Protease production by soil bacteria for green technology: Screening and optimization

Abstract Protease is a type of enzyme that hydrolyzes proteins into peptides and amino acids. The demand for protease for green technology in some industries like detergent, food, and leather is increasing nowadays. Some soil bacteria, especially the Bacillus strains, are known to have the ability to produce protease. Compared to other sources like plant and animal origin, microbial protease has more advantages as it can be produced at an industrial scale, short cultivation time, and are easy to harvest. This research aimed to screen the proteolytic bacteria from the bulk soil samples collected under mango trees and to study the optimum condition for protease production using the response surface methodology (RSM). Three bacterial strains (SH2CR, SH3CR, and SC4CR) were isolated and shown to have proteolytic activity. Based on 16S rRNA gene analysis, the strain SH2CR was close to Priestia megaterium NBRC 15308 T (96.97% similarity), while the strains SH3CR and SC4CR were related to Bacillus zanthoxyli strain 1433 T (100% similarity). One of them, SH2CR, was further studied using a fermenter at a one-liter production scale with the medium containing skim milk at 30°C. The best condition for protease production by SH2CR was achieved at 48 h incubation time, 300 rpm of agitation, and 1.25% skim milk.