Isolation and characterization of thermo-stable cellulase enzyme producing bacteria from a compost production site

Abstract

Thermophilic bacteria have adapted to thrive and function in high-temperature environments and are capable of producing thermo-stable enzymes that remain active between 50 °C and 120 °C. These enzymes have significant value in various industrial and biotechnological applications. Among them, cellulase plays a crucial role in the food, paper, fermentation, and textile industries, and cellulase production accounts for approximately 12% of the global enzyme market. Therefore, this study focused on isolating and characterizing thermo-stable cellulase-producing bacteria. Samples were collected from the compost production site at the Govijanaseva Department, Kadawatha (GPS coordinates: 7.035695438637899, 79.96050932347872). Morphologically distinct bacterial colonies were isolated using standard pour plate and streak plate methods on Nutrient Agar at room temperature. The isolates were screened for cellulase production using the Carboxymethyl Cellulose (CMC) agar plate assay. Secondary screening for enzyme activity was performed using the Di-nitrosalicylic acid (DNS) assay. Additionally, the effects of temperature and pH on crude cellulase extracts from the positive isolates were evaluated. The soil sample was collected at a temperature of 61 °C. Of the ten morphologically distinct bacterial isolates, eight (GV1, GV2, GV3, GV5, GV6, GV8, GV9, and GV10) tested positive for cellulase production. Isolate GV3 exhibited the highest cellulase activity at room temperature (0.38831 U mL⁻¹). Isolate GV10 showed the highest optimum temperature for activity at 70 °C, with an enzyme activity of 0.48994 U mL⁻¹, and an optimum pH of 8. Based on these findings, isolate GV10 is identified as the most promising candidate for use in industrial processes operating at elevated temperatures. Further optimization of growth conditions and assessment of additional factors influencing enzyme activity are recommended to support its application in various industrial and biotechnological sectors.