Genome shuffling of Lactobacillus plantarum 163 enhanced antibacterial activity and usefulness in preserving orange juice

Lactic acid bacteria have been used to inhibit the growth of spoilage bacteria in food and animal feeds. For instance, Lactobacillus plantarum 163 can inhibit efficiently the growth of both gram-positive and gram-negative bacteria. In our study, the antibacterial activity of L. plantarum 163 was further improved significantly by genome shuffling. The optimal conditions for protoplast formation and regeneration were 20 mg ml(-1) lysozyme and 5 mg ml(-1) mutanolysin for 30 min at 37 degrees C using 0 center dot 5 mol l(-1) sucrose as stabilizer. The protoplasts were inactivated under ultraviolet light for 120 s or heated at 58 degrees C for 20 min. After two rounds of genome shuffling, the inhibitory activity of strain F2-14 was improved by 2 center dot 45- and 1 center dot 99-fold, respectively, as compared to their parent strains. The prepared antibacterial peptides supernatant (APS) was added to the orange juice to inhibit spores of Alicyclobacillus acidoterrestris (SAA) at 45 and 28 degrees C. Results showed that the growth of A. acidoterrestris was significantly inhibited, and the decrease in total soluble solids, OD value and pH value was also delayed. After treatment with APS, the thermal sensitivity of spores was increased and its D value was reduced to 13 center dot 78, 3 center dot 87 and 1 center dot 47 min at 80, 90 and 95 degrees C respectively.