Jun-Liang Liu

Predominance of Trichoderma and Penicillium in cellulolytic aerobic filamentous fungi from subtropical and tropical forests in China, and their use in finding highly efficient β-glucosidase.

BackgroundCellulose is the most abundant biomass on earth. The major players in cellulose degradation in nature are cellulases produced by microorganisms. Aerobic filamentous fungi are the main sources of commercial cellulase. Trichoderma reesei has been explored extensively for cellulase production; however, its major limitations are its low β-glucosidase activity and inefficiency in biomass degradation. The aim of this work was to isolate new fungal strains from subtropical and tropical forests in China, which produce high levels of cellulase in order to facilitate development of improved commercial cellulases.ResultsWe isolated 305 fungal strains from 330 samples collected from subtropical and tropical virgin forests in China. Of these, 31 strains were found to have Avicelase activity of more than 0.2 U/ml in liquid batch cultivation. Molecular analyses of the 31 strains based on internal transcribed spacer sequences revealed that 18 were Trichoderma and 13 were Penicillium species. The best-performing isolate was Trichoderma koningiopsis FCD3-1, which had similar Avicelase activity to T. reesei Rut-C30. Most interestingly, strain FCD3-1 exhibited extracellular β-glucosidase activity of 1.18 U/ml, which was approximately 17 times higher than that of Rut-C30. One β-glucosidase secreted by FCD3-1 was purified, and its gene was cloned and identified. The β-glucosidase belonged to glycosyl hydrolase (GH) family 3, sharing the highest identity of 94% with a GH family 3 protein from Trichoderma atroviride IMI 206040, and was designated TkBgl3A. The optimal pH and temperature of TkBgl3A were 4.5 and 65°C, respectively. The enzyme retained over 90% activity for 360 hours at pH 4.0 and 30°C, which are the usual conditions used for simultaneous saccharification and fermentation (SSF) of cellulose to ethanol. The enzyme showed significantly higher specific activity toward natural substrate cellobiose (141.4 U/mg) than toward artificial substrate p-nitrophenyl-beta-D-glucopyranoside (108.0 U/mg).ConclusionsStrains of Trichoderma and Penicillium were the predominant cellulolytic fungi in subtropical and tropical forests in China. T. koningiopsis FCD3-1 was the most efficient producer of cellulase, and also produced a high level of β-glucosidase. The high specific activity toward cellobiose and stability under SSF conditions of the purified β-glucosidase from FCD3-1 indicates its potential application in SSF of cellulose to bioethanol.

Novel Carbohydrate-Binding Module Identified in a Ruminal Metagenomic Endoglucanase

ABSTRACT Endoglucanase C5614-1 comprises a catalytic module (CM) and an X module (XM). The XM showed no significant homology with known carbohydrate-binding modules (CBMs). Recombinant full-length endoglucanase could bind Avicel, whereas the CM could not. The XM could bind various polysaccharides. The results demonstrated that the XM was a new CBM.

A biotechnological process efficiently co-produces two high value-added products, glucose and xylooligosaccharides, from sugarcane bagasse

In this study, a co-production of two high value-added products, glucose and xylooligosaccharides (XOS), was investigated by utilizing sugarcane bagasse (SB) within a multi-product bio-refinery framework optimized by Box-Behnken design-based response surface methodology. The developed process resulted in a maximum cellulose conversion of xylan-removed SB, 98.69±1.30%, and a maximum extracted SB xylan conversion into XOS (xylobiose and xylotriose) of 57.36±0.79% that was the highest SB xylan conversion reported in the literature, employing cellulase from Penicillium oxalicum EU2106 and recombinant endo-β-1,4-xylanase in Pichia pastoris. Consequently, a mass balance analysis showed that the maximum yields of glucose and XOS were 34.43±0.32g and 5.96±0.09 g per 100 g raw SB. Overall, this described process may be a preferred option for the comprehensive utilization of SB.

Genome sequencing and analysis of Talaromyces pinophilus provide insights into biotechnological applications

Species from the genus Talaromyces produce useful biomass-degrading enzymes and secondary metabolites. However, these enzymes and secondary metabolites are still poorly understood and have not been explored in depth because of a lack of comprehensive genetic information. Here, we report a 36.51-megabase genome assembly of Talaromyces pinophilus strain 1–95, with coverage of nine scaffolds of eight chromosomes with telomeric repeats at their ends and circular mitochondrial DNA. In total, 13,472 protein-coding genes were predicted. Of these, 803 were annotated to encode enzymes that act on carbohydrates, including 39 cellulose-degrading and 24 starch-degrading enzymes. In addition, 68 secondary metabolism gene clusters were identified, mainly including T1 polyketide synthase genes and nonribosomal peptide synthase genes. Comparative genomic analyses revealed that T. pinophilus 1–95 harbors more biomass-degrading enzymes and secondary metabolites than other related filamentous fungi. The prediction of the T. pinophilus 1–95 secretome indicated that approximately 50% of the biomass-degrading enzymes are secreted into the extracellular environment. These results expanded our genetic knowledge of the biomass-degrading enzyme system of T. pinophilus and its biosynthesis of secondary metabolites, facilitating the cultivation of T. pinophilus for high production of useful products.