| Nisin is a heat-stable bacteriocin produced by Lactococcus lactis ssp. Lactis. It is bactericidal against many Gram-positive bacteria including Listeria monocytogenes and Staphylococcus aureus. But its use as food biopreservative is limited because the lack of effect against Gram-negative bacteria. To meet the wide array of challenges imposed by these trends, nisin combined with antimicrobial plant extracts, was studied in the article.1 Berberine and wood vinegar liquid were the highest effect and broad spectrum plants extract by the method of the diameter of inhibition zone. Both of them can inhibit Micrococcus luteus, Staphylococcus aureus, Escherichia coli, Bacillus subtilis, Saccharomyces cerevisiae. The inhibition zone of berberine and wood vinegar liquid was 21.800mm and 20.800mm to Micrococcus luteus, 17.720mm and 13.880mm to Staphylococcus aureus, 13.560mm and 12.560mm to Escherichia coli, 10.590mm and10.590mm to Saccharomyces cerevisiae, respectively.2 The mass ratio of nisin and berberine of the optimum combination was 1:3 at room temperature and pH 1 and the titer of the optimum combination reached 1263.1 IU/mg, a more than 0.27 times increase over nisin alone. The results showed the titre of wooden vinegar liquid combined with nisin was 1.48 times of the nisin product when the optimum mass ratio of wooden vinegar liquid to nisin was 5:1. The optimum temperature and pH for application of the combination were 25℃and pH3, respectively.3 The broad spectrum activities of nisin and the optimum combinations were examined against 3 food-related bacteria by the turbidimetric methods. The growth kinetics of the three bacteria were measured in the presence of nisin and the optimum combinations by monitoring absorbance at 600 nm and the results showed that the optimum combinations slowed the growth of the tested bacteria, most notably Bacillus subtilis, as compared with nisin alone and showed the synergistic activity against these bacteria. Nisin combined with wood vinegar liquid was better than combined with berberine on the broad spectrum activities.4 The pork treated with the optimum combination which was nisin combined with berberine was accepted in 15 days and treated with nisin alone was accepted in 12 days. However, the control was completely unaccepted after 8 days. So berberine has potential as an agent to enhance the antibacterial activity of nisin. The combination of nisin combined with wood liquid vinegar kept the eggplants fresh in 9 days, and the bean curd and pork fresh in 15 days, at the same time the fat of pork wasn't oxidized.5 The combination induced the leak of membrane, forming pores which allow the efflux of protein, potassiumions and calciumions; however, nisin alone induced the leak of potassiumions and amino acids. By the method of irradiating transmission electron microscope, the combination made the plasma membrane crenated, the edge of cell clouded, the cytomatrix distributed nonuniform and the organelle dissolved. DNA treaded with the combination appeared fluorescence under raviolet radiation by DNA gel electrophoresis. The combination can act on the membrane, cytomatrix, organelle, and combining with DNA, resulting in eventually cell death.6 The antioxidant activities of 1mL the combination of nisin and wooden vinegar liquid were the same as 0.1gVc and the scavenging capacities to superoxide radical of 50% the combination were the same as 0.5mg/mL Vc. |
