Optimization of alpha-amylase production for the green synthesis of gold nanoparticles.

Biocompatible gold nanoparticles have received considerable attention in recent years because of their promising applications in bioimaging, biosensors, biolabels, and biomedicine. The generation of gold nanoparticles using extra-cellular alpha-amylase for the reduction of AuCl(4) with the retention of enzymatic activity in the complex is being reported. The enhanced synthesis of particles has been brought about by optimizing the medium components for alpha-amylase. Response surface methodology and central composite rotary design (CCRD) were employed to optimize a fermentation medium for the production of alpha-amylase by Bacillus licheniformis at pH 8. The three variables involved in the study of alpha-amylase were fructose, peptone and soya meal. Only fructose had a significant effect on alpha-amylase production. The most optimum medium (medB) containing (%) fructose: 3, peptone: 1, soya meal: 2, resulted in a amylase activity of 201.381 U/ml which is same as that of the central level. The least optimum (medA) and most optimum (medB) media were compared for the synthesis of particles indicated by difference in color formation. Spectrophotometric analysis revealed that the particles exhibited a peak at 582 nm and the A(582) for the Med B was 8-fold greater than that of the Med A. The TEM analysis revealed that the particle size ranged from 10 to 50 nm.