Characterization and antimicrobial activity of Pediococcus species isolated from South African farm-style cheese

Pediococci are part of the non-starter lactic acid bacteria, LAB, contributing towards cheese ripening. This study was aimed at isolating, characterizing and evaluating the antimicrobial activity of Pediococcus species occurring among commercial and farm-style cheese. Logarithmic counts of LAB ranged from 6.9 to 9.4 cfu/g. Microscopic examination identified 110 (18%) of 606 isolates as presumptive pediococci distributed among farm-style cheese (pasteurized Gouda, young and matured; un-pasteurized aged Bouquet, aged and matured Gouda), in numbers of 33, 21, 28, 12 and 16, respectively. Pediococci were absent in commercial Cheddar cheese. Characterization of pediococci identified 49 Pediococcus acidilactici and 61 Pediococcus pentosaceus isolates. Fifty-two isolates from both species, 27 (24%) P. acidilactici and 25 (23%) P. pentosaceus, inhibited Lactococcus lactis NCDO 176 through the action of pediocins. Among these isolates, seven (6%) P. acidilactici and six (7%) P. pentosaceus inhibited Bacillus cereus ATCC 1178 while 17 (15%) P. acidilactici and 20 (18%) P. pentosaceus inhibited Listeria monocytogenes ATCC 7644. Inhibition levels were variable against L. monocytogenes ATCC 7644 and low against B. cereus ATCC 1178. Both Pediococcus species showed similar inhibition patterns; however, more isolates of P. pentosaceus inhibited L. lactis NCDO 176 and L. monocytogenes ATCC 7644 compared to P. acidilactici.