Cellulases from Chaetomium thermophile var. dissitum

Production of cellulase enzyme by Trichoderma reesei Cefl9 and its application in the production of bio-ethanol

The present study aimed at the production of cellulase enzyme from the cellulolytic fungi Trichoderma reesei CEF19 and subsequent application of the cellulase for the fermentation of ethanol. For the same, the cellulolytic fungi, Trichoderma reesei CEF19 was isolated and was allowed to produce cellulase enzyme using optimized conditions. The cellulase enzyme was extracted and purified with the help of ammonium sulphate precipitation, dialysis followed by ion exchange chromatography with DEAE-Sephadex column. The purified cellulase enzyme was characterized using SDS-PAGE analysis. The saccharification of the cellulosic substrates was done using the cellulase enzyme. The fermentation of saccharified cellulosic substrates into ethanol was carried out using Saccharomyces cerevisiae. From the results obtained, rice straw was found to be the better source for the ethanol production when compared to the other substrates.

Thermophilic fungi: their physiology and enzymes

Thermophilic fungi are a small assemblage in mycota that have a minimum temperature of growth at or above 20 degrees C and a maximum temperature of growth extending up to 60 to 62 degrees C. As the only representatives of eukaryotic organisms that can grow at temperatures above 45 degrees C, the thermophilic fungi are valuable experimental systems for investigations of mechanisms that allow growth at moderately high temperature yet limit their growth beyond 60 to 62 degrees C. Although widespread in terrestrial habitats, they have remained underexplored compared to thermophilic species of eubacteria and archaea. However, thermophilic fungi are potential sources of enzymes with scientific and commercial interests. This review, for the first time, compiles information on the physiology and enzymes of thermophilic fungi. Thermophilic fungi can be grown in minimal media with metabolic rates and growth yields comparable to those of mesophilic fungi. Studies of their growth kinetics, respiration, mixed-substrate utilization, nutrient uptake, and protein breakdown rate have provided some basic information not only on thermophilic fungi but also on filamentous fungi in general. Some species have the ability to grow at ambient temperatures if cultures are initiated with germinated spores or mycelial inoculum or if a nutritionally rich medium is used. Thermophilic fungi have a powerful ability to degrade polysaccharide constituents of biomass. The properties of their enzymes show differences not only among species but also among strains of the same species. Their extracellular enzymes display temperature optima for activity that are close to or above the optimum temperature for the growth of organism and, in general, are more heat stable than those of the mesophilic fungi. Some extracellular enzymes from thermophilic fungi are being produced commercially, and a few others have commercial prospects. Genes of thermophilic fungi encoding lipase, protease, xylanase, and cellulase have been cloned and overexpressed in heterologous fungi, and pure crystalline proteins have been obtained for elucidation of the mechanisms of their intrinsic thermostability and catalysis. By contrast, the thermal stability of the few intracellular enzymes that have been purified is comparable to or, in some cases, lower than that of enzymes from the mesophilic fungi. Although rigorous data are lacking, it appears that eukaryotic thermophily involves several mechanisms of stabilization of enzymes or optimization of their activity, with different mechanisms operating for different enzymes.

Purification and characterization of laccase from Chaetomium thermophilium and its role in humification

Chaetomium thermophilium was isolated from composting municipal solid waste during the thermophilic stage of the process. C. thermophilium, a cellulolytic fungus, exhibited laccase activity when it was grown at 45 degreesC both in solid media and in liquid media. Laccase activity reached a peak after 24 h in liquid shake culture. Laccase was purified by ultrafiltration, anion-exchange chromatography, and affinity chromatography. The purified enzyme was identified as a glycoprotein with a molecular mass of 77 kDa and an isoelectric point of 5.1. The laccase was stable for 1 h at 70 degreesC and had half-lives of 24 and 12 h at 40 and 50 degreesC, respectively. The enzyme was stable at pH 5 to 10, and the optimum pH for enzyme activity was 6. The purified laccase efficiently catalyzed a wide range of phenolic substrates but not tyrosine. The highest levels of affinity were the levels of affinity to syringaldazine and hydroxyquinone. The UV-visible light spectrum of the purified laccase had a peak at 604 nm (i.e., Cu type I), and the activity was strongly inhibited by Cu-chelating agents. When the hydrophobic acid fraction (the humic fraction of the water-soluble organic matter obtained from municipal solid waste compost) was added to a reaction assay mixture containing laccase and guaiacol, polymerization took place and a soluble polymer was formed. C. thermophilium laccase, which is produced during the thermophilic stage of composting, can remain active for a long period of time at high temperatures and alkaline pH values, and we suggest that this enzyme is involved in the humification process during composting.

Purification and characterization of two cellobiohydrolases from Chaetomium thermophile var. coprophile

Cellobiohydrolases I and II were purified to homogeneity from culture filtrates of a thermophilic fungus, Chaetomium thermophile var. coprophile, by using a combination of ion-exchange and gel filtration chromatographic procedures. The molecular weights of cellobiohydrolase I and II were estimated to be 60,000 and 40,000 and the enzymes were found to be glycoproteins containing 17 and 22.8% carbohydrate, respectively. The two forms differed in their amino-acid composition mainly with respect to threonine, alanine, methionine and arginine. Antibodies produced against either form of cellobiohydrolases failed to cross-react with the other. The tryptic maps of the two enzymes were found to be different. The temperature optima for cellobiohydrolase I and II were 75 and 70 degrees C, and they were optimally active at pH 5.8 and 6.4, respectively. Both enzymes were stable at higher temperatures and were able to degrade crystalline cellulosic materials.

[Description of 23 cellulolytic or non-cellulolytic clostridia isolated from a marine milieu]

Twenty-three obligately anaerobic mesophilic bacteria were isolated from marine environments. The isolates were rod-shaped, spore-forming bacteria and were placed in the genus Clostridium. They could be divided into three groups: 9 non-cellulolytic strains which used cellobiose as sole energy and carbon source; 6 pseudo-cellulolytic strains which fermented carboxymethyl-cellulose but degraded cellulose very slowly, and 8 cellulolytic bacteria. The morphological, physiological and biochemical characteristics indicated that, except for one strain which could be identified with C. aminovalerium and three strains which resembled C. sphenoides, these marine clostridia did not correspond to any previously described species.

Affinity chromatography of endoglucanase of Trichoderma viride by concanavalin A-agarose

Endoglucanase (C kappa cellulase) and cellobiase are often cross-contaminated in separation procedures by ion-exchange chromatography such as DEAE-cellulose. By using concanavalian A (Con A)-agarose chromatography, C kappa cellulase and cellobiase from Trichoderma virde can be separated. C kappa cellulase showed affinity toward Con A. indicating a glycoprotein containing alpha-D-mannopyransyl and alpha-D-glucopyranosyl end groups or internal 2-O-D-mannopyranosyl residues in sugar moieties. This method provides a way to estimate the quantities of C kappa enzyme produced by T. viride and possibly by other organisms.