Cellulase Production by Bacillus sp. and Pseudomonas sp. Isolated from Soil Compost Sites at Ogwa Community, Edo State, Nigeria

Abstract

This study investigates the cellulase enzyme activity of Bacillus sp. and Pseudomonas sp. isolated from soil compost, comparing their biochemical characteristics, purification parameters, and enzyme kinetics. The method used involved isolating bacteria from soil compost sites and identifying them through biochemical tests. Cellulase production was assessed using a cellulose-rich medium, and enzyme activity was measured via reducing sugar quantification. Physicochemical factors like pH and temperature were optimized to enhance cellulase yield. The species identified to be present include Bacillus sp. and Pseudomonas sp. Bacillus sp. exhibited higher cellulase activity with a zone-to-colony size ratio of 3.2 compared to Pseudomonas sp. (2.9). Morphological and biochemical characterizations confirmed Bacillus sp. as a Gram-positive rod, catalase, and oxidase positive, while Pseudomonas sp. was Gram-negative. Soil pH and temperature from three compost sites were within the optimal range for cellulase production, averaging pH 7.28 and temperatures between 24°C and 28°C. Partial purification of cellulase from Bacillus sp. showed a specific activity of 8.22 U/mg, with 76.75% yield, while Pseudomonas sp. yielded a specific activity of 6.67 U/mg and 58.49% yield. Kinetic analysis revealed Bacillus sp. had a higher substrate affinity (Km = 0.15±0.02 mM) and Vmax of 12.17±0.21 U/ml/min, compared to Pseudomonas sp. (Km = 0.22±0.04 mM; Vmax = 11.29±0.15 U/ml/min). Optimal pH for Bacillus sp. was 6.0, while Pseudomonas sp. exhibited optimum activity at pH 5.0. Temperature optima were 60°C for Bacillus sp. and 70°C for Pseudomonas sp. Heat stability tests showed that Bacillus sp. retained 80% of its activity at 50°C, while Pseudomonas sp. retained 90%. These findings suggest that Bacillus sp. may be more suited for industrial cellulase production, though both strains have valuable applications in composting and waste degradation.