Beneficial, safety, and antioxidant properties of lactic acid bacteria: A next step in their evaluation as potential probiotics

The role of lactic acid bacteria (LAB) as probiotics as health promoting factors for human or veterinary practice has gained increasing interest during the last three decades. This is reflected in screening approaches of LAB strains in line with minimal requirements for a “probiotic” with regard to safety and functionality. The latter might also include natural antioxidant properties, thereby constituting an additional benefit in substituting synthetic antioxidants. The in vitro antioxidant assays conducted in this study included the scavenging of the 2,2-diphenyl-1-picrylhydrazil (DPPH) free radical, metal (Fe(+2)) ion chelation, determining the scavenging properties of the hydroxyl and superoxide radicals, and anti-lipid peroxidation. Analysis of DPPH free radical scavenging property for the microorganisms included in current study, showed Streptococcus salivarius ST59HK to exhibit the highest activity at a level of 85.24%. The greatest Fe(+2) chelation activity with 98.2% was recorded for Str. salivarius ST62HK while the lowest was recorded for Str. salivarius ST48HK at 71.5%. The greatest and minimal hydroxyl radical scavenging levels were detected for Str. salivarius ST59HK (98.6%) and Lactiplantibacillus plantarum ST63HK (35.60%), respectively. Superoxide anion radical scavenging activity was highly exhibited by Str. salivarius ST61HK (54.62%) and the least exhibited by Enterococcus faecium ST651ea (18.7%). Lastly, the strains Lactobacillus gasseri ST16HK and E. faecium ST7319ea showed the highest and lowest anti-lipid peroxidation levels with 69.43% and 26.15%, respectively. Anti-oxidative properties appear to be strain specific and thus some of these strains could be potentially applied as natural antioxidants in fermented food products.