biofilms present a significant challenge in the food industry. This study explores the impact of different acidic conditions of culture media and food matrices on the development and removal of biofilms developed on stainless steel surfaces by wild-type (WT) strains as well as in two mutant derivatives, Δ and Δ that have defects in the general stress response and quorum sensing, respectively. Additionally, the study investigates the efficacy of nanoencapsulated carvacrol as an antimicrobial against biofilms developed in Tryptic Soy Broth (TSB) culture media acidified to different pH conditions (3.5, 4.5, 5.5, 6.5), and in food substrates (apple juice, strained yogurt, vegetable soup, semi-skimmed milk) having the same pH levels. No biofilm formation was observed for all strains at pH levels of 3.5 and 4.5 in both culture media and food substrates. However, at pH 5.5 and 6.5, increased biofilm levels were observed in both the culture media and food substrates, with the WT strain showing significantly higher biofilm formation (3.04–6.05 log CFU cm) than the mutant strains (2.30–5.48 log CFU cm). For both applications, the nanoencapsulated carvacrol demonstrated more potent antimicrobial activity against biofilms developed at pH 5.5 with 2.23 to 3.61 log reductions, compared to 1.58–2.95 log reductions at pH 6.5, with mutants being more vulnerable in acidic environments. In food substrates, nanoencapsulated carvacrol induced lower log reductions (1.58–2.90) than the ones in TSB (2.02–3.61). These findings provide valuable insights into the impact of different acidic conditions on the development of biofilms on stainless steel surfaces and the potential application of nanoencapsulated carvacrol as a biofilm control agent in food processing environments.

中文翻译：

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不同酸性条件和食品基质对单核细胞增生李斯特氏菌生物膜发育和使用纳米封装香芹酚去除的影响

生物膜给食品工业带来了重大挑战。本研究探讨了培养基和食品基质的不同酸性条件对野生型 (WT) 菌株以及具有缺陷的两种突变衍生物 Δ 和 Δ 在不锈钢表面形成的生物膜的形成和去除的影响。分别是一般应激反应和群体感应。此外，该研究还调查了纳米封装香芹酚作为抗菌剂对抗生物膜的功效，这些生物膜是在酸化至不同 pH 条件（3.5、4.5、5.5、6.5）的胰蛋白酶大豆肉汤 (TSB) 培养基中以及在食品基质（苹果汁、过滤酸奶）中开发的。 、蔬菜汤、半脱脂牛奶）具有相同的 pH 值。在 pH 值 3.5 和 4.5 的培养基和食品基质中均未观察到所有菌株形成生物膜。然而，在 pH 5.5 和 6.5 下，培养基和食品基质中的生物膜水平均增加，WT 菌株的生物膜形成量 (3.04–6.05 log CFU cm) 明显高于突变菌株 (2.30–5.48 log CFU cm)。 ）。对于这两种应用，纳米封装的香芹酚对在 pH 5.5 下形成的生物膜表现出更有效的抗菌活性，其抗菌活性降低了 2.23 至 3.61 个对数，而在 pH 6.5 下则降低了 1.58-2.95 个对数，突变体在酸性环境中更容易受到伤害。在食品基质中，纳米封装香芹酚引起的对数减少量 (1.58–2.90) 低于 TSB 中的对数减少量 (2.02–3.61)。这些发现为了解不同酸性条件对不锈钢表面生物膜形成的影响以及纳米封装香芹酚作为食品加工环境中生物膜控制剂的潜在应用提供了有价值的见解。