Indigenous Lactococcus lactis with Probiotic Properties: Evaluation of Wet, Thermally- and Freeze-Dried Raisins as Supports for Cell Immobilization, Viability and Aromatic Profile in Fresh Curd Cheese

Whole-Genome Sequence of Lactococcus lactis Subsp. lactis LL16 Confirms Safety, Probiotic Potential, and Reveals Functional Traits

Safety is the most important criteria of any substance or microorganism applied in the food industry. The whole-genome sequencing (WGS) of an indigenous dairy isolate LL16 confirmed it to be Lactococcus lactis subsp. lactis with genome size 2,589,406 bp, 35.4% GC content, 246 subsystems, and 1 plasmid (repUS4). The Nextera XT library preparation kit was used to generate the DNA libraries, and the sequencing was carried out on an Illumina MiSeq platform. In silico analysis of L. lactis LL16 strain revealed non-pathogenicity and the absence of genes involved in transferable antimicrobial resistances, virulence, and formation of biogenic amines. One region in the L. lactis LL16 genome was identified as type III polyketide synthases (T3PKS) to produce putative bacteriocins lactococcin B, and enterolysin A. The probiotic and functional potential of L. lactis LL16 was investigated by the presence of genes involved in adhesion and colonization of the host's intestines and tolerance to acid and bile, production of enzymes, amino acids, and B-group vitamins. Genes encoding the production of neurotransmitters serotonin and gamma-aminobutyric acid (GABA) were detected; however, L. lactis LL16 was able to produce only GABA during milk fermentation. These findings demonstrate a variety of positive features that support the use of L. lactis LL16 in the dairy sector as a functional strain with probiotic and GABA-producing properties.

Exploring the Potential of Sustainable Acid Whey Cheese Supplemented with Apple Pomace and GABA-Producing Indigenous Lactococcus lactis Strain

This study aimed to utilize two by-products, acid whey and apple pomace, as well as an indigenous Lactococcus lactis LL16 strain with the probiotic potential to produce a sustainable cheese with functional properties. Acid whey protein cheese was made by thermocoagulation of fresh acid whey and enhancing the final product by adding apple pomace, L. lactis LL16 strain, or a mixture of both. The sensory, the physicochemical, the proteolytic, and the microbiological parameters were evaluated during 14 days of refrigerated storage. The supplementation of the cheese with apple pomace affected (p ≤ 0.05) the cheese composition (moisture, protein, fat, carbohydrate, and fiber), the texture, the color (lightness, redness, and yellowness), and the overall sensory acceptability. The addition of the presumptive probiotic L. lactis LL16 strain decreased (p ≤ 0.05) the concentration of glutamic acid, thus increasing γ-aminobutyric acid (GABA) significantly in the acid whey cheese. The supplementation with apple pomace resulted in slightly (p < 0.05) higher counts of L. lactis LL16 on day seven, suggesting a positive effect of apple pomace components on strain survival. The symbiotic effect of apple pomace and LL16 was noted on proteolysis (pH 4.6-soluble nitrogen and free amino acids) in the cheese on day one, which may have positively influenced the overall sensory acceptance.