Purification and Characterization of β-mannanase Produced by Bacillus cereus Isolated from Termite Guts

Abstract

Termites are highly effective at breaking down lignocellulose. This study was aimed at isolating β-mannanase producing bacteria from termite guts, and to purify, and characterize the β‑mannanase produced. The termites were isolated from Ikeji environs. Of eight isolates isolated and screened Bacillus cereus showed better potential. The enzyme was produced using saw dust as substrate in a one-factor approach method. The most promising strain, identified as Bacillus cereus (accession number MW911450.1), exhibited the highest β-mannanase activity and was selected for further investigation. Purification of the enzyme led to an increase in specific activity from 0.89 to 10.0 mg/mL and a purification fold rise from 1 to 11, accompanied by a decrease in protein content from 56.5 to 3.4 mg/mL using Sephadex G-100. Optimal enzyme activity was observed at temperatures of 25°C and 30°C, with reduced activity at higher temperatures, notably 78% at 90°C. The enzyme showed peak production at pH 4, followed by a steady decline at higher pH levels, with the lowest activity at pH 11. The enzyme retained partial activity in the presence of formaldehyde but was destabilized by solvents such as DMSO, Tween 20, acetone, Triton X, and acetic acid. Inhibitor testing revealed that compounds like urea, sodium A, EDTA, and cysteine enhanced enzyme activity, while SDS inhibited it. Metal ion analysis showed that K⁺, Na⁺, Mg²⁺, and Zn²⁺ promoted activity, with K⁺ having the strongest effect, whereas Mn²⁺ had the least. Substrate concentration had a positive linear effect on enzyme activity, peaking at 0.5 mg/mL. The enzyme’s resilience to alkaline conditions and heat makes it attractive for breaking down hydraulic‑fracturing fluids in oil drilling, pulp bio‑bleaching in papermaking, and scouring/desizing steps in textile processing.