Increase in enzyme productivity by induced oxidative stress in Bacillus subtilis cultures and analysis of its mechanism using microarray data

Treatment of microbial cultures with chemical agents such as hydrogen peroxide (H2O2) and hypochlorous acid (HOCl) induces production of reactive oxygen species (ROS) in culture. These ROS inducing (treatment) agents increased the growth rate as well as the maximum specific levels of extracellular enzymes such as α-amylase and protease in Bacillus subtilis cultures. Treatment with hypochlorous acid increased maximum specific α-amylase level by 2.2-fold and maximum specific protease level by 2.6-fold, respectively. Similarly, treatment with H2O2 increased specific α-amylase and specific protease level by 1.5- and 1.9-fold, respectively. Increases in specific enzyme levels were correlated with levels of specific intracellular ROS in cultures. The mechanism of increase in enzyme productivity under induced oxidative stress was also traced at the genetic level through analysis of available microarray data. The microarray data showed an induced level of signal peptidase gene (sipT), which is the most important secretory apparatus component, and suggested that increased efficiency of secretory apparatus as a result of treatments with ROS inducing agents also leads to increased productivity of α-amylase.