Fermented Dairy Research Articles

Prevalence of fermented foods in the Dutch adult diet and validation of a food frequency questionnaire for estimating their intake in the NQplus cohort

BackgroundHumans have a long history of consuming fermented foods. However, their prevalence in human diets remains largely undetermined, and there is a lack of validated dietary assessment tools assessing the intake of different fermented products. This study aimed to identify fermented foods consumed in The Netherlands and determine the relative validity of a food frequency questionnaire (FFQ) compared to multiple 24-h recalls for estimating their intake.MethodsThe validation population consisted of 809 participants (53.1 ± 11.9 years) from a Dutch observational cohort (NQplus) who completed a FFQ and multiple 24-h recalls. Fermented foods from the FFQ and recalls were identified and aggregated into conventional food groups. Percent difference in mean intakes, quintile cross-classification, Spearman’s correlations, and Bland-Altman analyses were used to evaluate the agreement between the two dietary assessment methods.ResultsApproximately 16–18% of foods consumed by this population were fermented, and a further 9–14% were dishes containing a fermented ingredient. Fermented foods with the highest consumption included coffee (~ 453 g/day;~ 0.5% of daily energy intake), yoghurts (~ 88 g/day;~ 2.2%), beer (~ 84 g/day;~ 1.7%), wholegrain bread (~ 81 g/day;~ 9.4%), wine (~ 65 g/day;~ 2.7%), and cheese (~ 32 g/day;~ 5.0%). Mean percent difference between the FFQ and recalls was small for fermented beverages (coffee), breads (brown, white, wholegrain, rye), and fermented dairy (cheeses) (0.3–2.8%), but large for buttermilk and quark (≥53%). All fermented food groups had > 50% of participants classified into the same or adjacent quintile of intake (58%-buttermilk to 89%-fermented beverages). Strong Spearman’s correlations (crude/energy-adjusted rs ≥ 0.50) were obtained for fermented beverages (coffee, beer, wine), cereals/grains (wholegrain bread), and dairy (yoghurts). For ‘other bread’, quark, and buttermilk, correlations were low (rs < 0.20). Bland-Altman analyses revealed good agreement for fermented beverages (coffee, beer), breads (brown, wholegrain, rye, other), pastries, chocolate, and fermented dairy (cheeses) (mean difference: 0.1–9.3).ConclusionsFermented food groups with acceptable or good validity across all measures included commonly consumed foods in The Netherlands: fermented beverages (coffee), wholegrain and rye bread, and fermented dairy (cheeses). However, for less frequently consumed foods, such as quark and buttermilk, the levels of agreement were poor and estimates of intake should be interpreted with caution. This report provides the basis for developing a FFQ specific for fermented foods.

Enhanced Antioxidant Activity in Streptococcus thermophilus by High-Level Expression of Superoxide Dismutase.

Superoxide dismutase (SOD) plays an essential role in eliminating oxidative damage of lactic acid bacteria. Streptococcus thermophilus, an important probiotic lactic acid bacterium, often inevitably suffers from various oxidative stress during dairy fermentation. In this study, to confer high-level oxidative resistance, the sod gene from Lactobacillus casei was heterologous expressed in S. thermophilus S-3 using our previous constructed native constitutive promoter library. The enzyme activity of SOD was significantly enhanced in engineered S. thermophilus by promoter #14 (2070 U/mg). Furthermore, the strategy of multi-copy sod-expressing cassettes was employed to improve SOD activity. The maximum activity (2750 U/mg) was obtained by the two-copy sod recombinant, which was 1.5-fold higher than that of one-copy recombinant. In addition, the survival rate of multi-copy sod recombinants was increased about 97-fold with 3.5 mmol/L H2O2 treatment. To our knowledge, this is the first report of multi-copy sod gene expression in S. thermophilus, which exerts a positive effect on coping with oxidative stress to enhance the potential of industrial application.

Lysogenization of a Lactococcal Host with Three Distinct Temperate Phages Provides Homologous and Heterologous Phage Resistance.

Lactococcus lactis is the most widely exploited microorganism in global dairy fermentations. Lactococcal strains are described as typically harboring a number of prophages in their chromosomes. The presence of such prophages may provide both advantages and disadvantages to the carrying host. Here, we describe the deliberate generation of three distinct lysogens of the model lactococcal strain 3107 and the impact of additional prophage carriage on phage-resistance and anti-microbial susceptibility. Lysogen-specific responses were observed, highlighting the unique relationship and impact of each lysogenic phage on its host. Both homologous and heterologous phage-resistance profiles were observed, highlighting the presence of possible prophage-encoded phage-resistance factors. Superinfection exclusion was among the most notable causes of heterologous phage-resistance profiles with resistance observed against members of the Skunavirus, P335, P087, and 949 lactococcal phage groups. Through these analyses, it is now possible to identify phages that may pursue similar DNA injection pathways. The generated lysogenic strains exhibited increased sensitivity to the antimicrobial compounds, nisin and lysozyme, relative to the parent strain, although it is noteworthy that the degree of sensitivity was specific to the individual (pro)phages. Overall, the findings highlight the unique impact of each prophage on a given strain and the requirement for strain-level analysis when considering the implications of lysogeny.

Dairy lactococcal and streptococcal phage-host interactions: an industrial perspective in an evolving phage landscape.

Almost a century has elapsed since the discovery of bacteriophages (phages), and 85 years have passed since the emergence of evidence that phages can infect starter cultures, thereby impacting dairy fermentations. Soon afterward, research efforts were undertaken to investigate phage interactions regarding starter strains. Investigations into phage biology and morphology and phage-host relationships have been aimed at mitigating the negative impact phages have on the fermented dairy industry. From the viewpoint of a supplier of dairy starter cultures, this review examines the composition of an industrial phage collection, providing insight into the development of starter strains and cultures and the evolution of phages in the industry. Research advances in the diversity of phages and structural bases for phage-host recognition and an overview of the perpetual arms race between phage virulence and host defense are presented, with a perspective toward the development of improved phage-resistant starter culture systems.

Isolation and Evaluation of Anti-Listeria Lactococcus lactis from Vegetal Sources.

This chapter describes methods used to isolate, identify, and partially characterize lactic acid bacteria (LAB) which exhibit inhibitory activity against Listeria monocytogenes from foods. Vegetal (plant based) sourcesare rich in naturally occurring LAB and therefore provide an easily accessible source of strains with potential antimicrobial activity for use in food-processing applications. From our previous work, the majority of LAB with inhibitory activity against L. monocytogenes were identified as generally recognized as safe (GRAS) Lactococcus lactis. Although these bacteria are most commonly known for their role in industrial dairy fermentations, they are believed to have originally derived from natural plant-based habitats. These isolates with anti-Listeria activity were all found to carry the genes involved in the production of nisin, which is an approved food-grade preservative (E234). These isolates may find various applications for in situ production of nisin allowing control of L. monocytogenes in various fermented and non-fermented foods and other environments.

Precise Populations’ Description in Dairy Ecosystems Using Digital Droplet PCR: The Case of L. lactis Group in Starters

Lactococcus lactis group (composed of the lactis and cremoris subspecies, recently reassigned as two distinct species) plays a major role in dairy fermentations. Usually present in starter cultures, the two species enable efficient acidification and improve the organoleptic qualities of the final product. Biovar diacetylactis strains produce diacetyl and acetoin, aromas from the citrate metabolization. As these populations have distinct genomic and phenotypic characteristics, the proportions of each other will affect the final product. Today, there is no quantitative test able to distinguish between the two species and the biovar in dairy ecosystems. In this study, we developed a specific, reliable, and accurate strategy to quantify these populations using, species-, and diacetylactis-specific fluorescent probes in digital droplet PCR assays (ddPCR). Species were distinguished based on three single nucleotide polymorphisms in the glutamate decarboxylase gadB gene, and the citD gene involved in citrate metabolism was used to target the biovar. Used in duplex or singleplex, these probes made it possible to measure the proportion of each population. At 59°C, the probes showed target specificity and responded negatively to the non-target species usually found in dairy environments. Depending on the probe, limit of detection values in milk matrix ranged from 3.6 × 103 to 1.8 × 104 copies/ml. The test was applied to quantify sub-populations in the L. lactis group during milk fermentation with a commercial starter. The effect of temperature and pH on the balance of the different populations was pointed out. At the initial state, lactis and cremoris species represent, respectively, 75% and 28% of the total L. lactis group and biovar diacetylactis strains represent 21% of the lactis species strains. These ratios varied as a function of temperature (22°C or 35°C) and acidity (pH 4.5 or 4.3) with cremoris species promoted at 22°C and pH4.5 compared to at 35°C. The biovar diacetylactis strains were less sensitive to acid stress at 35°C. This methodology proved to be useful for quantifying lactis and cremoris species and biovar diacetylactis, and could complete 16S metagenomics studies for the deeply description of L. lactis group in complex ecosystems.

Increasing grass hay inclusion level on weaned dairy calf growth, intake, digestibility, and ruminal fermentation

The objective was to determine effects of increasing grass hay (GH) inclusion level on weaned dairy calf growth, intake, digestibility, and ruminal fermentation. Holstein calves (n = 45) were randomly assigned to 1 of 3 total mixed rations with increasing GH [10, 17.5, or 25% on a dry matter (DM) basis; LGH, MGH, or HGH, respectively]. Calves were weaned at 6 wk of age, housed individually, and studied from 7 to 16 wk of age. Rations, consisting of texturized calf starter (20% crude protein) and coarsely chopped GH, were offered ad libitum as separate components from 7 to 9 wk of age. After 9 wk, feed was offered as a total mixed ration containing the assigned level of GH and fed according to the clean bunk feeding strategy as a means of limiting refusals. Initial 9-wk body weight was 81.6 ± 9 kg (mean ± standard deviation). Intake and growth were measured weekly. Blood samples were collected at 9, 10, 12, 14, and 16 wk of age for analysis of plasma glucose and β-hydroxybutyrate. Total fecal collection (12 calves; 4 per treatment) was conducted at 11 and 15 wk of age for 4 d consecutively. Rumen samples were collected over the final 24 h of each fecal collection period to evaluate pH and volatile fatty acid profile. Feeds and feces were evaluated for DM, neutral detergent fiber, acid detergent fiber, and starch to estimate total-tract digestibility. Intake and weight gain were analyzed from 7 to 9 wk and 9 to 16 wk, representing pretreatment and treatment periods. No differences were observed between treatments from 7 to 9 wk. However, differences were found from 9 to 16 wk. Final body weight, average daily gain, DM intake, and metabolizable energy intake all decreased with increased GH. However, skeletal frame measurements did not vary between treatments. Plasma β-hydroxybutyrate tended to decrease with increased GH. No differences were observed in DM or starch digestibility, but neutral detergent fiber and acid detergent fiber digestibility increased with increased GH. Mean rumen pH and total volatile fatty acid did not change with increasing GH inclusion; however, there was an interaction with time indicating that ruminal fermentation patterns throughout the day were different for calves offered MGH and HGH versus those offered LGH. These results indicate that feeding levels of GH >10% reduce growth and intake before 16 wk and alter ruminal fermentation patterns.

Feeding various forages and live yeast culture on weaned dairy calf intake, growth, nutrient digestibility, and ruminal fermentation

The objective of this study was to determine effects of various forages and live yeast culture on intake, growth, nutrient digestibility, and ruminal fermentation of weaned dairy calves. Holstein calves (n = 45) were randomly assigned to 2 × 3 factorial treatments: live yeast culture or no yeast and alfalfa haylage (AH), corn silage (CS), or grass hay (GH). Calves were weaned at 6 wk of age, housed individually, and studied from 7 to 16 wk of age. Rations, consisting of an 18% crude protein texturized grower (yeast or no yeast) and assigned forage, were offered as separate components until 9 wk of age. After 9 wk, diets were offered as a total mixed ration (TMR). Concentrate intake was capped at 2.25 kg of dry matter (DM)/d, and forage was offered ad libitum. The TMR contained equal forage neutral detergent fiber (8 ± 0.5%) on a DM basis for each basal diet. Calves were fed TMR to limit concentrate intake, and additional forage was offered ad libitum after 8 h if the entire TMR allotment was consumed. Total fecal collection (12 calves) was conducted for 4 d at 11 and 15 wk of age. Feeds and feces were evaluated for DM, neutral detergent fiber, acid detergent fiber, and starch to calculate digestibility. On the last day of fecal collection, rumen samples were collected to evaluate pH and volatile fatty acid (VFA) profile. Metabolizable energy and DM intake was least for calves consuming GH compared with other forages. Forage intake (% of DM intake) increased as calves aged (AH = 20 to 44.4%, CS = 24.5 to 37.6%, GH = 11.3 to 32.3% at 10 and 16 wk of age, respectively). Calves on CS had the greatest average daily gain and empty body weight gain, and calves on GH had the least. Calves on GH tended to have the lowest final body weight. There were no differences in structural growth. Digestibility of DM decreased with age. Fiber digestibility was least for calves on CS, and starch digestibility was least for calves on AH. Mean and minimum rumen pH increased with age. Forage offered changed VFA profile and there was an interaction between yeast and forage on VFA profile. These results indicated that recently weaned calves perform well on AH, CS, or GH and have minimal benefit from yeast supplementation. Feeding GH reduced weight gain, but all calves achieved a level of gain to meet growth goals for breeding and freshening. Furthermore, the ability to consume large portions of the ration as forage allows for more economical diets to be fed.

Food-grade expression of nattokinase in Lactobacillus delbrueckii subsp. bulgaricus and its thrombolytic activity in vitro.

To produce nattokinase in a food-grade expression system and evaluate its thrombolytic activity in vitro. No nattokinase activity from reconstituted strains was observed in simulated gastric juice, but the enzyme was stable in intestinal fluid, the relative activity of which was found to be 60% after 4h. Due to the nattokinase being produced intracellularly by recombinant bacterial strains, the persistence of the bacteria in gastric juice ensured transmission of the nattokinase into intestinal juice. Because of subsequent disintegration of the bacteria, the highest nattokinase activity was observed after 3h at approximately 32%, following its carriage within the recombinant strains to the intestinal fluid. This study demonstrated that nattokinase from recombinant strains exhibited good thrombolytic activity in vitro and may be used by the dairy fermentation industry for the development of novel thrombolytic functional foods.

Integrated metabonomic-proteomic analysis reveals the effect of glucose stress on metabolic adaptation of Lactococcus lactis ssp. lactis CICC23200

A combined proteomic and metabonomic approach was used to investigate the metabolism of Lactococcus lactis ssp. lactis subjected to glucose stress treatment. A proteomic method was used to determine 1,427 altered proteins, including 278 proteins with increased expression and 255 proteins with decreased expression. A metabonomic approach was adopted to identify 98 altered metabolites, including 62 metabolites with increased expression and 26 metabolites with decreased expression. The integrated analysis indicated that the RNA and DNA mismatch repair process and energy metabolism were enhanced in response to high-glucose stress in L. lactis. Lactococcus lactis responded to glucose stress by up-regulating oxidoreductase activity, which acted on glycosyl bonds, hydrolase activity, and organic acid transmembrane transporter activity. This led to an improvement in the metabolic flux from glucose to pyruvate, lactate, acetate, and maltose. Down-regulation of amino acid transmembrane transporter, aminoacyl-transfer RNA ligase, hydroxymethyl-, formyl-, and related transferase activities resulted in a decrease in the nitrogen metabolism-associated metabolic pathway, which might be related to inhibition of the production of biogenic amines. Overall, we highlight the response of metabolism to glucose stress and provide potential possibilities for the reduced formation of biogenic amines in improved level of sugar in the dairy fermentation industry. Moreover, according to the demand for industrial production, sugar concentration in fermented foods should be higher, or lower, than a set value that is dependent on bacterial strain and biogenic amine yield.

Development of Lactococcus lactis Biosensors for Detection of Sulfur-Containing Amino Acids.

The sulfur-containing amino acids methionine and cysteine play an important role in food industry. These amino acids are used to confer a sulfur smell or meat-related aroma to food products. Besides their use as food additives, methionine and cysteine participate in flavor formation in dairy fermentations. For instance, the characteristic aroma of Cheddar cheeses is derived from methionine. Therefore, bacterial strains with the ability to overproduce and secrete these amino acids are relevant for the food industry. In addition, the quantification of these compounds in food matrices is a laborious task that involves sample preparation and specific analytical methods such as high-performance liquid chromatography. The ability of bacteria to naturally sense metabolites has successfully been exploited to develop biosensors. The presence of a specific metabolite is sensed by the biosensors, and it is subsequently translated into the expression of one or more reporter genes. In this study we aim to develop biosensors to detect methionine and cysteine, which are produced and secreted by wild-type Lactococcus lactis strains. We employed two strategies to create L. lactis biosensors, the first one is based on the methionine auxotrophy of this bacterium and the second strategy is based on a cysteine-responsive promoter. The characterization of the biosensors showed their specific response to the presence of these amino acids. Subsequently, we applied the methionine biosensor to quantify the presence of methionine in bacterial supernatants of wild-type L. lactis that naturally secretes methionine to benchmark the performance of our biosensors. The methionine biosensor responded linearly to the amounts of methionine present in the bacterial supernatants, i.e., the increases in the biosensor cell densities were proportional to the amounts of methionine present in the supernatants. The biosensors developed in this study tackle the limitations of amino acid quantification and the selection of strains with secretion of amino acids. These biosensors may eventually be used for screening of engineered strains to increase methionine and cysteine production, and may facilitate the detection of these amino acids in complex food matrices.

Investigation of Flavor-Forming Starter Lactococcus lactis subsp. lactis LDTM6802 and Lactococcus lactis subsp. cremoris LDTM6803 in Miniature Gouda-Type Cheeses.

Lactic acid bacteria (LAB) play an important role in dairy fermentations, notably as cheese starter cultures. During the cheese production and ripening period, various enzymes from milk, rennet, starter cultures, and non-starter LABs are involved in flavor formation pathways, including glycolysis, proteolysis, and lipolysis. Among these three pathways, starter LABs are particularly related to amino acid degradation, presumably as the origins of major flavor compounds. Therefore, we used several enzymes as major criteria for the selection of starter bacteria with flavor-forming ability. Lactococcus lactis subsp. lactis LDTM6802 and Lactococcus lactis subsp. cremoris LDTM6803, isolated from Korean raw milk and cucumber kimchi, were confirmed by using multiplex PCR and characterized as starter bacteria. The combinations of starter bacteria were validated in a miniature Gouda-type cheese model. The flavor compounds of the tested miniature cheeses were analyzed and profiled by using an electronic nose. Compared to commercial industrial cheese starters, selected starter bacteria showed lower pH, and more variety in their flavor profile. These results demonstrated that LDTM6802 and LDTM6803 as starter bacteria have potent starter properties with a characteristic flavor-forming ability in cheese.

Ecology of Lactobacilli Present in Italian Cheeses Produced from Raw Milk.

Among the bacterial genera that are used for cheese production, Lactobacillus is a key taxon of high industrial relevance that is commonly present in commercial starter cultures for dairy fermentations. Certain lactobacilli play a defining role in the development of the organoleptic features during the ripening stages of particular cheeses. We performed an in-depth 16S rRNA gene-based microbiota analysis coupled with internally transcribed spacer-mediated Lactobacillus compositional profiling of 21 common Italian cheeses produced from raw milk in order to evaluate the ecological distribution of lactobacilli associated with this food matrix. Statistical analysis of the collected data revealed the existence of putative Lactobacillus community state types (LCSTs), which consist of clusters of Lactobacillus (sub)species. Each LCST is dominated by one or two taxa that appear to represent keystone elements of an elaborate network of positive and negative interactions with minor components of the cheese microbiota. The results obtained in this study reveal the existence of peculiar cheese microbiota assemblies that represent intriguing targets for further functional studies aimed at dissecting the species-specific role of bacteria in cheese manufacturing.IMPORTANCE The microbiota is known to play a key role in the development of the organoleptic features of dairy products. Lactobacilli have been reported to represent one of the main components of the nonstarter bacterial population, i.e., bacteria that are not deliberately added to the milk, harbored by cheese, although the species-level composition of this microbial population has never been assessed in detail. In the present study, we applied a recently developed metagenomic approach that employs an internally transcribed spacer to profile the Lactobacillus population harbored by cheese produced from raw milk at the (sub)species level. The obtained data revealed the existence of particular Lactobacillus community state types consisting of clusters of Lactobacillus (sub)species that tend to cooccur in the screened cheeses. Moreover, analysis of covariances between members of this genus indicate that these taxa form an elaborate network of positive and negative interactions that define specific clusters of covariant lactobacilli.

From Waste to Taste-Efficient Production of the Butter Aroma Compound Acetoin from Low-Value Dairy Side Streams Using a Natural (Nonengineered) Lactococcus lactis Dairy Isolate.

Lactococcus lactis subsp. lactis biovar diacetylactis is widely used in dairy fermentations as it can form the butter aroma compounds acetoin and diacetyl from citrate in milk. Here, we explore the possibility of producing acetoin from the more abundant lactose. Starting from a dairy isolate of L. lactis biovar diacetylactis, we obtained a series of mutants with low lactate dehydrogenase (ldh) activity. One isolate, RD1M5, only had a single insertion mutation in the ldh gene compared to its parental strain as revealed by whole genome resequencing. We tested the ability of RD1M5 to produce acetoin in milk. With aeration, all the lactose could be consumed, and the only product was acetoin. In a simulated cheese fermentation, a 50% increase in acetoin concentration could be achieved. RD1M5 turned out to be an excellent cell factory for acetoin and was able to convert lactose in dairy waste into acetoin with high titer (41 g/L) and high yield (above 90% of the theoretical yield). Summing up, RD1M5 was found to be highly robust and to grow excellently in milk or dairy waste. Being natural in origin opens up for applications within dairies as well as for safe production of food-grade acetoin from low-cost substrates.

Biodiversity of Lactobacillus helveticus isolates from dairy and cereal fermentations reveals habitat-adapted biotypes.

For the present study, we collected 22 Lactobacillus helveticus strains from different dairy (n=10) and cereal (n=12) fermentations to investigate their biodiversity and to uncover habitat-specific traits. Biodiversity was assessed by comparison of genetic fingerprints, low-molecular-weight subproteomes, metabolic and enzymatic activities, growth characteristics and acidification kinetics in food matrices. A clear distinction between the dairy and cereal strains was observed in almost all examined features suggesting that the different habitats are domiciled by different L. helveticus biotypes that are adapted to the specific environmental conditions. Analysis of the low-molecular-weight subproteome divided the cereal isolates into two clusters, while the dairy isolates formed a separate homogeneous cluster. Differences regarding carbohydrate utilization were observed for lactose, galactose, sucrose and cellobiose as well as for plant-derived glucosides. Enzymatic differences were observed mainly for ß-galactosidase and ß-glucosidase activities. Further, growth temperature was optimal in the range from 33 to 37°C for the cereal strains, whereas the dairy strains showed optimal growth at 40°C. Taken together, adaptation of the various biotypes results in a growth benefit in the particular environment. Acidification and growth tests using either sterile skim milk or a wheat flour extract confirmed these results. Differentiation of these biotypes and their physiological characteristics enables knowledge-based starter culture development for cereal versus dairy products within one species.

Complete Genome Sequences of 28 Lactococcal Bacteriophages Isolated from Failed Dairy Fermentation Processes.

Lactococcus lactis is a Gram-positive lactic acid bacterium commonly used in the dairy industry for the production of fermented foods such as buttermilk and a wide variety of cheeses. Here, we report the complete genome sequences of 28 bacteriophages infecting different L. lactis industrial starter strains isolated from dairy plants throughout the world.

Associations between the Intake of Different Types of Dairy and Cognitive Performance in Dutch Older Adults: The B-PROOF Study.

Various dairy nutrients have been associated with cognitive performance. Several observational studies have explored associations between the intake of total dairy or some dairy subgroups and cognitive performance. However, studies on the potential impact of a broad variety of dairy subclasses are scarce. We examined cross-sectional associations between a wide assortment of dairy products and cognitive performance. A total of 619 Dutch community-dwelling adults aged ≥65 years completed a semi-quantitative Food Frequency Questionnaire. Cognitive performance was assessed with an extensive neuropsychological test battery; the tests were clustered into cognitive domains using z-scores. Linear and logistic regression analyses, adjusted for age, sex, BMI, education, smoking, alcohol consumption, habitual physical activity, total energy intake, and dietary factors, were performed to quantify the associations. The Benjamini–Hochberg method was used to correct for multiple testing. After full adjustment, higher skimmed dairy (β ± SD: 0.05 ± 0.02, p = 0.06), fermented dairy (0.04 ± 0.02, p = 0.09), and buttermilk (0.08 ± 0.03, p = 0.19) consumption were associated with better executive functioning. Logistic regression analyses indicated that a 30 g increase in Dutch cheese intake was associated with a 33% lower probability of poor information processing speed (PR = 0.67, 95% CI 0.47–0.97). No associations were observed between dairy consumption and attention and working memory or episodic memory.

Enterococcus hirae WEHI01 isolated from a healthy Chinese infant ameliorates the symptoms of type 2 diabetes by elevating the abundance of Lactobacillales in rats

Enterococcus hirae WEHI01 is a potential probiotic strain isolated from a healthy Chinese infant. This strain has previously been characterized as having cholesterol-lowering potential and good dairy fermentation performance. In this study, we used rat models with obesity and type 2 diabetes mellitus (T2DM) induced by a high fat and sucrose diet and low-dose streptozotocin, respectively, and we evaluated the effect of E. hirae WEHI01 on glycolipid metabolism, glycolipid-related gene expression, organ histopathology, and intestinal flora changes in the 2 models. Our results showed that administration of 5.0 × 109 cfu of E. hirae WEHI01 for 4 wk decreased serum lipid levels and regulated glycolipid metabolism in the liver of obese rats. Following continuous administration of the same concentration of E. hirae WEHI01 to a T2DM rat model for another 5 wk, E. hirae WEHI01 improved glucose tolerance, recovered body weight loss, and led to significant decreases in tumor necrosis factor-α, IL-6, IL-10, and total bile acid in serum. We also found that E. hirae WEHI01 restored the morphology of the pancreas, kidney, and liver, and changed the composition of the gut microbiota (i.e., decreased the Shannon index, increased the Simpson index, and substantially increased the abundance of Lactobacillales). Combining the results for the obese model and the T2DM model, we speculated that beneficial effects of E. hirae WEHI01 on T2DM could be due to (1) a significant increase in PPARA expression and a tendency for increased CYP7A1 expression in the liver of obese rats, promoting the conversion of cholesterol into bile acid and reducing serum total bile acid levels in T2DM model rats; or (2) a change in gut microbial diversity, especially elevated Lactobacillales abundance, which reduced the total bile acid in T2DM model rats. These results demonstrated that E. hirae WEHI01 has the potential to ameliorate type 2 diabetes in rats and provide a promising rationale for further research into the prevention and treatment of T2DM.

Association between dairy product consumption and hyperuricemia in an elderly population with metabolic syndrome

Background and aimsThe prevalence of hyperuricemia has increased substantially in recent decades. It has been suggested that it is an independent risk factor for weight gain, hypertension, hypertriglyceridemia, metabolic syndrome (MetS), and cardiovascular disease. Results from epidemiological studies conducted in different study populations have suggested that high consumption of dairy products is associated with a lower risk of developing hyperuricemia. However, this association is still unclear. The aim of the present study is to explore the association of the consumption of total dairy products and their subtypes with the risk of hyperuricemia in an elderly Mediterranean population with MetS. Methods and resultsBaseline cross-sectional analyses were conducted on 6329 men/women (mean age 65 years) with overweight/obesity and MetS from the PREDIMED-Plus cohort. Dairy consumption was assessed using a food frequency questionnaire. Multivariable-adjusted Cox regressions were fitted to analyze the association of quartiles of consumption of total dairy products and their subtypes with the prevalence of hyperuricemia. Participants in the upper quartile of the consumption of total dairy products (multiadjusted prevalence ratio (PR) = 0.84; 95% CI: 0.75–0.94; P-trend 0.02), low-fat dairy products (PR = 0.79; 95% CI: 0.70–0.89; P-trend <0.001), total milk (PR = 0.81; 95% CI: 0.73–0.90; P-trend<0.001), low-fat milk (PR = 0.80; 95% CI: 0.72–0.89; P-trend<0.001, respectively), low-fat yogurt (PR = 0.89; 95% CI: 0.80–0.98; P-trend 0.051), and cheese (PR = 0.86; 95% CI: 0.77–0.96; P-trend 0.003) presented a lower prevalence of hyperuricemia. Whole-fat dairy, fermented dairy, and yogurt consumption were not associated with hyperuricemia. ConclusionsHigh consumption of total dairy products, total milk, low-fat dairy products, low-fat milk, low-fat yogurt, and cheese is associated with a lower risk of hyperuricemia.

The Effect of Different Starter Cultures of Lactobacillus paracasei M104 and Pediococcus pentosaceus M103 on the Physicochemical and Microbial Qualities of Fermented Goat Milk

The utilization of starter cultures is vital for dairy fermentation industries. Lactobacillus paracasei M104 and Pediococcus pentosaceus M103 have been isolated from goat milk and were demonstrated to acidify goat milk during fermentation. This study was conducted to compare the physicochemical and microbial qualities of goat milk fermented using these starter cultures either as a single starter or combined in goat milk. The treatments were L. paracasei M104 (Lp) and P. pentosaceus M103 (Pp) as single starter culture fermentation and combined (Lp/Pp) fermentation at a ratio of 1:1 at 6% inoculation (v/v). For control treatment, goat milk was fermented using yogurt starter, i.e., a combination culture of Streptococcus thermophilus and L. bulgaricus (St/Lb) at a ratio of 1:1 at 6% (v/v). The fermentation was performed by incubating the inoculated goat milk at 37°C for 18 h. The pH and degree of acidity were measured every 2 h during the fermentation process, whereas the physicochemical (pH, degree of acidity, lactose, protein, and viscosity) and microbial (total lactic acid bacteria/LAB) qualities were measured after the fermentation process. Data analysis revealed that the different starter cultures had no significant effect (P &gt; 0.05) on the pH and degree of acidity, lactose and protein content, viscosity, and total LAB content. The goat milk fermented in this study had an average pH of 4.41 ± 0.11 and a degree of acidity of 1.26 ± 0.05%, a lactose content of 5.47± 0.80%, a protein content of 6.69± 1.52%, a viscosity of 1217 ± 395 cP, and a total LAB content of 9.57 ± 1.49 log CFU/mL. In conclusion, goat milk fermented using both single and combined starter cultures of L. paracasei M104 and P. pentosaceus M103 exhibited similar physicochemical and microbial qualities and required longer fermentation time compared with the control.