Lactobacillus plantarum (widespread member of the genus Lactobacillus) is one of the most studied species extensively used in food industry as probiotic microorganism and/or microbial starter. The exploitation of Lb. plantarum strains with their long history in food fermentation forms an emerging field and design of added-value foods. Lb. plantarum strains were also used to produce new functional (traditional/novel) foods and beverages with improved nutritional and technological features. Lb. plantarum strains were identified from many traditional foods and characterized for their systematics and molecular taxonomy, enzyme systems (α-amylase, esterase, lipase, α-glucosidase, β-glucosidase, enolase, phosphoketolase, lactase dehydrogenase, etc.), and bioactive compounds (bacteriocin, dipeptides, and other preservative compounds). This review emphasizes that the Lb. plantarum strains with their probiotic properties can have great effects against harmful microflora (foodborne pathogens) to increase safety and shelf-life of fermented foods.

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Lactobacillus plantarum with Functional Properties: An Approach to Increase Safety and Shelf-Life of Fermented Foods.

Lactic acid bacteria (LAB) are the most frequently used probiotics in fermented foods and beverages and as food supplements for humans or animals, owing to their multiple beneficial features, which appear to be partially associated with their antioxidant properties. LAB can help improve food quality and flavor and prevent numerous disorders caused by oxidation in the host. In this review, we discuss the oxidative stress tolerance, the antioxidant capacity related herewith, and the underlying mechanisms and signaling pathways in probiotic LAB. In addition, we discuss appropriate methods used to evaluate the antioxidant capacity of probiotic LAB. The aim of the present review is to provide an overview of the current state of the research associated with the oxidative stress tolerance and antioxidant capacity of LAB.

https://www.tandfonline.com/doi/pdf/10.1080/19490976.2020.1801944

Oxidative stress tolerance and antioxidant capacity of lactic acid bacteria as probiotic: a systematic review.

The group of Gram-negative bacteria capable of oxidising ethanol to acetic acid is called acetic acid bacteria (AAB). They are widespread in nature and play an important role in the production of food and beverages, such as vinegar and kombucha. The ability to oxidise ethanol to acetic acid also allows the unwanted growth of AAB in other fermented beverages, such as wine, cider, beer and functional and soft beverages, causing an undesirable sour taste. These bacteria are also used in the production of other metabolic products, for example, gluconic acid, l-sorbose and bacterial cellulose, with potential applications in the food and biomedical industries. The classification of AAB into distinct genera has undergone several modifications over the last years, based on morphological, physiological and genetic characteristics. Therefore, this review focuses on the history of taxonomy, biochemical aspects and methods of isolation, identification and quantification of AAB, mainly related to those with important biotechnological applications.

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Acetic Acid Bacteria in the Food Industry: Systematics, Characteristics and Applications.

Nutrients and bioactive components from vinegar: A fermented and functional food

Membrane-bound, pyrroloquinoline quinone-dependent, alcohol dehydrogenase functions as the primary dehydrogenase in the respiratory chain of acetic acid bacteria. In this study, an ability of the enzyme to directly react with ubiquinone was investigated in alcohol dehydrogenases purified from both Acetobacter aceti and Gluconobacter suboxydans by two different approaches. First, it was shown that the enzymes are able to reduce natural ubiquinones, ubiquinone-9 or -t0, in a detergent solution as well as a soluble short-chain homologue, ubiquinone-I. In order to show the reactivity of the enzyme with natural ubiquinone in a native membrane environment, furthermore, alcohol dehydrogenase was reconstituted into proteoliposomes together with natural ubiquinone and a terminal ubiquinol oxidase. The reconstitution was done by binding the detergent-free dehydrogenase at room temperature to proteoliposomes that had been prepared in advance from a ubiquinol oxidase and phospholipids containing ubiquinone by deterge...

Ethanol Oxidase Respiratory Chain of Acetic Acid Bacteria. Reactivity with Ubiquinone of Pyrroloquinoline Quinone-dependent Alcohol Dehydrogenases Purified from Acetobacter aceti and Gluconobacter suboxydans

Alcoholic fermentation is an essential step in producing high-quality vinegar and typically involves the use of pure yeast to initiate fermentation. In this study, two kinds of citrus vinegars were prepared with a pure culture of Saccharomyces cerevisiae and mixed cultures of Saccharomyces cerevisiae and Lactobacillus plantarum , respectively. During the alcoholic-fermentation stage, the contents of formic, lactic, and total organic acids were higher in the mixed cultures than in the pure culture. Mixed cultures citrus vinegar (MCCV) showed higher antioxidant activity than pure culture citrus vinegar (PCCV). The contents of sweet and umami free amino acids in MCCV were higher than those in PCCV. Meanwhile, flavor groups such as esters, alcohols, and aldehydes in MCCV also significantly improved. According to sensory analysis, MCCV showed higher intensity for sweet and umami attributes, as well as flowery and fruity attributes. Thus, mixed cultures of Saccharomyces cerevisiae and Lactobacillus plantarum in alcoholic fermentation can effectively improve the flavor and quality of citrus vinegar, thereby indicating additional economic benefits of fermentation.

Effects of mixed cultures of Saccharomyces cerevisiae and Lactobacillus plantarum in alcoholic fermentation on the physicochemical and sensory properties of citrus vinegar

Acetic acid bacteria (AAB) are important microorganisms in the vinegar industry. However, AAB have to tolerate the presence of ethanol and high temperatures, especially in submerged fermentation (SF), which inhibits AAB growth and acid yield. In this study, seven AAB that are tolerant to temperatures above 40 °C and ethanol concentrations above 10% (v/v) were isolated from Chinese vinegar Pei. All the isolated AAB belong to Acetobacter pasteurianus according to 16S rDNA analysis. Among all AAB, AAB4 produced the highest acid yield under high temperature and ethanol test conditions. At 4% ethanol and 30-40 °C temperatures, AAB4 maintained an alcohol-acid transform ratio of more than 90.5 %. High alcohol-acid transform ratio was still maintained even at higher temperatures, namely, 87.2, 77.1, 14.5 and 2.9% at 41, 42, 43 and 44 °C, respectively. At 30 °C and different initial ethanol concentrations (4-10%), the acid yield by AAB4 increased gradually, although the alcohol-acid transform ratio decreased to some extent. However, 46.5, 8.7 and 0.9% ratios were retained at ethanol concentrations of 11, 12 and 13%, respectively. When compared with AS1.41 (an AAB widely used in China) using a 10 L fermentor, AAB4 produced 42.0 g/L acetic acid at 37 °C with 10% ethanol, whereas AS1.41 almost stopped producing acetic acid. In conclusion, these traits suggest that AAB4 is a valuable strain for vinegar production in SF.

Screening and characterization of ethanol-tolerant and thermotolerant acetic acid bacteria from Chinese vinegar Pei

Cordyceps militaris has entered a large-scale artificial cultivation, and the solid culture medium of Cordyceps militaris are usually discarded. In this study, two kinds of liquid vinegars were prepared with discarded solid culture medium of Cordyceps militaris and rice, respectively. The contents of tartaric, methanoic, lactic and total organic acids were higher in cordyceps vinegar than in rice vinegar. Cordyceps vinegar showed higher antioxidant activity than rice vinegar. Moreover, cordyceps vinegar contained higher cordycepin and adenosine. The contents of sweet and umami free amino acids in cordyceps vinegar were higher than those in rice vinegar. Meanwhile, flavor groups such as esters and acids in cordyceps vinegar also significantly improved. According to sensory analysis, cordyceps vinegar showed higher intensity for sweet and umami attributes, as well as fruity attributes. Thus, discarded solid culture medium of Cordyceps militaris can be used to ferment liquid vinegar and improve the flavor and quality of vinegar, thereby indicating additional economic benefits of fermentation.

Fermenting liquid vinegar with higher taste, flavor and healthy value by using discarded Cordyceps militaris solid culture medium

The aim of this study was to understand the correlation between ethanol resistance and characteristics of PQQ-dependent ADH in acetic acid bacteria. Two ethanol-tolerant strains, FY-24 and DY-5, identified as Acetobacter pasteurianus were isolated from Chinese vinegar Pei. FY-24 and DY-5 maintained the growth and fermentation ability with 12 % (v/v) ethanol at 37 °C, but A. pasteurianus AS1.41 (widely used in China) could only be resistant to 10 % ethanol. ADH activities of FY-24 (6.13 U/mg) and DY-5 (5.41 U/mg) were much higher than that of AS1.41 (1.57 U/mg) at 8 % ethanol. Using purified ADH, it was shown that the ADHs from FY-24 and DY-5 exhibited a higher ethanol tolerance as ethanol increasing from 10 to 40 %. The optimum ethanol concentration for ADHs of FY-24 and DY-5 was 10 %, but was 5 % for that of AS1.41. Additionally, ADHs from FY-24 and DY-5 exhibited a higher resistance to temperature and acetic acid than that of AS1.41. From the amino acid sequence of ADH subunits, a certain amount of residues were found in the ADHs of FY-24 and DY-5 (411th D and 731th N in subunit I, 170th D in subunit II and 40th G in subunit III), which were different from that of AS1.41. The difference in amino acid residues might partly relate to the ethanol tolerance. Our results suggested that FY-24 and DY-5 could be developed for high ethanol acetic acid fermentation.

Correlation between ethanol resistance and characteristics of PQQ-dependent ADH in acetic acid bacteria

Selenium (Se) is one of the essential trace elements in the human body, and Se-enriched lactic acid bacteria (LAB) can improve the biological utilization value of inorganic Se. The aim of this study was to isolate Se-enriched LAB and study their effects on antioxidant activity and nitrite degradation. The Se-enriched LAB L.P2, which was nitrite-tolerant and could grow in 30 µg/mL sodium selenite (Na2SeO3) medium, was isolated from the traditional fermented Chinese sauerkraut. L.P2 belonged to Lactobacillus plantarum according to the 16S rDNA analysis. The biomass and lactic acid production of L.P2 reached to a maximum (9.52 log CFU/mL and 16.99 mg/mL) when 2.0 µg/mL Na2SeO3 was supplemented in the medium. Additionally, the nitrite degradation rate reached 85.76% when the initial concentration of Na2SeO3 was 2.0 µg/mL. The Se-enriched LAB enhanced the scavenging capacity of hydroxyl radical and superoxide free radical of L.P2 and improved the lipid peroxidation and ion-chelating abilities. Moreover, the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) in Se 4 group (4.0 µg/mL Na2SeO3 was added) reached 48.49 and 50.35 U/mg, respectively. Thus, Se 4 concentration was significantly higher than that of Se 0 group (with no Se added). In particular, SOD and GSH-Px enzymes correlated with nitrite degradation (P < 0.01). Collectively, our results indicate that Se supplementation can enhance the antioxidant capacity of LAB, contribute to its nitrite degradation, and thus may have potential applications in functional foods.

Yang Chen

Papers

Effects of mixed cultures of Saccharomyces cerevisiae and Lactobacillus plantarum in alcoholic fermentation on the physicochemical and sensory properties of citrus vinegar

Screening and characterization of ethanol-tolerant and thermotolerant acetic acid bacteria from Chinese vinegar Pei

Fermenting liquid vinegar with higher taste, flavor and healthy value by using discarded Cordyceps militaris solid culture medium

Correlation between ethanol resistance and characteristics of PQQ-dependent ADH in acetic acid bacteria

Effect of selenium supplements on the antioxidant activity and nitrite degradation of lactic acid bacteria