Purification of AS-CMP effluent by combined photosynthetic bacteria and coagulation treatment

The effluent from the pulping of E. urophylla by alkali sodium sulfite chemi mechanical process(AS-CMP) was characterized for its biodegradability by photosynthetic bacteria (PSB). Chemical coagulation post treatment of biotreated wastewater was also studied. One month continuous treatment in the laboratory indicated that the COD Cr , BOD 5 and SS removals in biotreatment stages reached 56%, 83% and 89% respectively, and the CH 2Cl 2 extractives decreased from 10.7 mg/L to 7.7 mg/L. In chemical coagulation post treatment stage, the effects of process conditions, such as coagulant dosage, pH value and the coordinated coagulation flocculation treatment of three kinds of coagulants on coagulation effectiveness were discussed. The optimum operating conditions were given.

Generation of Hydrogen from Photolysis of Organic Acids by Photosynthetic Bacteria

Photodecomposition of ten kinds of organic acids by Rhodopseudomonas palustris for producing hydrogen has been investigated. By using acetate as hydrogen donor, dynamics of hydrogen production and cell growth has been determined; the influences of acetate concentration, temperature, light intensity and the effects of the interaction among metal ions (Fe3+, Ni2+), acetate and glutamate in aqueous solution on hydrogen production have been examined for optimizing the conditions of H2 generation. The results show that H2 production is partially correlated with cell growth; Ni2+ inhibits hydrogen production, but enhances cell growth; Fe3+ promotes hydrogen production evidently. The highest rate of H2 production is 22.1 mL L-1 h-1 under the conditions of 35 ~ 37℃, 6000 ~ 8000 lx, 30 mmolL-1 of acetate, 9 mmolL-1 of glutamate, and 50 mmolL-1 of Fe3+.

Biological formation of 5-aminolevulinic acid by photosynthetic bacteria

In this study, 7 stains of Rhodopseudomonas sp. were selected from 36 photosynthetic bacteria stains storied in our laboratory. Rhodopseudomonas sp. strain 99 28 has the highest 5 aminolevulinic acid(ALA) production ability in these 7 strains. Rhodopseudomonas sp. 99 28 strain was mutated using ultraviolet radiation and a mutant strain L 1, which ALA production is higher than wild strain 99 28 about one times, was obtained. The elements affecting ALA formation of strain 99 28 and L 1 were studied. Under the optimal condition(pH 7 5, supplement of ALA dehydratase(ALAD) inhibitor, levulinic acid(LA) and precursors of ALA synthesis, glycine and succinat, 3000 lx of light density), ALA formation of mutant L 1 was up to 22 15 mg/L. Strain L 1 was used to treat wastewater to remove COD Cr and produce ALA. ALA production was 2 819 mg/L, 1 531 mg/L, 2 166 mg/L, and 2 424 mg/L in monosodium glutamate wastewater(MGW), succotash wastewater(SW), brewage wastewater(BW), and citric acid wastewater(CAW) respectively. More than 90% of COD Cr was removed in four kinds of wastewater. When LA, glycin and succinate were supplied, ALA production was dramatically increased, however, COD Cr could hardly be removed.

Effects of Photosynthetic Bacteria-enhanced Biological Floc Replacement Diets on Tilapia Growth,Water Environment and Water Microbial Diversity

With Oreochromis niloticus as the object of study,glucose was added as a carbon source to promote the formation of the biological flocs for replacing part of the feed,and three gradients were set up,namely Group A(all feed),Group B(replacement of 10%feed)and Group C(replacement of 20%feed),so as to explore the effects of photosynthetic bacteria-enhanced biological flocs on tilapia growth and water environment conditions.Meanwhile,the Biolog-ECO technology was applied to study the changes of microbial carbon metabolism diversity in aquaculture water.The results showed that the utilization of microbial carbon sources under different feed replacement gradients increased with the extension of the culture time.The overall performance was in order of 10%replacement>all feed>20%feed replacement.A suitable replacement rate could not only enhance the overall utilization of carbon sources by water microorganisms,but also save culture costs.The principal component analysis showed that the carbon source metabolism of the water microbial communities under different feed replacement gradients was significantly different.Specifically,polysaccharides,esters and amino acids were the preferred carbon sources of water microbes,while the utilization of amines and acids was low.

Treatment of Chinese Traditional Medicine Wastewater by Photosynthetic Bacteria

The influence factors treating wastewater of Chinese traditional medicine extraction by photosynthetic bacteria are tested and discussed. The results indicate that the method of photosynthetic bacteria can eliminate COD and BOD from wastewater in high efficiency. And it also has high load shock resistance. On the conditions of slight aerobic and semi-darkness, treating wastewater of Chinese traditional medicine extraction, the method has better efficiency to eliminate COD and BOD from the wastewater than those by anaerobic illumination and aerobic darkness treatments. After pretreatment of hydrolytic acidization, the removal rate of COD in the wastewater reached more than 85 %, and that rate of BOD reached more than 90% in the treating system of photosynthetic bacteria. It may be more feasible and advantageous than traditional anaerobic biological process to treat organic wastewater using PSB system.

Polydopamine-coated photoautotrophic bacteria for improving extracellular electron transfer in living photovoltaics

Living photovoltaics are microbial electrochemical devices that use whole cell–electrode interactions to convert solar energy to electricity.The bottleneck in these technologies is the limited electron transfer between the microbe and the electrode surface.This study focuses on enhancing this transfer by engineering a polydopamine(PDA)coating on the outer membrane of the photosynthetic microbe Synechocystis sp.PCC6803.This coating provides a conductive nanoparticle shell to increase electrode adhesion and improve microbial charge extraction.A combination of scanning electron microscopy(SEM),transmission electron microscopy(TEM),UV–Vis absorption,and Raman spectroscopy measurements were used to characterize the nanoparticle shell under various synthesis conditions.The cell viability and activity were further assessed through oxygen evolution,growth curve,and confocal fluorescence microscopy measurements.The results show sustained cell growth and detectable PDA surface coverage under slightly alkaline conditions(pH 7.5)and at low initial dopamine(DA)concentrations(1 mM).The exoelectrogenicity of the cells prepared under these conditions was also characterized through cyclic voltammetry(CV)and chronoamperometry(CA).The measurements show a three-fold enhancement in the photocurrent at an applied bias of 0.3 V(vs.Ag/AgCl[3 M KCl])compared to non-coated cells.This study thus lays the framework for engineering the next generation of living photovoltaics with improved performances using biosynthetic electrodes.

In vivo polydopamine coating of Rhodobacter sphaeroides for enhanced electron transfer

Recent advances in coupling light-harvesting microorganisms with electronic components have led to a new generation of biohybrid devices based on microbial photocatalysts.These devices are limited by the poorly conductive interface between phototrophs and synthetic materials that inhibit charge transfer.This study focuses on overcoming this bottleneck through the metabolically-driven encapsulation of photosynthetic cells with a bio-inspired conductive polymer.Cells of the purple non sulfur bacterium Rhodobacter sphaeroides were coated with a polydopamine(PDA)nanoparticle layer via the self-polymerization of dopamine under anaerobic conditions.The treated cells show preserved light absorption of the photosynthetic pigments in the presence of dopamine concentrations ranging between 0.05–3.5 mM.The thickness and nanoparticle formation of the membrane-associated PDA matrix were further shown to vary with the dopamine concentrations in this range.Compared to uncoated cells,the encapsulated cells show up to a 20-fold enhancement in transient photocurrent measurements under mediatorless conditions.The biologically synthesized PDA can thus act as a matrix for electronically coupling the light-harvesting metabolisms of cells with conductive surfaces.