Purification and functional characteristics of an endocellulase from Chaetomium thermophile var. coprophile

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.

Two endoxylanases active and stable at alkaline pH from the newly isolated thermophilic fungus, Myceliophthora sp. IMI 387099

Two extra-cellular endoxylanases (Xyl Ia and Ib) were purified to homogeneity from the newly isolated thermophilic fungus, Myceliophthora sp. IMI 387099. Xyl Ia and Ib, having a molecular mass of approximately 53 kDa and pI of 5.2 and 4.8, respectively, were optimally active at 75 degrees C and at pH 6.0. They were stable at pH 9.2 at 60 degrees C for 2 h, but less stable at pH 6.0 and above 50 degrees C. Mg+2, Zn+2, Ca+2, Co+2 and DTT increased their activity by 1.5-3.0-folds, while SDS and NBS completely inhibited their activity. Both xylanases were active on pNPX and pNPC, but their activity on pNPC was three times higher than that on pNPX. Xyl Ia was more active than Xyl Ib on pNP-alpha-L-Arap, while the latter preferred pNP-alpha-L-Araf. Both xylanases showed two to four times higher activity on rye and wheat arabinoxylans than on birchwood xylan, but Xyl Ib was more active than Xyl Ia on oat spelt xylan. Wheat insoluble pentosan was a good substrate for Xyl Ia, while Xyl Ib preferred wheat soluble arabinoxylan. Xyl Ia had lower Km and higher kcat/Km ratios than Xyl Ib towards all three xylans tested. Both xylanases degraded X4-X6 in an endo-fashion and catalysed hydrolysis and trans-xylosylation reactions. HPLC and LC/MS analysis showed that Xyl Ia and Ib released the unsubstituted X2-X6 as well as mono and di-methyl glucuronic acid substituted X3 and X2 from arabinoxylans.

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.