Lactobacillus delbrueckii subsp. lactis as a starter culture significantly affects the dynamics of volatile compound profiles of hard cooked cheeses

Metataxonomic Mapping of the Microbial Diversity of Irish and Eastern Mediterranean Cheeses

The distinct sensorial characteristics of local cheeses influence consumer preferences, and make an essential contribution to the local economy. Microbial diversity in cheese is among the fundamental contributors to sensorial and qualitative characteristics. However, knowledge regarding the existence of microbial patterns associated with regional production practices in ripened cheeses remains limited. The present research was conducted to test the hypothesis that the background metagenome of cheeses could be used as a marker of their origin. We compared Irish versus Eastern Mediterranean cheeses-namely Greek and Cypriot-using High Throughput Sequencing (HTS). The study identified a significantly distinct separation among cheeses originating from the three different countries, in terms of the total microbial community composition. The use of machine learning and biomarkers discovery algorithms defined key microbes that differentiate each geographic region. Finally, the development of interaction networks revealed that the key species developed mostly negative interactions with the other members of the communities, highlighting their dominance in the community. The findings of the present research demonstrate that metagenome could indeed be used as a biological marker of the origin of mature cheeses, and could provide further insight into the dynamics of microbial community composition in ripened cheeses.

Lactiplantibacillus plantarum LRCC5314 includes a gene for serotonin biosynthesis via the tryptophan metabolic pathway

As the functions of probiotics within the same species may not be shared, it is important to analyze the genetic characteristics of strains to determine their safety and usefulness before industrial applications. Hence the present study was undertaken to determine functional genes, and beneficial activities of strain LRCC5314, a bacterial strain isolated from kimchi through comparative genomic analysis. Phylogenetic analysis based on the 16S rRNA gene sequence showed that strain LRCC5314 was a member of the species L. plantarum. Whole genome size of strain LRCC5314 was sequence was 3.25 Mb long, with a G + C content of 44.5 mol% and 3,031 predicted genes. Strain LRCC5314 could metabolize hexoses through homofermentation, which produces only lactic acid from hexoses. According to gene annotation, strain LRCC-5314 contained genes of EPS production and CRISPR. Moreover, the strain contained genes that could encode a complete biosynthetic pathway for the production of tryptophan, which can be used as a precursor of serotonin. Notably, the tryptophan and serotonin activities strain LRCC5314 were higher than those of reference strains, L. plantarum ATCC 14917^T, DSM 20246, DSM 2601, and ATCC 8014, which reach tryptophan amount of 0.784 ± 0.045 μM/ml in MRS broth and serotonin concentration of 19.075 ± 0.295 ng/ml in HT-22 cells. These findings indicated that L. plantarum LRCC5314 could provide a source for serotonin production and could be used as a functional probiotic for stress regulation.

Influence of Monascus purpureus BD-M-4 on the physicochemical properties, proteolysis and volatile compounds of surface mould-ripened cheese

The effect of adjunct culture Monascus purpureus BD-M-4 on the physicochemical, proteolytic, and lipolytic properties of surface mold-ripened cheese were evaluated. During the maturation of Monascus-fermented cheese, the total microbiota count and the content of soluble nitrogen increased steadily, whereas the total protein content showed no significant difference. Moreover, a 17-fold increase in total free amino acids was observed in Monascus-fermented cheese. The use of adjunct culture M. purpureus BD-M-4 in the production of surface-ripened cheeses did not show a significant effect on the total fat content in the ripening period, nor did it change the lipolysis of cheese during ripening. Compared to 52 volatile compounds of the control cheese, a total of 62 compounds were detected in M. purpureus-fermented cheese, including 16 acids, 16 ketones, 11 alcohols, 5 aldehydes, 11 esters, and 3 unclassified compounds.