El-Sharoud W M, Zalma S A, Yousef A E
Food Safety and Microbial Physiology, Faculty of Agriculture, Mansoura University, Egypt.
Food Safety and Microbial Physiology, Faculty of Agriculture, Mansoura University, Egypt.
Int J Food Microbiol. 2022 Jun 16;371:109637. doi: 10.1016/j.ijfoodmicro.2022.109637. Epub 2022 Mar 23.
Food processors are keenly interested in natural alternatives to currently used chemical preservatives. Although bacteriocins of beneficial bacteria are one of the promising alternatives, low productivity of bacteriocin producers has been limiting the application of these agents in food processing. The present study was designed to examine the possibility of inducing the production of paenibacillin, a bacteriocin produced by Paenibacillus polymyxa OSY-DF, by exposing this organism to environmental stresses. Cold stress (15 °C for 105 min) caused 2- to 4-fold increase in the antibacterial and specific antibacterial activities of bioreaction's cell-free filtrate against Listeria innocua and Bacillus subtilis. Paenibacillin production increased when the organism was exposed during incubation to pH 6.0. Presence of 1% NaCl in the growth medium, application of oxidative stress by exposure to 3 ppm HO, and adjusting aeration to a relatively low rate were also found to induce the expression of paenibacillin but to a limited degree, when compared to the effect of cold stress. Exposure to pH 6 increased the transcription of the paenibacillin structural gene, paeA, whereas no significant change was noticed for the same gene under cold stress. Paenibacillin, produced in sufficient amounts under cold stress, was tested as a potential preservative to control the sporeforming bacterium, B. subtilis, in milk. The initial population of B. subtilis of ~7 log CFU/ml decreased to an undetectable level (≤ 1 log CFU/ml) within 24 h of incubation of treated milk held at 37 °C. Similarly, paenibacillin was active against L. innocua in milk; the treatment caused 5-log decrease in the organism's population after 7 days of incubation. Taken together, these results demonstrated increased expression of paenibacillin by exposure to selected environmental stresses, particularly cold stress, and that paenibacillin seems promising in the biopreservation of milk and potentially milk products.
食品加工企业对当前使用的化学防腐剂的天然替代品有着浓厚兴趣。尽管有益细菌的细菌素是一种很有前景的替代品，但细菌素产生菌的低生产率一直限制着这些制剂在食品加工中的应用。本研究旨在通过使多粘芽孢杆菌OSY-DF暴露于环境压力下，来检验诱导其产生芽孢杆菌素（一种由该菌产生的细菌素）的可能性。冷应激（15℃处理105分钟）使生物反应的无细胞滤液对无害李斯特菌和枯草芽孢杆菌的抗菌活性及比抗菌活性提高了2至4倍。当该菌在培养过程中暴露于pH 6.0时，芽孢杆菌素的产量增加。与冷应激的效果相比，在生长培养基中添加1%氯化钠、通过暴露于3 ppm过氧化氢施加氧化应激以及将通气量调节至相对较低水平，也能诱导芽孢杆菌素的表达，但程度有限。暴露于pH 6会增加芽孢杆菌素结构基因paeA的转录，而在冷应激下该基因未观察到显著变化。在冷应激下大量产生的芽孢杆菌素被作为一种潜在防腐剂进行测试，以控制牛奶中的产芽孢细菌枯草芽孢杆菌。在37℃孵育处理后的牛奶24小时内，初始浓度约为7 log CFU/ml的枯草芽孢杆菌数量降至不可检测水平（≤1 log CFU/ml）。同样，芽孢杆菌素对牛奶中的无害李斯特菌也有活性；处理后，该菌在孵育7天后数量减少了5个对数级。综上所述，这些结果表明，通过暴露于选定的环境压力，尤其是冷应激，芽孢杆菌素的表达增加，并且芽孢杆菌素在牛奶及潜在的奶制品生物保鲜方面似乎很有前景。
