Tannin-tolerant and Extracellular Tannase Producing Bacillus Isolated from Traditional Fermented Tea Leaves and Their Probiotic Functional Properties

Abstract

A total of 117 <i>Bacillus</i> strains were isolated from Miang, a culture relevant fermented tea of northern Thailand. These strains were collected from 16 sampling sites in north Thailand. In this collection 95 isolates were tannin-tolerant <i>Bacillus</i> capable of growth on nutrient agar supplemented with 0.5% (<i>w</i>/<i>v</i>) total tannins from tea leaves extract (TE). The strains were also positive for pectinase, xylanase and amylase activity, while 91 and 86 isolates were positive for cellulase and β-mannanase, respectively. Only 21 isolates producing extracellular tannase were selected for further characterization. Identification by 16S rRNA gene sequence analysis revealed that more than 50% (11 of 21 isolates) were <i>Bacillus</i> <i>tequilensis</i>, whereas the remaining were <i>B. siamensis</i> (3), <i>B. megaterium</i> (3), <i>B. aryabhattai</i> (3) and <i>B. toyonensis</i> (1). <i>B. tequilensis</i> K34.2 produced the highest extracellular tannase activity of 0.60 U/mL after cultivation at 37 °C for 48 h. In addition, all 21 isolates were resistant to 0.3% (<i>w</i>/<i>v</i>) bile salt, sensitive to gentamicin, erythromycin, vancomycin and kanamycin and also tolerant to acidic condition. Cell hydrophobicity varied from 9.4 to 80.4% and neutralized culture supernatants of some <i>Bacillus</i> isolates showed bacteriocin producing potentiality against <i>Samonella enterica</i> serovar Typhimurium TISTR 292. All tested probiotic properties indicated that <i>B. tequilensis</i> K19.3, <i>B. tequilensis</i> K34.2 and <i>B. siamensis</i> K19.1 had high probiotic potential. This is the first report describing tannin-tolerant <i>Bacillus</i> and their extracellular tannase producing capability in Miang, a traditional fermented tea of Thailand.