Gamma-aminobutyric acid (GABA), the inhibitory neurotransmitter, can be naturally synthesized by a group of lactic acid bacteria (LAB) which is commonly found in rich carbohydrate materials such as fruits and fermented foods. Thirty-six isolates of GABA-producing LAB were obtained from Thai fermented foods. Among these, Levilactobacillus brevis F064A isolated from Thai fermented sausage displayed high GABA content, 2.85 ± 0.10 mg/mL and could tolerate acidic pH and bile salts indicating a promising probiotic. Mulberry (Morus sp.) is widely grown in Thailand. Many mulberry fruits are left to deteriorate during the high season. To increase its value, mulberry juice was prepared and added to monosodium glutamate (MSG), 2% (w/v) prior to inoculation with 5% (v/v) of L. brevis F064A and incubated at 37 °C for 48 h to obtain the GABA-fermented mulberry juice (GABA-FMJ). The GABA-FMJ obtained had 3.31 ± 0.06 mg/mL of GABA content, 5.58 ± 0.52 mg gallic acid equivalent/mL of antioxidant activity, 234.68 ± 15.53 mg cyanidin-3-glucoside/mL of anthocyanin, an ability to inhibit growth of Bacillus cereus TISTR 687, Salmonella Typhi DMST 22842 and Shigella dysenteriae DMST 1511, and 10.54 ± 0.5 log10 colony-forming units (CFU)/mL of viable L. brevis F064A cell count. This GABA-FMJ was considered as a potential naturally functional food for human of all ages.
Bacterial cellulose (BC), a biopolymer, is synthesized by BC-producing bacteria. Almost all producing strains are classified in the family Acetobacteraceae. In this study, bacterial strain P285 was isolated from contaminated honey wine in a honey factory in northern Thailand. Based on 16S rRNA gene sequence identification, the strain P285 revealed 99.8% identity with Komagataeibacter mal-taceti LMG 1529 T. K. maltaceti P285 produced the maximum BC production at 20–30 °C and an initial media pH of 9.0. The highest BC production in modified mineral salt medium (MSM) was exhibited when glucose (16%, w/v) and yeast extract (3.2%, w/v) were applied as carbon and nitrogen sources, respectively. When sugarcane (8–16%, w/v) or honey (ratio of honey to water = 1: 4) supplemented with yeast extract was used, the BC production was greater. The characterization of BC synthesized by K. maltaceti P285 was undertaken using scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectrometry. Meanwhile, X-ray diffraction results confirmed the presence of crystalline cellulose (2θ = 18.330, 21.390 and 22.640°). The maximum temperature of BC degradation was observed at 314 °C. Tensile properties analysis of hydrated and dried BC showed breaking strength of 1.49 and 0.66 MPa, respectively. These results demonstrated that K. maltaceti P285 has a high potential for BC production especially when grown in high initial media pH. Therefore, the strain would be suitable as an agent to make BC, the value-added product in the related factories.
Assam tea plants (Camellia sinensis var. assamica) or Miang are found in plantations and forests of Northern Thailand. Leaf fermentation has been performed for centuries, but little information is available about their associated microbial community. One hundred and fifty-seven bacterial isolates were isolated from 62 Assam tea leaf samples collected from 6 provinces of Northern Thailand and classified within the phyla of Firmicutes, Actinobacteria, and Proteobacteria. Phayao and Phrae provinces exhibited the highest and the lowest bacterial diversities, respectively. The bacterial community structural pattern demonstrated significant differences between the west and the east sides. Since some Bacillus spp. have been reported to be involved in fermented Miang, Bacillus spp. isolated in this study were chosen for further elucidation. Bacillus siamensis ML122-2 exhibited a growth inhibitory effect against Staphylococcus aureus ATCC 25923 and MRSA DMST 20625, and the highest survival ability in simulated gastric and intestinal fluids (32.3 and 99.7%, respectively), autoaggregation (93.2%), cell surface hydrophobicity (50.0%), and bacterial adherence with Vero cells (75.8% of the control Lactiplantibacillusplantarum FM03-1). This B. siamensis ML122-2 is a promising probiotic to be used in the food industry and seems to have potential antibacterial properties relevant for the treatment of antibiotic-resistant infections.
Sixteen Bacillus isolates were obtained from leaves of Miang plant (Camellia sinensis (L.) Kuntze var. assamica (J.W. Mast.) Kitam.) collected from Miang gardens in Chiang Mai and Phrae provinces of Thailand. All bacterial isolates were identified within 3 species including B. licheniformis, B. siamensis and B. tequilensis based on 16S rRNA gene sequence. The culture broth of B. siamensis ML122-2, ML123-1 and ML124-1 could inhibit growth of Staphylococcus aureus ATCC 25923 and methicillin resistant S. aureus DMST 20625 while B. licheniformis ML071-1, ML073-1, ML075-1 and ML076-2 could inhibit growth of B. cereus TISTR 687 and S. aureus ATCC 25923 with the inhibitory value ranging between 242.4 -363.6 and 265.2 -340.9 AU/ml, respectively. Moreover, B. siamensis ML122-2 could tolerate tannin, 1% (w/v). Accordingly, B. siamensis ML122-2, ML123-1 and ML124-1 and B. licheniformis ML071-1, ML073-1, ML075-1 and ML076-2 may involve in biological control of Miang fermentation process. Bacillus tequilensis ML075-2 (MH796209) Bacillus tequilensis ML074-2 (MH796208) Bacillus tequilensis ML074-1 (MH796207) Bacillus tequilensis ML073-2 (MH796206) Bacillus tequilensis ML072-3 (MH796205) Bacillus tequilensis ML072-2 (MH796204) Bacillus tequilensis ML071-2 (MH796203) Bacillus siamensis ML121-1 (MH796211) Bacillus siamensis ML122-2 (MH796212) Bacillus siamensis ML123-1 (MH796213) Bacillus siamensis ML124-1 (MH796214) Bacillus siamensis KCTC 13613 T (KT781674) Bacillus licheniformis ML071-1 (MH796199) Bacillus licheniformis ML073-1 (MH796200) Bacillus licheniformis ML075-1 (MH796201) Bacillus licheniformis ML076-2 (MH796202) Bacillus licheniformis ATCC 14580 T (KY034369)Escherichia coli ATCC 43893 (HM194886) 100 95 90 87 0.02
Assam tea or Miang is a local name of Camellia sinensis var. assamica in northern Thailand. By the local wisdom, Assam tea leaves are used as the raw material in tea fermentation to produce “Fermented Miang” consumed by people in northern Thailand and the countries nearby. In this study, twenty-eight bacterial isolates were obtained from Assam tea leaf samples collected from Nan province, Thailand. Bacterial isolates were identified within 6 genera including Bacillus, Floricoccus, Kocuria, Lysinibacillus, Micrococcus and Staphylococcus. Among these, the strain ML061-4 shared 100.0 and 99.4% similarity of 16S rRNA and rpoB gene sequence with F. penangensis JCM 31735T, respectively. This is the first discovery of F. penangensis in Thailand. F. penangensis ML061-4 exhibited probiotic characteristics including lactic acid production (9.19 ± 0.10 mg/ml), antibacterial activities (Escherichia coli ATCC 25922 and E. coli O157:H7 DMST 12743), acid and bile salt tolerance (71.1 and 54.9%, respectively), autoaggregation (97.0%), coaggregation (66.0% with E. coli O157:H7), cell surface hydrophobicity (90.0%), bacterial adhesion (82.9% with Lactobacillus plantarum FM03-1), competitive inhibition (17.8% with E. coli O157:H7) and competitive exclusion (34.9% with E. coli O157:H7). Overall, the data suggested that F. penangensis ML061-4 had a great potential to be a probiotic.
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