Abstract:
A chemical defined medium at pH 6.0 , 30 ℃ , supplemented with nitrogen sources was more effective than that with carbon sources in increasing growth and specific activity of protease of B. subtilis TISTR 25. Gloutamate, asparagines, arginine , proline , and casein hydrolysate were good nitrogen sources, whereas citrate and succinate were good carbon sources. These carbon sources including glucose , when supplemented with glutamate , decreased protease production through the process of catabolite repression. It was also found that high concentration of amino acids such as case in hydrolysate , at concentration higher than 0.5 percent, and glutamate , at concentration higher than 100 mM , were also able to decrease protease production. Moreover, growth and protease activity in amino acid mixtures were higher than when cultured in single amino acid. Glutamate, asparagines, proline , and casein hydrolysate were comparable when using as nitrogen sources for the ability to induce protease and also for the production ratio of serine to metal protease. Studies of rifampin inhibitor and the effect of adding glucose at different growth phases suggest that the control of protease production in B. subtilis TISTR 25 should be at the transcriptional level. Due to the high influence of nitrogen source on protease production, the relationship between activities of protease and enzymes in nitrogen metabolism was studied. The results indicate that the pathway catalyzed by GS-GOGAT was more important than the GDH pathway in nitrogen metabolism In addition , protease production was inversely related to GS and GOGAT activities.