A lytic polysaccharide monooxygenase from Myceliophthora thermophila and its synergism with cellobiohydrolases in cellulose hydrolysis.

Lytic polysaccharide monooxygenases (LPMOs) have attracted vast attention because of their unique mechanism of oxidative degradation of carbohydrate polymers and the potential application in biorefineries. This study characterized a novel LPMO from Myceliophthora thermophila, denoted MtLPMO9L. The structure model of the enzyme indicated that it belongs to the C1-oxidizing LPMO, which has neither an extra helix in the L3 loop nor extra loop region in the L2 loop. This was confirmed subsequently by the enzymatic assays since MtLPMO9L only acts on cellulose and generates C1-oxidized cello-oligosaccharides. Moreover, synergetic experiments showed that MtLPMO9L significantly improves the efficiency of cellobiohydrolase (CBH) II. In contrast, the inhibitory rather than synergetic effect was observed when combining used MtLPMO9L and CBHI. Changing the incubation time and concentration ratio of MtLPMO9L and CBHI could attenuate the inhibitory effects. This discovery suggests a different synergy detail between MtLPMO9L and two CBHs, which implies that the composition of cellulase cocktails may need reconsideration.

Characterization of a new oligoalginate lyase from marine bacterium Vibrio sp.

A new oligoalginate lyase encoding gene, designed oal17A, was cloned from marine bacterium Vibrio sp. W13, and then expressed in Escherichia coli. The recombinant Oal17A was purified by NTA-Ni resin with maximal activity at 30°C and pH7.0. Oal17A exhibited broad substrate specificity, and preferred to degrade alginate than polyM or polyG into monosaccharide acid. The specific activity of Oal17A toward alginate, polyM and polyG was 21.14U/mg, 12.31U/mg and 7.43U/mg, respectively. With features of high-level expression and broad substrate specificity, Oal17A would be a potential tool for alginate monomer production process of alginate utilizing for biofuels and bioethanol production.