Characterisation of mannanase from Pontibacillus sp. CL43

Abstract

Lignocellulosic biomass is a renewable feedstock for biofuel production. Pretreatment is performed to destroy the biomass recalcitrant structure subsequently allow enzymes to hydrolyse cellulose and hemicellulose for sugars production. These sugars could be used for biofuel production. In chemical pretreatment of lignocellulosic biomass, metal salts (KCl, CaCl2 and MgCl2) and surfactants (Tween 20, Tween 80 and Triton X-100) are used. These compounds retain in the biomass after the treatment and affect the performance of enzymes in following hydrolysis process. Hence, enzymes with metal- and surfactant-tolerance characteristics are preferable in biofuel production. This project focused on characterising Pontibacillus sp. CL43 and its mannanase which is responsible for degradation of mannan, a component present in lignocellulosic biomass. Strain CL43 is a Gram positive bacterium with rod-shaped, endospore-forming, catalase- and oxidase-positive. Strain CL43 could hydrolyse bile esculin, casein, starch, xylan, Tween 20, Tween 40, Tween 60 and Tween 80. Strain CL43 was susceptible to ampicillin, carbenicillin, doxycycline, gentamicin, minocycline, neomycin, oxacillin, penicillin G, piperacillin, polymyxin B, rifampicin, streptomycin and tetracycline. Mannanase of strain CL43 exhibited optimal activity at 60 °C, pH 7 and 2% (w/v) NaCl. Mannanase activity was found to be stable in the presence of metal ions (Ca2+, Cd2+, Mn2+, K+, Mg2+ and Co2+ with relative activity ranged from 87-128%) and surfactants (Tween 20, Tween 40, Tween 60, Tween 80 and Triton X-100 with relative activity ranged from 88-107%). Mannanase of strain CL43 with good tolerance to these metal ions and surfactants indicated it is a good candidate to be used for lignocellulosic biomass hydrolysis.