Guyot N, Réhault-Godbert S, Slugocki C, Harichaux G, Labas V, Helloin E, Nys Y
URA, INRA, 37380, Nouzilly, France
URA, INRA, 37380, Nouzilly, France.
Poult Sci. 2016 Dec 1;95(12):2956-2970. doi: 10.3382/ps/pew271. Epub 2016 Sep 6.
Egg white is an important contributor to the protection of eggs against bacterial contaminations during the first half of incubation (day zero to 12), prior to the egg white transfer into the amniotic fluid to be orally absorbed by the embryo. This protective system relies on an arsenal of antimicrobial proteins and on intrinsic physicochemical properties that are generally unfavorable for bacterial multiplication and dissemination. Some changes in these parameters can be observed in egg white during egg storage and incubation. The aim of this work was to characterize changes in the antibacterial potential of egg white in embryonated eggs (FE) during the first half of incubation using unfertilized eggs (UF) as controls. Egg white samples were collected at day zero, 4, 8, and 12 and analyzed for pH, protein concentration, and protein profile. Antibacterial properties of egg white proteins were evaluated against Listeria monocytogenes, Streptococcus uberis, Staphylococcus aureus, Escherichia coli, and Salmonella Enteritidis. During incubation, differential variations of egg white pH and protein concentrations were observed between UF and FE. At equal protein concentrations, similar activities against L. monocytogenes and S. uberis were observed for FE and UF egg white proteins. A progressive decline in these activities, however, was observed over incubation time, regardless of the egg group (UF or FE). SDS-PAGE analysis of egg white proteins during incubation revealed discrete changes in the profile of major proteins, whereas the stability of some less abundant antimicrobial proteins seemed more affected. To conclude, the antibacterial activity of egg white proteins progressively decreased during the first half of egg incubation, possibly resulting from the alteration of specific antimicrobial proteins. This apparent decline may be partly counterbalanced in embryonated eggs by the increase in egg white protein concentration. The antibacterial potential of egg white is very effective during early stages of embryonic development but its alteration during incubation suggests that extra-embryonic structures could then progressively ensure protective functions.
在孵化的前半段（第0天至12天），即在蛋清转移到羊水中被胚胎口服吸收之前，蛋清对于保护鸡蛋免受细菌污染起着重要作用。这种保护系统依赖于一系列抗菌蛋白以及通常不利于细菌繁殖和传播的内在物理化学特性。在鸡蛋储存和孵化过程中，可以观察到这些参数的一些变化。这项工作的目的是以上未受精鸡蛋（UF）作为对照，表征孵化前半段胚胎鸡蛋（FE）中蛋清抗菌潜力的变化。在第0天、4天、8天和12天收集蛋清样本，并分析其pH值、蛋白质浓度和蛋白质谱。评估蛋清蛋白对单核细胞增生李斯特菌、乳房链球菌、金黄色葡萄球菌、大肠杆菌和肠炎沙门氏菌的抗菌特性。在孵化过程中，观察到UF和FE之间蛋清pH值和蛋白质浓度的差异变化。在蛋白质浓度相等的情况下，FE和UF蛋清蛋白对单核细胞增生李斯特菌和乳房链球菌的活性相似。然而，无论鸡蛋组别（UF或FE）如何，随着孵化时间的延长，这些活性都逐渐下降。孵化过程中蛋清蛋白的SDS-PAGE分析显示主要蛋白质谱有明显变化，而一些含量较少的抗菌蛋白的稳定性似乎受影响更大。总之，在鸡蛋孵化的前半段，蛋清蛋白的抗菌活性逐渐降低，这可能是由于特定抗菌蛋白的改变所致。在胚胎鸡蛋中，蛋清蛋白浓度的增加可能会部分抵消这种明显的下降。蛋清的抗菌潜力在胚胎发育早期非常有效，但其在孵化过程中的变化表明，胚胎外结构随后可能会逐渐发挥保护作用。
