Abstract
Enhancement of pullulanase production by Raoultella planticola DSMZ 4617 using optimized medium formulation was investigated in batch fermentation using 500-mL shake flask. The fermentations were carried out, firstly, to search for a suitable cultivation medium for enzyme production and followed by the evaluations on the influence of carbon and nitrogen sources and also initial culture pHs on the secretion of pullulanase by this bacterium. The modified mineral Czapek medium was found suitable to produce substantially high activity of pullulanase (320 times higher) as compared to ‘Ohba-Ueda’ medium. This bacterium was found superior in pullulanase production using sago starch and peptone as carbon and nitrogen sources, respectively. Using the optimized medium, the bacterium produced 0.95 U/mL of pullulanase at initial culture pH of 7 and incubation temperature of 30oC.
Highlights
Pullulanase (EC 3.2.1.41) is a direct debranching enzyme that catalyzes the hydrolysis of -1,6-glucosidic bonds of unmodified substrate, for example, amylopectin and/or glycogen and related polymers
Pullulanase production by R. planticola DSMZ 4617 in modified mineral Czapek medium (0.32 U/mL) was about 320 times higher than that obtained in fermentation using ‘Ohba-Ueda’ medium (0.001 U/mL)
This study clearly demonstrated that R. planticola DSMZ 4617 was a suitable microorganism for the production of pullulanase by using gelatinized sago starch as a carbon source
Summary
Pullulanase (EC 3.2.1.41) is a direct debranching enzyme that catalyzes the hydrolysis of -1,6-glucosidic bonds of unmodified substrate, for example, amylopectin and/or glycogen and related polymers. The main function of pullulanase was to improve the efficiency of starch saccharification process. It is because pullulanase would hydrolyze the branch points in the amylopectin residues whereas the glucoamylase has only to hydrolyze the linear 1,4--glucosidic linkages when pullulanase and glucoamylase are simultaneously used during saccharification process. The practical advantage of using pullulanase together with glucoamylase is that less glucoamylase activity would be used. This will allow a reduction in the use of glucoamylase up to 60% and less enzyme catalyzed polymerization of D-glucose to isomaltose takes place [2]
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