Cellulose hydrolysis by Bacteroides cellulosolvens

Mesophilic versus thermophilic anaerobic digestion of cattle manure: methane productivity and microbial ecology

In this study, productivity and physicochemical and microbiological (454 sequencing) parameters, as well as environmental criteria, were investigated in anaerobic reactors to contribute to the ongoing debate about the optimal temperature range for treating animal manure, and expand the general knowledge on the relation between microbiological and physicochemical process indicators. For this purpose, two reactor sizes were used (10 m(3) and 16 l), in which two temperature conditions (35°C and 50°C) were tested. In addition, the effect of the hydraulic retention time was evaluated (16 versus 20 days). Thermophilic anaerobic digestion showed higher organic matter degradation (especially fiber), higher pH and higher methane (CH₄) yield, as well as better percentage of ultimate CH₄ yield retrieved and lower residual CH₄ emission, when compared with mesophilic conditions. In addition, lower microbial diversity was found in the thermophilic reactors, especially for Bacteria, where a clear intensification towards Clostridia class members was evident. Independent of temperature, some similarities were found in digestates when comparing with animal manure, including low volatile fatty acids concentrations and a high fraction of Euryarchaeota in the total microbial community, in which members of Methanosarcinales dominated for both temperature conditions; these indicators could be considered a sign of process stability.

Dilute sulfuric acid hydrolysis of sugar maple wood extract at atmospheric pressure

Acid hydrolysis of hot-water wood extract was investigated. Sugar maple wood extract was obtained by hot-water extraction at 160 degrees C for 120min, followed by further concentration and solid removal by membrane filtration. Acid hydrolysis was performed at different temperatures (85 degrees C, 95 degrees C and 105 degrees C) and concentrations of sulfuric acid (wt.%: 1.5%, 3.1% and 6.2%). Hydrolyzate was analyzed by (1)H NMR spectroscopy. The concentrations of several major substances in the hydrolyzate were discussed in detail. Higher temperature, higher acid concentration and longer residence time all favor the depolymerization of hemicellulose wood extracts. Mainly xylose and acetic acid are recovered from the hydrolysis process.

Effect of biomass concentration and inoculum source on the rate of anaerobic cellulose solubilization

This study determines cellulose solubilization kinetics from controlled batch digestions and shows the effect of inoculum biomass concentrations. Separate measurements and analyzes were performed for sessile biomass (biofilms) and planktonic biomass (free suspensions). Experiments were conducted using either leachate enriched on cellulose or rumen fluid as inoculum to assess if the effect of biomass concentration was consistent for microbial populations from different source environments. All batch digestions were fitted to a first-order kinetic model (R(2) ranging from 0.94 to 0.99). Regression analysis used to compare the first-order hydrolysis rate showed that the first-order hydrolysis rate was most strongly correlated with the concentration of sessile biomass rather than with the concentration of total or planktonic biomass. The correlation between solubilization rate and sessile biomass was statistically the same for the rumen and leachate inoculated reactors indicating that at low concentration ratios of inoculum to cellulose, the rate of cellulose solubilization is dependant primarily on sessile biomass concentration rather than the species profile of the cellulolytic community.

Isolation and properties of a cellulosome-type multienzyme complex of the thermophilic Bacteroides sp. strain P-1

The extracellular form of cellulosome-type multienzyme complex of thermophilic Bacteroides sp. strain P-1 which was isolated from the anaerobic digester, is described. Multienzyme complex was isolated from the culture supernatant by an adsorption-desorption affinity chromatography on microcrystalline cellulose. The isolated multienzyme complex was found to form a complex that exhibited a high molecular weight (estimated at more than 1400 kDa) and was quite stable, requiring strong denaturing condition for dissociation. Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate resolved multienzyme complex into at least 12 subunits with the molecular weight range of 49 to 209 kDa, respectively. The isolated multienzyme complex showed cellulose-binding ability, cellulase and xylanase activities and effected the hydrolysis of crystalline cellulose and lignocellulosic materials in the form of corncob, corn hull, rice straw, and sugarcane bagasse.