Improvement of amidase production with high specific acyltransferase activity using Bacillus smithii IITR6B2

This work introduces an approach to increase the productivity of the whole-cell amidase's acyltransferase activity of the Bacillus smithii IITR6b2 in terms of its specific activity. Amidase has a wide range of substrate specificities. An increased amidase with acyl transfer activity will help produce an abundance of different hydroxamates and acid hydrazides with only a small amount of biocatalyst. Unlike the chemical process, it involves a greener approach using an aqueous media and one-step biotransformation. The statistical optimization of amidase production was done through Plackett-Burman design and Response Surface Methodology. After the screening, the ANOVA showed a p-value of <0.001 with a determination coefficient (R2) of 0.994. The four critical factors selected from the Plackett-Burman design were yeast extract, sodium chloride, manganese chloride, and trisodium citrate. After the Central Composite Design, the ANOVA revealed a p-value of <0.001 and a determination coefficient (R2) of 0.9887. The overall enzyme activity increased from 18 IU/ml to 91.30 IU/ml (a 5-fold increase), and specific enzyme activity from 16.1 IU/mg to 47.66 IU/mg (a nearly 3-fold increase). After validation of the predicted model from Response Surface Methodology, yeast extract had the maximum influence on amidase production and activity in combination with manganese chloride. Further, the produced enzyme was explored for the synthesis of pyrazine-2-carboxylic acid hydrazide in a solvent-free reaction system.