PVOH-based polymer matrices in the form of films were evaluated as carriers of living Lactococcus lactis subsp. Lactis. These lactic acid bacteria are capable of producing nisin, which is an effective antilisterial peptide. A low percentage (1:0.125 w/w) of yeast extract, gelatin, sodium caseinate, gelatin, or casein hydrolysates was incorporated in PVOH matrices with the aim of increasing the viability of bacteria in the film. The films were obtained by casting after incorporating L. lactis. Then they were evaluated for antilisterial activity in liquid medium at 37 °C for 24 h, and also at 4 °C for 21 days in order to simulate the storage of liquid foods in refrigeration conditions. The survival of the lactic acid bacteria was also evaluated at both temperatures during the experiment. L. lactis remained viable in all the films tested at 37 and 4 °C. The antimicrobial activity of the films was greater at 4 °C than at 37 °C. With regard to the effect of the film composition, the activity of the films was higher when protein hydrolysates and sodium caseinate were incorporated in the formulation. Films supplemented with protein hydrolysates or sodium caseinate inhibited growth of the pathogen during the 21 days of storage at 4 °C. At 37 °C, after 24 h the films had slowed the growth of the inoculated pathogen by between 2 and 4 log CFU/mL. Finally, as the films developed are intended to be used in the design of active packaging of foods, they were tested in pasteurized milk inoculated with 4 log CFU/mL of Listeria monocytogenes and stored at 4 °C for 21 days. The pathogen began to grow after the second day of storage with or without film, but when the films were added to the medium the growth of the pathogen was slowed down, without reaching >6 log CFU, whereas the control reached a maximum growth of 8.5 log CFU. The pH of the milk was monitored throughout the experiment, and it decreased with time. This was due to the generation of organic acids by the lactic bacteria. Buffering the food stabilized the pH without modifying the activity of the films. Thus, the current study shows that PVOH films supplemented with nutrients can act as carriers of L. lactis, and they can help to increase the safety of refrigerated dairy beverages and sauces.

中文翻译：

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乳酸菌嵌入的PVOH /蛋白质混合膜及其在巴氏杀菌牛奶中的抗李斯特菌活性。

以膜形式的基于PVOH的聚合物基质被评价为活乳球菌亚种的载体。乳杆菌。这些乳酸菌能够产生乳链菌肽，其为有效的抗李斯特菌肽。将低百分比（1：0.125 w / w）的酵母提取物，明胶，酪蛋白酸钠，明胶或酪蛋白水解物掺入PVOH基质中，目的是提高薄膜中细菌的活力。掺入乳酸乳球菌后通过流延获得薄膜。然后评估他们在液体培养基中在37°C下24小时以及在4°C下21天的抗李斯特菌活性，以模拟液体食品在冷藏条件下的储存。在实验过程中，还在两个温度下评估了乳酸菌的存活率。L. 在37°C和4°C下测试的所有薄膜中，乳酸菌均保持活力。膜的抗微生物活性在4°C时比在37°C时大。关于膜组合物的效果，当将蛋白水解产物和酪蛋白酸钠掺入制剂中时，膜的活性更高。补充有蛋白质水解产物或酪蛋白酸钠的薄膜在4°C下储存21天期间抑制病原体的生长。在37°C，24小时后，薄膜使接种病原体的生长减慢了2至4 log CFU / mL。最后，由于所开发的薄膜打算用于食品的主动包装设计，因此它们在接种4 log CFU / mL单核细胞增生李斯特菌的巴氏灭菌牛奶中进行了测试，并在4°C下保存21天。在有或没有膜的情况下储存第二天后，病原体开始生长，但是当将膜添加到培养基中时，病原体的生长速度减慢，没有达到> 6 log CFU，而对照达到了最大生长8.5登录CFU。在整个实验过程中都对牛奶的pH值进行监控，并且牛奶的pH值会随着时间下降。这是由于乳酸菌产生了有机酸。缓冲食物稳定了pH，而没有改变膜的活性。因此，当前的研究表明，补充有营养的PVOH薄膜可以作为乳酸乳球菌的载体，并且可以帮助提高冷藏乳制品饮料和调味料的安全性。而对照组达到了8.5 log CFU的最大增长。在整个实验过程中都对牛奶的pH值进行监控，并且牛奶的pH值会随着时间下降。这是由于乳酸菌产生了有机酸。缓冲食物稳定了pH，而没有改变膜的活性。因此，当前的研究表明，补充有营养的PVOH薄膜可以作为乳酸乳球菌的载体，并且可以帮助提高冷藏乳制品饮料和调味料的安全性。而对照组达到了8.5 log CFU的最大增长。在整个实验过程中都对牛奶的pH值进行监控，并且牛奶的pH值会随着时间下降。这是由于乳酸菌产生了有机酸。缓冲食物稳定了pH，而没有改变膜的活性。因此，当前的研究表明，补充有营养的PVOH薄膜可以作为乳酸乳球菌的载体，并且可以帮助提高冷藏乳制品饮料和调味料的安全性。