Production of Bacillus subtilis Amylases via Agroresidues and Their Application in Cassava Starch Hydrolysis

Amylases are highly important for biotechnology, represent a class of industrial enzymes and occupy the world enzyme market. The aim of this work was to isolate bacteria for the production of amylase. Freshly caught R. kanagurta fish samples were purchased from the Vizhinjam fish port, Kerala. Bacteria isolated from the intestines of R. kanagurta were cultured on a culture medium containing starch (1%) and kept in an incubator at 30 °C for 48 h. After the incubation period, the growth of bacteria on starch agar plates was analysed, and the samples that were able to grow in this medium were selected for further analyses. The α-amylase enzyme-producing bacteria, which produced a stronger halo in the primary screening stage, were selected for secondary screening and enzyme activity measurement. On the basis of these biochemical and morphological characteristics, isolate A3 was identified as Bacillus subtilis. A high amount of amylase wasproduced by the B. subtilis strain isolated from the gut sample (120 U/ml). Among the tested carbon sources, starch had the greatest influence on amylase (158 ± 2.5 U/ml) production by B. subtilis(A3), whereas a minimum amount of amylase was produced by B. subtiliswhen it utilized sucrose as a carbon source (111 ± 5.1 U/ml) (p<0.01). Among the tested nitrogen sources, ammonium sulfate had the greatest influence on amylase (152 ± 2.9 U/ml) production by B. subtilis, whereas the minimum amount of amylase produced by this organismwas when it utilized casein as a nitrogen source (134 ± 13 U/ml) (p<0.01). The maximum amylase yield (205 ± 1.5 U/ml) was obtained using the culture containing Mn2+ compared with all the other tested elements and the control (p<0.01).