Engineering peptidoglycan degradation related genes of Bacillus subtilis for better fermentation processes

In this study, Bacillus subtilis 168 Δupp was engineered to change the bacterial shapes. Namely, some peptidoglycan hydrolase related genes were inactivated individually or in different combinations, including sigD, lytE, lytF, lytC, lytD and lytG. Inactivations of these genes resulted in various intensities of blockages on cell division, leading to elongation of bacterial cells. The resulted fiber phenotypes showed different lengths ranging from tens of microns to several millimeters. Mutants with multiple gene inactivations such as ΔsigDΔlytEΔlytD showed more easily precipitated phenomenon, obviously increased growth rate, more sensitive to antibiotics and improved α-amylase production compared with that of B. subtilis 168 Δupp. Mutants ΔsigDΔlytEΔlytD and ΔsigDΔlytEΔlytCΔlytD also showed an increased tolerance to high osmotic pressure of sodium chloride, allowing unsterile fermentation, all of which contributes to reduced processing cost.