The water kefir grain inoculum determines the characteristics of the resulting water kefir fermentation process

Challenges in water kefir production and limitations in human consumption: A comprehensive review of current knowledge

Water kefir is a convenient dairy-free alternative to dairy-based fermented beverages. It is prepared by fermenting a sucrose solution with fresh and dried fruits using water kefir grains, and demineralized whey can be used in water kefir production. This review describes current knowledge on water kefir production and its health effects. The main aims of this paper are to focus on the microbial composition, potential health-promoting properties, limitations in human consumption, and challenges in the production of water kefir. Water kefir grains and substrates, including brown sugar, dried and fresh fruits, vegetables, and molasses, used in the production influence the fermentation characteristics and composition of water kefir. Lactic acid bacteria, acetic acid bacteria, and yeasts are the microorganisms involved in the fermentation process. Lactobacillus species are the most common microorganisms found in water kefir. Water kefir contains various bioactive compounds that have potential health benefits. Water kefir may inhibit the growth of certain pathogenic microorganisms and food spoilage bacteria, resulting in various health-promoting properties, including immunomodulatory, antihypertensive, anti-inflammatory, anti-ulcerogenic, antiobesity, hypolipidemic, and hepatoprotective activities.

Licuri Kernel (Syagrus coronata (Martius) Beccari): A Promising Matrix for the Development of Fermented Plant-Based Kefir Beverages

New licuri-based kefir beverages were obtained using water kefir grains as fermentation inoculum (1, 2.5, and 5%) under different fermentation times (24 and 48 h). Metagenomic sequencing of the kefir grains adapted to the aqueous licuri extract revealed Lactobacillus hilgardii and Brettanomyces bruxellensis to be predominant in this inoculum. The excellent adaptation of the kefir grains to the licuri extract raised the possibility of prebiotic action of these almonds. The beverages showed acidity values between 0.33 ± 0.00 and 0.88 ± 0.00 mg lactic acid/100 mL and pH between 3.52 ± 0.01 and 4.29 ± 0.04. The viability of lactic acid bacteria in the fermented beverages was equal to or greater than 108 CFU/mL, while yeasts were between 104 and 105 CFU/mL. There were significant differences (p < 0.05) in the proximate composition of the formulations, especially in the protein (1.37 ± 0.33-2.16 ± 0.84) and carbohydrate (5.86 ± 0.19-11.51 ± 1.26) contents. In addition, all the samples showed good stability in terms of acidity, pH, and viability for LAB and yeasts during 28 days of storage (4 °C). Overall, the beverages showed a dominant yellow-green color, non-Newtonian pseudoplastic behavior, and high mean scores in the sensory evaluation. This study provided evidence of the emerging potential of licuri in the plant-based beverage industry.

Microbial viability and nutritional content of water kefir grains under different storage conditions

Water kefir grains are an important source of probiotics, mainly containing lactic acid bacteria and yeasts. The aim of this study is to investigate the changes in microbial and chemical properties of water kefir grains during 1-month storage at +4°C and -18°C. The initial content of lactobacilli, lactococci, and yeast in water kefir grains was 6.06, 6.33, and 5.93 log CFU/g, respectively. The number of lactobacilli, Lactobacillus acidophilus, and Bifidobacterium spp. in the water kefir grains were comparable, with slight changes at the end of refrigerated storage (p > .05). Lactococci and yeasts decreased significantly after both storage conditions compared to the initial content (p < .05). The dry matter and ash contents remained unchanged during storage (p > .05). Water kefir grains contained significant amounts of calcium, vitamin B2, vitamin B6, vitamin B7, and vitamin B12. Storage at both +4°C and -18°C did not affect the mineral and vitamin contents, except for Cu and Vitamin B2. The results indicate that the water kefir grains remained viable after storage at both temperatures. If water kefir grains need to be stored, it is recommended to store them at +4°C in sugared water as it ensures better survivability of the microbiota of the grains.

Multi-omics characterization of the microbial populations and chemical space composition of a water kefir fermentation

In recent years, the popularity of fermented foods has strongly increased based on their proven health benefits and the adoption of new trends among consumers. One of these health-promoting products is water kefir, which is a fermented sugary beverage based on kefir grains (symbiotic colonies of yeast, lactic acid and acetic acid bacteria). According to previous knowledge and the uniqueness of each water kefir fermentation, the following project aimed to explore the microbial and chemical composition of a water kefir fermentation and its microbial consortium, through the integration of culture-dependent methods, compositional metagenomics, and untargeted metabolomics. These methods were applied in two types of samples: fermentation grains (inoculum) and fermentation samples collected at different time points. A strains culture collection of ∼90 strains was established by means of culture-dependent methods, mainly consisting of individuals of Pichia membranifaciens, Acetobacter orientalis, Lentilactobacillus hilgardii, Lacticaseibacillus paracasei, Acetobacter pomorum, Lentilactobacillus buchneri, Pichia kudriavzevii, Acetobacter pasteurianus, Schleiferilactobacillus harbinensis, and Kazachstania exigua, which can be further studied for their use in synthetic consortia formulation. In addition, metabarcoding of each fermentation time was done by 16S and ITS sequencing for bacteria and yeast, respectively. The results show strong population shifts of the microbial community during the fermentation time course, with an enrichment of microbial groups after 72 h of fermentation. Metataxonomics results revealed Lactobacillus and Acetobacter as the dominant genera for lactic acid and acetic acid bacteria, whereas, for yeast, P. membranifaciens was the dominant species. In addition, correlation and systematic analyses of microbial growth patterns and metabolite richness allowed the recognition of metabolic enrichment points between 72 and 96 h and correlation between microbial groups and metabolite abundance (e.g., Bile acid conjugates and Acetobacter tropicalis). Metabolomic analysis also evidenced the production of bioactive compounds in this fermented matrix, which have been associated with biological activities, including antimicrobial and antioxidant. Interestingly, the chemical family of Isoschaftosides (C-glycosyl flavonoids) was also found, representing an important finding since this compound, with hepatoprotective and anti-inflammatory activity, had not been previously reported in this matrix. We conclude that the integration of microbial biodiversity, cultured species, and chemical data enables the identification of relevant microbial population patterns and the detection of specific points of enrichment during the fermentation process of a food matrix, which enables the future design of synthetic microbial consortia, which can be used as targeted probiotics for digestive and metabolic health.

Physical, chemical, and sensory properties of water kefir produced from Aronia melanocarpa juice and pomace

Water kefir is widely consumed all over the world due to its potential health benefits. The aim of this current study was to compare non-fermented juice and fermented beverage of water kefir produced from Aronia melanocarpa juice and pomace in terms of chemical, physical and sensory quality as well as valorisation of pomace in the production of water kefir. When compared to water kefir made with aronia juice, less reduction in total phenolic content (TPC), total flavonoid content (TFC) and total anthocyanin content (TAC) was observed in samples made with aronia pomace during the fermentation process. Similarly, greater antioxidant activity was demonstrated in water kefir made with aronia pomace than juice. Based on sensory evaluation, no difference was found in overall acceptability, taste, aroma/odor, and turbidity of water kefir made with aronia pomace before and after fermentation. Results indicated that aronia pomace has potential in water kefir production.

Influence of Substrate on the Fermentation Characteristics and Culture-Dependent Microbial Composition of Water Kefir

Water kefir is a sparkling fermented beverage produced by fermenting water kefir grains in a sucrose solution containing dried fruits or fruit extracts. The objective of this study was to investigate the influence of substrate composition on the fermentation kinetics and culture-dependent microbial composition of water kefir. First, the impact of different fruit substrates and nitrogen limitation was examined. Fermentation of different fruit-based media with a single water kefir culture demonstrated that the substrate mainly influenced the type and ratio of the organic acids produced. These organic acid profiles could be linked to the culture-dependent microbial composition. In addition, the microbial composition and the associated dominant microorganisms observed were influenced by the water kefir fermentation conditions. Investigation of the effect of nitrogen limitation on the fermentation kinetics of several water kefir cultures showed that under such conditions, the fermentative capacity of the cultures declined. However, this decline was not immediate, and specific water kefir microorganisms may have enabled some cultures to maintain a higher fermentative capacity for longer. Thus, the water kefir fermentation kinetics and characteristics could be linked to the substrate composition, microorganisms present, and the process conditions under which the fermentations were performed.

Obtention of New Edible Biofilms from Water Kefir Grains in Comparison with Conventional Biofilms from Taro (Colocasia esculenta) and Cassava (Manihot esculenta) Starch

Microorganism biomass is a sustainable and innovative source of biopolymers, such as proteins and polysaccharides, that is suitable for the development of biodegradable films. The aim of this research was to evaluate the synthesis, morphology, rheology, and morphological and mechanical properties on the production of edible biofilms based on water kefir grains, and compare them with edible films based on thermoplastic compounds from starch (TPS) obtained from taro (Colocasia esculenta) and cassava (Manihot esculenta). Edible biofilms were prepared in solution with 30% wt/wt glycerol relative to starch mass and kefir grain biofilms using the casting method. A stationary rheological analysis was performed on the film-forming suspensions of kefir, taro starch, and cassava starch. Once the films were obtained, a physicochemical and morphological characterization was carried out. Results of the characterization showed the following main aspects: The results indicated an increase in biomass production using muscovado and pineapple peel. The film-forming suspensions had a dilating behavior; however, the results obtained not only show the viscoelastic behavior but also the elastic limit (σ0), which varied from 0.077 to 0.059 Pa for suspensions of water kefir grains and from 0.077 to 0.072 Pa for starch suspensions. These elastic limit variations can be defined as the minimum shear stress required to start the flow, and all these rheological data were adjusted to the Herschel–Bulkley model; the morphological and mechanical characterization of the films obtained showed homogeneous surfaces with transparency and without cracks; regarding the water activity, values lower than 6 were obtained, which indicates that there will be no growth of any microorganism, and the hardness data showed differences between those obtained from kefir and taro and cassava starch. The similar results of the rheological characterization in the formation of the kefir biofilm and the conventional edible starch films, in addition to the similar results in the water activity below 6 and the hardness, points to an attractive alternative capable of replacing the conventional materials with a mass production of biofilms of probiotic microorganisms. The results also revealed that water kefir grains biomass is a viable and innovative source of biodegradable materials, and these grains can be an alternative to conventional established starch materials.

Backslopping Time, Rinsing of the Grains During Backslopping, and Incubation Temperature Influence the Water Kefir Fermentation Process

For eight backslopping steps, eight series of water kefir fermentation processes differing in backslopping time and rinsing of the grains during each backslopping step and eight series of fermentation processes differing in incubation temperature and backslopping time were followed. Short backslopping times resulted in high relative abundances of Liquorilactobacillus nagelii and Saccharomyces cerevisiae, intermediate backslopping times in high relative abundances of Leuconostoc pseudomesenteroides, and long backslopping times in high relative abundances of Oenococcus sicerae and Dekkera bruxellensis. When the grains were rinsed during each backslopping step, the relative abundances of Lentilactobacillus hilgardii and Leuc. pseudomesenteroides increased and those of D. bruxellensis and Liql. nagelii decreased. Furthermore, rinsing of the grains during each backslopping step resulted in a slightly higher water kefir grain growth and lower metabolite concentrations. The relative abundances of Liquorilactobacillus mali were highest at 17°C, those of Leuc. pseudomesenteroides at 21 and 25°C, and those of Liql. nagelii at 29°C. With a kinetic modeling approach, the impact of the temperature and rinsing of the grains during the backslopping step on the volumetric production rates of the metabolites was determined.

From Milk Kefir to Water Kefir: Assessment of Fermentation Processes, Microbial Changes and Evaluation of the Produced Beverages

The aim of the present study was to investigate the feasibly of using traditional milk kefir grains for the production of water kefir-like beverages and assess the changes in the physicochemical characteristics and the microbial populations of the fermented beverages. To this end, experiments of milk fermentation were primarily conducted at different temperatures and upon selection of the optimal, a gradual substitution of the substrate was performed by replacing milk from a sucrose-based solution. After the successful fermentation of the sucrose substrate, fruit juices were used as fermentation substrates. Sensory evaluation of the sugar-based beverages was also performed in order to access their acceptability for consumption. According to the results, the transition from milk to water kefir is indeed feasible, leading to the production of beverages with relatively higher ethanol concentrations (up to 2.14 ± 0.12% w/v) than milk kefir and much lower lactic acid concentrations (up to 0.16 ± 0.01% w/v). During the fermentation of the sugary substrates, yeasts seemed to be dominant over lactic acid bacteria, in contrast to what was observed in the case of milk kefir, where LAB dominated. The sensory evaluation revealed that all sugar-based beverages were acceptable for consumption, with the fruit-based ones obtaining, though, a better score in all attributes.

Microorganisms in Whole Botanical Fermented Foods Survive Processing and Simulated Digestion to Affect Gut Microbiota Composition

Botanical fermented foods have been shown to improve human health, based on the activity of potentially beneficial lactic acid bacteria (LAB) and yeasts and their metabolic outputs. However, few studies have explored the effects of prolonged storage and functional spices on microbial viability of whole fermented foods from fermentation to digestion. Even fewer have assessed their impact on the gut microbiota. Our study investigated the effects of production processes on LAB and yeast microbial viability and gut microbiota composition. We achieved this by using physicochemical assessments and an in vitro gastrointestinal and a porcine gut microbiota model. In low-salt sauerkraut, we assessed the effects of salt concentration, starter cultures, and prolonged storage, and in tibicos, prolonged storage and the addition of spices cayenne, ginger, and turmeric. In both food matrices, LAB counts significantly increased (p<0.05), reaching a peak of 7–8 log cfu/g, declining to 6–6.5 log cfu/g by day 96. Yeast viability remained at 5–6 log cfu/g in tibicos. Ginger tibicos had significantly increased LAB and yeast viability during fermentation and storage (p<0.05). For maximum microbial consumption, tibicos should be consumed within 28days, and sauerkraut, 7weeks. Simulated upper GI digestion of both products resulted in high microbial survival rates of 70–80%. The 82% microbial survival rate of cayenne tibicos was significantly higher than other treatments (p<0.05). 16S rRNA sequencing of simulated porcine colonic microbiota showed that both spontaneously fermented sauerkraut and tibicos increase the relative abundance of Megasphaera 85-fold. These findings will inform researchers, producers, and consumers about the factors that affect the microbial content of fermented foods, and their potential effects on the gut.

Water kefir: Factors affecting grain growth and health-promoting properties of the fermented beverage

Nowadays, the interest in the consumption of healthy foods has increased as well as the homemade preparation of artisanal fermented product. Water kefir is an ancient drink of uncertain origin, which has been passed down from generation to generation and is currently consumed practically all over the world. Considering the recent and extensive updates published on sugary kefir, this work aims to shed light on the scientific works that have been published so far in relation to this complex ecosystem. We focused our review evaluating the factors that affect the beverage microbial and chemical composition that are responsible for the health attribute of water kefir as well as the grain growth. The microbial ecosystem that constitutes the grains and the fermented consumed beverage can vary according to the fermentation conditions (time and temperature) and especially with the use of different substrates (source of sugars, additives as fruits and molasses). In this sense, the populations of microorganisms in the beverage as well as the metabolites that they produce varies and in consequence their health properties. Otherwise, the knowledge of the variables affecting grain growth are also discussed for its relevance in maintenance of the starter biomass as well as the use of dextran for technological application.

Tradition as a Stepping Stone for a Microbial Defined Water Kefir Fermentation Process: Insights in Cell Growth, Bioflavoring, and Sensory Perception

A process development from a traditional grain-based fermentation to a defined water kefir fermentation using a co-culture of one lactic acid bacterium and one yeast was elaborated as a prerequisite for an industrially scalable, controllable, and reproducible process. Further, to meet a healthy lifestyle, a low ethanol-containing product was aimed for. Five microbial strains—Hanseniaspora valbyensis, Dekkera bruxellensis, Saccharomyces cerevisiae, Liquorilactobacillus nagelii, and Leuconostoc mesenteroides—were used in pairs in order to examine their influence on the fermentation progress and the properties of the resulting water kefir products against grains as a control. Thereby, the combination of H. valbyensis and L. mesenteroides provided the best-rated water kefir beverage in terms of taste and low ethanol concentrations at the same time. As a further contribution to harmonization and reduction of complexity, the usage of dried figs in the medium was replaced by fig syrup, which could have been proven as an adequate substitute. However, nutritional limitations were faced afterward, and thus, an appropriate supplementation strategy for yeast extract was established. Finally, comparative trials in 5-L scale applying grains as well as a defined microbial consortium showed both water kefir beverages characterized by a pH of 3.14, and lactic acid and aromatic sensory properties. The product resulting from co-culturing outperformed the grain-based one, as the ethanol level was considerably lower in favor of an increased amount of lactic acid. The possibility of achieving a water kefir product by using only two species shows high potential for further detailed research of microbial interactions and thus functionality of water kefir.

Metagenomic and phytochemical analyses of kefir water and its subchronic toxicity study in BALB/c mice

BACKGROUND

In recent years, researchers are interested in the discovery of active compounds from traditional remedies and natural sources, as they reveal higher therapeutic efficacies and improved toxicological profiles. Among the various traditional treatments that have been widely studied and explored for their potential therapeutic benefits, kefir, a fermented beverage, demonstrates a broad spectrum of pharmacological properties, including antioxidant, anti-inflammation, and healing activities. These health-promoting properties of kefir vary among the kefir cultures found at the different part of the world as different media and culture conditions are used for kefir maintenance and fermentation.

METHODS

This study investigated the microbial composition and readily found bioactive compounds in water kefir fermented in Malaysia using 16S rRNA microbiome and UHPLC sequencing approaches. The toxicity effects of the kefir water administration in BALB/c mice were analysed based on the mice survival, body weight index, biochemistry profile, and histopathological changes. The antioxidant activities were evaluated using SOD, FRAP, and NO assays.

RESULTS

The 16S rRNA amplicon sequencing revealed the most abundant species found in the water kefir was Lactobacillus hilgardii followed by Lactobacillus harbinensis, Acetobacter lovaniensis, Lactobacillus satsumensis, Acetobacter tropicalis, Lactobacillus zeae, and Oenococcus oeni. The UHPLC screening showed flavonoid and phenolic acid derivatives as the most important bioactive compounds present in kefir water which has been responsible for its antioxidant activities. Subchronic toxicity study showed no toxicological signs, behavioural changes, or adverse effects by administrating 10 mL/kg/day and 2.5 mL/kg/day kefir water to the mice. Antioxidants assays demonstrated enhanced SOD and FRAP activities and reduced NO level, especially in the brain and kidney samples.

CONCLUSIONS

This study will help to intensify the knowledge on the water kefir microbial composition, available phytochemicals and its toxicological and antioxidant effects on BALB/c mice since there are very limited studies on the water kefir grain fermented in Malaysia.

An update on water kefir: Microbiology, composition and production

Water kefir is a sparkling, slightly acidic fermented beverage produced by fermenting a solution of sucrose, to which dried fruits have been added, with water kefir grains. These gelatinous grains are a symbiotic culture of bacteria and yeast embedded in a polysaccharide matrix. Lactic acid bacteria, yeast and acetic acid bacteria are the primary microbial members of the sugary kefir grain. Amongst other contributions, species of lactic acid bacteria produce the exopolysaccharide matrix from which the kefir grain is formed, while yeast assists the bacteria by a nitrogen source that can be assimilated. Exactly which species predominate within the grain microbiota, however, appears to be dependent on the geographical origin of the grains and the fermentation substrate and conditions. These factors ultimately affect the characteristics of the beverage produced in terms of aroma, flavour, and acidity, for example, but can also be controlled and exploited in the production of a beverage of desired characteristics. The production of water kefir has traditionally occurred on a small scale and the use of defined starter cultures is not commonly practiced. However, as water kefir increases in popularity as a beverage - in part because of consumer lifestyle trends and in part due to water kefir being viewed as a health drink with its purported health benefits - the need for a thorough understanding of the biology and dynamics of water kefir, and for defined and controlled production processes, will ultimately increase. The aim of this review is to provide an update into the current knowledge of water kefir.

The Type and Concentration of Inoculum and Substrate as Well as the Presence of Oxygen Impact the Water Kefir Fermentation Process

Eleven series of water kefir fermentation processes differing in the presence of oxygen and the type and concentration of inoculum and substrate, were followed as a function of time to quantify the impact of these parameters on the kinetics of this process via a modeling approach. Increasing concentrations of the water kefir grain inoculum increased the water kefir fermentation rate, so that the metabolic activity during water kefir fermentation was mainly associated with the grains. Water kefir liquor could also be used as an alternative means of inoculation, but the resulting fermentation process progressed slower than the one inoculated with water kefir grains, and the production of water kefir grain mass was absent. Substitution of sucrose with glucose and/or fructose reduced the water kefir grain growth, whereby glucose was fermented faster than fructose. Lacticaseibacillus paracasei (formerly known as Lactobacillus paracasei), Lentilactobacillus hilgardii (formerly known as Lactobacillus hilgardii), Liquorilactobacillus nagelii (formerly known as Lactobacillus nagelii), Saccharomyces cerevisiae, and Dekkera bruxellensis were the main microorganisms present. Acetic acid bacteria were present in low abundances under anaerobic conditions and only proliferated under aerobic conditions. Visualization of the water kefir grains through scanning electron microscopy revealed that the majority of the microorganisms was attached onto their surface. Lactic acid bacteria and yeasts were predominantly associated with the grains, whereas acetic acid bacteria were predominantly associated with the liquor.

Potential of Bacteria from Alternative Fermented Foods as Starter Cultures for the Production of Wheat Sourdoughs

Microbial strains for starter culture-initiated sourdough productions are commonly isolated from a fermenting flour-water mixture. Yet, starter culture strains isolated from matrices other than sourdoughs could provide the dough with interesting metabolic properties and hence change the organoleptic properties of the concomitant breads. Furthermore, the selection of sourdough starter cultures does not need to be limited to lactic acid bacteria (LAB), as other food-grade microorganisms are sometimes found in sourdoughs. Therefore, different strains belonging to LAB, acetic acid bacteria (AAB), and coagulase-negative staphylococci (CNS) that originated from different fermented food matrices (fermenting cocoa pulp-bean mass, fermented sausage, and water kefir), were examined as to their prevalence in a wheat sourdough ecosystem during 72-h fermentations. Limosilactobacillus fermentum IMDO 222 (fermented cocoa pulp-bean mass isolate) and Latilactobacillus sakei CTC 494 (fermented sausage isolate) seemed to be promising candidates as sourdough starter culture strains, as were the AAB strains Acetobacter pasteurianus IMDO 386B and Gluconobacter oxydans IMDO A845 (both isolated from fermented cocoa pulp-bean mass), due to their competitiveness in the wheat flour-water mixtures. Wheat breads made with G. oxydans IMDO A845 sourdoughs were significantly darker than reference wheat breads.

Probiotic Potential of Lactobacillus paracasei CT12 Isolated from Water Kefir Grains (Tibicos)

The water kefir grains are a multi-species starter culture used to produce fermented beverages of sucrose solution with or without fruit extracts. The water kefir grains are known in Mexico as Tibicos, which are mainly used to produce Tepache, a traditional Mexican drink made by fermenting pineapple peel. The microbiota of Tibicos mainly include lactic acid bacteria (LAB) and since most probiotics belong to this group, Tibicos may represent a potential source of probiotic bacteria. Moreover, several bacteria isolated from kefir samples have been recognized as probiotics. Hence, the aim of this study was to assess the probiotic properties of a Lactobacillus strain isolated from Tibicos. The isolated, designed as CT12, was identified as Lactobacillus paracasei by sequencing 16S RNA gene. L. paracasei CT12 showed a survival rate of ca. 57% and 40% following simulated gastric and intestinal digestion, respectively. Besides, the strain was sensitive to ampicillin and erythromycin, and exhibited hydrophobicity (97-99%), autoaggregation (ca. 70%) and mucin adhesion properties (up to 90%), while no possessed haemolytic capacity. Furthermore, its cell-free supernatant displayed relevant antimicrobial, antifungal and antioxidant capacity. Hence, L. paracasei CT12 appears to possess a potential probiotic value.

The Buffer Capacity and Calcium Concentration of Water Influence the Microbial Species Diversity, Grain Growth, and Metabolite Production During Water Kefir Fermentation

Eight water kefir fermentation series differing in buffer capacity and calcium concentration of the water used for fermentation were studied during eight backslopping steps. High buffer capacities resulted in high pH values and high calcium concentrations resulted in low pH values at the end of each backslopping step. When the water buffer capacity and/or calcium concentration were below certain minima, the water kefir grain growth decreased gradually over multiple backsloppings. High water buffer capacities resulted in high concentrations of residual total carbohydrate concentrations and low metabolite concentrations. Further, high water buffer capacities resulted in high ratios of lactic acid bacteria to yeasts, which was reflected in high molar ratios of the concentrations of lactic acid to ethanol and acetic acid to ethanol. The most prevalent microorganisms of the water kefir grain inoculum and grains of all fermentation series at the end of the eighth backslopping step were Lactobacillus hilgardii, Lactobacillus nagelii, Lactobacillus paracasei, Bifidobacterium aquikefiri, Saccharomyces cerevisiae, and Dekkera bruxellensis. These microbial communities were influenced by the water buffer capacity and had an impact on the substrate consumption and metabolite production during water kefir fermentation.

In situ production and characterization of cloud forming dextrans in fruit-juices

Turbidity in beverages is typically achieved by addition of emulsion based cloud systems. Their intrinsic instability necessitates the widespread use of technological measures and use of food additives to prevent emulsion decay. In this work, we explored the possibility to establish a new generation of natural, stable clouding systems based on bacterial dextrans. Lactobacillus hordei TMW 1.1907 originating from water kefir was used to produce dextrans in sucrose supplemented apple or grape juices. By varying the fermentation conditions, two distinct types of dextran molecules could be produced at yields ranging from 2.5 to 8.5 g/L. The dextran-containing fermentates showed an unchanged turbidity after pasteurization at acidic pH and subsequent storage for three months. No sedimentation of particles occurred upon storage. Neutralization of the acidic fruit juices to pH 7 prior to fermentation significantly increased the dextran yields. The molecular weight, rms radii and turbidity of dextrans produced at 20 °C were higher than those produced at 30 °C. Characterization of the isolated dextrans by asymmetric flow field-flow fractionation coupled to multi-angle laser light scattering revealed a random-coil like structure and rms radii ranging from 66.0 to 87.4 nm. The averaged molar masses of the cloud forming dextrans were in the approximate range of 103.1 to 141.6 MDa. In conclusion, our results demonstrate the possibility to ferment fruit juices for in situ production of dextrans exhibiting novel techno-functional properties beyond gelling and thickening.

Shotgun Metagenomics of a Water Kefir Fermentation Ecosystem Reveals a Novel Oenococcus Species

Water kefir is a fruity, sour, slightly alcoholic and carbonated beverage, which is made by fermentation of an aqueous sucrose solution in the presence of dried figs and water kefir grains. These polysaccharide grains contain lactic acid bacteria (LAB), yeasts, and sometimes bifidobacteria and/or acetic acid bacteria, which consume sucrose to produce exopolysaccharides, lactic acid, acetic acid, ethanol, and carbon dioxide. Shotgun metagenomic sequencing was used to examine the microbial species diversity present at two time points during water kefir fermentation in detail, both in the water kefir liquor and on the water kefir grains, hence representing four samples. Lactobacillus harbinensis, Lactobacillus hilgardii, Lactobacillus nagelii, Lactobacillus paracasei, and a Lactobacillus species similar to Lactobacillus hordei/mali were present in the water kefir examined, along with Bifidobacterium aquikefiri and two yeast species, namely Saccharomyces cerevisiae and Dekkera bruxellensis. In addition, evidence for a novel Oenococcus species related to Oenococcus oeni and Oenococcus kitaharae was found. Its genome was derived from the metagenome and made available under the name of Candidatus Oenococcus aquikefiri. Through functional analysis of the four metagenomic data sets, it was possible to link the production of lactic acid, acetic acid, ethanol, and carbon dioxide to subgroups of the microbial species found. In particular, the production of mannitol from fructose was linked to L. hilgardii, Candidatus O. aquikefiri, and B. aquikefiri, whereas glycerol production was associated with S. cerevisiae. Also, there were indications of cross-feeding, for instance in the case of amino acid supply. Few bacterial species could synthesize a limited number of cofactors, making them reliant on the figs or S. cerevisiae. The LAB species in turn were found to be capable of contributing to water kefir grain growth, as dextransucrase-encoding genes were attributed to L. hilgardii, L. hordei/mali, and Candidatus O. aquikefiri.

Harnessing the Power of Microbiome Assessment Tools as Part of Neuroprotective Nutrition and Lifestyle Medicine Interventions

An extensive body of evidence documents the importance of the gut microbiome both in health and in a variety of human diseases. Cell and animal studies describing this relationship abound, whilst clinical studies exploring the associations between changes in gut microbiota and the corresponding metabolites with neurodegeneration in the human brain have only begun to emerge more recently. Further, the findings of such studies are often difficult to translate into simple clinical applications that result in measurable health outcomes. The purpose of this paper is to appraise the literature on a select set of faecal biomarkers from a clinician’s perspective. This practical review aims to examine key physiological processes that influence both gastrointestinal, as well as brain health, and to discuss how tools such as the characterisation of commensal bacteria, the identification of potential opportunistic, pathogenic and parasitic organisms and the quantification of gut microbiome biomarkers and metabolites can help inform clinical decisions of nutrition and lifestyle medicine practitioners.

Sensor systems for bacterial reactors: A new flavin-phenol composite film for the in situ voltammetric measurement of pH

Monitoring pH within microbial reactors has become an important requirement across a host of applications ranging from the production of functional foods (probiotics) to biofuel cell systems. An inexpensive and scalable composite sensor capable of monitoring the pH within the demanding environments posed by microbial reactors has been developed. A custom designed flavin derivative bearing an electropolymerisable phenol monomer was used to create a redox film sensitive to pH but free from the interferences that can impede conventional pH systems. The film was integrated within a composite carbon-fibre-polymer laminate and was shown to exhibit Nernstian behaviour (55 mV/pH) with minimal drift and robust enough to operate within batch reactors.