Abstract
A total of 117 Bacillus 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 Bacillus capable of growth on nutrient agar supplemented with 0.5% (w/v) 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 Bacillus tequilensis, whereas the remaining were B. siamensis (3), B. megaterium (3), B. aryabhattai (3) and B. toyonensis (1). B. tequilensis 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% (w/v) 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 Bacillus isolates showed bacteriocin producing potentiality against Samonella enterica serovar Typhimurium TISTR 292. All tested probiotic properties indicated that B. tequilensis K19.3, B. tequilensis K34.2 and B. siamensis K19.1 had high probiotic potential. This is the first report describing tannin-tolerant Bacillus and their extracellular tannase producing capability in Miang, a traditional fermented tea of Thailand.
Highlights
Fermented tea leaves, called “Miang”, is a traditional fermented food product made from Camellia sinensis var. assamica that has been important in the sociocultural lifestyle of northern Thailand for over several hundred years
We have found that all tannin-tolerant Bacillus isolates were positive for pectinase, amylase and xylanase (Figure 1b)
Bacillus spp. diversity from traditional Miang, a fermented tea leaves product of northern Thailand was for the first time identified and characterized in this study
Summary
Fermented tea leaves, called “Miang”, is a traditional fermented food product made from Camellia sinensis var. assamica that has been important in the sociocultural lifestyle of northern Thailand for over several hundred years. A typical Miang production process mainly consists of fermentation of steamed tea leaves without adding other nutritional substances in a variety of containers such as bamboo basket or clay jar for several days or up to a year without the use of any preservatives. Number of studies have described bioactive benefits and human health-relevant effects of tea phenolic compounds, including reducing the risk of cardio vascular disease, improving oral hygiene, cancer prevention, reduction of cholesterol level, and modulating blood pressure [7,8,9,10]. Due to the potential for such health relevant bioactive metabolites, traditional Miang fermentation and its use as the functional food or nutraceuticals was proposed and targeted [1]
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