Probiotic traits of lactic acid bacteria isolated from aerial surfaces of pomegranate

Abstract

Lactic acid bacteria isolated from aerial plant surfaces of pomegranate viz., Lactococcus lactis subsp. cremoris PB6, Lactobacillus brevis PFR77, L. lactis subsp. cremoris PFL9, Enterococcus faecium PB119 and L. lactis subsp. lactis PFL4 were tested for hemolysis, antibiotic susceptibility, gelatinase activity, tolerance to low pH and bile, resistance to digestive enzymes and antibacterial activity against human pathogens. All the isolates were non-hemolytic and non-gelatinolytic. These isolates were sensitive to clinically important antibiotics (amoxyclav, ampicillin, chloramphenicol, doxycycline, erythromycin, gentamycin, methicillin, penicillin G, Rifampicin and tetracycline), whereas resistance was recorded in case of norfloxacin and vancomycin. They could survive for more than 2h at pH 3 and the survival period of PB6, PFR77 and PFL9 was 3 h. Thus, the tolerance level of these LAB isolates was higher than the suggested values which indicate their good tolerance to stomach pH. In case of PB6, PFR77 and PFL9, around 80% of population survived in presence of 0.3% bile for 6 h. Also, they could survive at 1% concentration for 6 h. Thus, these isolates had good bile salt tolerance. All the isolates inhibited the growth of Gram positive and Gram negative bacterial pathogens with greater inhibition zones. PB6, PFR77 and PFL9 showed 60-70% survival in presence of trypsin whereas in presence of pepsin the survival decreased in between 50 and 60%. These isolates also showed good resistance to amylase and lipase. Thus, these LAB may be good candidates in formulation of probiotic preparations.