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Investigation of the optimized dextran-degrading enzyme conditions on the decomposition of different molecular weights of pure dextran using response surface methodology.

Boontiwa Ninchan, Wirat Vanichsriratana, Klanarong Sriroth

The elimination of various molecular weights of contaminated dextran in sugar processing is quite complicated, especially using enzymatic decomposition. Many factors including enzyme concentration, retention time, pH, temperature, and sucrose concentration affect enzyme hydrolysis. The optimizing conditions of various molecular weights of dextran removal were investigated using response surface methodology. The optimum hydrolyzed conditions of 1,500 ?g/mL of all molecular weights of pure dextran from the one-factor-at-a-time (OFAT) experiments were: dextranase (Amano Enzyme Inc., Japan) at 5-15 ppm total soluble solids for 5-15 min at 50-65?C with pH 4.5-6.5 and sucrose concentration at 15-25%. The results from the OFAT experiments used a Box-Benhken experimental design with four factors and three levels that achieved fit models that predicted the dextran removal under different conditions of various molecular weights of pure dextran. The low molecular weight of pure dextran (LMW) makes it a less complex structure with smaller molecules and it is easily degraded; therefore, it showed the highest percentage of dextran removal under a wide range of conditions of dextran decomposition than the higher molecular forms consisting of medium molecular weight (MMW) and high molecular weight (HMW) under the same conditions as shown using contour plots. The complete hydrolysis conditions that were calculated from the predicted models all of molecular weights of pure dextran were pH 5.5 and sucrose concentration 15-15.2% with slightly different temperatures of 53.2, 52.4, and 51.5?C and dextranase concentration at 12.4, 13.1, and 14.8 ppm total soluble solids for LMW, MMW, and HMW, respectively.