Search

Membrane aerated biofilm reactor （MABR） effectively combines biofilm technology and membrane separation technology，which has great potential in wastewater denitrification. This paper focuses on the stability and nitrogen removal performance of MABR，which is used to treat soybean processing wastewater and simulated domestic wastewater. The results showed that when HRT was 12 h，aeration pressure was 10 kPa and C/N ratio was 5，MABR had the best treatment effect on simulated domestic sewage，and the average removal rates of COD，ammonia nitrogen and TN were 92.0%，86.5% and 83.3% respectively. When HRT was 8 h and aeration pressure was 10 kPa，MABR had the best treatment effect on soybean processing wastewater. The volume loads of COD，ammonia nitrogen， TN were 1 320，125.5，184 g/（m3·d） respectively，and the average removal rate had reached 84.2%，81.5%， 79.7% respectively，which was superior to the traditional biofilm method for nitrogen removal.

Electrocatalytic nitrate reduction into ammonia is promising for its restricted activity and selectivity in wastewater treatment, however, it remains challenging. In this work, Co3O4 nanosheet electrodes with rich oxygen vacancies (OVs) (Co3O4−x/NF) are prepared and then applied as efficient catalysts for selective electrocatalytic reduction of nitrate to ammonia. The resulting Co3O4−x/NF electrodes exhibit high NO3−-N removal efficiency and NH4+-N selectivity, at 93.7% and 85.4%, respectively. X-Ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance spectra (EPR) results clearly reveal the formation of OVs in Co3O4−x/NF. The electrochemical characterization results confirm that OVs can effectively improve electron transfer as well as the electrochemically active area. The Co2+/Co3+ ratio of Co3O4−x/NF increases after the electrocatalytic reduction of nitrate, highlighting the crucial role played by Co2+ in mediating ammonia production via the Co2+/Co3+ cycle. These findings offer valuable guidelines for the development of more efficient and sustainable approaches for nitrate-contaminated wastewater treatment and ammonia synthesis. [ABSTRACT FROM AUTHOR]

Abstract Background Lignin materials are abundant and among the most important potential sources for biofuel production. Development of an efficient lignin degradation process has considerable potential for the production of a variety of chemicals, including bioethanol. However, lignin degradation using current methods is inefficient. Given their immense environmental adaptability and biochemical versatility, bacterial could be used as a valuable tool for the rapid degradation of lignin. Kraft lignin (KL) is a polymer by-product of the pulp and paper industry resulting from alkaline sulfide treatment of lignocellulose, and it has been widely used for lignin-related studies. Results Beta-proteobacterium Cupriavidus basilensis B-8 isolated from erosive bamboo slips displayed substantial KL degradation capability. With initial concentrations of 0.5–6 g L-1, at least 31.3% KL could be degraded in 7 days. The maximum degradation rate was 44.4% at the initial concentration of 2 g L-1. The optimum pH and temperature for KL degradation were 7.0 and 30°C, respectively. Manganese peroxidase (MnP) and laccase (Lac) demonstrated their greatest level of activity, 1685.3 U L-1 and 815.6 U L-1, at the third and fourth days, respectively. Many small molecule intermediates were formed during the process of KL degradation, as determined using GC-MS analysis. In order to perform metabolic reconstruction of lignin degradation in this bacterium, a draft genome sequence for C. basilensis B-8 was generated. Genomic analysis focused on the catabolic potential of this bacterium against several lignin-derived compounds. These analyses together with sequence comparisons predicted the existence of three major metabolic pathways: β-ketoadipate, phenol degradation, and gentisate pathways. Conclusion These results confirmed the capability of C. basilensis B-8 to promote KL degradation. Whole genomic sequencing and systematic analysis of the C. basilensis B-8 genome identified degradation steps and intermediates from this bacterial-mediated KL degradation method. Our findings provide a theoretical basis for research into the mechanisms of lignin degradation as well as a practical basis for biofuel production using lignin materials.

Perfluorooctanoic acid (PFOA) as an emerging persistent organic pollutant is hard to be degraded by conventional methods because of its stable physical and chemical properties. Microbial transformation is an attractive remediation approach to prevent and clean up PFOA contamination. To date, several strains of wild microbes have been reported to have limited capacity to degrade PFOA, selection of superior strains degrading PFOA become urgently necessary. Here, we report the application of genome shuffling to improve the PFOA-degrading bacterium Pseudomonas Parafulva YAB-1. The initial mutant populations of strain YAB1 were generated by nitrosoguanidine and ultraviolet irradiation mutagenesis respectively, resulting in mutants YM-9 and YM-19 with slightly improved PFOA-degrading ability. YM-9 and YM-19 were used as the starting strains for three rounds of recursive protoplast fusion. The positive mutants were screened on inorganic salt medium plates containing different concentrations of PFOA and selected based on their PFOA degradability in shake-flask fermentation test. The best performing recombinant F3-52 was isolated after three rounds of genome shuffling. In batch fermentation, the PFOA degradation rate of mutant F3-52 was up to 58.6%, which was 1.8-fold higher than that of the parent strain YAB1, and 1.6-fold higher than the initial mutants YM-9 and YM-19. Pass-generation test indicated that the heredity character of F3-52 was stable. The results demonstrated that genome shuffling was an efficient method for improving PFOA degradation of Pseudomonas Parafulva YAB1. The bred mutant F3-52 with 58.6% PFOA-degrading rate could be used for the environmental control of PFOA pollutant. [ABSTRACT FROM AUTHOR]

Ficus tikoua(F. tikoua) was a potential species for antimony (Sb) phytoremediation due to its wide growth in the mining area. However, little was known about its tolerance mechanisms toward Sb. The determination of the distribution and chemical speciation of Sb inF. tikouais essential for understanding the mechanisms involved in Sb accumulation, transportation, and detoxification. The present study investigated the subcellular distribution and chemical forms of Sb inF. tikoua. The plant was exposed to different Sb concentrations (0, 30, 90, and 180 μmol/L) for 30 days. The results showed thatF. tikouapossessed a marked ability to tolerate and accumulate Sb. The proportional Sb increased with increasing Sb concentration in the solution, and the highest Sb concentration occurred in roots (1274.5–1580.9 mg/kg), followed by stems (133.5–498.9 mg/kg) and leaves (4.1–15.7 mg/kg). In the subcellular sequestration of Sb inF. tikoua, the largest accumulation of Sb occurred in cell walls (72.4–87.5%) followed by cytoplasmic organelles (8.2–18.6%) and cytoplasmic supernatant. The results suggested that cell walls act as important protective barriers against Sb toxicity inF. tikoua. Although Sb in all plant tissues found primarily in the fractions extracted by ethanol and distilled water, the current study found that the Sb amounts in the HAc-extractable fraction, HCl-extractable fraction, and residue fraction increased at the highest Sb level (180 μmol/L) compared to that under lower Sb levels. These results indicate that excessive Sb accumulated inF. tikouaunder Sb stress is bound to non-dissolved or low-bioavailable compounds, a biochemical mechanism that benefitsF. tikouabecause it helps alleviate Sb toxicity. [ABSTRACT FROM PUBLISHER]