Isolation and characterization of lactic acid bacteria from xi-gua-mian (fermented watermelon), a traditional fermented food in Taiwan

Abstract

Young watermelon fruit was peeled and pickled for fermentation to produce a unique fermented food named xi-gua-mian (fermented watermelon) in Taiwan. In this study, we investigated the LAB microflora in xi-gua-mian. A total of 176 LAB isolates were identified; 118 cultures were isolated from the xi-gua-mian sample collected from three different farmers markets and 58 from six young watermelon fruit samples. These isolates were characterized phenotypically and then divided into seven groups (A to G) by restriction fragment length polymorphism analysis, sequencing of 16S ribosomal DNA and other genotypic analysis. Lactobacillus plantarum was the most abundant LAB found in xi-gua-mian samples collected in southern Taiwan, Tainan City and Pediococcus pentosaceus was the most abundant LAB in northern Taiwan, Taoyuan County. We found that LAB stains are similar in samples collected in the same geographic region but significant variations were observed between samples collected among different regions. On the other hand, a greater LAB diversity was observed in the young watermelon fruit samples. In addition, 10 Lactococcus lactis subsp. lactis showed inhibitory activity against the indicator strain L. sakei subsp. sakei JCM 1157T. This is the first report describing the distribution and varieties of LAB existing in the xi-gua-mian and the young watermelon fruits.