Inulinase Activity of Thermophilic Bacteria isolated from Hot Springs of Penen Village, North Sumatera, Indonesia

Inulinase is an enzyme that catalyzes inulin to produce D-fructose as the end product which is considered as safe alternative sweetener to sucrose. This enzyme can be extracted from plants and vegetables but it is difficult to obtain it in high quantity and the production cost also high. The main problem in utilizing this enzyme in industrial is the instability against fluctuation of temperature that usually occurs in industrial process. Therefore thermophilic microbial inulinase has great potential for these industrial needs. The aim of this study was to isolate and characterize the thermophilic bacteria that possess the inulinase activity from hot springs in Penen Village, North Sumatera. To screening the inulinase producing bacteria, the modified Czapex Dox agar supplemented with 1,5% inulin powder was used. The temperature used for incubation is 48 °C. The clear zone surrounds the bacteria after Lugol's iodine treatment on medium indicated the nucleolytic activity. As 4 isolates of thermophilic bacteria namely UTMP 11, UTMP 14, UTMP 15 and UTMP 17 showed the inulolytic activity. The biochemical characterization of these isolates showed negative in catalase test, negative on citrate test, non-motil, negative Gram staining, and rod-shaped morphology. Molecularly, this bacteria identified as Bacillus subtilis strain JCM 1465 and Bacillus tequilensis strain 10b. From the result, these isolates have potential as source of thermophilic inulinase production in food industry for the production of fructose.