Optimization of thermostable α-amylase production by Streptomyces erumpens MTCC 7317 in solid-state fermentation using cassava fibrous residue

Abstract

Production of α-amylase under solid state fermentation by Streptomyces erumpens MTCC 7317 was investigated using cassava fibrous residue, one of the major solid waste released during extraction of starch from cassava (Manihot esculenta Crantz). Response surface methodology (RSM) was used to evaluate the effect of the main variables, i.e., incubation period (60 h), moisture holding capacity (60%) and temperature (500C) on enzyme production by applying a full factorial Central Composite Design. Varying the inoculum concentration (5-25%) of S. erumpens showed that 15% inoculum (v/w, 2.5 x 106 CFU/ml) was the optimum for α-amylase production. Among the different nitrogen sources supplemented, beef extract was most suitable for enzyme production. The application of S. erumpens enzyme in liquefaction of soluble starch and cassava starch was studied. The maximum hydrolysis of soluble starch (85%) and cassava starch (70%) was obtained with the application of 5 ml crude enzyme (17185 units) after 5 h of incubation.