Biofilm Fermentation: A Propitious Method for the Production of Protease Enzyme by Bacillus subtilis RB14

Abstract

To fulfill present day demand for protease enzyme, more productive strains and suitable fermentation systems are needed. A new technique, biofilm fermentation, is thought to be more propitious for the production of protease enzyme than conventionally used submerged fermentation. In this study, protease production in biofilm fermentation and submerged fermentation of Bacillus subtilis RB14 is investigated and compared using the same medium (No. 3). Protease production was found to be two times higher in biofilm fermentation than in submerged fermentation. Therefore, it can be said that combining the biofilm strategy and medium improvement with optimization of fermentation conditions will lead to a superior outcome for protease production. Biofilm fermentation of B. subtilis RB14 offered higher protease production in starch and organic nitrogen source containing medium and optimum temperature and initial pH for protease production were 40°C and 10, respectively. Biofilm formation was not reduced up to 0.05 mM of different salt concentrations. The produced enzyme was most reactive at pH 8.0 and 50°C and was stable at 30–50°C and pH 7–12. When no other additives were used, the enzyme remains active in reaction for maximum of 40 min. It was also observed that the enzyme activity was completely inhibited by aluminum chloride but enhanced by calcium chloride and magnesium sulphate. After analyzing the regulatory networks, it was found that regulation of alkaline protease gene (aprE) and regulation of biofilm formation are correlated and parallel, that is, the reason behind higher production of protease in biofilm fermentation.