Production and properties of alpha-amylase from Citrobacter species

Amylase production by Citrobacter sp. isolated from potato was optimized in batch culture studies under shake flask conditions. Effects and interactions of best sources and levels of carbon and nitrogen estimated by 4 x 5 and 4 x 4 factorial experimental arrangements were significant (P < 0.01) on amylase production. Optimal alpha-amylase yield was obtained in a medium containing sorghum flour (2.0 % w/v) and a mixture of (NH4)2SO4 + soybean meal (1.5% w/v) with an initial medium pH of 8.0. Under optimum conditions, amylase yield was maximal (0.499 U/ml) after 60h incubation at room temperature (28oC ± 2oC). Characterization studies showed that the enzyme had maximum activity at 60oC, retained 100% of its original activities at 60oC for 2h, was maximally active at pH 7.0 and retained 100% of original activities at pH 9.0 for 2h. Enzyme activity was stimulated by urea, Mg2+, Ca2+ and Zn2+ but inhibited by Hg2+.