In vitro assessment of two novel Cellulases from Trabulsiella odontotermitis for agricultural waste utilization

Abstract

Background The production of agricultural wastes still growing as a consequence of the population growing. However, the majority of these residues are under-utilized due their chemical composition, which is mainly composed by cellulose. Actually, the search of cellulases with high efficiency to degrade this carbohydrate remains as the challenge. In the present experiment, two genes encoding an endoglucanase (EC 3.2.1.4) and β-glucosidase (EC 3.2.1.21) were overexpressed in Escherichia coli and their recombinant enzymes (egl-FZYE and cel-FZYE, respectively) characterized. Those genes were found in Trabulsiella odontermitis which was isolated from the gut of termite Heterotermes sp. Additionally, the capability to release sugars from agricultural wastes was evaluated in both enzymes, alone and in combination. Results The results have shown that optimal pH was 6.0 and 6.5, reaching an activity of 1051.65 ± 47.78 and 607.80 ± 10.19 U/mg at 39 °C, for egl-FZYE and cel-FZYE, respectively. The Km and Vmax for egl-FZYE using CMC as substrate were 11.25 mg/mL and 3921.57 U/mg, respectively, whereas using Avicel were 15.39 mg/mL and 2314.81 U/mg, respectively. The Km and Vmax for cel-FZYE using Avicel as substrate were 11.49 mg/mL and 2105.26 U/mg, respectively, whereas using CMC the enzyme did not had activity. Both enzymes had effect on agricultural wastes, and their effect was improved when they were combined reaching an activity of 955.1 ± 116.1, 4016.8 ± 332 and 1124.2 ± 241 U/mg on corn stover, sorghum stover and pine sawdust, respectively. Conclusions Both enzymes were capable of degrading agricultural wastes, and their effectiveness was improved up to 60% of glucose released when combined. In summary, the results of the study demonstrate that the recombinant enzymes exhibit characteristics that indicate their value as potential feed additives and that the enzymes could be used to enhance the degradation of cellulose in the poor-quality forage generally used in ruminant feedstuffs.

Host-Specific Diversity of Culturable Bacteria in the Gut Systems of Fungus-Growing Termites and Their Potential Functions towards Lignocellulose Bioconversion

“…Among them, T. odontotermitis is specific to termites only. Recently, two cellulase-encoding genes (egl-FZYE and cel-FZYE) that represent endoglucanase and β-glucosidase, respectively, have been cloned from the gut bacterium T. odontotermitis [79]. The expressed enzymes have been reported to effectively degrade agricultural wastes such as corn stover, pine sawdust, and sorghum stover [79]; this agrees with our observations.…”

“…Recently, two cellulase-encoding genes (egl-FZYE and cel-FZYE) that represent endoglucanase and β-glucosidase, respectively, have been cloned from the gut bacterium T. odontotermitis [79]. The expressed enzymes have been reported to effectively degrade agricultural wastes such as corn stover, pine sawdust, and sorghum stover [79]; this agrees with our observations. The cellulose-degrading Chryseobacterium species have been isolated from the gut system of cockroaches and termites [80].…”