudies-other

ACCESS DATA

Similar Datasets

Project description:BACKGROUND:A complete saccharification of plant polymers is the critical step in the efficient production of bio-alcohols. Beta-glucosidases acting in the degradation of intermediate gluco-oligosaccharides produced by cellulases limit the yield of the final product. RESULTS:In the present work, we have identified and then successfully cloned, expressed, purified and characterised 4 highly active beta-glucosidases from fibre-adherent microbial community from the cow rumen. The enzymes were most active at temperatures 45-55°C and pH 4.0-7.0 and exhibited high affinity and activity towards synthetic substrates such as p-nitrophenyl-beta-D-glucopyranoside (pNPbetaG) and pNP-beta-cellobiose, as well as to natural cello-oligosaccharides ranging from cellobiose to cellopentaose. The apparent capability of the most active beta-glucosidase, herein named LAB25g2, was tested for its ability to improve, at low dosage (31.25 units g-1 dry biomass, using pNPbetaG as substrate), the hydrolysis of pre-treated corn stover (dry matter content of 20%; 350 g glucan kg-1 dry biomass) in combination with a beta-glucosidase-deficient commercial Trichoderma reseei cellulase cocktail (5 units g-1 dry biomass in the basis of pNPbetaG). LAB25g2 increased the final hydrolysis yield by a factor of 20% (44.5 ± 1.7% vs. 34.5 ± 1.5% in control conditions) after 96-120 h as compared to control reactions in its absence or in the presence of other commercial beta-glucosidase preparations. The high stability (half-life higher than 5 days at 50°C and pH 5.2) and 2-38000 fold higher (as compared with reported beta-glucosidases) activity towards cello-oligosaccharides may account for its performance in supplementation assays. CONCLUSIONS:The results suggest that beta-glucosidases from yet uncultured bacteria from animal digestomes may be of a potential interest for biotechnological processes related to the effective bio-ethanol production in combination with low dosage of commercial cellulases.

Project description:BackgroundThe discovery of enzymes named lytic polysaccharide monooxygenases (LPMOs) has had a major impact on the efficiency of current commercial cellulase cocktails for saccharification of lignocellulosic biomass. However, the notion that LPMOs use molecular oxygen as a co-substrate and require two externally delivered electrons per catalytic cycle poses a challenge in the development of efficient large-scale industrial processes. Building on the recent discovery that H2O2, rather than O2, is the co-substrate of LPMOs, we show here how cellulose degradation by the LPMO-containing commercial cellulase cocktail Cellic® CTec2 can be controlled and boosted by supplying the reaction with H2O2.ResultsThe controlled supply of anaerobic hydrolysis reactions with H2O2 and sub-stoichiometric amounts of reductant increased apparent LPMO activity by almost two orders of magnitude compared to standard aerobic reactions utilizing O2 and stoichiometric amounts of reductant. Improved LPMO activity was correlated with enhanced saccharification rates and yields for a model cellulosic substrate (Avicel) as well as industrial lignocellulosic substrates (sulfite-pulped Norway spruce and steam-exploded birch), although the magnitude of the effects was substrate dependent. Improvements in lignocellulose conversions were achieved at low H2O2 feeding rates (in the range of 90-600 µM h-1). Tight control of LPMO reactions by controlled supply of H2O2 under anaerobic conditions was possible.ConclusionWe report saccharification rates and yields for a model substrate (Avicel) and industrial lignocellulosic substrates that, at low H2O2 feeding rates, are higher than those seen under standard aerobic conditions. In an industrial setting, controlling and supplying molecular oxygen and stoichiometric amounts of reductant are challenging. The present report shows that the use of small amounts of a liquid bulk chemical, H2O2, provides an alternative to the currently available processes, which likely is cheaper and more easy to control, while giving higher product yields.

Dataset Information

Characterization of Rice Straw Prehydrolyzates and Their Effect on the Hydrolysis of Model Substrates Using a Commercial endo-Cellulase, β-Glucosidase and Cellulase Cocktail.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets