Biochemical characterization of an isolated 50 kDa beta-glucosidase from the thermophilic fungus Myceliophthora thermophila M.7.7

Author(s)

Bonfa, Emily Colferai ^[1] ; de Souza Moretti, Marcia Maria ^[1] ; Gomes, Eleni ^[1] ; Bonilla-Rodriguez, Gustavo Orlando ^[1]

Affiliation

^[1] Sao Paulo State Univ Unesp, Inst Biosci Humanities & Exact Sci Ibilce, Sao Jose do Rio Preto Campus, Sao Jose Do Rio Preto, SP - Brazil

• Document type: Journal article
• Source: BIOCATALYSIS AND AGRICULTURAL BIOTECHNOLOGY; v. 13, p. 311-318, JAN 2018.
• Web of Science Citations: 3

Abstract

This study characterized a 50 kDa beta-glucosidase (BGL50) produced by the thermophilic fungus Myceliophthora thermophila M.7.7 in solid state cultivation using a mixture of (1:1) sugarcane bagasse and wheat bran. The crude extract zymogram showed two isoforms of beta-glucosidase with approximately 50 and 200 kDa, which were separated by gel filtration chromatography. The characterization of BGL50 showed optimum activity at 60 degrees C and pH 5.0 when 4-nitrophenyl beta-D-glucopyranoside (pNPG) was used as the substrate, whereas when using cellobiose, the highest activity was observed at 50 degrees C and pH 4.5. Several ions and reagents produced different effects on the enzyme activity depending on the substrate and there was complete inhibition with Cu2+ and Fe3+ for both substrates. In addition, nine phenolic compounds showed no inhibitory effects on the enzyme, a significant feature since beta-glucosidase is used for the saccharification of lignocellulosic biomass that generates several phenolic compounds. Kinetic studies revealed competitive inhibition by glucose when pNPG was used, with a K-i value of 1.5 mM and a significantly lower K-m (0.52 mM) than for cellobiose (8.50 mM). The thermodynamic parameters showed that BGL50 is very stable at 60 degrees C displaying a half-life of 855.6 min but it is easily denatured above this temperature. The results emphasize the importance of investigating potential beta-glucosidases based on cellobiose instead of using only pNPG since, in the industrial process, the enzyme will act on this natural substrate. In addition, understanding the thermostability of the enzyme is an important contribution to enzyme technology. (AU)

• FAPESP's process: 10/12624-0 - Application of physical-chemical and enzymatic methods in the saccharification of sugar cane bagasse: studies on microorganisms, fermentative processes and hydrolyses methods
• Grantee: Eleni Gomes
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 11/23991-7 - Functional and structural analysis of microbial and plant hydrolases with potential use in biotechnological or industrial processes
• Grantee: Gustavo Orlando Bonilla Rodriguez
• Support Opportunities: Regular Research Grants