Tenea Gabriela N, Angamarca Evelyn, Cifuentes Victor, Hidalgo Jazmin
Biofood and Nutraceutics Research and Development Group, Faculty of Engineering in Agricultural and Environmental Sciences, Universidad Técnica del Norte, Ibarra, Ecuador.
Front Microbiol. 2024 Mar 13;15:1344735. doi: 10.3389/fmicb.2024.1344735. eCollection 2024.
Lactic acid bacteria (LAB) produce various metabolites (i.e. metabiotics) with inhibitory capacity towards harmful foodborne pathogens.
This study aimed to design several antimicrobial formulations based on metabiotics obtained from different native LAB species ( UTNGt5, UTNGt28, and UTNGt21O) and to detect the possible mode of action towards two multidrug resistant spp. strains isolated from avocado ( var. ) fruits. Additionally, the formulation with the highest inhibitory activity was tested on avocados at the immature (firm) ripeness stage to evaluate their effect on microorganisms' growth and fruit quality attributes post-harvest.
Out of the top five formulations showing the highest bactericidal effect at their minimum inhibitory concentration (1 x MIC) on both spp. targets one candidate annotated P11 (consisting of UTNGt21O and UTNGt28; 1:3, v/v) was selected. Co-cultivation of strains with P11 formulation results in cell viability reduction by 98%, by impairing the integrity of the cell membrane inducing cytoplasm molecule content leakage, protein profile changes, and finally bacterial death. Even though the total coliforms, spp., r spp., molds, and yeasts counts were not fully eliminated by day 13 of storage, a statistically significant reduction ( < 0.05) in viable cell counts were observed by day 8 upon the P11 treatment compared with non-treated control (C) and treated with a commercial disinfectant (T1) samples, suggesting that P11 formulation inhibited microbial colonization during storage. Likewise, no visible dark spots were observed on the mesocarp (pulp) upon the treatment with P11, whereas T1 and C fruits showed greater dark spots on the pulp as indicative of damage. The quality attributes, such as pH, total soluble solids, total titratable acidity, antioxidant capacity, and total polyphenol content, were not affected by the treatment. Principal Component Analysis (PCA) conducted on these five variables showed a clear separation of samples according to the maturity stage regardless of the treatment.
These results suggest that the active metabolites from LAB strains might create a barrier between the exocarp and mesocarp, inhibiting the microorganisms colonization, reducing fruit damage, and lengthening the fruit quality and safety after harvest.
乳酸菌（LAB）产生多种对有害食源性病原体具有抑制能力的代谢产物（即后生元）。
本研究旨在基于从不同本地乳酸菌菌株（UTNGt5、UTNGt28和UTNGt21O）获得的后生元设计几种抗菌配方，并检测其对从鳄梨（品种 ）果实中分离出的两种耐多药 菌株的可能作用方式。此外，对未成熟（硬）成熟阶段的鳄梨测试了具有最高抑制活性的配方，以评估它们对采后微生物生长和果实品质属性的影响。
在对两种 目标菌株的最低抑菌浓度（1×MIC）下显示出最高杀菌效果的前五种配方中，选择了一种标注为P11的候选配方（由UTNGt21O和UTNGt28组成；1:3，v/v）。将 菌株与P11配方共培养会导致细胞活力降低98%，这是通过破坏细胞膜完整性、诱导细胞质分子内容物泄漏、蛋白质谱变化，最终导致细菌死亡。尽管在储存第13天时总大肠菌群、 菌株、 菌株、霉菌和酵母菌数量并未完全消除，但与未处理对照（C）和用商业消毒剂处理（T1）的样品相比，在P11处理后第8天观察到活菌数量有统计学显著减少（ ＜0.05），这表明P11配方在储存期间抑制了微生物定殖。同样，用P11处理后果肉上未观察到明显的黑斑，而T1和C果实的果肉上黑斑更多，表明有损伤。处理并未影响pH、总可溶性固形物、总可滴定酸度、抗氧化能力和总多酚含量等品质属性。对这五个变量进行的主成分分析（PCA）表明，无论处理如何，样品根据成熟阶段都有明显分离。
这些结果表明，乳酸菌菌株的活性代谢产物可能在外果皮和中果皮之间形成一道屏障，抑制微生物定殖，减少果实损伤，并延长采后果实的品质和安全性。
