Environmental Effects on Transglutaminase Production and Cell Sporulation in Submerged Cultivation of Bacillus circulans

Abstract

In this research, the effects of pH, temperature, and oxygen on growth kinetics of a newly isolated strain of Bacillus circulans from the Amazon and their correlations with transglutaminase (TGase) production and cell sporulation were investigated. Statistical experimental methods were used to optimize these parameters, while induction of sporulation was achieved by oxygen culture control. Full factorial composite experimental design and response surface methodology were experimentally tested. The model showed that temperature has a positive and significant effect on TGase production (P < 0.05) while pH and temperature, associated with anoxic conditions, have a marked effect on cell sporulation which is consistently linked with TGase production. The contour plot of results showed that the best culture conditions for TGase production of B. circulans were 30 degrees C, initial pH 8.5, and the highest production was obtained in late-stationary culture phase with maximal specific enzyme activity of 655 U g(-1) of cells (0.37 U/mL). A correlation between enzyme production and cell sporulation, as mediated by oxygen culture conditions, was also demonstrated and, although demonstrated only for B. subtilis, it corroborates the molecular mechanisms involved in this process. It can be suggested that B. circulans BL32 is a strong biological system for the industrial production of TGases.