Characterization of a bi-functional cellulase produced by a gut bacterial resident of Rosaceae branch borer beetle, Osphranteria coerulescens (Coleoptera: Cerambycidae)

- A novel cellulolytic Bacillus sp. was obtained from the digestive tract of a wood boring insect, Osphranteria coerulescens.
- Unlike most alkaliphilc cellulase from Bacillus spp. the novel enzyme represented the optimum activity at pH 5.
- It has broad temperature and pH stability and retained more than 70% of its activity between 20-70 °C and about 60% of its activity between pH 5.0-10.
- Screening of cellulase activity using gram's iodine and Congo red indicators demonstrated different results.

A cellulolytic bacterium was obtained from the digestive tract of Osphranteria coerulescens. The breakdown of woody and cellulosic substances by this insect may be relative in part to its symbiont bacteria. Under optimal cultural conditions the novel isolate produced 5.35 U/ml cellulase after 72 h. The enzyme was purified to 36 fold with a 0.59% yield and showed a specific activity of 9.0 U/mg. It presented its maximum activity at 60 °C and pH 5, while it was stable in a wide range of temperature from 20 to 60 °C and pH from 5 to 10. The purified enzyme had a molecular weight of 42.50 kDa based on SDS-PAGE and zymogram analyses. It demonstrated high ions and solvent stability and its activity was stimulated by Mn2+, Na+, DMSO and chloroform. The enzyme could hydrolyze CMC, avicel, cellulose and sawdust. TLC analysis represented the cellobiose as the hydrolytic product of CMC. With regard to endo/exo glucanase activity and wide pH, temperature and solvent stability, it has potential for industrial application.