Studies on mixed fungal culture for cellulase and hemi-cellulase production part-1: Optimization of medium for the mixed culture ofTrichoderma reesei D1-6 andAspergillus Pt 2804
TL;DR: For enhanced production of cellulase and xylanase by the mixed culture of T. reesei D1-6 and A. wentii Pt 2804, the composition of medium has been optimized.
Abstract: For enhanced production of cellulase and xylanase by the mixed culture ofT. reesei D1-6 andA. wentii Pt 2804, the composition of medium has been optimized.
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TL;DR: The current status of the technology for bioconversion of biomass by fungi is reviewed, with focus on mutagenesis, co-culturing and heterologous gene expression attempts to improve fungal lignocellulolytic activities to create robust fungal strains.
Abstract: The development of alternative energy technology is critically important because of the rising prices of crude oil, security issues regarding the oil supply, and environmental issues such as global warming and air pollution. Bioconversion of biomass has significant advantages over other alternative energy strategies because biomass is the most abundant and also the most renewable biomaterial on our planet. Bioconversion of lignocellulosic residues is initiated primarily by microorganisms such as fungi and bacteria which are capable of degrading lignocellulolytic materials. Fungi such as Trichoderma reesei and Aspergillus niger produce large amounts of extracellular cellulolytic enzymes, whereas bacterial and a few anaerobic fungal strains mostly produce cellulolytic enzymes in a complex called cellulosome, which is associated with the cell wall. In filamentous fungi, cellulolytic enzymes including endoglucanases, cellobiohydrolases (exoglucanases) and β-glucosidases work efficiently on cellulolytic residues in a synergistic manner. In addition to cellulolytic/hemicellulolytic activities, higher fungi such as basidiomycetes (e.g. Phanerochaete chrysosporium) have unique oxidative systems which together with ligninolytic enzymes are responsible for lignocellulose degradation. This review gives an overview of different fungal lignocellulolytic enzymatic systems including extracellular and cellulosome-associated in aerobic and anaerobic fungi, respectively. In addition, oxidative lignocellulose-degradation mechanisms of higher fungi are discussed. Moreover, this paper reviews the current status of the technology for bioconversion of biomass by fungi, with focus on mutagenesis, co-culturing and heterologous gene expression attempts to improve fungal lignocellulolytic activities to create robust fungal strains.
735 citations
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TL;DR: Many techniques are available in the fermentation medium designer’s toolbox (borrowing, component swapping, biological mimicry, one-at-a-time, statistical and mathematical techniques—experimental design and optimization), and considerable advantage can be gained by logical application of the techniques, combined with good experimental design.
Abstract: Many techniques are available in the fermentation medium designer’s toolbox (borrowing, component swapping, biological mimicry, one-at-a-time, statistical and mathematical techniques—experimental design and optimization, artificial neural networks, fuzzy logic, genetic algorithms, continuous fermentation, pulsed batch and stoichiometric analysis). Each technique has advantages and disadvantages, and situations where they are best applied. No one ‘magic bullet’ technique exists for all situations. However, considerable advantage can be gained by logical application of the techniques, combined with good experimental design.
289 citations
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TL;DR: In this review the state of the art of lignocellulose bioconversion by solid substrate fermentation (SSF) is presented and their application in novel solid state bioreactors with on-line process control is discussed.
218 citations
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TL;DR: High cellulase activity and high yields were attributed to the growth of T. reesei on a hemicellulose fraction during its first phase and then on a cellulose fraction of wheat straw during its later phase for cellulase production, as well as to the close contact of hyphae with the substrate in solid-state fermentation.
Abstract: Cellulase yields of 250 to 430 IU/g of cellulose were recorded in a new approach to solid-state fermentation of wheat straw with Trichoderma reesei QMY-1. This is an increase of ca. 72% compared with the yields (160 to 250 IU/g of cellulose) in liquid-state fermentation reported in the literature. High cellulase activity (16 to 17 IU/ml) per unit volume of enzyme broth and high yields of cellulases were attributed to the growth of T. reesei on a hemicellulose fraction during its first phase and then on a cellulose fraction of wheat straw during its later phase for cellulase production, as well as to the close contact of hyphae with the substrate in solid-state fermentation. The cellulase system obtained by the solid-state fermentation of wheat straw contained cellulases (17.2 IU/ml), β-glucosidase (21.2 IU/ml), and xylanases (540 IU/ml). This cellulase system was capable of hydrolyzing 78 to 90% of delignified wheat straw (10% concentration) in 96 h, without the addition of complementary enzymes, β-glucosidase, and xylanases.
198 citations
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TL;DR: This work investigated an approach to enhance the production of these enzymes by co-culturing Trichoderma reesei and Aspergillus niger in a bioreactor to convert cellulose substrate into soluble sugars through a synergetic action of enzyme complex simultaneously produced by these two fungi.
169 citations
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TL;DR: The initial results suggest that the selective technique for isolating hyper-cellulase-producing mutants of Trichoderma will be of considerable use in the development of commercially useful cellulolytic strains.
Abstract: The development of an agar plate screening technique has allowed the isolation of a range of mutants of Trichoderma reesei capable of synthesizing cellulase under conditions of high catabolite repression. The properties of one of these mutants (NG-14) is described to illustrate the use of this technique. NG-14 produced five times the filter paper-degrading activity per ml of culture medium and twice the specific activity per mg of excreted protein in submerged culture when compared with the best existing mutant, QM9414. NG-14 also showed enhanced endo-beta-glucanase and beta-glucosidase production. Although these mutants were isolated as cellulase producers in the presence of 5% glycerol on agar plates, in similar liquid medium, NG-14 exhibits only partial derepression of the cellulase complex. Since the proportions of filter paper activity, endo-beta-glucanase, and cellobiase were not the same in mutants NG-14 and QM9414, and the yields of each enzyme under conditions repressive for cellulase synthesis were different, differential control of each enzyme of the cellulase complex is implied. These initial results suggest that the selective technique for isolating hyper-cellulase-producing mutants of Trichoderma will be of considerable use in the development of commercially useful cellulolytic strains.
283 citations
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TL;DR: A mutant, D1-6, was isolated and found to be a distinctly superior strain compared to QM 9414 and several other progenies of this parent and the note presents the possibilities of isolating not only hyperproducing strains but also those which are catabolic repression resistant.
Abstract: A short note on a strain improvement program of Trichoderma reesei QM 9414 initiated in 1976. A mutant, D1-6, was isolated and found to be a distinctly superior strain compared to QM 9414 and several other progenies of this parent. The note presents the possibilities of isolating not only hyperproducing strains but also those which are catabolic repression resistant. In fact, D1-6 is both a hyperproducer and a catabolite repression resistant mutant. (Refs. 7).
40 citations