Screening, Characterization And Application Of Dextranase From Isolated Strains

Dextranase (α-1,6-D-glucan-6-glucanohydrolase; E.C.3.2.1.11) is a glucoside hydrolase that catalyzes the endohydrolysis of the predominant α-1,6 glycosidic bonds of dextran. The enzyme is extensively used in medical industries. In addition to preparing dextran and its derivative, dextranase plays a crucial role in the prevention and treatment of dental caries.In this study, novel strains produced dextranse were screened from soil samples. The active strain was then identified as Talaromyces pinophilus by the methods of morphology and internal transcribed spacer ribosomal DNA (ITS rDNA) analysis. The fermentation conditions suitable for enzyme production optimized preliminarily were as follows:4.5% dextran T7,3% KNO3, initial pH value 3.0,2% inoculum size, speed of shake flask with 50 mL liquid in a 250 mL flask was 180 r/min, culture temperature 33℃, and incubation time was 5 d. Next, the enzyme was purified by ammonium sulfate fractionation and Sepharose 6B chromatography and its enzymatic properties were studied. The enzyme was approximately 58 kDa with an optimum temperature of 45℃ and pH of 6.0. Identified as an endodextranase, the enzyme with substrate specificity hydrolyzed dextran T70 into isomaltose and isomaltotriose. Dextranase activity was increased by SDS and Urea, and strongly inhibited by Zn2+, Cu2+ and Tris.Finally, the catalytic applications of the enzyme were explored preliminarily. The dextranase was used to degrade polymers to controllable molecular weights with a yield of 82.60%. The enzyme and Penicillium aculeatum dextranase have inhibition and degradation to Streptococcus mutans biofilm and no microbial toxicity. The results laid the foundation of controllable molecular weights dextrans production process and the control efficacy against dental caries and safety of the enzyme and P. aculeatum dextranase were preliminary studied.