Trichoderma reesei

About: Trichoderma reesei is a research topic. Over the lifetime, 3832 publications have been published within this topic receiving 152877 citations. The topic is also known as: Trichoderma reesi.

Expression of Biomass-Degrading Enzymes Is a Major Event during Conidium Development in Trichoderma reesei†

Abstract: The conidium plays a critical role in the life cycle of many filamentous fungi, being the primary means for survival under unfavorable conditions. To investigate the transcriptional changes taking place during the transition from growing hyphae to conidia in Trichoderma reesei, microarray experiments were performed. A total of 900 distinct genes were classified as differentially expressed, relative to their expression at time zero of conidiation, at least at one of the time points analyzed. The main functional categories (FunCat) overrepresented among the upregulated genes were those involving solute transport, metabolism, transcriptional regulation, secondary metabolite synthesis, lipases, proteases, and, particularly, cellulases and hemicellulases. Categories overrepresented among the downregulated genes were especially those associated with ribosomal and mitochondrial functions. The upregulation of cellulase and hemicellulase genes was dependent on the function of the positive transcriptional regulator XYR1, but XYR1 exerted no influence on conidiation itself. At least 20% of the significantly regulated genes were nonrandomly distributed within the T. reesei genome, suggesting an epigenetic component in the regulation of conidiation. The significant upregulation of cellulases and hemicellulases during this process, and thus cellulase and hemicellulase content in the spores of T. reesei, contributes to the hypothesis that the ability to hydrolyze plant biomass is a major trait of this fungus enabling it to break dormancy and reinitiate vegetative growth after a period of facing unfavorable conditions.

Purification and Characterization of Exo-β-d-Glucosaminidase from a Cellulolytic Fungus,Trichoderma reesei PC-3-7

Abstract: Cellulose, chitin, and chitosan consist of β-1,4-linked glucopyranoses, and their differences are in functional groups at the C-2 positions of their constituent sugars, i.e., the hydroxyl, acetamido, and amino groups, respectively. Chitin is one of the most abundant forms of biomass next to cellulose (9). On the other hand, chitosan, a partially or fully deacetylated form of chitin, has been found only in the cell walls of limited groups of fungi in nature (2). Chitosan has had various applications, e.g., as a carrier of immobilized enzymes and a metal-removal and cohesive reagent for purification of waste streams (27). In commercial use, chitosan is obtained by chemical deacetylation of chitin. It also has biological activities. One such activity is to elicit plant defense reactions. This defense system includes formation of fungal cell wall-degrading enzymes such as endo-β-1,3-glucanase and chitinase (19) and production of phytoalexin (10). The other biological activity of chitosan is growth inhibition of bacteria and fungi (15). Chitosanases have been found in a variety of microorganisms, including bacteria and fungi (1, 6, 12, 24, 26, 30, 31). Furthermore, plant chitosanases, which also provide defensive reactions to attacks by fungal pathogens, were recently reported (5). Most purified chitosanases have been characterized as endo-type enzymes which cleave chitosans at random, and their reaction velocities are highly dependent on the degree of acetylation (D.A.) of the chitosan. On the other hand, the purification and characterization of an exo-type chitosanase called exo-β-d-glucosaminidase, which releases glucosamine (GlcN) continuously from the nonreducing end of the substrate, have so far been reported only for an actinomycete, Nocardia orientalis (21). Biological degradation of naturally occurring chitin in a partially deacetylated form is thought to be carried out by a two-step process (26). First, endo-type enzymes such as chitinase and chitosanase hydrolyze the chitinous material to oligosaccharides consisting of N-acetylglucosamine (GlcNAc) and GlcN. Second, the resulting oligomers are degraded completely to GlcNAc and GlcN by two exo-type enzymes, exo-β-d-N-acetylglucosaminidase and exo-β-d-glucosaminidase. However, the latter enzyme has not been studied at all except for that in N. orientalis. On the other hand, the former enzyme is distributed widely from animals to microorganisms, and its enzymological properties are well-characterized. The genus Trichoderma, which belongs among deuteromycetes, is known as a high-cellulase producer. Trichoderma reesei secretes at least two cellobiohydrolases (exo type; EC 3.1.2.91), four endoglucanases (EC 3.1.2.4), and two β-glucosidases (EC 3.1.2.20). These enzymes have already been purified or their genes have been cloned (22). Trichoderma harzianum is known as a mycoparasite and secretes multiple chitin-degrading enzymes, including endochitinase (EC 3.1.2.13), exochitinase, and exo-β-d-N-acetylhexosaminidase, and some of their genes have been cloned (4, 8, 11, 25). We found that T. reesei secretes multiple chitosanolytic enzymes into a culture medium under cellulase-noninducible conditions. In this paper, we describe the identification, purification, and characterization of the exo-β-d-glucosaminidase from the hyper-cellulolytic fungus T. reesei PC-3-7. We also discuss the catalytic mechanism of exo-β-d-glucosaminidase on the basis of 1H nuclear magnetic resonance (NMR) spectroscopy of the hydrolysate. To our knowledge, this is the first report on the exo-β-d-glucosaminidase from eukaryotes.

Production of lactic acid from cellobiose and cellotriose by Lactobacillus delbrueckii mutant Uc-3.

Abstract: Cellulosic biomass represents an abundant natural renewable carbon resource for the production of valuable fuels and biomaterials for both short- and long-term sustainability. The production of value-added products from such renewable feedstock is a present need and perhaps economically and environmentally feasible process. Lactic acid is a commercially viable product, and world consumption of it is estimated to be more than 60,000 metric tons per year. Lactic acid has a wide range of applications in pharmaceutical, cosmetic, textile, and chemical industries (6, 14, 16, 17). It has the potential to become a commodity chemical as feedstock for biodegradable polymers, oxygenated chemicals, plant growth regulators, environmentally friendly solvents, and special chemical intermediates. The process for converting cellulosic material into lactic acid is yet not feasible due to the high cost of enzymes involved in cellulose hydrolysis (18, 19, 20) and also to the use of a fastidious organism (10). The process may involve either a two-step process with complete conversion to sugar, followed by fermentation to lactic acid, or a one-step process in which the saccharification of cellulose by cellulases coupled with fermentation to eliminate the inhibition caused by glucose (8, 13). During the hydrolysis of cellulosic material by cellulases, the main bottlenecks are cellulase inhibition by glucose and cellobiose (strong inhibitors of cellobiohydrolase), which remarkably slow down the rate of hydrolysis. In simultaneous saccharification and fermentation (SSF), glucose inhibition is totally removed but cellobiose inhibition remains as it is (4, 9, 15). The addition of -glucosidase at the beginning of SSF is recommended for the removal of cellobiose inhibition, but sometimes it is not feasible because of rapid deactivation of enzyme (11). In some cases, cellobiose inhibition was removed by supplementation of the medium with additional cellobiase, leading to a remarkable improvement in lactic acid production in fed-batch SSF (10). However, in simple-batch operations in SSF with cellulase from Trichoderma reesei and Lactobacillus delbrueckii, the supplementation of medium with fresh cellobiase did not improve the overall process (12). To remove these bottlenecks, it is advantageous to use a lactic acid-pro

Synergy between pretreatment lignocellulose modifications and saccharification efficiency in two brown rot fungal systems.

Abstract: Brown rot wood-degrading fungi distinctly modify lignocellulose and completely hydrolyze polysaccharides (saccharification), typically without secreting an exo-acting glucanase and without removing lignin. Although each step of this two-step approach evolved within the same organism, it is unknown if the early lignocellulose modifications are made to specifically facilitate their own abbreviated enzyme system or if enhancements are more general. Because commercial pretreatments are typically approached as an isolated step, answering this question has immense implication on bioprocessing. We pretreated spruce and pine blocks with one of two brown rot fungi, Gloeophyllum trabeum or Fomitopsis pinicola. Wood harvested at weeks 1, 2, 4, and 8 showed a progression of weight loss from time zero due to selective carbohydrate removal. Hemicellulose losses progressed faster than cellulose loss. This “pretreated” material was then saccharified with commercially relevant Trichoderma reesei cellulases or with cellulases from the brown rot fungi responsible for degrading the wood to test for synergy. With increased decay, a significant increase in saccharification efficiency was apparent but not limited to same-species enzyme sources. We also calculated total sugar yields, and calculations that compensate for sugars consumed by fungi suggest a shorter residence time for fungal colonization than calculations based solely on saccharification yields.