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Improving the biological nitrogen fixation of rhizosphere bacteria in rice is expected to improve plant growth and productivity. Most studies have focused on the application of a single N2-fixing bacterium on rice plants. Little is known about the beneficial impacts of a bacterial consortium, which is known as the microbial synthetic community (SynCom) on rice growth, and the extent of the interaction with the microbial community. The study investigated the effect of a SynCom on rice growth and productivity. A SynCom consisting of three bacteria Azosprillium sp. NL1, Bradyrhizobium sp. NL2, and Azotobacter sp. NL3 was designed to increase the survival and density of root microorganisms. The microbial culture collections used for the reconstitution experiment were established using bacterium-free soil. A profound increase in bacterial root microbiota survival and density was observed in plants inoculated with either mono- or multi-synthetic microbial consortia. SynCom is essential for rice plant growth by improving shoot ramification and root development. The results showed that SynCom could increase the total root nitrogen-fixing (%Ndfa) value by 51.6%, with Azotobacter sp. NL3 being the most dominant. High levels of indole acetic acid production in the range of 0.65–0.8 ng per g root were observed in Azosprillium sp. NL1 and Azotobacter sp. NL3. This indicates Azotobacter sp. NL3 is a nitrogen-fixing rhizosphere bacterium that is dominant in rice-amended soils. These results support the early application of the designed SynCom as a feasible strategy for the induction of nitrogen fixation, suggesting a role for earlier effects on rhizosphere colonization and tillering of plants.

Squalene, a natural triterpene with important roles as antioxidant, skin hydrating, cardioprotection and detoxifier, has attracted the attention of researchers in the world. This study investigated the optimal culture conditions for squalene production and to develop a method for squalene extraction and purification from cell suspension of Thraustochytrium sp. TN22. The results showed that squalene production by the strain Thraustochytrium sp. TN22 was optimum at 2% glucose, 0.5% yeast extract and 0,14% mixture of vitamins (B1, B6 and B12) at 28 oC for 2 days of cultivation. At the optimum conditions, the dry biomass, squalene content and productivity were approximately 9.3 g/L, 9.9 mg/g DCW and 95.3 mg/L, respectively. Time-dependence on cell lysis and extraction solvents were selected as the extraction parameters. The obtained results showed that the highest squalene production of 178.1 mg/100 g biomass was obtained in cell lysate at alkaline medium (pH = 10), at 60 oC for 6 hours and nhexan was the best solvent for squalene extraction. Squalene was then purified on silica gel column using n-hexan as the mobile phase and 90% purity of squalene was archived. Our obtained results are promising for the commercial productions of various value-added compounds from species belong to the genus Thrautochytrium in Vietnam. [ABSTRACT FROM AUTHOR]

Schizochytrium mangrovei PQ6 contains many important polyunsaturated fatty acids, such as docosahexaenoic acid (DHA, C22: 6-3), eicosahexaenoic acid (EPA, C20: 5-3) and docosapentaenoic acid (DPA, C22: 5-6). These fatty acids are essential for survival and growth of many marine fish larvae. In this paper, fresh biomass of S. mangrovei PQ6 was used for culturing rotifer Brachionus plicatilis. In the first formula (L1), rotifers were fed on baker's yeast; in second formula (L2), rotifers were fed on mixed two microalgae, Nannochloropsis oculata and Chaetoceros gracilis; in the third formula (L3), rotifers were fed on S. mangrovei PQ6 biomass. The results indicated that S. mangrovei PQ6 biomass can replace baker's yeast and autotrophic microalgae in feeding rotifers. Total lipid, total fatty acid and polyunsaturated fatty acid contents of rotifers fed on formula 3 (S. mangrovei PQ6) were higher than those within others. High polyunsaturated fatty acid (C ≥ 20) in omega-3 and 6 groups; DHA and DPA contents of rotifers fed on S. mangrovei PQ6 were the highest, accounting for 39.81% of total fatty acid; 41.95% and 8.24% polyunsaturated fatty acids, corresponding to 20.52; 12.15 and 2.4 mg/g of dried weight, respectively. The survival rate of black sleeper's larvae was highest when they were fed on rotifers grown on L3 formula (51.20 ± 0.89%), followed by L2 formula (48.70 ± 2.67%) and the lowest with L1 formula (43.44 ± 1.54%) (P < 0.05). However, among three formulas, no significant difference was found in the growth of black sleeper's larvae (P > 0.05). These results suggest that biomass of S. mangrovei PQ6 can replace traditional feed like autotrophic microalgae or baker's yeast for biomass culture of the Brachionus plicatilis rotifer for rearing black sleeper's larvae to enhance seed quality to meet demands of market. [ABSTRACT FROM AUTHOR]

Photosynthesis is an important physiological process in plants. It plays a crucial role in plant growth and development. In this study, we investigated the impact of zerovalent cobalt nanoparticles on the photosynthesis and expressing of gene involving in this process in leave of soybean Glycine max (L.) Merr "DT26" at different growth stages. The results showed that treatment of zerovalent cobalt nanoparticles made in Vietnam and USA (with two doses of 0.17 and 16.67 mg/kg of soybean seed) enhanced the photosynthesis of soybean by increasing the content of chlorophyll a and the ratio of Fv/Fm compared with the control (without treatment of zerovalent cobalt nanoparticles). These values tended to increase and reached the maximum value at 40 days and then decreased in at 70 days. The expression level of photosynthesis-related genes of soybean leaves also changed depending on the soybean's growth stage and concentration of zerovalent cobalt nanoparticles being treated. The genes psaA, Lhca, psaB, Cytb6f (belonging to photosystem I) and psbA, psbB, psbC, psbD, psbE (belonging to photosystem II) in the experimental fomulas were higher expressed than that in control group at 20 and 70 days. However, at 40 days, the expression levels of these genes were significantly different. Obtained results supplied the basis for understanding the active mechanism of the above genes to control/regulates photosynthetic activity of plants with and without the presence of zerovalent cobalt nanoparticles as well as under stress conditions. [ABSTRACT FROM AUTHOR]