Isolation of a thermophilic Anoxybacillus flavithermus sp. nov. and production of thermostable α-amylase under solid-state fermentation (SSF)

Abstract

A new bacteria was isolated from hot-spring water of Gazligol, Afyonkarahisar in Turkey. Based on morphological and biochemical tests and 16S rRNA gene sequence analysis, the isolate belonged to the Anoxybacillus flavithermus species which has 99% similarity with the bacterium DNA. The production of α-amylase by thermophilic Anoxybacillus flavithermus was investigated under solid-state fermentation by using some agricultural waste as substrates. Solid substrates such as rice husk, banana husk, millet, water melon husk, lentil bran, wheat bran and maize oil cake were studied for enzyme production. Of these, rice husk was proved as the best substrate for α-amylase production (1,271 U/mg). The maximum α-amylase production was observed as 1,803 U/mg at 72 h, 1,000 μm particle size, 70% initial moisture content (w/v), and 40% inoculum level (v/w). Among the various nitrogen sources tested, 1% peptone (3,170 U/mg) was found to be the best nitrogen source for α-amylase production. As additional carbon sources, 1% starch (2,364 U/mg) enhanced α-amylase production. The optimum temperature for the activity of α-amylase was found to be 70°C. The enzyme was optimally active at pH 6.0 and stable in the pH range of 6.0–8.0.