Production of Antimicrobial Substances by Lactic Acid Bacteria I: Determination of Hydrogen Peroxide

Abstract

Restoration of the balance of different ecological niches has been proposed as a way to control the income of pathogenic microorganisms. The genus Lactobacillus has been used in different human and animal tracts as probiotic microorganisms with this objective in mind. The characteristics of the strains proposed as probiotics have been published or patented under the process of elaboration of different types of products. One of the mechanisms suggested to control the vaginal ecosystem is the production of antagonistic substances (lactic acid, bacteriocins, or H2O2). The H2O2-producing microorganisms present in the vagina of healthy women have been suggested as some of the bacteria responsible for maintenance of ecological balance, mainly in pregnant women. The absence of these microorganisms is related to a higher risk of: bacterial vaginosis, recurrent urinary tract infections by Escherichia coli, and acquisition of human immunodeficiency virus type 1 (HIV-1). Bauer has proposed that H2O2-producing lactobacilli also might exert control over vaginal cancer through specific interactions of reactive oxygen species, such as superoxide anion, hydroxyl radicals, and hypochlorous acid. The conversion of H2O2 into more toxic compounds during the oxidative process is potentiated by peroxidase and halures. This enzyme and some halures, such as chloride and bromide, are present in vaginal washes in sufficient amounts to allow an optimal environment for successful inhibition of pathogens. In vitro tests provide an approach for determining the ability of lactobacilli to produce H2O2. The H2O2 amounts produced in such systems are probably not a direct reflection of what happens in the vaginal tract of women or animals, which is not yet know. However, there is a registered patent with an H2O2-generating L. crispatus strain, also supporting the use of H2O2-producing lactobacilli to restore the vaginal ecosystem.

Advances in the design of probiotic products for the prevention of major diseases in dairy cattle

“…The H 2 O 2 production was qualitatively determined according to the previously published technique [16]. The plate method employing horseradish peroxidase incorporated in tetramethyl-benzidine (TMB) agar medium was used as a Wrst screening of H 2 O 2 production.…”

“…BrieXy, LAPTg agar (1% agar) plates with 10 6 -10 7 CFU ml ¡1 of each pathogen were prepared, as described previously [16]. Standardized aliquots (25 l) of cell-free supernatant obtained from the third subculture of the LAB strains grown in LAPTg or MRS broth were placed into wells made into the agar pathogens plates.…”

Lactobacillus rhamnosus L60, a potential probiotic isolated from the human vagina

“…Such co-aggregation could be an important factor in maintaining vaginal health because it produces an area around the pathogen where the concentration of antimicrobial substances produced by the lactobacilli is increased. L60 also produces H 2 O 2 , whose toxicity is due to the oxidative effect of the molecule itself or its metabolites (OH, O 2 ) (Tomas et al, 2004).…”

A Simple Method for the Efficient Isolation of Genomic DNA from Lactobacilli Isolated from Traditional Indian Fermented Milk (dahi)

“…The present effort in India focuses on determining the diversity of Lactobacillus species in dairy products such as traditional fermented milk (dahi) and cheeses to result in a formidable repertoire of diverse Lactobacillus strains that could be functionally and genetically explored in the immediate and near future to reveal strains that have strong functional and probiotic attributes, and various industrially important uses. These strains could then be exploited to produce various useful compounds [low-molecular mass compounds such as hydrogen peroxide (H 2 O 2 ) [5], carbon dioxide (CO 2 ) [6], diacetyl (2,3-butanedione) [7]; high molecular mass compounds such as bacteriocins [8] and other uncharacterized compounds; commercial Lactic Acid [9]; exopolysaccharides [10]; low calorie sweeteners [11]; alcohols for industrial, transportation and beverage use [12]; oils and fats [13]; and by the use of genetically modified strains, vitamins [14], enzymes [15] and hormones [16].…”