Isolation and characterization of endoglucanase produced by microbes residing in the gut of coptotermes curvignathus holmgren termite

This research was carried out to isolate and identify endoglucanase producing microbes from the digestive system of wood termite Coptotermes curvignathus Holmgren as well as to characterize endoglucanase produced by these microbes based on their optimum pH, temperature, and enzymatic activity. Five endoglucanases producing bacteria were isolated, four were molecularly identified as aerobic Bacillus spp. and the other one was an unknown anaerobic bacterium. Based on Sodium Dodecyl Sulfate- Polyacrylamide Gel Electrophoresis (SDS-PAGE) analysis, endoglucanases produced by these isolates were similar in molecular size, at 11 kDa. These endoglucanases were relatively smaller than the endoglucanases that is produced in Reticulitermes speratus salivary glands, which were reported at 41 kDa and 42 kDa. Reticulitermes speratus is phylogenetically close to Coptotermes curvignathus Holmgren, and both feed on wood. Identities of the endoglucanase producing bacteria were further confirmed using BIOLOG phenotypic analysis. Isolates TG117 was identified as Bacillus thuringiensis, NA45/1 as B. cereus, TG111 as B. pseudomycoides, and TG005 as B. mycoides. Among the five endoglucanases tested, endoglucanase produced by B. cereus NA45/1 showed the highest enzymatic activity, 0.40 UmL-1 at pH9 and 45°C. Endoglucanase B. cereus NA45/1 also had significantly higher enzymatic activity when compared to the commercial cellulase from Aspergillus niger (C1184 Sigma). Endoglucanase B. pseudomycoides TG111 performed optimally at alkaline condition pH9 and 70°C with enzymatic activity at 0.23 UmL-1. Endoglucanase B. thuringiensis TG117 had the highest enzymatic activity at 0.21 UmL-1 when acted in an acidic condition, pH5 and at temperature, 40°C. Both isolates B. mycoides TG005 and unknown anaerobic ST1 has their maximum enzymatic activity at pH6 and temperature at 55°C. This study showed that C. curvignathus Holmgren had a wide range of endoglucanases, where optimum temperature and pH for maximum enzymatic activities varies widely. With this array of endoglucanases, C. curvignathus Holmgren that feed mainly on living plant-based diet would be able break down cellulose into oligomers and reducing sugars that will subsequently be broken down to fermentable glucoses to sustain life.

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