Influence of the use of mycotoxin detoxifying agents in dairy cattle feeding on natural whey starter biodiversity

Natural whey cultures (NWCs) are undefined cheese-starter obtained by the traditional back-slopping procedures. NWCs are currently used in the manufacture of different European long ripened cheeses and their core microbiome is mainly composed by Lactobacillus helveticus, Lb. delbrueckii, Limosilactobacillus fermentum and Streptococcus thermophilus. In last years it has become common practice to add inert sorbents to the dairy cattle diet to reduce mycotoxins bioavailability. Although the effects of these compounds on raw milk composition and its yield are described, no information is available about their influence on the dairy products microbiota. In this study a multidisciplinary approach was applied to investigate how two mycotoxin detoxifying agents (sodium smectite and lignocellulose-based material (B1), leonardite and betaine (B2)), added to cows' diet, modify the NWCs microbiota in a Grana-like cheese manufacture. Microbiological and flow cytometry assay showed that content and viability of lactic acid bacteria (LAB) were not affected by the detoxifying agents. Moreover, no significant differences were also observed in any of the kinetic parameters of acidification, highlighting as the addition of detoxifying B1 and B2 agents to the cow diet did not influence the acidifying activity of the whey cultures. RAPD-PCR fingerprinting and metagenomic analysis obtained from the total DNA of whey samples underlined differences in the NWCs bacterial community and in the relative abundance of Bacteroidetes that increased when B1 and B2 were included in the diet. Considering the LAB biotypes isolated from NWCs, two out six St. thermophilus biotypes were detected only in control samples, conversely none of the Lb. helveticus found in control samples were isolated from B1 and B2. We may conclude that the two mycotoxin detoxifying agents did not affect LAB content and the acidifying activity of the NWCs, but were able to modify their bacterial community. In particular, we showed that the B1 and B2 binders can promote or prevent the growth of different St. thermophilus and Lb. helveticus biotypes.