Preliminary evaluation of irradiated medium and the optimization of conditions for a catalase produced by Bacillus firmus GL3

摘要

In this study, a hidden pitfall in the production of commercial tryptose soya agar (TSA) media sterilized with cobalt 60 irradiation was identified, and the applicability of TSA media was also determined. In addition, a strain of Bacillus firmus (B. firmus) with a high catalase activity, named GL3, was screened, and the conditions affecting the activity of its catalase were optimized. The 5 kinds of irradiated TSA media, named A, B, C, D, and E, were stored for 0 days, 15 days, 30 days, and 45 days, and their growth promoting ability, inhibitory properties, and sterility were analyzed to guarantee their suitability. The irradiated TSA media C had abnormal colony counts when Staphylococcus aureus (S. aureus) ATCC 6538 and Bacillus ginsengihumi (B. ginsengihumi) were used as the inocula, and both bacteria resumed normal growth when the media were stored for 15 days or the catalase was added. Screening of the significant variables and optimization of the catalase activity was performed using a Plackett-Burman design (PBD) and response surface methodology (RSM). The GL3 exhibited high catalase activity and stable catalase properties at 20-60 degrees and pH 7.0-10.0. Under optimal conditions, the activity of catalase reached 20,668 U/mL. The abnormal counts of plates can be eliminated by increasing the storage days of the irradiated media during the effective period or by adding optimal fermentation liquid from B. firmus GL3. The high catalase activity and stable enzymatic properties of B. firmus GL3 have potential uses in industrial food applications.