94 research outputs found
Ethanol production of semi-simultaneous saccharification and fermentation from mixture of cotton gin waste and recycled paper sludge
Ethanol production from the steam-exploded mixture of 75% cotton gin waste and 25% recycled paper sludge in various conditions was investigated by semi-simultaneous saccharification and fermentation (SSSF) consisting of a pre-hydrolysis and a simultaneous saccharification and fermentation (SSF). Four cases were studied: 24-h pre-hydrolysis + 48-h SSF (SSSF 24), 12-h pre-hydrolysis + 60-h SSF (SSSF 12), 72-h SSF, and 48-h hydrolysis + 24-h fermentation (SHF). The ethanol concentration, yield, and productivity of SSSF 24 were higher than those of the other operations. A model of SSF was used to simulate the data for four components in SSF. The analysis of the reaction rates of cellobiose, glucose, cell, and ethanol using the model and the parameters from the experiments showed that there was a transition point of the rate-controlling step at which the cell growth control in the initial 2 h was changed to the cellobiose reaction control in later period during ethanol production of SSF from the mixture
Enzymatic removal of cellulose from cotton/polyester fabric blends
The production of light-weight polyester fabrics from a polyester/cotton blended fabric, by means of the enzymatic removal of the cellulosic part of the material, was investigated. The removal of cotton from the
blended fabric yielded more than 80% of insoluble microfibrillar material by the combined action of high beating effects and cellulase hydrolysis.Other major features of this enzymatic process for converting cotton fibers into microfibrillar material are bath ratio, enzyme dosage and treatment time
A homologous production system for Trichoderma reesei secreted proteins in a cellulase-free background
Recent demands for the production of biofuels from lignocellulose led to an increased interest in engineered cellulases from Trichoderma reesei or other fungal sources. While the methods to generate such mutant cellulases on DNA level are straightforward, there is often a bottleneck in their production since a correct posttranslational processing of these enzymes is needed to obtain highly active enzymes. Their production and subsequent enzymatic analysis in the homologous host T. reesei is, however, often disturbed by the concomitant production of other endogenous cellulases. As a useful alternative, we tested the production of cellulases in T. reesei in a genetic background where cellulase formation has been impaired by deletion of the major cellulase transcriptional activator gene xyr1. Three cellulase genes (cel7a, cel7b, and cel12a) were expressed under the promoter regions of the two highly expressed genes tef1 (encoding translation elongation factor 1-alpha) or cdna1 (encoding the hypothetical protein Trire2:110879). When cultivated on d-glucose as carbon source, the Îxyr1 strain secreted all three cellulases into the medium. Related to the introduced gene copy number, the cdna1 promoter appeared to be superior to the tef1 promoter. No signs of proteolysis were detected, and the individual cellulases could be assayed over a background essentially free of other cellulases. Hence this system can be used as a vehicle for rapid and high-throughput testing of cellulase muteins in a homologous background
Expression of Trichoderma reesei cellulases CBHI and EGI in Ashbya gossypii
To explore the potential of Ashbya gossypii as a
host for the expression of recombinant proteins and to
assess whether protein secretion would be more similar to
the closely related Saccharomyces cerevisiae or to other
filamentous fungi, endoglucanase I (EGI) and cellobiohydrolase
I (CBHI) from the fungus Trichoderma reesei were
successfully expressed in A. gossypii from plasmids
containing the two micron sequences from S. cerevisiae,
under the S. cerevisiae PGK1 promoter. The native signal
sequences of EGI and CBHI were able to direct the
secretion of EGI and CBHI into the culture medium in A.
gossypii. Although CBHI activity was not detected using 4-
methylumbelliferyl-ÎČ-D-lactoside as substrate, the protein
was detected by Western blot using monoclonal antibodies.
EGI activity was detectable, the specific activity being
comparable to that produced by a similar EGI producing S.
cerevisiae construct. More EGI was secreted than CBHI, or
more active protein was produced. Partial characterization
of CBHI and EGI expressed in A. gossypii revealed
overglycosylation when compared with the native T. reesei
proteins, but the glycosylation was less extensive than on
cellulases expressed in S. cerevisiae.Fundação para a CiĂȘncia e a Tecnologia (FCT
A process for energy-efficient high-solids fed-batch enzymatic liquefaction of cellulosic biomass
The enzymatic hydrolysis of cellulosic biomass is a key step in the biochemical production of fuels and chemicals. Economically feasible large-scale implementation of the process requires operation at high solids loadings, i.e., biomass concentrations >15% (w/w). At increasing solids loadings, however, biomass forms a high viscosity slurry that becomes increasingly challenging to mix and severely mass transfer limited, which limits further addition of solids. To overcome these limitations, we developed a fed-batch process controlled by the yield stress and its changes during liquefaction of the reaction mixture. The process control relies on an in-line, non-invasive magnetic resonance imaging (MRI) rheometer to monitor real-time evolution of yield stress during liquefaction. Additionally, we demonstrate that timing of enzyme addition relative to biomass addition influences process efficiency, and the upper limit of solids loading is ultimately limited by end-product inhibition as soluble glucose and cellobiose accumulate in the liquid phase
Correlating the ability of lignocellulosic polymers to constrain water with the potential to inhibit cellulose saccharification
Expressing accessory proteins in cellulolytic Yarrowia lipolytica to improve the conversion yield of recalcitrant cellulose
Surface properties correlate to the digestibility of hydrothermally pretreated lignocellulosic Poaceae biomass feedstocks
Visualization of Miscanthus Ă giganteus cell wall deconstruction subjected to dilute acid pretreatment for enhanced enzymatic digestibility
- âŠ