A Novel Exo-Glucanase Explored from a <i>Meyerozyma</i> sp. Fungal Strain

Abstract

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˚C -27˚C, 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˚C and could remain fairly stable after 4-hr incubation at acid conditions (pH 3 -5) or wide temperature ranges (30˚C -80˚C). 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.

Newly Isolated Penicillium sp. for Cellulolytic Enzyme Production in Soybean Hull Residue

“…Statistical analysis allowed contour curves construction (Fig. 3), confirming temperature and pH optimization for both enzymes activity, which were similar to the conditions optimized by other researchers using different microorganisms [19,23,27]. In relation to stability at different pH values, xylanase and avicelase showed higher stability between 4.5 and 5.5, that is, about 50% activity reduction after 108 and 144 h, respectively (Fig.…”

“…Storage at -20°C showed a significant difference from that under refrigeration (4°C) for xylanase, but not for avicelase. Most studies found in the literature only evaluated avicelase stability at high temperatures, which presents lower stability [27,[29][30][31] than that obtained in the present study. Half-life (t1/2), kinetic thermal denaturation constant (Kd), and D-value for different enzymes are shown in Table 4.…”

“…Vol.63: e20170710, 2020 www.scielo.br/babt coauthors [26] reported a 3.6 U/g activity for avicelase obtained from Myceliophthora thermophila JCP 1-4 fungus, from 55 to 70°C. Kuo et al, [27] obtained 0.2 U/mL with improved avicelase activity from the isolated Meyerozyma caribica cultivated at 25-27°C, for 6 days.…”

A snapshot of microbial diversity and function in an undisturbed sugarcane bagasse pile

“…For example, the Meyerozyma, which was cultured five times showed none of the four enzyme activities. However, an isolate from this species was previously shown to have exoglucanase activity, which we did not test for here [76]. In the targeted approach however, the yeast isolates mostly expressed one or two enzymes.…”

“…In the selective culturing some isolates of the same species were cultured under more than one condition (Additional file 1). For example, strains most similar to Thielavia terrestris (RP40, 41,43,44,45,54,76,77,78,80,81,83) were cultured at 50°C, on CMC, xylan and guaiacol. While most of the partial 16S or ITS sequences of the cultured strains were 99-100% identical to a sequence of a known species in the databases, some showed slightly less similarity (Additional file 1).…”