Antioxidant Properties of Food-Derived Lactic Acid Bacteria: A Review

The mechanisms of antioxidant action of lactic acid bacteria (LAB) have not been fully explained. This review aimed to characterise the antioxidant properties that can be presented by LAB strains isolated from food. The review presents a definition and classification of the antioxidants, mechanisms of antioxidant action of LAB, discusses the most popular antioxidant assays, taking into account the mechanisms underlying each test and the practice of assessing antioxidant capacity, and presents examples of studies of food-derived LAB and fermented food with antioxidant properties. LAB are an important part of the human microbiota, and their role in antioxidant processes is extremely important. They can respond quickly and effectively to free radicals by enhancing antioxidant activity, chelating metal ions, producing antioxidant enzymes and other metabolites, and thus mitigating the damage caused by oxidative stress. This review also presents methods for testing antioxidant properties that can be used for LAB screening. The most commonly used methods are the classical methods of testing antioxidant activity, such as DPPH (2,2-diphenyl-1-picrylhydrazyl), ABTS (2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)), or FRAP (Ferric Reducing Antioxidant Power) assays. We recommend using at least three different assays. It is important to consider whether to test live or inactivated cells, post-culture supernatant, cell lysates, protein fractions or purified exopolysaccharides. In conclusion, due to their properties, lactic acid bacteria strains may prove to be an interesting and natural alternative to synthetic antioxidants used in food production. Lactic acid bacteria have been shown to be not only useful as microorganisms that support the proper functioning of the digestive tract or as probiotics, but also allow their antioxidant properties to be noticed and strengthen the defence against oxidative stress.