Exploring the Role of Lactic Acid Bacteria Blends in Shaping the Volatile Composition of Fermented Dairy and Rice-Based Beverages: A Step towards Innovative Plant-Based Alternatives.

Plant-based products are currently gaining consumers' attention due mainly to the interest in reducing the consumption of foods of animal origin. A comparison of two fermentative processes utilizing dairy milk and a rice beverage was conducted in the present study, using a commercial lactic acid bacteria strain combination (CH) and a selected mixture of lactic acid bacteria from yogurt (LLV). Cell viability and physicochemical characteristics (total soluble solids, pH, total acidity) were determined to describe the samples before and after fermentation, as well as the volatile composition (gas chromatography-mass spectrometry) and the sensory profile (Rate-All-That-Apply test). Results of the analyses showed significant differences among samples, with a clear effect of the raw material on the volatile profile and the sensory characterization, as well as a significant effect of the microbial combination used to ferment the matrices. In general, the selected LLV strains showed a greater effect on both matrices than the commercial combination. Dairy samples were characterized by a volatile profile represented by different chemical families (ketones, lactones, acids, etc.), which contributed to the common descriptive attributes of milk and yogurt (e.g., dairy, cheese). In contrast, rice beverages were mainly characterized by the presence of aldehydes and alcohols (cereal, legume, nutty).

A methodology for the selection and characterization of riboflavin-overproducing Weissella cibaria strains after treatment with roseoflavin.

Fermentative processes by lactic acid bacteria can produce metabolites of interest to the health and food industries. Two examples are the production of B-group vitamins, and of prebiotic and immunomodulatory dextran-type exopolysaccharides. In this study, three riboflavin- and dextran-producing Weissella cibaria strains (BAL3C-5, BAL3C-7 and BAL3C-22) were used to develop a new method for selection and isolation of spontaneous riboflavin-overproducing W. cibaria mutants. This method was based on the selection of strains resistant to roseoflavin. The DNA sequencing of the FMN riboswitch of bacterial cell populations treated with various roseoflavin concentrations, revealed the existence of at least 10 spontaneous and random point mutations at this location. Folding and analysis of the mutated FMN riboswitches with the RNA fold program predicted that these mutations could result in a deregulation of the rib operon expression. When the roseoflavin-treated cultures were plated on medium supporting dextran synthesis, the most promising mutants were identified by the yellow color of their mucous colonies, exhibiting a ropy phenotype. After their isolation and recovery in liquid medium, the evaluation of their riboflavin production revealed that the mutant strains synthesized a wide range of riboflavin levels (from 0.80 to 6.50 mg/L) above the wild-type level (0.15 mg/L). Thus, this was a reliable method to select spontaneous riboflavin-overproducing and dextran-producing strains of W. cibaria. This species has not yet been used as a starter or adjunct culture, but this study reinforces the potential that it has for the food and health industry for the production of functional foods or as a probiotic. Furthermore, analysis of the influence of FMN present in the growth medium, on rib mRNA and riboflavin levels, revealed which mutant strains produce riboflavin without flavin regulation. Moreover, the BAL3C-5 C120T mutant was identified as the highest riboflavin-overproducer. Determination of its chromosomal DNA sequence and that of BAL3C-5, revealed a total identity between the 2 strains except for the C120T mutation at the FMN riboswitch. To our knowledge, this work is the first demonstration that only a single alteration in the genome of a lactic acid bacteria is required for a riboflavin-overproducing phenotype.

Biotechnological Potential and Safety Evaluation of Dextran- and Riboflavin-Producing Weisella cibaria Strains for Gluten-Free Baking.

Gluten consumption causes several immunological and non-immunological intolerances in susceptible individuals. In this study, the dextran-producing Weissella cibaria BAL3C-5 and its derivative, the riboflavin-overproducing strain BAL3C-5 C120T, together with a commercial bakery yeast, were used to ferment gluten-free (GF)-doughs obtained from corn and rice flours at two different concentrations and supplemented with either quinoa, buckwheat, or chickpea to obtain laboratory-scale GF bread. The levels of dextran, riboflavin, and total flavins were determined in the fermented and breads. Both strains grew in fermented doughs and contributed dextran, especially to those made with corn plus quinoa (~1 g/100 g). The highest riboflavin (350-150 µg/100 g) and total flavin (2.3-1.75 mg/100 g) levels were observed with BAL3C-5 C120T, though some differences were detected between the various doughs or breads, suggesting an impact of the type of flour used. The safety assessment confirmed the lack of pathogenic factors in the bacterial strains, such as hemolysin and gelatinase activity, as well as the genetic determinants for biogenic amine production. Some intrinsic resistance to antibiotics, including vancomycin and kanamycin, was found. These results indicated the microbiological safety of both W. cibaria strains and indicated their potential application in baking to produce GF bread.

Fermented foods: An update on evidence-based health benefits and future perspectives.

In recent years, an unstoppable trend toward minimally processed foods has increased the popularity of fermented foods as a beneficial nutritional and functional strategy. Within food fermentations, complex microbial communities trigger different biochemical reactions that result in the release of multiple bioactive compounds with beneficial effects on human health. In the present review the latest studies on fermented foods are summarized. Special attention has been paid on the health benefits of main fermented foods available nowadays, the principal bioactive compounds responsible for such properties as well as the future trends of research studies regarding their potentialities. This review emphasizes the need of clinical evidence to ensure that fermented foods may entail a significant improvement on well-being. Fermented foods may represent a non-invasive strategy to face multiple disorders, as hypertension, diabetes, hyperlipidemia, oxidative stress and multiple cognitive disordes, among others. Release of bioactive compounds, microbial enzymatic conversions or probiotic activities are the main responsible for such interesting properties. However, the need of well-designed clinical trials is a must in order to obtain conclusive results. Bioavailability and biodisponibility of bioactive compounds as well as the design of precision probiotics are also another focus of interest in which it must be deepen.

Recent advances in Kombucha tea: Microbial consortium, chemical parameters, health implications and biocellulose production.

In the present review the latest research studies on Kombucha tea are summarized. Special attention has been paid on microbial population, chemical parameters, biocellulose production, and mainly, on the latest evidences of the biological activities of Kombucha tea. Kombucha tea is a fermented sweetened black or green tea which is obtained from a fermentative process driven by a symbiotic culture of yeast, acetic acid bacteria and lactic acid bacteria. In the last years, its consumption has increasingly grown due to its multiple and potential benefits on human health. This fact has motivated a significant increase in the number of research studies that are focused on the biological activities of this beverage. In this context, this review gathers the main studies that have analyzed the different properties of Kombucha tea (as antioxidant, antimicrobial, antidiabetic, antitumoral, anti-inflammatory, antihypertensive, hepatoprotective, hypocholesterolemic, and probiotic activities). It is highlighted that nowadays few human-based evidences are available to prove the beneficial effect of Kombucha tea on humans' health. In conclusion, further work on Kombucha tea is needed since nowadays few information is available on both clinical studies and the characterization of bioactive compounds and their properties.

Wine aroma profile modification by Oenococcus oeni strains from Rioja Alavesa region: selection of potential malolactic starters.

Previously six selected Oenococcus oeni strains (P2A, P3A, P3G, P5A, P5C and P7B) have been submitted to further characterization in order to clarify their potential as malolactic starters. Laboratory scale vinifications gave an insight of the most vigorous strains: both P2A and P3A strains were able to conclude malolactic fermentation (MLF) in less than 15 days. The remaining strains showed good viability and were able to successfully finish MLF in the established analysis time, except for the strain P5A, which viability was totally lost after inoculation. Also spontaneous fermentation was not initiated. None of the strains was biogenic amine producer; however, P5C strain significantly increased the concentration of volatile phenol-precursor hydroxycinnamic acids after MLF. Regarding the evolution of wine aromatic compounds, main changes were detected for both ethyl and acetate esters after MLF; however, key aromatic compounds including alcohols, terpenes or acids were also found to significantly increase. Principal component analysis classified the strains in two distinct groups, each one correlated with different key volatile compounds. P2A, P3A, P3G and P5C strains were mainly linked to esters, while P7B and the commercial strain Viniflora OENOS showed higher score for diverse compounds as hexanoic acid, ß-damascenone, linalool or 2-phenylethanol. These results confirmed the specific impact of each strain on wine aroma profile, which could lead to the production of wines with individual characteristics, in which the reliability and safety of MLF is also ensured.