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Lactic acid bacteria isolated from food sources can be introduced as probiotics because of their healthpromoting and nonpathogenic characteristics. Eight lactic acid bacteria from idli batter fermented with Piper betle leaves were selected to screen the antioxidant potential and biofilm-forming ability. Five isolates exhibited good antioxidant potential and biofilm formation and showed antagonistic activity against the pathogenic biofilm-forming Staphylococcus aureus. Further, in vitro probiotic properties of five isolates exhibited excellent acid tolerance, bile tolerance, simulated gastrointestinal juice tolerance, auto-aggregation and co-aggregation and hydrophobicity and showed resistance to antibiotics such as ciprofloxacin, nalidixic acid, norfloxacin and colistin. Isolates also showed positive bile salt hydrolase activity, cholesterol assimilation, b-galactosidase production and mucin binding ability. The isolate KJBB10 exhibited good adhesion and pathogen exclusion percentage with human colon cancer cells (HCT-15 and HT-29). Hence, the isolates KJBB10, KJBB56 and KJBC06 can be used as beneficial probiotic starter cultures for the formulation of functional foods. Reducing activity assayReducing activity of ICFE of potent isolates was assayed by the method of Oyaizu (1986). 0.5 mL of 1% potassium ferricyanide was mixed with the same In vitro probiotic evaluation of LAB V. Sadishkumar and K. Jeevaratnam 330 * indicates the significance of result at P ≤ 0.001. ** indicates the significance of result at P ≤ 0.05. *** indicates the significance of result at P ≤ 0.10 using one-tailed hypothesis. † Ascorbate inhibition percentage. ‡ Expressed in equivalent to cysteine (lg). § Hydroxyl radical scavenging percentage. ¶ Expressed as % DPPH scavenging = [1-(A 515 of sample/A 515 of control)] 9 100. In vitro probiotic evaluation of LAB V. Sadishkumar and K. Jeevaratnam * Indicates the significance of result at P ≤ 0.001. ** Indicates the significance of result at P ≤ 0.05. *** Indicates the significance of result at P ≤ 0.10 using one-tailed hypothesis. † Time delay for bile tolerance was calculated as time taken to increase OD 560 by 0.3 units. ‡ Expressed in %. § Expressed in miller units.

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Bacteriocins are natural antimicrobial agents mainly act against closely related bacteria and at times unrelated organisms including various food spoilage and pathogenic organisms. Bacteriocins from Lactic Acid Bacteria (LAB) have been widely used for food preservation because of their safety nature. In this study, bacteriocin from Pediococcus pentosaceus KJBC11 was purified with the recovery of 15%, using cell adsorption‐desorption technique, gel permeation chromatography, hydrophobic interaction chromatography, and reversed phase HPLC successively. Molecular weight of bacteriocin KJBC11 was determined to be 4.5 kDa using Tricine SDS‐PAGE. The bacteriocin KJBC11 showed strong inhibitory activity against various Gram‐positive and Gram‐negative pathogens. Bacteriocin KJBC11 activity was not altered when treated with amylase, lipase, and trypsin but inactivated by protease and proteinase enzyme treatment. It was heat stable (100°C, 1 hr) and exhibited strong antimicrobial activity within the pH 3–7. Its mode of action was bactericidal in nature as revealed against Listeria monocytogenes showing leakage of internal contents out of the cell. Bacteriocin KJBC11 could belong to Class IIa‐pediocin like bacteriocins based on its characteristics as well as the presence of pediocin gene in the genome of the isolate KJBC11. Practical applications Studies on Lactic Acid Bacteria and bacteriocin have attracted increasing attention for a long time, due to their established role in food fermentation and preservation. The antimicrobial properties of bacteriocin became a trademark approach to achieve food safety and to counter the menace of antibiotic resistant pathogens. This study revealed a potent bacteriocin with wide range of antibacterial activity against various foodborne and clinically important pathogens to have potential application in food preservation and biomedicine.