Studies on α‐amylase production by Bacillus licheniformis MIR‐61

Abstract An acid α‐amylase hyperproducing strain, designated as MIR‐61, was isolated in a screening procedure from South American soil samples. MIR‐61, a 60°C thermoresistant strain, was identified using 98 biochemical and morphological tests and characterized as Bacillus licheniformis by numerical taxonomy. Batch cultures of B. licheniformis MIR‐61 showed extracellular α‐amylase and α‐glucosidase activities during the exponential growth phase. The production of α‐amylase was studied at free and constant pH values at 37 and 45°C. Maximum α‐amylase activity (4,767 kU/dm3 in a liquid medium) was detected at 45°C at a constant pH (7.0) in the late exponential phase. The α‐amylase production by B. licheniformis MIR‐61 is 10 to 300 times higher than the enzyme production reported in strains of the same species. Optimum α‐amylase activity was found at 50 to 67°C in an acid pH range from 5.5 to 6.0. These properties would allow its use in starch industry processes.