Antibacterial and antioxidant activities of a novel biosynthesized selenium nanoparticles using Rosa roxburghii extract and chitosan: Preparation, characterization, properties, and mechanisms.

Developing efficient and safe antibacterial agents to inhibit pathogens including Physalospora piricola and Staphylococcus aureus is of great importance. Herein, a novel compound composed of Rosa roxburghii procyanidin, chitosan and selenium nanoparticle (RC-SeNP) was bio-synthesized, with the average diameter and zeta potential being 84.56 nm and -25.60 mV, respectively. The inhibition diameter of the RC-SeNP against P. piricola and S. aureus reached 18.67 mm and 13.13 mm, and the maximum scavenging activity against DPPH and ABTS reached 96.02% and 98.92%, respectively. Moreover, the RC-SeNP completely inhibited the propagation P. piricola and S. aureus on actual apples, suggesting excellent in vivo antimicrobial capacity. The transcriptome analysis and electron microscope observation indicated that the antibacterial activity would be attributed to adhering to and crack the cell walls as well as damage the cytomembrane and nucleus. Moreover, the RC-SeNP effectively maintained the vitamin C, total acid, and water contents of red bayberry, demonstrating potential application for fruit preservation. At last, the RC-SeNP showed no cell toxicity and trace selenium residual dose (0.03 mg/kg on apple, 0.12 mg/kg on red bayberry). This study would enlighten future development on novel nano-bioantibacterial agents for sustainable agriculture.

Improved lipid productivity of Scenedesmus obliquus with high nutrient removal efficiency by mixotrophic cultivation in actual municipal wastewater.

This study was aimed to assess the growth and lipid productivity improvement of a green microalga Scenedesmus obliquus by mixotrophic cultivation, via addition of sodium acetate (NaAc) into actual municipal wastewater (AMW). Moreover, the nutrient removal efficiency of the culture media in terms of carbon, nitrogen, and phosphorus was investigated. The results showed that the S. obliquus grew better in the AMW than in the BG11 medium (0.20 g L-1 vs 0.16 g L-1 in dry cell weight), and the final algal lipid productivity was higher (9.02 mg L-1 d-1 vs 7.75 mg L-1 d-1, P < 0.05). Further, the addition of NaAc significantly stimulated the algal growth and lipid productivity. Specifically, the highest improvement was obtained by the NaAc-addition of 1 g L-1, where the algal dry cell weight increased 2.40 times than that in the AMW with little organic carbon (0.48 mg L-1 vs 0.20 mg L-1, P < 0.01), and the corresponding algal lipid productivity increased 2.44 time (22.08 mg L-1 d-1 vs 9.02 mg L-1 d-1, P < 0.01). Meanwhile, the addition of 1 g L-1 of NaAc significantly increased the microalga-driven nitrogen and phosphorus removal efficiency, respectively by 1.75 and 2.23 times (82.20% vs 46.85% for total nitrogen, and 76.35% vs 34.18% for total phosphorus). In summary, this study confirmed the feasibility of using organic carbon-supplemented AMW to replace the artificial media for microalgae-based lipid production and nutrient recycling.

Sulfitobacter alexandrii sp. nov., a new microalgae growth-promoting bacterium with exopolysaccharides bioflocculanting potential isolated from marine phycosphere.

Marine phycosphere harbors unique cross-kingdom associations with enormous ecological significance in aquatic ecosystems as well as relevance for algal biotechnology industry. During our investigating the microbial composition and bioactivity of marine phycosphere microbiota (PM), a novel lightly yellowish and versatile bacterium designated strain AM1-D1T was isolated from cultivable PM of marine dinoflagellate Alexandrium minutum amtk4 that produces high levels of paralytic shellfish poisoning toxins (PSTs). Strain AM1-D1T demonstrates notable bioflocculanting bioactivity with bacterial exopolysaccharides (EPS), and microalgae growth-promoting (MGP) potential toward its algal host. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain AM1-D1T was affiliated to the members of genus Sulfitobacter within the family Rhodobacteraceae, showing the highest sequence similarity of 97.9% with Sulfitobacter noctilucae NB-68T, and below 97.8% with other type strains. The complete genome of strain AM1-D1T consisted of a circular 3.84-Mb chromosome and five circular plasmids (185, 95, 15, 205 and 348 Kb, respectively) with the G+C content of 64.6%. Low values obtained by phylogenomic calculations on the average nucleotide identity (ANI, 77.2%), average amino acid identity (AAI, 74.7%) and digital DNA-DNA hybridization (dDDH, 18.6%) unequivocally separated strain AM1-D1T from its closest relative. The main polar lipids were identified as phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, diphosphatidylglycerol, one unidentified phospholipid and one unidentified lipid. The predominant fatty acids (> 10%) were C18:1 ω7c, C19:0 cyclo ω8c and C16:0. The respiratory quinone was Q-10. The genome of strain AM1-D1T was predicted to encode series of gene clusters responsible for sulfur oxidation (sox) and utilization of dissolved organic sulfur exometabolites from marine dinoflagellates, taurine (tau) and dimethylsulfoniopropionate (DMSP) (dmd), as well as supplementary vitamin B12 (cob), photosynthesis carotenoids (crt) which are pivotal components during algae-bacteria interactions. Based on the evidences by the polyphasic characterizations, strain AM1-D1T represents a novel species of the genus Sulfitobacter, for which the name Sulfitobacter alexandrii sp. nov. is proposed. The type strain is AM1-D1T (= CCTCC 2017277T = KCTC 62491T).

The effects of fluoride on neuronal function occurs via cytoskeleton damage and decreased signal transmission.

It has been reported that fluoride exposure may cause serious public health problems, particularly neurotoxicity. However, the underlying mechanisms remain unclear. This study used Neuro-2A cells to investigate the effects of fluoride on the cytoskeleton. The Neuro-2A cells were exposed to 0, 1, 2, 4 and 6 mM sodium fluoride (NaF) for 24 h. Cell viability and lactate dehydrogenase (LDH) release were examined. It was observed that exposure to NaF reduced cell viability, disrupted cellular membrane integrity, and high levels of LDH were released. The observed changes occurred in a dose response manner. Morphologic observations showed that cell became rounded and were loosely adherent following exposure to NaF. Axon spines and normal features disappeared with high dose NaF treatment. The expression of MAP2 and synaptophysin decreased, particularly at 4 mM and 6 mM (P < 0.05) for MAP2. These results corroborate the morphologic observations. The content of glutamate and NMDAR (glutamate receptor) protein were assessed to help understand the relationship between synapses and neurotransmitter release using ELISA and Western-blot. Compared with the control, glutamate and NMDAR expression declined significantly at 4 mM and 6 mM (P < 0.05) group. Finally, the ultrastructural changes observed with increasing doses of NaF were: disappearance of synapses, mitochondrial agglutination, vacuole formation, and cellular edema. Taken together, NaF exposure disrupted cellular integrity and suppressed the release of neurotransmitters, thus effecting neuronal function. These findings provide deeper insights into roles of NaF in neuron damage, which could contribute to a better understanding of fluoride-induced neurotoxicity.

Aerated swine lagoon wastewater: a promising alternative medium for Botryococcus braunii cultivation in open system.

To understand the potential of using swine lagoon wastewater to cultivate Botryococcus braunii for biofuel production, growth characteristics of B. braunii 765 cultivated in aerated swine lagoon wastewater (ASLW) without sterilization and pH adjustment were investigated. The results showed that the alga strain could maintain competitive advantage over the 26-day cultivation. The highest dry biomass of alga grown in ASLW was 0.94 mg L(-1) at day 24, which was 1.73 times that grown in BG11 medium, an artificial medium normally used for B. braunii cultivation. And the algal hydrocarbon content was 23.8%, being more than twice that in BG11 medium. Additionally, after the 26-day cultivation, about 40.8% of TN and 93.3% of TP in ASLW were removed, indicating also good environmental benefits of algal bioremediation.

Growth characteristics of Botryococcus braunii 765 under high CO2 concentration in photobioreactor.

To understand the potential of cultivating Botryococcus braunii with flue gas (normally containing high CO(2)) for biofuel production, growth characteristics of B. braunii 765 with 2-20% CO(2) aeration were investigated. The results showed that the strain could grow well without any obvious inhibition under all tested CO(2) concentrations with an aeration rate of 0.2 vvm, even without any culture pH adjustment (ranged from 6.0 to 8.0). The maximum biomass among all conditions was 2.31 g L(-1) on 25th day at 20% CO(2). Hydrocarbon content and algal colony size increased with the increase of CO(2) concentration. A negative correlation between algal biomass and culture total phosphorus was observed (from -0.828 to -0.911, P<0.01). Additionally, 2% sodium hypochlorite solution was used for photobioreactor sterilization to cultivate B. braunii.