Enhancement of transglutaminase production in Streptomyces mobaraensis as achieved by treatment with excessive MgCl2.

In this study, we first tested the capacity for eight different salts as stress-mediated bioprocesses in the production of transglutaminase (TGase). A significant effect on the cell growth and TGase production was obtained with the highest yield of TGase being observed at 96 h of incubation (4.3 U/ml) when the basic medium was supplemented 0.10 M MgCl(2), as opposed to that observed with the basic medium control (2.1 U/ml at 120 h). Data from Western blot assays showed that transformation of pro-TGase to its mature enzyme occurred more rapidly in MgCl(2) medium. Furthermore, total protease, metalloprotease, and serine protease were also synthesized at a faster rate in the medium containing MgCl(2). The results demonstrate that MgCl(2) enhanced the production of key proteases involved in the activation of TGase biosynthesis. To explore the mechanism, viability assay was performed. The results show that MgCl(2) induced the mycelia differentiation, decreased cell growth rate, and stimulated cell death. We argue that TGase production was promoted by the stimulation of mycelium differentiation induced by MgCl(2) stress.