초록
<P><B>Abstract</B></P> <P>Levan, a unique homopolysaccharide consisting of fructose residues linked by β-(2, 6) bonds, possess promising physiochemical and physiological properties with numerous potential applications. In this study, a novel levan-producing levansucrase was characterized from <I>Brenneria goodwinii</I>. The polysaccharide produced by the recombinant enzyme from sucrose was structurally determined to be levan-type fructan connected by β-(2, 6) linkages. The optimum pH was measured to be pH 6.0 for both sucrose hydrolysis and transfructosylation. The optimum temperature was 35, 45, and 40°C for transfructosylation, sucrose hydrolysis, and total activity, respectively. Higher sucrose concentration greatly favored to levan biosynthesis. The purified recombinant enzyme produced 185g/L levan from 50% (w/v) sucrose at pH 6.0 and 35°C for 12h. The molecular weight of the produced levan polysaccharide reached 1.3×10<SUP>8</SUP> Da, which was much higher than the ones produced by many reported levansucrases.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A novel levansucrase was characterized from <I>B. goodwinii.</I> </LI> <LI> The polysaccharide biosynthesized from sucrose was determined to be levan. </LI> <LI> The enzyme displayed maximal transfructosylation activity at pH 6.0 and 35°C. </LI> <LI> The enzyme produced 185g/L levan from 50% (w/v) sucrose. </LI> <LI> The molecular weight of the produced levan reached 1.3×10<SUP>8</SUP> Da. </LI> </UL> </P>