A total of 51 pentose utilizing lactic acid bacteria (LAB) were isolated from acid-forming bacteria in the midgut of healthy mature Eri silkworm using de Man, Rogosa and Sharpe (MRS) agar containing 10 g/L xylose (MRS-xylose) as the carbon source supplemented with 0.04% (w/v) bromocresol purple. Further analysis of 16S rRNA gene sequences revealed the highest prevalence of up to 35 enterococci isolates, which included 20 isolates of Enterococcus mundtii, followed by Entercoccus faecalis (eight isolates), Weissella cibaria (four isolates), Enterococcus hirae (two isolates), Enterococcus lactis (one isolate), and Enterococcus faecium (one isolate). All 51 LAB isolates showed positive growth on MRS containing a range of polysaccharides as the sole carbon source. All isolates were able to grow and form clear zones on MRS supplemented with 1 g/L xylose, while E. faecalis SC1, E. faecalis SCT2, and E. hirae SX2 showed tannin tolerance ability up to 5 g/L. Moreover, five isolates showed antimicrobial activity against Eri silkworm pathogens, including Bacillus cereus, Staphylococcus aureus, and Proteus vulgaris, with E. hirae SX2 having the highest inhibitory effect. Supplementation of live E. hirae SX2 on castor leaves significantly improved the weight and reduced the silkworm mortality when compared with the control group (p < 0.05). This cocci LAB can be considered as the new probiotic for Eri culture. Additionally, this finding presented the perspective of non-mulberry silkworm that could also be used as the model for further applying to new trends of the sericulture industry.

Tea (Camellia sinensis var. assamica) is a traditional and economically important non-alcoholic beverage-producing plant grown in large plantations in the northern region of Thailand and has a diverse community of endophytic bacteria. In this study, a total of 70 bacterial isolates were isolated from healthy asymptomatic samples of tea leaves from five different tea gardens in Chiang Mai, Thailand. Based on 16S rDNA sequence analysis, these bacterial isolates were taxonomically grouped into 11 different genera, namely Bacillus, Curtobacterium, Enterobacter Microbacterium, Moraxella, Neobacillus, Priestia, Pseudarthrobacter, Pseudomonas, Sporosarcina, and Staphylococcus. All these isolates were evaluated for their potential to produce indole-3-acetic acid (IAA), siderophores, and cellulolytic enzymes while having phosphate-solubilizing and tannin tolerance capacity. Most isolated bacterial endophytes belonged to the Bacillus genus and exhibited multiple plant-growth-promoting abilities. All bacterial endophytes could produce varied concentrations of the indole-related compounds, and the strain Curtobacterium citreum P-5.19 had the highest production of IAA at 367.59 µg/mL, followed by Pseudarthrobacter enclensis P-3.12 at 266.97 µg/mL. Seventy-eight percent (78%) of the total isolates solubilized inorganic phosphate, while 77%, 65%, and 52% were positive for extracellular proteases, cellulases, and pectinases, respectively. Remarkably, 80% of the isolates were capable of growth on nutrient agar supplemented with 1% (w/v) tannic acid. C. citreum P-5.19 and P. enclensis P-3.12 were selected for evaluation of plant growth promotion, and it was found that both bacterial endophytes enhanced seed germination rate and improved seedling growth parameters such as fresh and/or dry weight, root length, and shoot lengths of sunflower and tomato seeds. The selected bacterial endophytes isolated from tea leaves in this study could be used in bioformulation for plant growth promotion and advancing sustainable agricultural practices contributing to the decreased use of chemical inputs. This is the first report of an endophytic bacterium, Pseudarthrobacter enclensis, being isolated from C. sinensis.

This research demonstrated an excellent potential approach for utilizing Miang fermentation broth (MF-broth), a liquid residual byproduct from the Miang fermentation process as a health-targeted beverage. One hundred and twenty yeast strains isolated from Miang samples were screened for their potential to ferment MF-broth and four isolates, P2, P3, P7 and P9 were selected, based on the characteristics of low alcoholic production, probiotic properties, and tannin tolerance. Based on a D1/D2 rDNA sequence analysis, P2 and P7 were identified to be Wikerhamomyces anomalus, while P3 and P9 were Cyberlindnera rhodanensis. Based on the production of unique volatile organic compounds (VOCs), W. anomalus P2 and C. rhodanensis P3 were selected for evaluation of MF-broth fermentation via the single culture fermentation (SF) and co-fermentation (CF) in combination with Saccharomyces cerevisiae TISTR 5088. All selected yeasts showed a capability for growth with 6 to 7 log CFU/mL and the average pH value range of 3.91–4.09. The ethanol content of the fermented MF-broth ranged between 11.56 ± 0.00 and 24.91 ± 0.01 g/L after 120 h fermentation, which is categorized as a low alcoholic beverage. Acetic, citric, glucuronic, lactic, succinic, oxalic and gallic acids slightly increased from initial levels in MF-broth, whereas the bioactive compounds and antioxidant activity were retained. The fermented MF-broth showed distinct VOCs profiles between the yeast groups. High titer of isoamyl alcohol was found in all treatments fermented with S. cerevisiae TISTR 5088 and W. anomalus P2. Meanwhile, C. rhodanensis P3 fermented products showed a higher quantity of ester groups, ethyl acetate and isoamyl acetate in both SF and CF. The results of this study confirmed the high possibilities of utilizing MF-broth residual byproduct in for development of health-targeted beverages using the selected non-Saccharomyces yeast.

Miang, a traditional fermented tea produced from Camellia sinensis var. assamica, is of notable cultural and socio-economic relevance in Northern Thailand. Traditionally, the non-filamentous fungi-based process (NFP) in western Lanna uses only young tea leaves, resulting in substantial amounts of mature leaves being discarded as agricultural waste. This study aimed to utilize the mature tea leaves by adapting the filamentous fungi growth-based process (FFP) of eastern Lanna using selected tannin-tolerant microorganisms, including Aspergillus niger MLF3, Cyberlindera rhodanensis P3, and Lactiplantibacillus pentosus A14-6. Study on fermentation dynamics and bioactive compound formation based on a 2-step fermentation process: 3-day solid-state fermentation with A. niger MLF3, followed by 7-day submerged fermentation by co-culture of C. rhodaninsis P3, and L. pentosus A14-6 in 500 mL sterile distilled water at 30 °C. Increased activities of polysaccharide-degrading enzymes and organic acids were clearly observed during solid-state fermentation, while the significant changes in polyphenol, antioxidant, and reducing sugar content in cell-free supernatant (CFS) were found after submerged fermentation. The obtained CFS shows inhibitory effects of 90 ± 2.5% and 95 ± 1.8% on α-glucosidase and α-amylase, respectively. Analysis of CFS by E-tongue and E-nose clearly indicated the influence of microbial mixture on the taste and aroma of the fermented products. These results demonstrate not only a high-yielding strategy for the effective biotransformation of mature tea leaves into functional drink products but also significant implications for reducing agricultural waste.

This study evaluated the ability of a yeast strain isolated from traditional fermented tea leaves (Camellia sinensis var. assamica), Miang from northern Thailand, to grow and produce ethanol in the presence of tannin. Among 43 Miang samples, 25 yeast isolates displayed gas-forming character in the presence of 1% (w/v) tannin, but only ML1-1 and ML1-2 isolates were confirmed as ethanol-producing yeast capable of tannin tolerance. These isolates were further identified to be Pichia occidentalis and Saccharomyces cerevisiae, respectively, based on D1/D2 domain sequence analysis. S. cerevisiae ML1-2 was selected for further studies and exhibited growth at 20–35 °C, pH 4–7, and tolerance to high sugar concentrations of up to 350 g/L. Supplementation of 1% (w/v) tannin had no effect on sugar utilization and ethanol production, while delayed sugar consumption and ethanol production were observed in the reference strain S. cerevisiae TISTR 5088. However, 5 and 10% (w/v) tannin showed inhibitory effects on the growth and ethanol production of the selected yeast isolates. During the fermentation under high tannin conditions derived by mixing Java plum fruit with ground seed, S. cerevisiae ML1-2 showed significant advantages in growth and enhanced the content of ethanol, polyphenols, tannin, and flavonoids compared to S. cerevisiae TISTR 5088. This indicated its potential for high-tannin substrate-based bioconversion for the production of either fuel ethanol or functional alcoholic beverages.