Selection and characterization of mixed starter cultures for lactic acid fermentation of carrot, cabbage, beet and onion vegetable mixtures

Microbial communities of a variety of 75 homemade fermented vegetables

Fermentation is an ancient practice of food preservation. Fermented vegetables are popular in Eastern European and Asian countries. They have received a growing interest in Western countries, where they are mainly manufactured at domestic and artisanal scales and poorly characterized. Our aim was to investigate the microbial communities and the safety of French homemade fermented vegetables, in the frame of a citizen science project. Fermented vegetables and the data associated with their manufacture were collected from citizens and characterized for pH, NaCl concentration, and microbiology by culturomics and 16S DNA metabarcoding analysis. Lactic acid bacteria (LAB) and yeast isolates were identified by 16S rRNA gene sequencing and D1/D2 domains of the large subunit of the rRNA gene, respectively. The 75 collected samples contained 23 types of vegetables, mainly cabbage, followed by carrots and beets, and many mixtures of vegetables. They were 2 weeks to 4 years old, and their median pH was 3.56, except for two samples with a pH over 4.5. LAB represented the dominant viable bacteria. LAB concentrations ranged from non-detectable values to 8.7 log colony-forming units (CFU)/g and only depended on the age of the samples, with the highest most frequently observed in the youngest samples (<100 days). The 93 LAB isolates identified belonged to 23 species, the two mains being Lactiplantibacillus pentosus/plantarum and Levilactobacillus brevis. The other microbial groups enumerated (total aerobic bacteria, halotolerant bacteria, Gram-negative bacteria, and acetic acid bacteria) generally showed lower concentrations compared to LAB concentrations. No pathogenic bacteria were detected. Viable yeasts were observed in nearly half the samples, at concentrations reaching up to 8.0 log CFU/g. The 33 yeast clones identified belonged to 16 species. Bacterial metabarcoding showed two main orders, namely, Lactobacillales (i.e., LAB, 79% of abundance, 177 of the 398 total ASVs) and Enterobacterales (19% of abundance, 191 ASVs). Fifteen LAB genera were identified, with Lactiplantibacillus and Levilactobacillus as the most abundant, with 41 and 12% of total reads, respectively. Enterobacterales members were mainly represented by Enterobacteriaceae and Yersiniaceae. This study is the first wide description of the microbiota of a large variety of homemade fermented vegetables and documents their safety.

Microbial and Physicochemical Dynamics of Kocho, Fermented Food from Enset

Over 20 million Ethiopians depend on enset (Ensete ventricosum) as a staple or costaple food. "Kocho," "Bulla," and "Amicho" are the three main food types obtained from enset. This review aimed to summarize the physicochemical and microbial dynamics of kocho. It is the most common food obtained from the scraped pseudostem and decorticated corm of enset after a long period of fermentation. The quality of kocho depends on the maturity of the enset plant, the enset processing method, the fermentation period, and the dynamics of microorganisms during the fermentation process. Microorganisms play a significant role in kocho fermentation to enhance its nutritional quality, improve sensory properties, and reduce spoilage and disease-causing agents. The populations of microbes available in kocho fermentation include lactic acid bacteria (LAB), Enterobacteriaceae, acetic acid bacteria (AAB), yeasts and molds, and Clostridium spp., which have both positive and negative impacts on kocho quality. There is a visible variation in microbial dynamics during kocho fermentation caused by the fermentation period. As the fermentation day increases, species of LAB also increase, whereas counts of Enterobacteriaceae decrease. This is due to a decrease in pH, which leads to an increase in titratable acidity. Moisture content also slightly decreases as fermentation progresses. Dynamics in the microbial population and physicochemical parameters ensure the development of desirable qualities in kocho and enhance the acceptability of the final product. Organic acids (such as lactic acid, acetic acid, and propionic acid), bacteriocins, phenolic compounds, flavonoids, and tannins are bioactive compounds produced by microorganisms during Kocho fermentation. Further research is needed on the molecular identification of microorganisms during Kocho fermentation.

Production of glycerolamines based conjugated γ-aminobutyric acids using microbial COX and LOX as successor enzymes to GAD

Gamma-aminobutyric acid (γ-ABA) can be produced by various microorganisms including bacteria, fungi and yeasts using enzymatic bioconversion, microbial fermentation or chemical hydrolysis. Regenerating conjugated glycerol-amines is valid by the intervention of microbial cyclooxygenase [COX] and lipooxygenase [LOX] enzymes produced via lactobacillus bacteria (LAB) as successor enzymes to glutamate decarboxylases (GAD). Therefore, the aim of this review is to provide an overview on γ-ABA production, and microbiological achievements used in producing this signal molecule based on those fermenting enzymes. The formation of aminoglycerides based conjugated γ-ABA is considered the key substances in controlling the host defense against pathogens and is aimed in increasing the neurotransmission effects and in suppressing further cardiovascular diseases.

A Novel Symbiotic Beverage Based on Sea Buckthorn, Soy Milk and Inulin: Production, Characterization, Probiotic Viability, and Sensory Acceptance

Nowadays, vegan consumers demand that food products have more and more properties that contribute to the prevention of some diseases, such as lower fat content, increased mineral content (calcium, iron, magnesium, and phosphorus), pleasant flavor, and low calorie values. Therefore, the beverage industry has tried to offer consumers products that include probiotics, prebiotics, or symbiotics with improved flavor and appearance and beneficial effects on health. The possibility of producing beverages based on soy milk with sea buckthorn syrup or sea buckthorn powder supplemented with inulin and fermented with the Lactobacillus casei ssp. paracasei strain was examined. The aim of this study was to obtain a novel symbiotic product that exploits the bioactive potential of sea buckthorn fruits. Tests were carried out in the laboratory phase by fermenting soy milk, to which was added sea buckthorn syrup (20%) or sea buckthorn powder (3%) and inulin in proportions of 1% and 3%, with temperature variation of fermentation (30 and 37 °C). During the fermentation period, the survivability of prebiotic bacteria, pH, and titratable acidity were measured. The storage time of beverages at 4 °C ± 1 °C was 14 days, and the probiotic viability, pH, titratable acidity, and water holding capacity were determined. Novel symbiotic beverages based on sea buckthorn syrup or powder, inulin, and soy milk were successfully obtained using the Lactobacillus casei ssp. paracasei strain as a starter culture. Moreover, the inulin added to the novel symbiotic beverage offered microbiological safety and excellent sensory attributes as well.

Response mechanisms to acid stress of acid-resistant bacteria and biotechnological applications in the food industry

Acid-resistant bacteria are more and more widely used in industrial production due to their unique acid-resistant properties. In order to survive in various acidic environments, acid-resistant bacteria have developed diverse protective mechanisms such as sensing acid stress and signal transduction, maintaining intracellular pH homeostasis by controlling the flow of H⁺, protecting and repairing biological macromolecules, metabolic modification, and cross-protection. Acid-resistant bacteria have broad biotechnological application prospects in the food field. The production of fermented foods with high acidity and acidophilic enzymes are the main applications of this kind of bacteria in the food industry. Their acid resistance modules can also be used to construct acid-resistant recombinant engineering strains for special purposes. However, they can also cause negative effects on foods, such as spoilage and toxicity. Herein, the aim of this paper is to summarize the research progress of molecular mechanisms against acid stress of acid-resistant bacteria. Moreover, their effects on the food industry were also discussed. It is useful to lay a foundation for broadening our understanding of the physiological metabolism of acid-resistant bacteria and better serving the food industry.

Improved antioxidant capacity of three Brassica vegetables by two-step controlled fermentation using isolated autochthone strains of the genus Leuconostoc spp. and Lactiplantibacillus spp

The aim of this study was to determine the evolution of total phenolic content and antioxidant activity during controlled fermentation of three different Brassicaceae and compare it with spontaneous fermentations. The two-step controlled fermentation was carried out with lactic acid bacteria selected by their biotechnological properties. The selected bacteria were genotypically identified as Leuconostoc mesenteroides ssp. jonggajibkimchii, Ln. mesenteroides ssp. dextranicum, Lactiplantibacillus plantarum ssp. argentoratensis, L. plantarum and L. pentosus. The total phenolic content did not show a trend when comparing the different fermentations; it depended on the type of extract and vegetable. The controlled fermentation exhibited higher antioxidant activity than spontaneous fermentations for all the vegetables during the process. The extracts of red cabbage exhibited a total phenolic content and antioxidant activity higher than chinese and white cabbage, regardless of the type of fermentation.

Ensiled Mixed Vegetables Enriched Carbohydrate Metabolism in Heterofermentative Lactic Acid Bacteria

This study evaluated the fermentation quality, nutritive profile, in vitro fermentation, and microbial communities colonising sorghum ensiled with an unsalable vegetable mixture (chopped beans, carrot, and onion (1:1:1) ) including: (1)−100% sorghum; (2)−80% sorghum + 20% vegetable mix or (3)−60% sorghum + 40% vegetable mix, on a dry matter (DM) basis, with or without a probiotic inoculant. Samples were obtained across 0, 1, 3, 5,7, and 101 days ensiling and after 14 d aerobic exposure. The V4 region of the 16S rRNA gene and the ITS1 region were sequenced to profile bacterial, archaeal, and fungal communities. Compared to the 0% DM, ethanol increased (p < 0.01) from 8.42 to 20.4 ± 1.32 mM with 40% DM vegetable mix inclusion, while lactate decreased from 5.93 to 2.24 ± 0.26 mM. Linear discriminant analysis revealed that relative abundances of 12 bacterial taxa were influenced by silage treatments (log LDA score ≥ 4.02; p ≤ 0.03), while predicted functional pathways of alternative carbohydrate metabolism (hexitol, sulfoquinovose and glycerol degradation; N-acetyl glucosamine biosynthesis; log LDA score ≥ 2.04; p ≤ 0.02) were similarly enriched. This study indicated that carbohydrate metabolism by heterofermentative lactic acid bacteria can increase the feed value of sorghum when ensiled with an unsalable vegetable mixture at 40%DM, without requiring a high quantity of lactate.

Freeze-Dried Powder of Fermented Chili Paste-New Approach to Cured Salami Production

Fermented chili powders were obtained through the freeze-drying of fermented chili pastes and used as a condiment, acidifier, antioxidant, colorant, and microbial starter carrier in fermented salami production. Fermented chili powders were examined regarding carbohydrates, organic acids, vitamin C, phenolic compounds, carotenoids, and aroma profile. High concentrations of lactic (10.57-12.20%) and acetic acids (3.39-4.10%) were recorded. Vitamin C content was identified in the range of 398-1107 mg/100 g, with maximum values for C. annuum cv. Cayenne chili powder. Phenolic compounds showed values between 302-771 mg/100 g. Total carotenoid content was identified between 544-2462 µg/g, with high concentrations of capsanthin esters. Aroma profile analysis evidenced specific compounds (1-hexanol, 2-hexanol, hexenal, E-2-hexenal) with sensory importance and a more complex spectrum for Capsicum chinense cultivar. Plant-specific lactic acid bacteria showed dominance both in fermented chili paste, chili powder, and salami. Lactic and acetic acids from the fermented chili powder reduced the pH of the filling immediately, having a stabilizing effect on the meat. Nor molds or pathogens were identified in outer limits. Based on these results, fermented chili powders could be used as starter carriers in the production of fermented meat products for exceptional sensory properties and food safety management.

Unsalable Vegetables Ensiled With Sorghum Promote Heterofermentative Lactic Acid Bacteria and Improve in vitro Rumen Fermentation

This study characterized the nutritive and microbial profiles and the fermentation characteristics of silage with the following compositions on a dry matter (DM) basis: (1) 100% sorghum, (2) 70% sorghum + 30% carrot or pumpkin, and (3) 40% sorghum + 60% carrot or pumpkin. The treatments were further divided based on the addition or no addition of a probiotic inoculant. After 70 days of ensiling, the silage was incubated for 48 h using the in vitro batch culture technique. Crude protein and non-fiber carbohydrates in the silage increased (P ≤ 0.01) by 5.7 percent point (pp) and 9.6 pp, respectively, with pumpkin at 60% DM. The V4 region of the 16S rRNA gene was sequenced to profile pre-ensiled and ensiled archeal and bacterial communities. Silages containing carrot or pumpkin strongly influenced the microbial structure (PERMANOVA: R² = 0.75; P < 0.001), despite the ensiled treatments being dominated by Lactobacillus spp., except for the control, which was dominated by Weissella and Pediococcus spp. (P < 0.01). Linear discriminant analysis indicated that carrot and pumpkin silages were responsible for the increased relative abundance of Lactobacillus and Acinetobacter spp. (log LDA score ≥ 2), respectively. After 48 h of incubation, carrot and pumpkin inclusion increased (P < 0.01) the in vitro DM digestibility by 22.5 and 31.3%, increased the total volatile fatty acids (VFAs) by 16 and 20.6% (P < 0.01), respectively, and showed a tendency (P = 0.07) to increase the gas production. Therefore, this study supports the use of carrot or pumpkin in sorghum silages to maximize feed digestibility and total VFA concentrations.

Utilization of Oenococcus oeni strains to ferment grape juice: Metabolic activities and beneficial health potential

This study aimed to investigate the behavior of Oenococcus oeni MS9 and MS46 strains in sterile grape juice (SGJ, pH 4.0) incubated at 30 °C, in terms of growth and glucose, organic acids and total phenolic compounds utilization. In addition, their antimicrobial activity and the changes in antioxidant properties of fermented juice with selected strain were evaluated. Both strains grew without lag period by ~1.40 log CFU/mL at 12 days with maximum growth rates of about 0.019 h^-1. After this time the MS9 and MS46 strains counts declined by 0.6 log units and remained unchanged respectively. O. oeni MS46 was evaluated in SGJ for low inoculum size (~10⁴ CFU/mL). In this condition it also grew without lag period by 3.11 ± 0.01 log CFU/mL with a μmax of 0.05 h^-1. Glucose and L-malic and citric acids were simultaneously utilized but at different rates and extents, yielding mainly lactic acid with concomitant pH reduction. Acetic acid ranged between 11 and 19 mmol/L. Total phenolic compounds significantly decreased in fermented SGJ with strain MS9 but not MS46. In this last condition, the antioxidant activity increased by 21%. In addition, both O. oeni strains showed antibacterial properties against Escherichia coli 700, Salmonella Typhimurium and Listeria monocytogenes. O. oeni strains, especially MS46, with the ability to growth in SGJ, high malolactic potential and adequate sugars and organic acids profiles from the sensorial viewpoint may be used to ferment grape juice with safer and healthier properties than fresh juice.

Aggrandizement of fermented cucumber through the action of autochthonous probiotic cum starter strains of Lactiplantibacillus plantarum and Pediococcus pentosaceus

Purpose

Cucumber fermentation is traditionally done using lactic acid bacteria. The involvement of probiotic cultures in food fermentation guarantees enhanced organoleptic properties and protects food from spoilage.

Methods

Autochthonous lactic acid bacteria were isolated from spontaneously fermented cucumber and identified to species level. Only strains adjudged as safe for human consumption were examined for their technological and functional characteristics. Strain efficiency was based on maintaining high numbers of viable cells during simulated GIT conditions and fermentation, significant antioxidant activity, EPS production, nitrite degradation, and antimicrobial ability against Gram-positive and Gram-negative foodborne pathogens.

Result

Two strains, Lactiplantibacillus plantarum NPL 1258 and Pediococcus pentosaceus NPL 1264, showing a suite of promising functional and technological attributes, were selected as a mixed-species starter for carrying out a controlled lactic acid fermentations of a native cucumber variety. This consortium showed a faster lactic acid-based acidification with more viable cells, at 4% NaCl and 0.2% inulin (w/v) relative to its constituent strains when tested individually. Sensory evaluation rated the lactofermented cucumber acceptable based on texture, taste, aroma, and aftertaste.

Conclusion

The results suggest that the autochthonous LAB starter cultures can shorten the fermentation cycle and reduce pathogenic organism’ population, thus improving the shelf life and quality of fermented cucumber. The development of these new industrial starters would increase the competitiveness of production and open the country’s frontiers in the fermented vegetable market.

Physicochemical and microbiological evaluation of antioxidant-rich traditional black carrot beverage: Kanji

BACKGROUND

Daucus carota subsp. sativus (Black carrots) are underutilized in context to their nutritional properties. In this study, Kanji, a naturally fermented probiotic beverage, was prepared using Daucus carota subsp. sativus (var. Punjab Black Beauty). Analysis of the physicochemical and microbiological profile of the naturally fermented Kanji was investigated to boost its utilization for commercial purpose.

RESULTS

The physicochemical parameters observed in the fermented Kanji beverage were pH 3.47, total soluble solids 3°B, lactic acid 0.99%, total sugars 36.32 mg/mL, total reducing sugars 27.16 mg/mL, flavonoids 38.14 mg/mL, phenols 40.8 mg/mL, antioxidant activity 79.96% and ascorbic acid 110 mg/100 mL. The microbiological analysis revealed an exponential increase in lactic acid bacterial count from 3.96 to 8.33 log CFU/mL. Out of 11 bacterial strains isolated from Kanji, the bacterial strain with high growth potential was genotypically characterized as Pediococcus acidilactici with accession number MK028218.

CONCLUSION

The lactic acid bacterial Kanji beverage was characterized as a potential plant-based probiotic with high antioxidant activity. This functional autochthonous starter from the Kanji can be used for selective fermentation of black carrots for Kanji ascertaining its microbiological safety, unique flavor and aroma, and consumption as a commercial non-dairy-based probiotic beverage.

Hydrogen sulfide toxicity in the gut environment: Meta-analysis of sulfate-reducing and lactic acid bacteria in inflammatory processes

BACKGROUND

Hydrogen sulfide is the final product of sulfate-reducing bacteria metabolism. Its high concentration in the gut can affect adversely bowel environment and intestinal microbiota by toxicity and pH lowering.

AIM OF REVIEW

The aim of the review was to give observations related to the properties of bacterial communities inhabiting the gut, with the emphasis on sulfate-reducing bacteria and lactic acid bacteria.

KEY SCIENTIFIC CONCEPTS OF REVIEW

The conduction of meta-analysis was another goal, since it gave statistical observation of the relevant studies. The review literature consisted of more than 160 studies, published from 1945 to 2019. Meta-analysis included 16 studies and they were chosen from the Web of Science database. The systematic review gave important information about the development of gut inflammation, with emphasis on sulfate-reducing and lactic acid bacteria. Oppositely from sulfate-reducing bacteria, probiotic properties of lactic acid bacteria are effective inhibitors against inflammatory bowel disease development, including ulcerative colitis. These facts were confirmed by the conducted meta-analysis. The results and observations gained from the systematic review represent the emphasized importance of gut microbiota for bowel inflammation. On the other side, it should be stated that more studies in the future will provide even better confirmations.

Degradation Trends of Some Insecticides and Microbial Changes during Sauerkraut Fermentation under Laboratory Conditions

The aim of this study was to monitor the degradation of three insecticides licensed for the control of cabbage moths during the 14-day fermentation period of sauerkraut samples. The hypothesis of this study is that the different sauerkraut fermentation processes could affect the degradation of applied insecticides. For this purpose, the fresh cabbage leaves contaminated with (λ-cyhalothrin, malathion, and chlorpyrifos-methyl) were left for fermentation with and without (natural) starter addition (Lactobacillus plantarum 112), and vacuum-packed as a control under laboratory conditions. The pH values and microbial growth were periodically monitored in sauerkraut samples during the fermentation period. During this time, the insecticide residues were determined in control and treatment samples using LC-MS-MS. In control samples, the degradation of chlorpyrifos-methyl and malathion was higher with rates of 69 and 98%, respectively, compared with the sauerkraut samples (12 and 59%; 31 and 34%, respectively) 14 days after the insecticide application. At the end of fermentation (14 d), no significant reduction in λ-cyhalothrin was detected in both treatments and control (13-19% reduction). The current study demonstrated that the presence of the lactic acid bacteria in the sauerkraut fermentation accelerated pH decline (below 4.0), and these fermentation conditions probably decelerated the degradation of malathion and chlorpyrifos-methyl. The results showed that the stability of different insecticides varied during the same fermentation process.

Optimization of gamma-aminobutyric acid production by probiotic bacteria through response surface methodology

Background and Objectives:

Gamma-aminobutyric acid (GABA) is a non-protein four-carbon amino acid that has many physiological properties, including reducing blood pressure, accelerating protein synthesis in the brain, and treatment of insomnia and depression. This amino acid is produced by a number of lactic acid bacteria, fungi and yeasts. The objective of the present study was to identify probiotic bacteria with the maximum ability to generate GABA and optimize the bacterial culture conditions having the highest potential for GABA production.

Materials and Methods:

The potential of GABA production by Lactobacillus delbrueckii ssp. bulgaricus, Lactobacillus rhamnosus, Lactobacillus casei, Streptococcus thermophilus, Lactobacillus brevis and Lactococcus lactis ssp. lactis in the culture medium of MRS broth was assessed by High Performance Liquid Chromatography (HPLC). In order to increase the rate of GABA produced by the bacteria having the highest potential for GABA production, the conditions of the culture medium including pH (3.5 to 6.5) “temperature (25 to 45°C), time (12 to 96 h) and glutamic acid (GA) concentration (25 to 650 mmol) were optimized by the Box-Behnken’s Response Surface Method (RSM).

Results:

Lactobacillus brevis had the highest potential of GABA production (5960.8 mg/l). The effect of time and GA concentration was significant on the amount of GABA production. The best conditions of culture medium to achieve the highest amount of GABA production by Lactobacillus brevis (19960 mg/l) were temperature 34.09°C, pH 4.65, GA concentration 650 mmol and time 96 h.

Conclusion:

The results showed that by optimization of the culture medium conditions of probiotic bacteria we can produce more GABA in culture medium.

Lactic Acid Fermentation of Arthrospira platensis (Spirulina) in a Vegetal Soybean Drink for Developing New Functional Lactose-Free Beverages

The main objective of this study was to evaluate the suitability of Arthrospira platensis F&M-C256 (spirulina) biomass in a vegetal soybean drink or in water, as substrate for lactic acid fermentation by the probiotic bacterium Lactiplantibacillus plantarum ATCC 8014 (LAB8014) and to evaluate the fermented products in terms of bacteria content and organic acids content, biochemical composition, total phenolics, and phycocyanin content, in vitro digestibility, in vitro and in vivo antioxidant activity. After 72 h of fermentation, a bacterial concentration of about 10.5 log CFU mL^–1 in the broths containing the soybean drink + spirulina + LAB8014 (SD + S + LAB8014) or water + spirulina + LAB8014 (W + S + LAB8014) was found. Lactic acid concentration reached similar values (about 1.7 g L^–1) in the two broths, while a different acetic acid concentration between SD + S + LAB8014 and W + S + LAB8014 broths was observed (7.7 and 4.1 g L^–1, respectively). A. platensis biomass was shown to be a suitable substrate for LAB8014 growth. After fermentation, both broths contained a high protein content (>50%). In both broths, total phenolics, in vitro and in vivo antioxidant activity increased after fermentation (+35, +20, and +93% on average, respectively), while phycocyanin content decreased (−40% on average). Digestibility of W + S + LAB8014 broth statistically improved after fermentation. This study highlights the potential of A. platensis F&M-C256 biomass as a substrate for the production of new functional lactose-free beverages.

Simulation Study for the Degradation of Some Insecticides during Different Black Table Olive Processes

The aim of this study was to determine the effects of different olive processing methods on deltamethrin (DEL), dimethoate (DIM), and imidacloprid (IMI), the most commonly preferred synthetic insecticides for controlling olive pests such as the olive fruit fly. The hypothesis is that the fermentation could accelerate the degradation process of the insecticides. For this purpose, olives were left for fermentation (natural black olives) without and with starter addition (two Lactobacillus plantarum strains 112 and 123) and processed as dehydrated black olives. To monitor the degradation rate of insecticides, olives were first polluted with the insecticides and then the residues were detected periodically during the processes. The insecticide degradation rates were found to be significantly higher in natural black olives and natural black olives inoculated with both starters compared with those of crude olives and dehydrated black olives. At the end of fermentation (after 60 d), 53-61% of deltamethrin, 66-68% of dimethoate, and 42-50% of imidacloprid were removed in natural black olives and natural black olives inoculated with both starters. In dehydrated olives, the degradation of deltamethrin, dimethoate, and imidacloprid was lower with rates of 9.7, 40, and 13.4%, respectively. The current study demonstrated that natural and starter-added natural black olive processing accelerated the degradation of deltamethrin, dimethoate, and imidacloprid.

Dual-Purpose Inoculants and Their Effects on Corn Silage

This study was conducted to screen dual-purpose lactic acid bacteria (LAB) from uncontrolled farm-scale silage, and then we confirmed their effects on corn silage. The LAB were isolated from eight farm-scale corn silages, and then we screened the antifungal activity against Fusarium graminearum and the carboxylesterase activity using spectrophotometer with p-nitrophenyl octanoate as substrate and McIlvane solution as buffer. From a total of 25 isolates, 5M2 and 6M1 isolates were selected as silage inoculants because presented both activities of antifungal and carboxylesterase. According 16S rRNA gene sequencing method, 5M2 isolate had 100.0% similarity with Lactobacillus brevis, and 6M1 isolate had 99.7% similarity with L. buchneri. Corn forage was ensiled in bale silo (500 kg) for 72 d without inoculant (CON) or with mixture of selected isolates at 1:1 ratio (INO). The INO silage had higher nutrient digestibility in the rumen than CON silage. Acetate was higher and yeasts were lower in INO silage than in CON silage on the day of silo opening. In all days of aerobic exposure, yeasts were lower in INO silage than CON silage. The present study concluded that Lactobacillus brevis 5M2 and L. buchneri 6M1 confirmed antifungal and carboxylesterase activities on farm-scale corn silage.

Genotypic and phenotypic characterization of food-associated Lactobacillus plantarum isolates for potential probiotic activities

Lactic acid bacterium, Lactobacillus plantarum, has been applied, for centuries, for food and drink fermentations. Given the benefits associated with fermented products, Lb. plantarum strains have captured considerable industrial and scientific interest, so that they are included as fundamental components of functional foods. Indeed, some strains are marketed as probiotics. In the present study, food- and gut-associated Lb. plantarum isolates were genetically characterized by multilocus sequence typing (MLST) and phenotypically characterized for properties that could influence their probiotic potential. MLST and phylogenetic analysis stratified 22 Lb. plantarum isolates into six lineages. The isolates were further phenotypically characterized by an in vitro assay to assess their potential gut community influence via a limited number of assays including acidification activity, strain displacement activity and their intrinsic range of antibiotic resistance. Given growing recognition of the benefits of fermented foods, and the prevalence of Lb. plantarum in these applications, this study highlights analysis of a subset of preliminary important strain-specific features. These features are of interest to all stakeholders, to inform isolate comparison and selection for current functional food associations, and that can serve as a basis for future strain and food-microbe fermentation product development.

Production of Lactic Acid from Seaweed Hydrolysates via Lactic Acid Bacteria Fermentation

Biodegradable polylactic acid material is manufactured from lactic acid, mainly produced by microbial fermentation. The high production cost of lactic acid still remains the major limitation for its application, indicating that the cost of carbon sources for the production of lactic acid has to be minimized. In addition, a lack of source availability of food crop and lignocellulosic biomass has encouraged researchers and industries to explore new feedstocks for microbial lactic acid fermentation. Seaweeds have attracted considerable attention as a carbon source for microbial fermentation owing to their non-terrestrial origin, fast growth, and photoautotrophic nature. The proximate compositions study of red, brown, and green seaweeds indicated that Gracilaria sp. has the highest carbohydrate content. The conditions were optimized for the saccharification of the seaweeds, and the results indicated that Gracilaria sp. yielded the highest reducing sugar content. Optimal lactic acid fermentation parameters, such as cell inoculum, agitation, and temperature, were determined to be 6% (v/v), 0 rpm, and 30 °C, respectively. Gracilaria sp. hydrolysates fermented by lactic acid bacteria at optimal conditions yielded a final lactic acid concentration of 19.32 g/L.

Vegetable By-Product Lacto-Fermentation as a New Source of Antimicrobial Compounds

Background: One of the main objectives of the food industry is the shelf life extension of food products, taking into account the safety requirements and the preference of consumers attracted by a simple and clear label. Following this direction, many researchers look to find out antimicrobials from natural sources. Methods: Tomato, carrot, and melon by-products were used as substrates for lactic acid fermentation using seven strains belonging to the Lactobacillus genus, L. plantarum, L. casei, L. paracasei, and L. rhamnosus. The obtained fermented by-products were then extracted and the antimicrobial activity toward fourteen pathogenic strains of Listeria monocytogenes, Salmonella spp., Escherichia coli, Staphylococcus Aureus, and Bacillus cereus was tested through agar well diffusion assay. Results: All the extracts obtained after fermentation had highlighted antimicrobial activity against each pathogen tested. In particular, a more effective activity was observed against Salmonella spp., L. monocytogenes, S. aureus, and B. cereus, while a lower activity was observed against E. coli. Conclusion: Lactic acid fermentation of vegetable by-products can be a good strategy to obtain antimicrobials useful in food biopreservation.

Towards Sustainable Lactic Acid Production: Avoiding Gypsum as a Byproduct by using Selective Liquid-Phase Adsorption

The utilization of biomass is one of the major challenges for the transition from fossil to renewable resources. Often, the separation of the desired product from the reaction mixture is the most energy-intensive step. Liquid-phase adsorption is a promising separation technology that could significantly improve downstream processing in biorefineries. Highly hydrophobic adsorbents were applied for the separation of lactic acid (LA) from aqueous solutions and to avoid the formation of gypsum as a byproduct. High uptakes and selectivity were obtained in single-solute and co-adsorption experiments. Porous hyper-crosslinked polymers (HCP) and polymer-based spherical activated carbon performed best and showed excellent selectivity for the selective removal of LA. Desorption experiments revealed that HCP was the ideal adsorbent for the separation of LA from aqueous solution and enabled the production of gypsum-free LA.

Probiotic Beverage From Pineapple Juice Fermented With Lactobacillus and Bifidobacterium Strains

Pineapple is an economically significant plant and the third most important fruit crop in the tropical and subtropical regions of the world. In this study, fermentation of pineapple juice with probiotic bacteria Lactobacillus and Bifidobacterium strains as well as changes of some properties in the beverage during storage were investigated. All tested strains exhibited good growth properties on pineapple juice without supplementation of any nutrient compounds. After 24 h fermentation, the cell counts of lactobacilli passed the level of 5^*10⁹ cfu/ml, while the cell number of bifidobacteria reached a level of 10⁹ cfu/ml. The highest volumetric productivity (3.5^*10⁸ cfu/ml^*h) was observed in L. plantarum 299V. The ratios of lactic acids to acetic acids in the cases of L. plantarum 299V and L. acidophilus La5 were 5.37 and 9.91, respectively. In the case of B. lactis Bb-12, the concentrations of lactic acid and acetic acid were 6 mM and 23 mM in natural juices, and 15 and 21 mM in the case of supplementation with prebiotics at the 16^th h of fermentation, respectively. Additionally, supplementation with prebiotics at the initiation of fermentation resulted 7 mM lactic acid and 23 mM acetic acid at the end of fermentation. Fructose was the most preferred sugar for both lactobacilli and bifidobacteria. Both total phenolic content and antioxidant capacity increased slightly during fermentation and dropped during the storage period. The microbial population did not change significantly during the first month of storage. After the storage period (2 months), the probiotic bacteria lost about 0.11 log cfu/ml viability after treatment with 0.3% pepsin for 135 min, and a further 0.1 log cfu/ml after treatment with 0.6% bile salts. These values were 10 times higher than data from the fresh fermented pineapple juice. Our results are very promising and may serve as a good base for developing probiotic pineapple juice.

Inhibitory Effect of Lactobacillus plantarum FL75 and Leuconostoc mesenteroides FL14 against Foodborne Pathogens in Artificially Contaminated Fermented Tomato Juices

Tomatoes and tomato based-foods contain beneficial microorganisms and various organic acids that have important nutritional values for human. The objective of this study was to access the physiochemical properties of fermented tomatoes juices and to evaluate the competitiveness of lactic acid bacteria (LAB) against Listeria monocytogenes, Listeria innocua, and Salmonella spp., in artificially contaminated tomato juice. Microbial counting (LAB, fungi Salmonella spp., and Listeria spp.) was performed after fermentation and weekly during storage. Different organic acids (Lactic, succinic, and acetic) and ethanol were also monitored using HPLC method. Color parameters were also determined. The results showed an increase of lactic and acetic acid content, during fermentation and storage of juices inoculated with Lactobacillus plantarum and Leuconostoc mesenteroides at 25°C. Besides, citric acid and ethanol revealed higher content at the end of storage compared to that registered at 4°C. The pH from tomatoes juices decreased from an initial value of 4.5 to below 3.2. Alongside, foodborne pathogen population was significantly suppressed in tomatoes juices when the samples were coinoculated with LAB strains. Moreover, the inhibition of Salmonella species was faster compared to that of Listeria. After four weeks of storage at 4°C, Lb. plantarum and Lc. mesenteroides showed high survival rate, while pathogenic bacteria, yeasts, and molds cell numbers decreased drastically in all the contaminated vials. This work highlights the efficiency of Lb. plantarum and Lc. mesenteroides as potential starters for developing nutritious and safe fermented tomato juice products.

High Levels of CO2 Induce Spoilage by Leuconostoc mesenteroides by Upregulating Dextran Synthesis Genes

During nonventilated storage of carrots, CO2 gradually accumulates to high levels and causes modifications in the carrot's microbiome toward dominance of Lactobacillales and Enterobacteriales The lactic acid bacterium Leuconostoc mesenteroides secretes a slimy exudate over the surface of the carrots. The objective of this study was to characterize the slime components and the potential cause for its secretion under high CO2 levels. A proteomic analysis of the exudate revealed bacterial glucosyltransferases as the main proteins, specifically, dextransucrase. A chemical analysis of the exudate revealed high levels of dextran and several simple sugars. The exudate volume and dextran amount were significantly higher when L. mesenteroides was incubated under high CO2 levels than when incubated in an aerated environment. The treatment of carrot medium plates with commercial dextransucrase or exudate protein extract resulted in similar sugar profiles and dextran production. Transcriptome analysis demonstrated that dextran production is related to the upregulation of the L. mesenteroides dextransucrase-encoding genes dsrD and dsrT during the first 4 to 8 h of exposure to high CO2 levels compared to aerated conditions. A phylogenetic analysis of L. mesenteroides YL48 dsrD revealed a high similarity to other dsr genes harbored by different Leuconostoc species. The ecological benefit of dextran production under elevated CO2 requires further investigation. However, this study implies an overlooked role of CO2 in the physiology and fitness of L. mesenteroides in stored carrots, and perhaps in other food items, during storage under nonventilated conditions.IMPORTANCE The bacterium Leuconostoc mesenteroides is known to cause spoilage of different types of foods by secreting a slimy fluid that damages the quality and appearance of the produce. Here, we identified a potential mechanism by which high levels of CO2 affect the spoilage caused by this bacterium by upregulating dextran synthesis genes. These results have broader implications for the study of the physiology, degradation ability, and potential biotechnological applications of Leuconostoc.

The Influence of Viable Cells and Cell-Free Extracts of Lactobacillus casei on Volatile Compounds and Polyphenolic Profile of Elderberry Juice

In this study, four strains of Lactobacillus casei, as viable cells or cell-free extracts (CFE), were added to elderberry juice in order to evaluate their effect on phenolic and aromatic profile. Two of them were able to grow in juice while the others showed zero-growth. The same strains were lysed and added as extracts in elderberry juice. Multivariate statistical analysis show a separation among samples containing growing cells, non-growing cells, CFE, highlighting the particularities of specific strains. Juices added with CFE presented the highest amount of esters. The strains showing growth phenotype cause an increase of phenyllactic acids. The highest concentration of volatile compounds, particularly of alcohols, terpenes and norisoprenoids (responsible for typical elderberry notes) was observed in samples with strains showing zero-growth. Moreover, a significant increase in anthocyanin content was observed in these samples, suggesting the possible use of Lactobacillus for increasing specific molecules, even for non-multiplying bacterial cell. Considering that this is the first study concerning the use of non-growing cells in fruit juice, the potential of strains is still to be explored and it may have a significant technological application in the development of a microbial collection useful for fruit juice industry.

Carrot Juice Fermentations as Man-Made Microbial Ecosystems Dominated by Lactic Acid Bacteria

Spontaneous vegetable fermentations, with their rich flavors and postulated health benefits, are regaining popularity. However, their microbiology is still poorly understood, therefore raising concerns about food safety. In addition, such spontaneous fermentations form interesting cases of man-made microbial ecosystems. Here, samples from 38 carrot juice fermentations were collected through a citizen science initiative, in addition to three laboratory fermentations. Culturing showed that Enterobacteriaceae were outcompeted by lactic acid bacteria (LAB) between 3 and 13 days of fermentation. Metabolite-target analysis showed that lactic acid and mannitol were highly produced, as well as the biogenic amine cadaverine. High-throughput 16S rRNA gene sequencing revealed that mainly species of Leuconostoc and Lactobacillus (as identified by 8 and 20 amplicon sequence variants [ASVs], respectively) mediated the fermentations in subsequent order. The analyses at the DNA level still detected a high number of Enterobacteriaceae, but their relative abundance was low when RNA-based sequencing was performed to detect presumptive metabolically active bacterial cells. In addition, this method greatly reduced host read contamination. Phylogenetic placement indicated a high LAB diversity, with ASVs from nine different phylogenetic groups of the Lactobacillus genus complex. However, fermentation experiments with isolates showed that only strains belonging to the most prevalent phylogenetic groups preserved the fermentation dynamics. The carrot juice fermentation thus forms a robust man-made microbial ecosystem suitable for studies on LAB diversity and niche specificity.

IMPORTANCE The usage of fermented food products by professional chefs is steadily growing worldwide. Meanwhile, this interest has also increased at the household level. However, many of these artisanal food products remain understudied. Here, an extensive microbial analysis was performed of spontaneous fermented carrot juices which are used as nonalcoholic alternatives for wine in a Belgian Michelin star restaurant. Samples were collected through an active citizen science approach with 38 participants, in addition to three laboratory fermentations. Identification of the main microbial players revealed that mainly species of Leuconostoc and Lactobacillus mediated the fermentations in subsequent order. In addition, a high diversity of lactic acid bacteria was found; however, fermentation experiments with isolates showed that only strains belonging to the most prevalent lactic acid bacteria preserved the fermentation dynamics. Finally, this study showed that the usage of RNA-based 16S rRNA amplicon sequencing greatly reduces host read contamination.

Lactic acid fermentation of apricot juice by mono- and mixed cultures of probiotic Lactobacillus and Bifidobacterium strains

Apricot is a popular fruit in the world with rich in carbohydrates, vitamins and elements as well as has high antioxidant capacity. In this study, fermentation of this juice by mono- and mixed cultures was investigated. All tested strains exhibited good growth properties on apricot juice without any nutrient supplementation. In monoculture fermentation, 7.2, 7.25, 7.06 and 7.16 log (cfu/mL h) cell yields were observed for Bifidobacterium lactis Bb-12, Bifidobacterium longum Bb-46, Lactobacillus casei 01 and Lactobacillus acidophilus La-5 strains, respectively, and higher cell yields were obtained in the mixed culture fermentation. The antioxidant capacity increased slightly during fermentation. The concentration of acetic acid (27-48 mM) were about doubled in cases of the mixed culture fermentations than of monoculture fermentations (18-30 mM), while the levels of lactic acid were similar (70-90 mM). The relatively high values of these properties offer the potential for development of novel probiotic apricot juice.

The Nutritive Value of Organic and Conventional White Cabbage (Brassica Oleracea L. Var. Capitata) and Anti-Apoptotic Activity in Gastric Adenocarcinoma Cells of Sauerkraut Juice Produced Therof

White cabbage is one of the most important vegetables grown both in Poland and worldwide. Cabbage contains considerable amounts of bioactive compounds such as glucosinolates, vitamin C, carotenoids, and polyphenols. Some experiments indicate that vegetables from organic production contain more bioactive compounds than those from conventional production, however, only a few studies have been conducted on cruciferous plants. The presented study has proved that organic fresh cabbage, compared to the conventional one, contained significantly less total flavonoids in both years of experiments (3.95 ± 0.21 mg/100 g FW and 3.71 ± 0.33 mg/100 g FW), several flavonoid compounds, total chlorophylls (1.51 ± 0.17 mg/100 g FW and 1.30 ± 0.22 mg/100 g FW) carotenoids, nitrites (0.55 ± 0.04 mg/kg FW and 0.45 ± 0.02 mg/kg FW), and nitrates (0.50 ± 0.13 g/kg FW and 0.47 ± 0.11 g/kg FW). The organic sauerkraut juice, compared to the conventional one, contained significantly more total polyphenols (5.39 ± 0.22 mg/100 g FW and 9.05 ± 1.10 mg/100 g FW) as well as several flavonoids. Only CONV sauerkraut juice produced with the highest N level of fertilization induced a statistical significant increase of the level of necrosis of human stomach gastric adenocarcinoma cell line AGS.

Complete genome sequence of bacteriocin-producing Lactobacillus plantarum KLDS1.0391, a probiotic strain with gastrointestinal tract resistance and adhesion to the intestinal epithelial cells

Lactobacillus plantarum KLDS1.0391 is a probiotic strain isolated from the traditional fermented dairy products and identified to produce bacteriocin against Gram-positive and Gram-negative bacteria. Previous studies showed that the strain has a high resistance to gastrointestinal stress and has a high adhesion ability to the intestinal epithelial cells (Caco-2). We reported the entire genome sequence of this strain, which contains a circular 2,886,607-bp chromosome and three circular plasmids. Genes, which are related to the biosynthesis of bacteriocins, the stress resistance to gastrointestinal tract environment and adhesive performance, were identified. Whole genome sequence of Lactobacillus plantarum KLDS1.0391 will be helpful for its applications in food industry.