Department of Agricultural and Food Sciences, University of Bologna, Piazza Goidanich 60, 47521, Cesena, Italy.
University Department of Marine Studies, University of Split, 21000, Split, Croatia.
Sci Rep. 2022 Aug 1;12(1):13158. doi: 10.1038/s41598-022-17408-4.
The consumers' demand for safe foods without chemical additives increased the research for green solutions, based on natural antimicrobials. Plants can be an important source of bioactive compounds able to prevent the development of foodborne pathogens and spoilage microflora. This paper aimed to characterize phenolic extracts (PEs) and essential oils (EOs) obtained from Mediterranean Rubus fruticosus leaves and Juniperus oxycedrus needles and to evaluate their antimicrobial effects against Listeria monocytogenes Scott A. The growth dynamics with sub-lethal concentrations of plant derivatives were modeled and flow cytometry was used to better evidence the effect on cell viability and culturability. The results showed that these plant derivatives affected the growth of L. monocytogenes, increasing lag phase (about 40 h in the presence of PEs vs. 8 h in the control) and decreasing the final cell load of at least 1 log cycle with respect to the control. R. fruticosus EO was the most effective, determining an initial decrease of cell counts of about 6 log cycles, followed by a restart of growth after 10 h, with rate similar to the control (0.08 with R. fruticosus EO vs. 0.09 ((log CFU/ml)/h in the control) but significantly lower final cell load (7.33 vs. 8.92 log CFU/ml). According to flow cytometry, only R. fruticosus EO induced a relevant increase of dead cells, while the other plant derivatives determined different extent of sub-lethal cell injury. The discrepancy observed in some cases between viability and culturability could indicate the presence of cells not able to grow in culture media, whose fate needs to be further investigated to assess their potential recovery, thus bringing to an overestimation of the antimicrobial effect of these substances. This research contributed to increase the knowledge of these underused raw materials such as blackberry leaves and juniper needles that can be exploited in food and other industries.
消费者对不含化学添加剂的安全食品的需求增加了对基于天然抗菌剂的绿色解决方案的研究。植物可以是具有防止食源性病原体和腐败微生物群发展的生物活性化合物的重要来源。本文旨在对从地中海悬钩子叶片和刺柏针中提取的酚提取物 (PE) 和精油 (EO) 进行表征，并评估其对单核细胞增生李斯特菌斯科特 A 的抗菌作用。使用模型研究了植物衍生物的亚致死浓度对生长动力学的影响，并使用流式细胞术更好地证明了对细胞活力和可培养性的影响。结果表明，这些植物衍生物影响了单核细胞增生李斯特菌的生长，增加了迟滞期（在 PE 存在时约为 40 h，而在对照中为 8 h），并使最终细胞负荷比对照至少减少了 1 个对数周期。R. fruticosus EO 是最有效的，初始细胞计数减少约 6 个对数周期，然后在 10 h 后重新开始生长，与对照相似（用 R. fruticosus EO 为 0.08 ((log CFU/ml)/h），但最终细胞负荷显著降低（7.33 与 8.92 log CFU/ml）。根据流式细胞术，只有 R. fruticosus EO 诱导了明显增加的死细胞，而其他植物衍生物则导致了不同程度的亚致死细胞损伤。在某些情况下，活力和可培养性之间的差异可能表明存在无法在培养基中生长的细胞，需要进一步研究其命运，以评估它们的潜在恢复能力，从而高估这些物质的抗菌效果。这项研究有助于增加对黑莓叶和刺柏针等未充分利用的原材料的了解，这些原材料可用于食品和其他行业。
