PRODUCTION AND PROPERTIES OF A RAW-STARCH-DEGRADING AMYLASE FROM THE THERMOPHILIC AND ALKALIPHILIC BACILLUS SP. TS-23

The optimum temperature and initial medium pH for amylase production b y Bacillus sp. TS-23 were 55 degrees C and 8.5 respectively. Maximum a mylase activity was obtained in a medium containing peptone and solubl e starch as nitrogen and carbon sources. Activity staining revealed th at two amylases with molecular masses of 150 and 42 kDa were produced when maltose, soluble starch or amylose was used as carbon source for growth, whereas only the 150 kDa protein was detected in the medium co ntaining water-insoluble carbon sources. A raw-starch-degrading amylas e was purified from culture supernatant of Bacillus sp, TS-23. The mol ecular mass of the purified amylase was estimated at 42 kDa by electro phoresis. The enzyme had a pi of 4.2, The optimal pH and temperature f or activity were 9.0 and 70 degrees C respectively. The thermoactivity of the purified enzyme was enhanced in the presence of 5 mM Ca2+; und er this condition, enzyme activity could be measured at a temperature of 90 degrees C, The enzyme was strongly inhibited by Hg2+, Pb2+, Zn2, Cu2+ and EDTA, but less affected by Ni2+ and Cd2+. The enzyme prefer entially hydrolysed high-molecular-mass substrates with an alpha-1,4-g lucosidic bond except glycogen. The raw starches were partly degraded by the purified amylase to yield predominantly oligosaccharides with d egrees of polymerization 3, 4 and 5.