Enhanced antimicrobial activity against Alicyclobacillus acidoterrestris in apple juice by genome shuffling of Lactobacillus acidophilusNX2‐6

Abstract

AbstractFood safety and quality are seriously compromised by the growth of spoilage bacteria in food. Various lactic acid bacteria (LAB) may inhibit the growth of spoilage bacteria in food and animal feed. In our study, the antibacterial activity of Lactobacillus acidophilus NX2‐6 was improved by genome shuffling. The starting populations were obtained via 60Coγ‐ray, diethyl sulfate mutagenesis, and UV mutagenesis of protoplasts. The optimal conditions for protoplast formation and regeneration were found to be 30 mg/ml of lysozyme at 37°C for 40 min. The protoplasts were inactivated by UV irradiation for 110 s or by heating at 58°C for 30 min. After two rounds of genome shuffling, the inhibitory activity of strain F50 was improved by 5.6‐fold compared to the original strain. The shuffled strain has broad‐spectrum antibacterial activity and is a promising candidate for bio‐preservative. The antibacterial substances produced by L. acidophilus NX2‐6 can be applied to the preservation of apple juice. The results showed that the growth of Alicyclobacillus acidoterrestris in apple juice was significantly inhibited by the addition of 0.1% culture supernatant with acidocin NX2‐6 at 28°C and 0.2% culture supernatant with acidocin NX2‐6 at 45°C for 30 days. The sugar−acid ratio, pH value, clarity, and fruit flavor of apple juice were well maintained during storage. This study showed that genome shuffling was an effective strategy to improve the bacterial inhibitory activity of LAB and that the shuffled LAB and their metabolites are expected to be used as bio‐based food protectors for food safety.