Enhancement of hydrolytic activity of thermophilic alkalophilic α-amylase from Bacillus sp. AAH-31 through optimization of amino acid residues surrounding the substrate binding site

Enhanced Production, Enzymatic Activity, and Thermostability of an α-Amylase from Bacillus amyloliquefaciens in Lactococcus lactis

A novel α-amylase gene (BAA) from Bacillus amyloliquefaciens was cloned into Lactococcus lactis, designing two recombinant α-amylases to facilitate extracellular secretion. Following optimizing the expression conditions, the highest yield of BAA (88.12 mmol/L) was achieved upon 36 h induction and 5 ng/mL nisin concentration. Determining the enzymatic properties of BAA revealed its poor stability and activity at high temperatures, hindering its widespread application. Therefore, we used computer-aided design to generate a mutant, S275L, which exhibited significantly improved activity and thermostability: an 18.7% increase in enzymatic activity (3767.38 U/mg), a 10 °C increase in optimal temperature, and a 49.2% improvement in stability at 60 °C. Molecular dynamics simulations and force analysis confirmed these enhancements. Finally, the mutant S275L's potential was further analyzed for starch hydrolysis on poultry feed. Therefore, the mutant S275L holds promising as an enzyme agent for enhanced feed digestibility and quality.

Cow dung is an ideal fermentation medium for amylase production in solid-state fermentation by Bacillus cereus

Amylase production by Bacillus cereus IND4 was investigated by solid state fermentation (SSF) using cow dung substrate. The SSF conditions were optimized by using one-variable-at-a-time approach and two level full factorial design. Two level full factorial design demonstrated that moisture, pH, fructose, yeast extract and ammonium sulphate have significantly influenced enzyme production (p < 0.05). A central composite design was employed to investigate the optimum concentration of these variables affecting amylase production. Maximal amylase production of 464 units/ml of enzyme was observed in the presence of 100% moisture, 0.1% fructose and 0.01% ammonium sulphate. The enzyme production increased three fold compared to the original medium. The optimum pH and temperature for the activity of amylase were found to be 8.0 and 50 °C, respectively. This enzyme was highly stable at wide pH range (7.0-9.0) and showed 32% enzyme activity after initial denaturation at 50 °C for 1 h. This is the first detailed report on the production of amylase by microorganisms using cow dung as the low cost medium.