Presence of cellulolytic and xylanolytic activities in the gut fluid of grasshopper Oxya velox

Abstract

Insect guts, particularly of phytophagous insects, are considered as intriguing bioprospecting sources of cellulase and xylanase due to their use in biofuel industry. In this study, the activities of cellulase and xylanase were identified in the gut fluid of grasshopper, Oxya velox, and characterized. Qualitative assays of gut fluid carried out for endo-β-1,4-D-glucanase (EC 3.2.1.4) and endo-β-1,4-D-xylanase (EC 3.2.1.8) activities, using substrate-agar plate method, revealed clear transparent zones against the red-stained background. When measured by dinitrosalicylic acid method, the gut fluid had 0.759 ± 0.005 U and 0.303 ± 0.002 U of endoglucanase and endoxylanase activities, respectively, per mg of protein. In the gel zymogram, four distinct cellulolytic protein bands and one xylanolytic protein band were detected against substrates carboxymethyl cellulose and xylan, respectively. The optimal temperature and pH of both endo-β-1,4-D-glucanase and endo-β-1,4-D-xylanase were 55EC and 5, respectively. Preincubation at 70EC for 20 min resulted in almost complete loss of endo-β-1,4-D-glucanase activity as shown by zymography. The presence of both cellulase and xylanase activities suggested that O. velox could be considered as a model for studying the process of lignocellulose digestion in insect gut; the insect could also serve as a good source of enzymes for biofuel production.

Keywords

• oxya velox
• cellulase
• xylanase
• gut fluid
• biofuel