Antibacterial spectrum and physiochemical property of bacteriocin-like inhibitory substances from Bacillus thuringiensis BRC-ZLL5
To add value to Bacillus thuringiensis (Bt) products,extraction of bacteriocins from Bt fermentation supernatants is needed.This paper aimed to study the extraction methods and the property of Bt bacteriocin-like inhibitory substances (BLIS).In this study,antibacterial spectrum and physiochemical property of Bt BRC-ZLL5 BLIS were investigated using Listeria monocytogenes (Lm) as one of the indicator strains.The results showed that BRC-ZLL5 BLIS were active against Listeria,Pseudomonas aeruginosa and Streptococcusfaecalis,but not against itself and 4 probiotics.The activity of BRC-ZLL5 BLIS against Lm 100525 existed for 6-18 h after incubation,peaking at 12 h after incubation.The molecular weight (Mr) of BRC-ZLL5 BLIS was less than 1.43 × 104.The BRC-ZLL5 BLIS were pH stable (pH 3-9) and heat-resistant:compared with that at 4 ℃,the activity of BRC-ZLL5 BLIS was significantly increased after treatment at 50-90 ℃ for 30 min; it retained 32％ activity after treatment at 121 ℃ for 15 min.The antibacterial activity ofBRC-ZLL5 BLIS was increased with addition of lipase Ⅱ (P ＜ 0.01) while completely.lost after treatment with proteinase K,α-chymotrypsin VⅦ and α-chymotrypsin Ⅱ (P ＜ 0.01).This study provides a model for utilization of Bt fermentation supernatants with high efficiency.
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