Journal of Microbiology

Research Support, Non-U.S. Gov'ts

Degradation of Crystalline Cellulose by the Brown-rot Basidiomycete Fomitopsis palustris: Jeong-Jun Yoon , Young-Kyoon Kim; J. Microbiol. 2005;43(6):487-492.; DOI: https://doi.org/2301 [pii]

Abstract: This study demonstrated that the brown rot basidiomycete Fomitopsis palustris was able to degrade crystalline cellulose (Avicel). This fungus could also produce the three major cellulases (exoglucanases, endoglucanases, and -glucosidase) when the cells were grown on 2.0% Avicel. Avicel degraded by F. palustris showed a decrease in relative crystallinity from 83% to 78.5% after 14 days of incubation. The characterization study indicated that optimum pH was 4.5 and optimum temperature was 70oC for exoglucanase (cellobiohydrolase) activity. Hydrolysis of Avicel by the crude enzyme from F. palustris yielded 1.6 mg/ml of glucose after 43 h, which corresponded to a cellulose conversion degree of 3.2%. Therefore, this study revealed for the first time that the brown rot basidiomycete F. palustris produces cellulases capable of yielding soluble sugars from crystalline cellulose.

Purification and Characterization of Thermostable β-Glucosidase from the Brown-Rot Basidiomycete Fomitopsis palustris Grown on Microcrystalline Cellulose: Jeong-Jun Yoon , Ki-Yeon Kim , Chang-Jun Cha; J. Microbiol. 2008;46(1):51-55.; DOI: https://doi.org/10.1007/s12275-007-0230-4

Abstract: An extracellular β-glucosidase was purified 154-fold to electrophoretic homogeneity from the brown-rot basidiomycete Fomitopsis palustris grown on 2.0% microcrystalline cellulose. SDS-polyacrylamide gel electrophoresis gel gave a single protein band and the molecular mass of purified enzyme was estimated to be approximately 138 kDa. The amino acid sequences of the proteolytic fragments determined by nano-LC- MS/MS suggested that the protein has high homology with fungal β-glucosidases that belong to glycosyl hydrolase family 3. The Kms for p-nitorophenyl-β-D-glucoside (p-NPG) and cellobiose hydrolyses were 0.117 and 4.81 mM, and the Kcat values were 721 and 101.8 per sec, respectively. The enzyme was competitively inhibited by both glucose (Ki= 0.35 mM) and gluconolactone (Ki= 0.008 mM), when p-NPG was used as substrate. The optimal activity of the purified β-glucosidase was observed at pH 4.5 and 70°C. The F. palustris protein exhibited half-lives of 97 h at 55°C and 15 h at 65°C, indicating some degree of thermostability. The enzyme has high activity against p-NPG and cellobiose but has very little or no activity against p-nitrophenyl-β-lactoside, p-nitrophenyl-β-xyloside, p-nitrophenyl-α-arabinofuranoside, xylan, and carboxymethyl cellulose. Thus, our results revealed that the β-glucosidase from F. palustris can be classified as an aryl-β-glucosidase with cellobiase activity.

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