Comparison of submerged and solid state fermentation systems effects on the catalytic activity of Bacillus sp. KR-8104 α-amylase at different pH and temperatures

► The impact of temperature and pH on the performance of α-amylase was determined. ► Positive effect of low pH on amylase performance at high temperature was recorded. ► Distinction in amylase performance obtained from SSF and SmF systems was revealed. ► Reliance of enzyme performance on production mode is valuable for specific purpose. In this research the production of α-amylase by Bacillus sp. KR-8104 at different temperatures in submerged fermentation (SmF) was studied. Then the effects of temperature and pH on the α-amylase activity that was produced through SmF were investigated using response surface methodology (RSM) and the results compared to those obtained from solid-state fermentation (SSF). The maximum and minimum α-amylase production was recorded at 37°C (3824UL−1) and 30°C (662UL−1), respectively. Despite an increase in dextrin consumption, a significant decrease in the production of α-amylase at 45°C (3035UL−1) was recorded, compared to that observed at 37°C. To determine the mechanism for the correlation between the temperature and α-amylase performance, the effect of temperature and pH on the crude α-amylase activity was optimized. It was found that a reduced cubic mathematical model was the best equation for predicting the activity of α-amylase. The study also highlighted the positive effect of acidic pH on the performance of crude α-amylase at elevated temperatures. Comparing the results obtained from SSF and SmF systems demonstrated a difference in performance. Specifically, while the α-amylases generated during SSF showed the highest activity at 70°C and pH 4, the maximum activity of the SmF-produced enzyme was achieved at 60°C and pH 3.38.