Effect of yeast culture supernatant on the probiotic properties and biochemical characteristics of three probiotics, in vitro and in vivo evaluation of yeast-probiotic combination against the pathogen V. anguillarum

Research hypothesis: If yeast and probiotics enhance each other they might provide improved protection against pathogens. Growth, aggregation, biofilm formation and hydrophobicity as well as evaluation, of pH lactic acid, free amino nitrogen and reducing sugars in the growth media were estimated for probiotics in the presence of three ratios of yeast cell free supernatant (CFS). The effect of the best working ratio of each probiotic with yeast in terms of the characteristics examined, on the fish pathogen Vibrio anguillarum properties, namely aggregation, biofilm formation and hydrophobicity, was studied in vitro. Then an in vivo examination on Artemia franciscana nauplii was performed following administration of yeast and probiotic bacteria at the selected ratios and a challenge test with the pathogen to examine any possible protection offered in terms of Artemia survival.

研究假设：若酵母菌与益生菌存在协同增效作用，则二者或可提升对病原微生物的防护效能。本研究针对三种不同比例的酵母菌无细胞上清液（Cell Free Supernatant, CFS）环境中的益生菌，对其生长、聚集、生物膜形成与疏水性，以及培养基内的pH值、乳酸含量、游离氨基氮和还原糖水平进行了测定与评估。针对每种益生菌与酵母菌的最优作用配比，本研究体外探究了其对前述检测特征的影响，以及该配比下对鱼类病原菌鳗弧菌（Vibrio anguillarum）的聚集、生物膜形成及疏水性等特性的作用。随后，本研究以选定配比的酵母菌与益生菌制剂饲喂卤虫无节幼体（Artemia franciscana nauplii），并开展病原菌攻毒试验，以评估其对卤虫存活率的潜在防护效果。