Effect of temperature on batch elastase production by Bacillus sp. EL31410.

Abstract

The production of elastase by Bacillus sp. EL31410 at various temperatures was investigated. In order to study the effect of temperature on elastase fermentation, different cultivation temperatures, ranging from 39 degrees C to 28 degrees C, were evaluated in shake flask. The result indicated that 37 degrees C was best for cell growth at earlier stage; while maximum elastase activity was obtained when the cells were cultivated at 30 degrees C. This result was verified by batch fermentation in 5-L bioreactor under 37 degrees C and 30 degrees C temperature, respectively. The specific cell growth rate at 37 degrees C was higher than that at 30 degrees C during earlier stage of cultivation. The maximum value [5.5 U/(h x g DCW)] of elastase formation rate occurred at 24 h at 30 degrees C compared to 4.6 U/(h x g DCW) at 30 h at 37 degrees C. Based on these results, two-stage temperature shift strategy and oscillatory temperature cultivation mode were evaluated in the next study. When compared to single temperature of 37 degrees C or 30 degrees C, both two-stage temperature shift strategy and oscillatory temperature strategy improved biomass but did not yield the same result as expected for elastase production. The maximum biomass (both 8.6 g/L) was achieved at 30 h at 37 degrees C, but at 42 h using two-stage temperature cultivation strategy. The highest elastase production (652 U/ml) was observed at 30 degrees C in batch process. It was concluded that cultivation at constant temperature of 30 degrees C was appropriate for elastase production by Bacillus sp. EL31410.