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.

Second-generation lactic acid production requires the development of sustainable and economically feasible processes and renewable lignocellulose biomass as a starting raw material. Weizmannia coagulans MA42 was isolated from a soil sample in Chiang Mai province, Thailand and showed the highest production of L-lactic acid and lignocellulolytic enzymes (cellulase, β-mannanase, xylanase, β-glucosidase, β-mannosidase, and β-xylosidase) compared to other isolates. Weizmannia coagulans MA42 was able to grow, secrete lignocellulolytic enzymes, and directly produce L-lactic acid in the medium containing various lignocellulosic feedstocks as the sole carbon source. Moreover, L-lactic acid production efficiency was improved after the substrates were pretreated with diluted sulfuric acid and diluted sodium hydroxide. The highest L-lactic acid production efficiency of 553.4 ± 2.9, 325.4 ± 4.1, 326.6 ± 4.4, 528.0 ± 7.2, and 547.0 ± 2.2 mg/g total available carbohydrate was obtained from respective pretreated substrates including sugarcane bagasse, sugarcane trash, corn stover, rice straw, and water hyacinth. It is suggested that structural complexity of the lignocellulosic materials and properties of lignocellulolytic enzymes are the key factors of consolidated bioprocessing (CBP) of lignocellulosic feedstocks to lactic acid. In addition, the results of this study indicated that W. coagulans MA42 is a potent bacterial candidate for CBP of a variety of lignocellulosic feedstocks to L-lactic acid production; however, further bioprocess development and genetic engineering technique would provide higher lactic acid production efficiency, and this would lead to sustainable lactic acid production from lignocellulosic feedstocks.