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Probiotic viability, metabolite concentrations, physicochemical parameters, and volatile compounds were characterized in Gueuze beers formulated with probiotic lactic acid bacteria (LAB) and yeast. Additionally, the sensory profile of the beers and the resistance of the probiotics to digestion were determined. The use of 2 International Bitterness Units resulted in high concentrations of probiotic LAB but a decline in probiotic yeast as pH decreased. Secondary fermentation led to the consumption of maltose, citric acid, and malic acid, and the production of lactic and propionic acids. Carbonation and storage at 4 °C had minimal impact on probiotic viability. The addition of probiotic LAB resulted in a distinct aroma profile with improved sensory characteristics. Our results demonstrate that sour beers produced with probiotic LAB and a probiotic yeast, and fermented using a two-step fermentation process, exhibited optimal physicochemical parameters, discriminant volatile compound profiles, promising sensory characteristics, and high probiotic concentrations after digestion., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

This study aimed to transform raspberry pomace, a by-product of the berry industry, into a sustainable, fiber-rich functional ingredient using convective drying. Drying experiments were conducted at temperatures of 50, 60, 70, 80, and 90 °C to identify the optimal conditions that balance process efficiency and preservation of functional and bioactive properties. The best results were achieved at 70 °C, where a high drying rate ( DR ) of 0.46 kg H 2 O·kg -1 db·min -1 , effective moisture diffusivity ( D eff ) of 1.53 × 10 -10 m 2 ·s -1 , and activation energy ( E a ) of 34.90 kJ·mol -1 were observed. The Page model accurately represented the drying behavior ( R 2 = 0.9965-0.9997). Total dietary fiber (TDF) content remained stable across temperatures (52.52-64.76 g·100 g -1 db), while soluble dietary fiber (SDF) increased by 43.40%, resulting in a solubility (SOL) of 71.8%, water-holding capacity (WHC) of 8.2 mL·g -1 db, and oil-holding capacity (OHC) of 3.0 mL·g -1 db. High retention of bioactive compounds was achieved at 70 °C, including phenolics (32.10 mg GAE·g -1 db) and anthocyanins (25.84 mg C3G·g -1 db), resulting in significant antioxidant activities (DPPH: 33.29 mg AAE·g -1 db, IC 50 0.016 mg·mL -1 ; ABTS: 35.85 mg AAE·g -1 db, IC 50 0.029 mg·mL -1 ). These findings demonstrated the potential of convective drying at 70 °C to efficiently transform raspberry pomace into a high-quality functional ingredient. This process promotes sustainable production and waste reduction in the berry industry.

The food and beverage industries in Mexico generate substantial effluents, including nejayote, cheese-whey, and tequila vinasses, which pose significant environmental challenges due to their extreme physicochemical characteristics and excessive organic load. This study aimed to assess the potential of Chlorella vulgaris in bioremediating these complex wastewaters while also producing added-value compounds. A UV mutagenesis treatment (40 min) enhanced C. vulgaris adaptability to grow in the effluent conditions. Robust growth was observed in all three effluents, with nejayote identified as the optimal medium. Physicochemical measurements conducted pre- and post-cultivation revealed notable reductions of pollutants in nejayote, including complete removal of nitrogen and phosphates, and an 85 % reduction in COD. Tequila vinasses exhibited promise with a 66 % reduction in nitrogen and a 70 % reduction in COD, while cheese-whey showed a 17 % reduction in phosphates. Regarding valuable compounds, nejayote yielded the highest pigment (1.62 mg·g -1 ) and phenolic compound (3.67 mg·g -1 ) content, while tequila vinasses had the highest protein content (16.83 %). The main highlight of this study is that C. vulgaris successfully grew in 100 % of the three effluents (without additional water or nutrients), demonstrating its potential for sustainable bioremediation and added-value compound production. When grown in 100 % of the effluents, they become a sustainable option since they don't require an input of fresh water and therefore do not contribute to water scarcity. These findings offer a practical solution for addressing environmental challenges in the food and beverage industries within a circular economy framework., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Probiotic-enriched beers have emerged as an innovative solution for delivering beneficial microorganisms, particularly appealing to consumers seeking non-dairy options. However, navigating the complex beer environment presents challenges in effectively cultivating specific probiotic strains. This review aims to promote innovation and distinctiveness within the brewing industry by providing insights into current research on the integration of probiotic microorganisms into beer production, thereby creating a functional beverage. The review explores the effects of probiotic incorporation on the functional, technological, and sensory attributes of beer, distinguishing contributions from bacterial and yeast, as well as potential health benefits. Probiotic microorganisms encounter hurdles during beer production, including ethanol, hops, CO 2 levels, pH, oxygen, and nutrients. Ethanol tolerance mechanisms vary among bacteria and yeasts, with specific lactic acid bacteria showing resistance to hop compounds. Hops, crucial for beer categorization, exert a timing-dependent impact on probiotics-early isomerization impedes growth, while late additions yield non-isomerized antibacterial properties. Effective probiotic integration necessitates precise post-fermentation addition stages to ensure viability and flavor. The sensory impact and consumer reception of probiotic-enriched beers require further exploration. Probiotics must endure storage conditions to qualify as functional beer, while limited research investigates health advantages, urging enhanced production techniques, sensory optimization, and clinical validation., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Wastewater disposal is a major environmental issue that pollutes water, causing eutrophication, habitat destruction, and economic impact. In Mexico, food-processing effluents pose a huge environmental threat due to their excessive nutrient content and their large volume discharged every year. Some of the most harmful residues are tequila vinasses, nejayote, and cheese whey. Each liter of tequila generates 13-15 L of vinasses, each kilogram of cheese produces approximately 9 kg of cheese whey, and each kilogram of nixtamalized maize results in the production of 2.5-3.3 L of nejayote. A promising strategy to reduce the contamination derived from wastewater is through microalgae-based wastewater treatment. Microalgae have a high adaptability to hostile environments and they can feed on the nutrients in the effluents to grow. Moreover, to increase the viability, profitability, and value of wastewater treatments, a microalgae biorefinery could be proposed. This review will focus on the circular bioeconomy scheme focused on the simultaneous food-processing wastewater treatment and its use to grow microalgae biomass to produce added-value compounds. This strategy allows for the revalorization of wastewater, decreases contamination of water sources, and produces valuable compounds that promote human health such as phycobiliproteins, carotenoids, omega-3 fatty acids, exopolysaccharides, mycosporine-like amino acids, and as a source of clean energy: biodiesel, biogas, and bioethanol., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Cesar E. Najar-Almanzor reports financial support was provided by CONACYT- Mexico. Tlalli Uribe-Velazquez reports financial support was provided by CONACYT- Mexico., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Gut metagenome in pediatric subjects with metabolic syndrome (MetS) and type-2 diabetes mellitus (T2DM) has been poorly studied, despite an alarming worldwide increase in the prevalence and incidence of obesity and MetS within this population. The objective of this study was to characterize the gut microbiome taxonomic composition of Mexican pediatric subjects with MetS and T2DM using shotgun metagenomics and analyze the potential relationship with metabolic changes and proinflammatory effects. Paired-end reads of fecal DNA samples were obtained through the Illumina HiSeq X Platform. Statistical analyses and correlational studies were conducted using gut microbiome data and metadata from all individuals. Gut microbial dysbiosis was observed in MetS and T2DM children compared to healthy subjects, which was characterized by an increase in facultative anaerobes (i.e., enteric and lactic acid bacteria) and a decrease in strict anaerobes (i.e., Erysipelatoclostridium , Shaalia , and Actinomyces genera). This may cause a loss of gut hypoxic environment, increased gut microbial nitrogen metabolism, and higher production of pathogen-associated molecular patterns. These metabolic changes may trigger the activation of proinflammatory activity and impair the host's intermediate metabolism, leading to a possible progression of the characteristic risk factors of MetS and T2DM, such as insulin resistance, dyslipidemia, and an increased abdominal circumference. Furthermore, specific viruses ( Jiaodavirus genus and Inoviridae family) showed positive correlations with proinflammatory cytokines involved in these metabolic diseases. This study provides novel evidence for the characterization of MetS and T2DM pediatric subjects in which the whole gut microbial composition has been characterized. Additionally, it describes specific gut microorganisms with functional changes that may influence the onset of relevant health risk factors., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (© 2023 Carrizales-Sánchez, Tamez-Rivera, García-Gamboa, García-Cayuela, Rodríguez-Gutiérrez, Elizondo-Montemayor, García-Rivas, Pacheco, Hernández-Brenes, and Senés-Guerrero.)

Since 2011, a massive influx of pelagic brown algae Sargassum has invaded coastlines causing environmental and economic disaster. Valorizing this plentiful macroalgae can present much needed economic relief to the areas affected. Here the production of biodiesel and a high-value alginate stream using Sargassum biomass collected from the coast of Quintana Roo, Mexico is reported. Biomass was pretreated via AEA (Alginate Extraction Autohydrolysis) and enzymatic saccharification via fungal Solid State Fermentation, releasing 7 g/L total sugars. The sugar mixture was fermented using engineered Yarrowia lipolytica resulting in 0.35 g/L total lipid titer at the lab tube scale. Additionally, the capability of extracting 0.3875 g/g DW of a high-value, purified alginate stream from this material is demonstrated. The findings presented here are promising and suggest an opportunity for the optimization and scale up of a biodiesel production biorefinery for utilization of Sargassum seaweeds during seasons of high invasion., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Sourdough (SD) fermentation is a traditional biotechnological process used to improve the properties of baked goods. Nowadays, SD fermentation is studied for its potential health effects due to the presence of postbiotic-like components, which refer to a group of inanimate microorganisms and/or their components that confer health benefits on the host. Some postbiotic-like components reported in SD are non-viable microorganisms, short-chain fatty acids, bacteriocins, biosurfactants, secreted proteins/peptides, amino acids, flavonoids, exopolysaccharides, and other molecules. Temperature, pH, fermentation time, and the composition of lactic acid bacteria and yeasts in SD can impact the nutritional and sensory properties of bread and the postbiotic-like effect. Many in vivo studies in humans have associated the consumption of SD bread with higher satiety, lower glycemic responses, increased postprandial concentrations of short-chain fatty acids, and improvement in the symptoms of metabolic or gastrointestinal-related diseases. This review highlights the role of bacteria and yeasts used for SD, the formation of postbiotic-like components affected by SD fermentation and the baking process, and the implications of functional SD bread intake for human health. There are few studies characterizing the stability and properties of postbiotic-like components after the baking process. Therefore, further research is necessary to develop SD bread with postbiotic-related health benefits., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The reviewer MT declared a shared parent affiliation with the author TR to the handling editor at the time of review., (Copyright © 2022 Pérez-Alvarado, Zepeda-Hernández, Garcia-Amezquita, Requena, Vinderola and García-Cayuela.)

Isolation and functional characterization of microorganisms are relevant steps for generating starter cultures with functional properties, and more recently, those related to improving mental health. Milk kefir grains have been recently investigated as a source of health-related strains. This study focused on the evaluation of microorganisms from artisanal Mexican milk kefir grains regarding probiotic properties, in vitro fermentability with commercial prebiotics (lactulose, inulin, and citrus pectin), and γ-aminobutyric acid (GABA)-producing capacity. Microorganisms were identified belonging to genera Lactococcus , Lactobacillus , Leuconostoc , and Kluyveromyces . The probiotic properties were assessed by aggregation abilities, antimicrobial activity, antibiotic susceptibility, and resistance to in vitro gastrointestinal digestion, showing a good performance compared with commercial probiotics. Most of isolates maintained a concentration above 6 log colony forming units/mL after the intestinal phase. Specific isolates of Kluyveromyces (BIOTEC009 and BIOTEC010), Leuconostoc (BIOTEC011 and BIOTEC012), and Lactobacillus (BIOTEC014 and BIOTEC15) showed a high fermentability in media supplemented with commercial prebiotics. The capacity to produce GABA was classified as medium for L. lactis BIOTEC006, BIOTEC007, and BIOTEC008; K. lactis BIOTEC009; L. pseudomesenteroides BIOTEC012; and L. kefiri BIOTEC014, and comparable to that obtained for commercial probiotics. Finally, a multivariate approach was performed, allowing the grouping of 2-5 clusters of microorganisms that could be further considered new promising cultures for functional dairy food applications.

Cactus berry (Myrtillocactus geometrizans) is a scarcely studied Mexican wild fruit. These fruits could contribute to reduce the risk of degenerative chronic diseases due to their bioactive profile. The aim of this work was to study the betalains and phenolic profile in cactus berry, their in vitro biological activities and gastrointestinal digestive stability and bioaccessibility. 43 metabolites were identified by HPLC-DAD-ESI-QTOF (8 betaxanthins, 8 betacyanins, 13 flavonoids, 6 phenolic acids). Phyllocactin and Isorhamnetin rhamnosyl-rutinoside (IG2) were the most abundant metabolites (5876 and 396 µg/g dw) which were also bioaccessible (16 and 21%, respectively). Pulps showed higher (p ≤ 0.05) antioxidant activity by the Oxygen Radical Absorbance Capacity (27 mM Trolox equivalents). The anti-hyperglycemic activity was highest (p ≤ 0.05) in peel and pulp tissues (85% α-glucosidase and 8% α-amylase inhibition). An 83% inhibition of hyaluronidase showed high anti-inflammatory activity. Cactus berry fruit should be considered a promising fruit candidate for a sustainable healthy diet., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Since long ago, pelagic Sargassum mats have been known to be abundant in the Sargasso Sea, where they provide habitat to diverse organisms. However, over the last few years, massive amounts of pelagic Sargassum have reached the coast of several countries in the Caribbean and West Africa, causing economic and environmental problems. Aiming for lessening the impacts of the blooms, governments and private companies remove the seaweeds from the shore, but this process results expensive. The valorization of this abundant biomass can render Sargassum tides into an economic opportunity and concurrently solve their associated environmental problems. Despite the diverse fields where algae have found applications and the relevance of this recurrent situation, Sargassum biomass remains without large scale applications. Therefore, this review aims to present the potential uses of these algae, identifying the limitations that must be assessed to effectively valorize this bioresource. Due to the constraints identified for each of the presented applications, it is concluded that a biorefinery approach should be developed to effectively valorize this abundant biomass. However, there is an urgent need for investigations focusing on holopelagic Sargassum to be able to truly valorize this seaweed., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Diabetes mellitus type 2 (T2DM) is associated with hyperglycemia, insulin resistance, and gut dysbiosis. Probiotics and prebiotics can ameliorate T2DM through different mechanisms of action, such as reducing oxidative stress, or the inhibition of pro-inflammatory markers, among others. Multiple studies in vitro and in vivo have demonstrated the reduction of hyperglycemia, depressive behaviors, obesity, oxidative stress, and insulin resistance in diabetic patients through the consumption of dairy products, such as yogurt, fermented milk, and cheese, enriched with potential probiotic strains, prebiotic ingredients, and synbiotics (understood as a combination of both). Therefore, this review aims to provide an updated overview about the impact of dairy foods with probiotics, prebiotics, or synbiotics to prevent and manage T2DM, the mechanism of action related to the host health, and the future tendencies for developing new dairy foods. Despite the addition of probiotics, prebiotics, and synbiotics to dairy products could be highly beneficial, more evidence, especially from clinical trials, is needed to develop evidence-based T2DM prevention guidelines., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Childhood obesity and T2DM have shown a recent alarming increase due to important changes in global lifestyle and dietary habits, highlighting the need for urgent and novel solutions to improve global public health. Gut microbiota has been shown to be relevant in human health and its dysbiosis has been associated with MetS, a health condition linked to the onset of relevant diseases including T2DM. Even though there have been recent improvements in the understanding of gut microbiota-host interactions, pediatric gut microbiota has been poorly studied compared to adults. This review provides an overview of MetS and its relevance in school-age children, discusses gut microbiota and its possible association with this metabolic condition including relevant emerging gut microbiome-based interventions for its prevention and treatment, and outlines future challenges and perspectives in preventing microbiota dysbiosis from the early stages of life.

The gut-brain-microbiota axis consists of a bilateral communication system that enables gut microbes to interact with the brain, and the latter with the gut. Gut bacteria influence behavior, and both depression and anxiety symptoms are directly associated with alterations in the microbiota. Psychobiotics are defined as probiotics that confer mental health benefits to the host when ingested in a particular quantity through interaction with commensal gut bacteria. The action mechanisms by which bacteria exert their psychobiotic potential has not been completely elucidated. However, it has been found that these bacteria provide their benefits mostly through the hypothalamic-pituitary-adrenal (HPA) axis, the immune response and inflammation, and through the production of neurohormones and neurotransmitters. This review aims to explore the different approaches to evaluate the psychobiotic potential of several bacterial strains and fermented products. The reviewed literature suggests that the consumption of psychobiotics could be considered as a viable option to both look after and restore mental health, without undesired secondary effects, and presenting a lower risk of allergies and less dependence compared to psychotropic drugs.

Background: Prickly pears are potential candidates for the development of low-cost functional foods because they grow with low water requirements in arid regions of the world. They are sources of betalains and phenolic compounds, which have been reported to contribute to human health. The study of the biological activity of different varieties and of their isolated bioactive constitutes is fundamental in the design of functional foods. In this context, our objective is the assessment of the ability of Spanish and Mexican prickly-pear cultivars to inhibit enzymes related to type 2 diabetes and the inflammatory response, and the contribution of their bioactive compounds to their nutra-pharmaceutical potential., Results: Prickly pear peels presented the highest antioxidant activity due to their high isorhamnetin glycoside content. Isorhamnetin glycosides showed significantly higher antioxidant and anti-inflammatory activity than aglycone, particularly isorhamnetin glucosyl-rhamnosyl-pentoside (IG2), which also reported antihyperglycemic activity. Morada, Vigor, and Sanguinos whole fruits exhibited moderate α-amylase inhibition and higher α-glucosidase inhibition, which is ideal for lowering glucose absorption in hyperglycemia management. Sanguinos peels presented the highest anti-inflammatory activity because of their high indicaxanthin content and isorhamnetin glycoside profile., Conclusions: In the design of prickly pear functional foods, technological processing should prioritize the retention or concentration of these bioactive compounds to preserve (or increase) their natural antioxidant, antihyperglycemic and anti-inflammatory activity. Peels of red and orange varieties should be further evaluated for antioxidant and anti-inflammatory purposes while whole fruits of red and purple varieties could be considered possible candidates for hyperglycemia management. © 2019 Society of Chemical Industry., (© 2019 Society of Chemical Industry.)

The carotenoid and carotenoid ester profile in astringent persimmon (Diospyros kaki Thunb., var. Rojo Brillante) was composed by 13 free xanthophylls, 8 hydrocarbon carotenes and 17 carotenoid esters. The stability and biaoccessibility of these carotenoids was determined by an adaptation of the INFOGEST protocol. Results showed that the stability of persimmon carotenoids ranged from 61 to 74%, depending on the digestion phase, being (all-E)-β-cryptoxanthin and (all-E)-antheraxanthin 3-O-palmitate the most stable carotenoids. At the final step of the digestion (oral + gastric + duodenal phase), only traces of (all-E)-antheraxanthin, (all-E)-lutein and (all-E)-β-cryptoxanthin were found in control samples due to the low efficiency of carotenoid micellization, which was affected by the high pectin content naturally present in persimmon tissues. Processing increased the overall carotenoid bioaccessibility to 54% in pressurized samples and to 25% in thermal treated ones. This effect depended on the processing technology as well as on the chemical structure of the carotenoid, being (all-E)-β-cryptoxanthin and (all-E)-β-cryptoxanthin laurate the most bioaccessible carotenoids in pressurized samples and (all-E)-β-cryptoxanthin laurate and (all-E)-antheraxanthin the most bioaccessible ones in pasteurized ones., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Background: Addition of persimmon fruit, which is highly rich in carotenoids, to dairy products represents an alternative to obtain functional foods. However, carotenoid bioaccessibility is strongly influenced by fat content and food composition. That is why in vitro bioaccessibility of individual carotenoids was evaluated in persimmon-based dairy products formulated with whole (3.6% fat) or skimmed milk (0.25% fat) and different freeze-dried persimmon tissues., Results: Unambiguous identification of seven xanthophylls (neoxanthin, violaxanthin, antheraxanthin, lutein, zeaxanthin, lutein epoxide and β-cryptoxanthin) and three hydrocarbon carotenes (α-carotene, β-carotene and lycopene) was achieved using high-performance liquid chromatography with a reverse-phase C-30 column. Total carotenoid content declined up 71% through the digestion process. In vitro bioaccessibility of carotenoids was significantly higher in dairy products formulated with whole milk than those with skimmed milk, representing a difference of more than 21% (in the formulation using persimmon whole fruit as ingredient). Furthermore, addition of whole milk to any type of persimmon tissue significantly improved the bioaccessibility of total provitamin A carotenoids, reaching the highest values (38%) with whole fruit and whole milk., Conclusion: The higher fat content in whole milk exerted a significant influence on carotenoid bioaccessibility, especially when using freeze-dried persimmon whole fruit. © 2017 Society of Chemical Industry., (© 2017 Society of Chemical Industry.)

The aim of the study was to evaluate the potential use of Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS) for fast and reliable detection of strains producing the lantibiotics nisin, lacticin 481 and lacticin 3147 in a large collection of lactococci. A total of one hundred lactococcal isolates from traditional ewe's and goat's raw milk cheeses were identified to the species level as Lactococcuslactis by MALDI-TOF MS based on comparison with lactococcal entries in the BioTyper database. Mass spectra in the range 2000-4000Da of the identified isolates were compared to reference spectra of three lactococcal strains producing lacticin 481 (IFPL 330), lacticin 3147 (IFPL 105) and nisin (IFPL 503). Only eight isolates had mass spectra with peaks that could be unequivocally identified as lacticin 481 (2900.47Da) or nisin (3330.31Da). None of the assayed isolates matched the mass spectra corresponding to the two-peptide lacticin 3147 (2847.97 and 3306.29Da). The results obtained by MALDI-TOF MS were genetically validated by amplification of the corresponding structural gene coding for lacticin 481, nisin and lacticin 3147. MALDI-TOF MS can be used as a fast and reliable technique to screen a large number of lactococcal isolates for the ability to produce the lantibiotics nisin, lacticin 481 and lacticin 3147., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Lactobacilli are widespread in natural environments and are increasingly being investigated as potential health modulators. In this study, we have adapted the broad-host-range vector pNZ8048 to express the mCherry protein (pRCR) to expand the usage of the mCherry protein for analysis of gene expression in Lactobacillus. This vector is also able to replicate in Streptococcus pneumoniae and Escherichia coli. The usage of pRCR as a promoter probe was validated in Lactobacillus acidophilus by characterizing the regulation of lactacin B expression. The results show that the regulation is exerted at the transcriptional level, with lbaB gene expression being specifically induced by co-culture of the L. acidophilus bacteriocin producer and the S. thermophilus STY-31 inducer bacterium.

Hydroxyacid dehydrogenases limit the conversion of α-keto acids into aroma compounds. Here we report that inactivation of the panE gene, encoding the α-hydroxyacid dehydrogenase activity in Lactococcus lactis, enhanced the formation of 3-methylbutanal and 3-methylbutanol. L. lactis IFPL953ΔpanE was an efficient strain producing volatile compounds related to cheese aroma.

Formation of cheese aroma compounds by Lactococcus lactis from amino acid catabolism depends on a complex network of reactions, which involve enzymes such as aminotransferases, dehydrogenases, lyases, and decarboxylases, among others. Based on the ability of some L. lactis strains to grow with low requirements of amino acids, we have studied in L. lactis IFPL730 the effect of the branched chain amino acid (BCAA) content on the expression of functional genes related to amino acid catabolism and aroma compound formation (araT, bcaT, kivD, ytjE and panE). L. lactis IFPL730 growth rate decreased under leucine, valine or isoleucine starvation but the strain reached similar viable counts at the stationary phase in all culture conditions studied. The level of expression of some genes encoding enzymes involved in amino acid catabolism changed significantly (P<0.05) when those conditions were compared. Specially, α-ketoisovalerate decarboxylase (kivD), BCAA-specific aminotransferase (bcaT) and C-S lyase (yjtE) gene expressions increased markedly by both isoleucine and valine starvation. In addition to gene expression, formation of volatile compounds was determined in all growth conditions. The results showed that BCAA starvation conditions caused a significant increase (P<0.05) in the formation of metabolic end products related to cheese aroma, such as 3-methylbutanal and 3-methylbutanol., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Fluorescent reporter genes are valuable tools for real-time monitoring of gene expression in living cells. In this study we describe the construction of novel promoter-probe vectors containing a synthetic mCherry fluorescent protein gene, codon-optimized for lactic acid bacteria, divergently linked, or not, to a gene encoding the S65T and F64L variant of the green fluorescent protein. The utility of the transcriptional fusion vectors was demonstrated by the cloning of a single or two divergent promoter regions and by the quantitative evaluation of fluorescence during growth of Lactococcus lactis, Enterococcus faecalis, and Escherichia coli.

The effect of dietary flavan-3-ols on the adhesion of potential probiotic lactobacilli strains to intestinal cells was unraveled. The inhibitory activity of these compounds on intestinal cells was highlighted. The cytotoxic effect was shown to depend on both the compound's chemical structure (galloylation and polymerization) and degree of differentiation of intestinal cells. The effect of flavan-3-ols on bacteria adhesion differed greatly between compounds, strains, and intestinal cells. All flavan-3-ols inhibited significantly Lactobacillus acidophilus LA-5 and Lactobacillus plantarum IFPL379 adhesion except epigallocatechin gallate, which enhanced L. acidophilus LA-5 adhesion to Caco-2. Procyanidins B1 and B2 increased remarkably the adhesion of Lactobacillus casei LC115 to HT-29 cells, whereas epigallocatechin increased L. casei LC115 adhesion to Caco-2. These data showed the potential of flavan-3-ols to alter gut microecology by modifying adhesion of lactobacilli strains to intestinal cells.

Lactobacillus acidophilus La-5 is a probiotic strain used in dairy products. Production of bacteriocin by L. acidophilus La-5 was achieved when it was grown in co-cultures with the yogurt starter species Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus. However, bacteriocin induction was not observed when heat-killed cells were used as inducers. This study demonstrates that L. acidophilus La-5 produces lactacin B and that the bacteriocin expression is controlled by an auto-induction mechanism involving the secreted peptide IP&#95;1800. The transcript level of the lactacin B gene cluster expression was investigated in co-cultures between L. acidophilus La-5 and S. thermophilus STY-31 and a remarkable increase of the bacteriocin structural gene (lbaB) transcription was observed. However, lbaB was transcribed constitutively in uninduced L. acidophilus La-5 cells, but the levels of the secreted bacteriocin were not enough to be detected by the agar diffusion assay. A new method for bacteriocin detection was formulated based on the monitoring on real time of Lactobacillus sakei subsp. sakei growth in presence of the supernatant and the cell wall extracts of pure and induced L. acidophilus La-5. These results showed that part of lactacin B secreted remains adhered to cell envelope.