Purpose: This study aimed to identify dominant bacterial species present in fermented taro skins and determine their antimicrobial potential against diarrhea-causing bacteria.
Methods: Three samples of cooked taro skins were obtained from a taro processing facility and incubated at 21°C. Aerobic plate count and LAB count of the sample were determined at 0, 24, and 34 h. Selected bacterial isolates were identified by sequencing the 16S rRNA gene. Culture supernatants of representative LAB isolates were evaluated on their bactericidal properties against Salmonella Typhimurium and Listeria monocytogenes. Moreover, the supernatants were neutralized with NaOH or treated with proteinase K before being further assessed on their antimicrobial activity.
Results: During fermentation, the LAB count of cooked taro skins increased from 3.0 log CFU/g to 8.7 log CFU/g in 34 h. All samples showed a dominance of LAB in the microbial populations. LAB constituted 91% of 37 sequenced isolates. Leuconostoc mesenteroides was the dominant LAB species (75%), with Lactococcus lactis and Weissella soli also present. These LAB species showed varying antimicrobial activity against tested diarrhea-causing bacteria. Salmonella Typhimurium died in culture supernatants of L. mesenteroides and W. soli within 2 h; L. monocytogenes died in a culture supernatant of L. mesenteroides within 8 h. Compared with control, the supernatants still showed antimicrobial effects after being neutralized. The proteinase treatment reduced the inhibition zones of the supernatants against the tested pathogens.
Significance: This study indicates the presence of beneficial LAB in fermented taro skins. The LAB species could potentially be utilized to enhance food safety.