Effect of using mycotoxin-detoxifying agents in dairy cattle feed on natural whey starter biodiversity

Cultivable microbial diversity, peptide profiles, and bio-functional properties in Parmigiano Reggiano cheese

Introduction

Lactic acid bacteria (LAB) communities shape the sensorial and functional properties of artisanal hard-cooked and long-ripened cheeses made with raw bovine milk like Parmigiano Reggiano (PR) cheese. While patterns of microbial evolution have been well studied in PR cheese, there is a lack of information about how this microbial diversity affects the metabolic and functional properties of PR cheese.

Methods

To fill this information gap, we characterized the cultivable fraction of natural whey starter (NWS) and PR cheeses at different ripening times, both at the species and strain level, and investigated the possible correlation between microbial composition and the evolution of peptide profiles over cheese ripening.

Results and discussion

The results showed that NWS was a complex community of several biotypes belonging to a few species, namely, Streptococcus thermophilus, Lactobacillus helveticus, and Lactobacillus delbrueckii subsp. lactis. A new species-specific PCR assay was successful in discriminating the cheese-associated species Lacticaseibacillus casei, Lacticaseibacillus paracasei, Lacticaseibacillus rhamnosus, and Lacticaseibacillus zeae. Based on the resolved patterns of species and biotype distribution, Lcb. paracasei and Lcb. zeae were most frequently isolated after 24 and 30 months of ripening, while the number of biotypes was inversely related to the ripening time. Peptidomics analysis revealed more than 520 peptides in cheese samples. To the best of our knowledge, this is the most comprehensive survey of peptides in PR cheese. Most of them were from β-caseins, which represent the best substrate for LAB cell-envelope proteases. The abundance of peptides from β-casein 38-88 region continuously increased during ripening. Remarkably, this region contains precursors for the anti-hypertensive lactotripeptides VPP and IPP, as well as for β-casomorphins. We found that the ripening time strongly affects bioactive peptide profiles and that the occurrence of Lcb. zeae species is positively linked to the incidence of eight anti-hypertensive peptides. This result highlighted how the presence of specific LAB species is likely a pivotal factor in determining PR functional properties.

Effects of Tail Vegetable Fermented Feed on the Growth and Rumen Microbiota of Lambs

This study explored the impact of integrating fermented feed into the starter diet of lambs, focusing on growth, health, serum antioxidants, immune markers, rumen fermentation, and microbial communities. Thirty-six ten-day-old female Tail Han lambs were randomly divided into three experimental groups, which were separately fed with alfalfa hay (LA group), tail vegetable fermented feed (LB group), and tail vegetable fermented feed supplemented with 0.1% microbial inoculants (LC group) during the experimental period. This study assessed the influence of fermented feed on various parameters, including growth performance, fiber degradation, rumen fermentation, enzymatic activities, and ruminal histomorphology. The results indicate that compared to the control group, the addition of fermented feed can increase the daily weight gain of lambs. Simultaneously, the addition of fermented feed can enhance the total antioxidant capacity of serum (p < 0.05). The addition of fermented feed promoted the increased height of villi in the duodenum or jejunum of lambs (p < 0.05), and the ratio of villi height to crypt depth in the LB and LC groups was also improved (p < 0.05). The addition of fermented feed increased the richness and diversity of the rumen microbial community in lambs (p < 0.05), primarily increasing the relative abundance of Ruminococcus_1, Ruminococcaceae_UCG-005, Lachnospiraceae, and Lachnospiraceae_NK4A136_group.

Application of flow cytometry for rapid bacterial enumeration and cells physiological state detection to predict acidification capacity of natural whey starters

Natural whey starter cultures are undefined microbial communities mainly consisting of thermophilic lactic acid bacteria (LAB). The technological pressure that shapes the natural whey starter community before and during the back-slopping procedure can impact the amount and viability of the different thermophilic LAB. Traditional culture-dependent analytical methods are useful for evaluating natural whey cultures based on plate enumeration with various culture media and are commonly used as self-control procedures in dairy items. These methods have high variability and require days to obtain results. As the dairy industry has been searching for a solution to this problem for a long time, researchers must explore alternative methods for the technological evaluation of natural whey and assessment of the health status of the thermophilic acidifying bacteria community in the cheesemaking process. The flow cytometry approach has been considered an alternative to classical methods in this work sector. This study compared bacterial enumeration by plate counting and flow cytometry on natural whey samples. Flow cytometry results showed positive agreement with a tendency to overestimate, linearity, and correlation with plate counting. Other parameters have also been introduced for evaluating a natural whey starter, measuring the physiological state of the cells. Specifically, cell-wall damage and metabolic activity were also evaluated, allowing us to quantify the number of cells even in sub-optimal physiological conditions.