Cellulolytic potential of thermophilic species from four fungal orders

Abstract

Elucidation of fungal biomass degradation is important for understanding the turnover of biological materials in nature and has important implications for industrial biomass conversion. In recent years there has been an increasing interest in elucidating the biological role of thermophilic fungi and in characterization of their industrially useful enzymes. In the present study we investigated the cellulolytic potential of 16 thermophilic fungi from the three ascomycete orders Sordariales, Eurotiales and Onygenales and from the zygomycete order Mucorales thus covering all fungal orders that include thermophiles. Thermophilic fungi are the only described eukaryotes that can grow at temperatures above 45°C. All 16 fungi were able to grow on crystalline cellulose but their secreted enzymes showed widely different cellulolytic activities, pH optima and thermostabilities. Interestingly, in contrast to previous reports, we found that some fungi such as Melanocarpus albomyces readily grew on crystalline cellulose and produced cellulases. These results indicate that there are large differences in the cellulolytic potential of different isolates of the same species. Furthermore, all the selected species were able to degrade cellulose but the differences in cellulolytic potential and thermostability of the secretome did not correlate to the taxonomic position. PCR amplification and sequencing of 22 cellulase genes from the fungi showed that the level of thermostability of the cellulose-degrading activity could not be inferred from the phylogenetic relationship of the cellulases.

Optimization and Characterization of Thermostable Endo and Exocellulases by <i>Humicola sp</i>. SKESMBKU03

“…Though cellulase activity decreased at elevated temperatures still substantial activity was maintained. Thermostability profile of cellulase showed that enzyme was thoroughly stable at 50-60°C for 1hr.The results are in consensus with findings of Busk and Lange, (2013) who reported that with increase in temperature there is a decrease in the stability of cellulase activity by Talaromyces leycettanus.…”

Microbial xylanases and their industrial application in pulp and paper biobleaching: a review

“…Induction can also be achieved by various synthetic alkyl, aryl β- d xylosides and methyl β- d -xyloside (Thomas et al 2013). The paper of poor quality is a superb source of carbon and inducer for xylanase in Thermoascus aurantiacus (Busk and Lange 2013). These compounds enable the production of xylanolytic enzymes in the absence of xylan and xylooligosaccharides.…”

Extremophiles: An Overview of Microorganism from Extreme Environment

“…hot springs, deep sea) of the earth. The organisms with the highest growth temperatures (103-110 0 C) are members of the genera Pyrobaculum, Pyrodictium, Pyrococcus and Melanopyrus belonging to archea, within fungi the Ascomycete and Zygomycete family have high growth temperature (Busk and Lange, 2013) while in case of bacteria, Thermotoga maritime and Aquifex pyrophilus exhibit the highest growth temperatures of 90 and 95 0 C respectively (Haki and Rakshit, 2003;Kumar et al, 2011). These properties imply extremely important implications because enzymes that have been isolated from such microorganisms show unique features are extremely thermostable and usually resistant against some chemical denaturants.…”