Studies on screening and optimization of amylase enzyme production using bacteria isolated from soil

Abstract

Various inevitable parameters have been studied, searching for prospect enhancement of amylase enzyme production using limited energy, time and resources. These parameters include microbes, culture conditions and carbon sources. The present study aimed at screening and optimization of soil bacteria for their ability to degrade starch and produce amylase enzyme. The starch agar plate method was used to screen bacteria and submerged fermentation was for enzyme production. The mean bacterial counts of samples from Kasarawa (KS), Runjin sambo (RS) and Kalambaina (KL) area were 4.5×106, 6.6×106 and 4.1×106 CFU/g respectively. The mean hydrolysis zone of RS 23.3mm was maximal followed by KL 16.8mm and KS 16.3mm in diameter. Morphological and biochemical characteristics of the screened isolate were identified as KS-1 (Bacillus subtilis), RS-1 (Bacillus licheniformis) and KL-2 (Bacillus cereus). Production of amylase enzyme depends on growth parameters and energy sources which enzyme activity was optimal at 48hrs and 72hrs for Bacillus licheniformis and Bacillus subtilis respectively. The increased in temperature showed increased in enzyme activity by three (3) of the bacterial species between 25 and 55°C. The enzyme activity ranged from B. subtilis 1.78 to 4.55, B. licheniformis 2.97 to 6.52 and B. cereus 1.31 to 3.03Uml-1. Meanwhile, all the isolates differed significantly. The enzyme activity of B. licheniformis was optimal at pH 7 (5.02Uml-1) and pH 8 (4.44Uml-1). The B. subtilis and B. cereus enzyme activity ranged from 2.04 to 4.85Uml-1 and 1.51 to 3.85Uml-1 respectively followed the same decreased trend as B. licheniformis. The best-observed carbon source was starch 5.67Uml-1 used by B. licheniformis, 3.89Uml-1 B. cereus and 3.55Uml-1 B. subtilis. In contrast, the nitrogen source was yeast extract utilized best by B. licheniformis 4.55Uml-1, B. subtilis 3.61Uml-1 and B. cereus 3.13Uml-1. The study presented Bacillus sp. 48hrs, 50°C, neutral pH, starch and yeast extract as the best parameters observed for amylase enzyme production.