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Milk kefir fermentation has been used in households for generations. Consumption of milk kefir has been associated with various health benefits, presumably from the probiotics of yeast and bacteria that make up the kefir grains. In addition, many of the microbes are known to produce novel antimicrobial compounds that can be used for other applications. The microbes living inside kefir grains differ significantly depending on geographical location and production methods. In this study, we aimed to use metagenomic analysis of fermented milk by using three different kefir grains (kefir 1, kefir 2, and kefir 3) from different US sources. We analyzed the microbial compositions of the three milk fermentation samples. This study revealed that each sample contains unique and distinct groups of microbes, kefir 1 showed the least diversity, and kefir 3 showed the highest diversity. Kefir 3 is rich in Proteobacteria while kefir 2 is dominated by the Firmicutes. Using bacterial indicator growth analyses carried out by continuous readings from microplate-based bioreactor assays suggested that kefir 2 fermentation filtrate has higher antibacterial property. We have screened 30 purified cultures of kefir 2 sample and isolated two lactic acid bacteria strains with higher antibacterial activities; the two strains were identified as Leuconostoc mesenteroides 28–1 and Lentilactobacillus kefiri 25–2 by 16S genomic PCR with confirmed antibacterial activities of fermentation filtrate after growing under both aerobic and anaerobic conditions. [ABSTRACT FROM AUTHOR]

Fermented milk has been shown to have beneficial effects on human health exerted through its bioactive peptides. The lactose-fermenting brown rot fungus Neolentinus lepideus has been shown to ferment milk; however, its ability to produce bioactive peptides has not been explored. This study, therefore, aimed to investigate the ability N. lepideus for the production of antihypertensive peptides in fermented milk and to characterize the peptides. Here we have used 9% skim milk as the substrate and fermented it with the mycelia of N. lepideus. The fermented milk exhibited higher angiotensin I-converting enzyme (ACE) inhibitory activity as compared to the commercially available sour milk containing Ile-Pro-Pro and Val-Pro-Pro. As a result of isolation and purification by reverse-phase high-performance liquid chromatography, followed by peptide sequencing and MS analysis, the dipeptide Tyr-Pro (YP) was identified as an active peptide. The concentration of YP in the fermented milk reached up to 450 μg/ml, which was > twofold higher than the IC50 for ACE inhibition. Subsequently, the antihypertensive effect of YP was validated through intravenous injection of the peptide, which exhibited a significant lowering of blood pressure in a rat model of genetic hypertension. In addition, the transcriptomic analysis revealed the probable role of the carboxypeptidases for the increased yield of YP. These results together indicated that the fermentation with basidiomycete fungus could be a viable approach to produce bioactive peptides, and may, therefore, be applicable in the development of a cost-effective mass production system for functional peptides. [ABSTRACT FROM AUTHOR]

The purpose of the current work was to investigate the capability of multivariate curve resolution-alternating least squares (MCR-ALS) to extract relevant information from Fourier transform near-infrared (FT-NIR) spectra acquired on-line with a fibre probe during milk lactic acid fermentation. The fermentation trials were conducted replicating twice a factorial design with three different starter cultures ( Streptococcus thermophilus and Lactobacillus bulgaricus alone or as 1:1 mixed culture) and three different incubation temperatures (37, 41 and 45 °C), for a total of 18 experiments. The runs were monitored for 7.5 h through pH measurement, dynamic oscillatory test for rheological properties evaluation and FT-NIR spectra acquisition. The obtained MCR-ALS models successfully described the experimental FT-NIR spectra recorded (99.9 % of explained variance, 0.63665 % lack of fit, and standard deviation of the residuals lower than 0.0072). The three spectral profiles obtained by MCR-ALS pointed to the characteristic coagulation phases of milk lactic acid fermentation. The concentration profiles defined as a function of time for each run were strongly dependent on starter and temperature tested, in agreement with pH and rheological results. MCR-ALS applied to FT-NIR spectroscopy provides to the dairy industry a control system which could be implemented in-line as reliable management method for monitoring fermentation processes and to define the coagulation profile no matter the operative conditions adopted for the process. [ABSTRACT FROM AUTHOR]

Forty-four lactic acid bacteria (LAB) isolated from traditional Sayram ropy fermented milk (SRFM) in southern Xinjiang of China. Further two strains were selected based on their high viscosity-producing activity. Based on the API 50 CHL strip and 16S rDNA sequence analysis, strain MB 2-1 was a Gram-positive, rod-shaped Lactobacillus helveticus and strain MB 5-1 was identified as Streptococcus thermophilus. Both the two LAB strains were grown in the milk fermentations for pure and mixed cultures and were evaluated for their growth, acidification properties, EPS production, and ability to increase the apparent viscosity of fermented milk, respectively. L. helveticus MB 2-1 displayed a high increasing in viable cell counts and the acidifying capacity in pure cultures, whereas the relatively high EPS production and viscosity-producing capacity detected in pure culture with S. thermophilus MB 5-1 as starter culture. In addition, the mixed culture of the two strains showed a higher cell growth, EPS production, and high viscosity-producing capacity at 37 °C. Values of apparent viscosity were 4.03- and 2.41-fold higher in mixed culture than for pure cultures of L. helveticus MB 2-1 and S. thermophilus MB 5-1, respectively. There was a positive correlation between the viscosity and high molecular weight EPS production with pure and mixed cultures. Our data showed two strains combination, with high viscosity-producing and acidifying capacity, can be used in mixed cultures for the manufacture of fermented milk with improved functional properties. [ABSTRACT FROM AUTHOR]

Isothermal calorimetry is a powerful technique for the study of kinetics of physical, chemical, and biological processes, for example, of their temperature dependence. A new heat conduction calorimeter that simultaneously makes measurements on four samples at four different temperatures is presented in this article. Results from tests with four biological systems (milk fermentation, carrot juice spoilage, sunflower seed germination, and moss respiration) are shown. In all the cases, the instrument could measure the heat production rate-and thus the process rate-at the different temperatures used. [ABSTRACT FROM AUTHOR]

Microbial exopolysaccharides (EPSs) synthesized by lactic acid bacteria (LAB) play a major role in the manufacturing of fermented dairy products. EPS production is characterized by a large variety in terms of quantity, chemical composition, molecular size, charge, type of sidechains and rigidity of the molecules. Monosaccharide unit's composition, linkages, charge and size determine the EPS' intrinsic properties and their interactions with other milk constituents. EPSs contribute to texture, mouthfeel, taste perception and stability of the final product. Furthermore, it was reported that EPS from food grade organisms, particularly LAB, have potential as food additives and as functional food ingredients with both health and economic benefits. A better understanding of structure-function relationships of EPS in a dairy food matrix and of EPS biosynthesis remain two major challenges for further applications of EPS and the engineering of functional polysaccharides. [ABSTRACT FROM AUTHOR]

Lactobacillus helveticus grown in milk with pH control at 6.2 had a slower growth rate (μ=0.27 h-1) and produced less exopolysaccharide (49 mg l-1) but increased lactic acid production (425 mM) compared to cultures without pH control (μ=0.5 h-1, 380 mg exopolysaccharide l-1, and 210 mM lactate), respectively. Both cultures displayed a mixed-acid fermentation with formation of acetate, which is linked not only to citrate metabolism, but also to alternative pathways from pyruvate. [ABSTRACT FROM AUTHOR]