A Novel Exo-Glucanase Explored from a Meyerozyma sp. Fungal Strain

Isolating cellulase-secreting microbes followed-by screening their cellulolytic activities has been an essential approach to discover novel and potential cellulases for cellulolytic industrial applications. This study was aimed to explore competitive exoglucanases by screening avicelase activities for 92 fungal strains isolated from environmental airborne-fungal-spore samples. Results showed that an isolated fungal strain numbered 58 exhibited the best avicelase activity of 0.209 U/mL when cultured for six days at pH 5.0 - 5.3 and 25℃ - 27℃, and was lately identified as a yeast strain of Meyerozyma sp. (96% ITS fragment similar with Meyerozyma caribbica, HG970748). Based on amino acid sequences revealed from LC/MS/MS, the target exoglucanase was identical to 1,4-beta-D-glucan cellobiohydrolases and was named Mc-CBHI which had optimal avicelase reaction conditions of pH 5 and 70℃ and could remain fairly stable after 4hr incubation at acid conditions (pH 3 - 5) or wide temperature ranges (30℃ - 80℃). Additionally, the Mc-CBHI (~70 kDa and ~3.6% of crude enzyme) had specific FPase and avicelase activities of 0.179 U/mg and 0.126 U/mg, respectively (which were about 40% - 50% activities of a commercial cellulase Accellerase-1000). These results demonstrated that the newly-found Mc-CBHI could become one of potential exoglucanase resources for related cellulolytic industrial applications.