The study, published in LWT - Food Science and Technology, reports on the isolation and characterisation of three strains of Bacillus amyloliquefaciens from a range of traditional Korean soy sauces – revealing that all three were found to survive a simulated gastrointestinal model and showed anti-microbial, amylase and protease activity.
Led by Sangki Lee from Dankook University, Republic of Korea, and supported by a grant from the Korean Rural Development Administration (RDA), the team screened for probiotic Bacillus strains in products from 17 regions of Korea, identifying three strains of Bacillus amyloliquefaciens: MKSK-E1, MKSK-J1 and MKSK-M1.
“All three strains, MKSK-E1, J1 and M1, isolated from Korean traditional soy sauce possess great potential as probiotics for human and animal use and as fermentation starter cultures,” wrote the team.
“This was supported by probiotic characteristics such as high survivability in the artificial modified digestive tract system, wide antimicrobial spectra, and safety confidence such as antibiotic susceptibility, nonhemolysis and non-biogenic amine formation,” they said.
Lee and colleges explained that the three isolated strains, which were designated as MKSK-E1, MKSKJ1 and MKSK-M1, were rod-shape, gram-positive and spore forming aerobes.
“The strains showed catalase and oxidase activity, and grew in the presence of 0e15% NaCl and at 20-90 C,” they said – noting that 16S rRNA gene sequences and API 50 CHB results showed the isolates were members of the genus Bacillus. These three strains also showed close sequence homology (97% to 98%) to other Bacillus species including B. amyloliquefaciens, B. subtilis, B. methylotrophicus and B. vallismortis.
The relative survival rate of MKSK-E1, J1 and M1 were 93.14%, 91.85% and 95.98%, respectively, after exposure to a model of gastric fluids.
Furthermore, tests of a 3% bile salt solution showed MKSK-M1 had the highest tolerance (99.31%) after a three-hour incubation, followed by MKSK-E1 (92.50%) and MKSK-J1 (90.31%).
“Our three probiotic Bacillus strains showed strong tolerance against gastric juice compared to other reported values for probiotic Lactobacilli and Bacilli,” the authors said.
The Korean researchers also revealed that all three isolates showed antimicrobial activity against the following bacteria: Stap. aureus, B. cereus, E. coli, S. sonnei, S. flexneri, Pseudo. fluorescens, and K. pneumoniae.
Additionally, all three strains exhibited amylase and protease activity, and utilised more than 19 carbohydrates among 49 tested carbohydrates, they revealed.
“Our findings suggest that all three selected Bacillus strains may possess the ability to remain viable after consecutive exposure to the gastrointestinal tract of humans and animals and to be functionally effective in the intestine,” concluded Lee and colleagues.
Source: LWT - Food Science and Technology
Published online ahead of print, doi: 10.1016/j.lwt.2016.08.040
“Probiotic characteristics of Bacillus strains isolated from Korean traditional soy sauce”
Authors: Sangki Lee, et al
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