Yanan Liu

Influence of Cosubstrates on Iopromide Degradation by Pseudomonas sp. I-24

Iopromide has been frequently detected in different environmental compartments. However, the biodegradation of iopromide was limited, and significantly different removal efficiencies by various methods were reported. In this study, a Pseudomonas sp. I-24 isolated from activated sludge in a sewage treatment plant was used to degrade iopromide. Four different cosubstrates were selected as the cometabolic carbon and energy sources. The results showed that cosubstrate starch was able to increase catabolic enzymatic activity and enhance iopromide degradation. The degradation efficiency of iopromide was as high as 88.24xa0%, which was much higher as compared with other cosubstrates (38.58–51.44xa0%) and blank sample (2.81xa0%). Additionally, the highest enzymatic activity of 0.182xa0mU for iopromide degradation was also obtained when adding starch as a cosubstrate, somehow supporting that higher enzymatic activity resulted in higher degradation efficiency for iopromide. Although little was illuminated about the molecular mechanism during the degradation process of iopromide with starch addition, the two-dimensional gel electrophoresis results indicated that the iopromide-degrading cells growing with cosubstrate starch underwent significant physiological changes.

Degradation of p-Nitrophenol in Soil by Dielectric Barrier Discharge Plasma

Dielectric barrier discharges (DBDs) were utilized for the remediation of soil contaminated with p-nitrophenol (PNP). The effect of treatment time, applied discharge voltage, initial PNP concentration, pH of contaminated soil, and airflow rate were investigated in this study. The results showed that 63.2xa0% of the PNP in the contaminated soil was degraded in 50xa0min with a voltage of 38.2xa0kV with no airflow. This degradation reaction followed the first order reaction kinetics. The degradation by ozone alone was compared with the plasma treatment to identify the role of ozone. Chromatographic analysis was applied to monitor the intermediates produced during the oxidation process, and the main byproducts were maleic acid, p-benzoquinone, 4-nitrocatechol, methanoic acid, acetic acid, oxalic acid, NO2−, and NO3−. Possible pathways for the degradation of PNP in this system were deduced, which would provide evidence for the researches about the remediation of soils polluted by organic pollutants.

Isolation and identification of an iopromide-degrading strain and its application in an A2/O system

An iopromide (IOPr)-degrading bacterium was isolated from activated sludge of a wastewater treatment plant in Shanghai. Based on its morphology, physiological-biochemical characteristics and a phylogenetic analysis of its 16S rRNA sequence, the bacterium was identified and named as Pseudomonas sp. I-24. The optimum condition for degrading IOPr was at 30°C and pH 7.0. After 5 days, strain I-24 could degrade 30 mg/L IOPr by 99% in a basal salts medium with a 5% (V/V) inoculum and 200 mg/L starch as the primary substrate. When applied to an Anaerobic-Anoxic/Aerobic (A2/O) process, with the coexistence of other bacteria, the strain I-24 got lower (61.3%) IOPr removal, but in two A2/O systems (with and without I-24 inoculation), the CODcr removal were both approximately 95%. The trial dosed with strain I-24 showed better IOPr removal than the un-dosed one. I-24 sustained its abundance in the A2/O system during the experiment.

Production of lactic acid from thermal pretreated food waste through the fermentation of waste activated sludge: Effects of substrate and thermal pretreatment temperature

Valorization of organic-rich waste stream to lactic acid by the mixed microbial consortium has attracted tremendous research interests in recent years. In this study, thermal pretreatment was involved in co-fermentation of food waste (FW) and waste activated sludge (WAS) to enhance lactic acid production. First, sole FW was observed as the most suitable substrate employing thermal pretreatment for the generation of lactic acid. The fermentation time for reaching the maximal plateau was significantly shortened at a corresponding thermal pretreatment temperature. The mechanism study found that the enhancement of lactic acid yield was in accordance with the acceleration of solubilization and hydrolysis. Furthermore, the physicochemical characteristics of fermentative substrate and surface morphology of the fermentation mixture varied with the pretreatment temperatures. Further investigations of microbial community structure also revealed that the proportions of key microorganisms such as Bacillus and Lactobacillus were changed by the thermal pretreatment.

Efficient bioconversion of organic wastes to high optical activity of l -lactic acid stimulated by cathode in mixed microbial consortium

Lactic acid is one of the emerging top biomass derived platform chemicals that can be fermented from organic wastes. This study evaluated the potential of Cathodic Electro-Fermentation (CEF) as a novel approach to enhance the yield of high optical activity (OA) of l-lactic acid from organic wastes using mixed microbial consortium. The fermentation process was stimulated through the cathode applied withxa0-100u202fmV versus standard hydrogen electrode (SHE), which contributed to 4.73 times higher lactic acid productivity (0.6578u202fgu202fL-1 h-1) compared to that in the open circuit control (0.1392u202fgu202fL-1 h-1), and an improved OA of l-lactic acid was also observed (42.3% vs. 3.6% of the open circuit control). The study elucidated that the optimal voltage atxa0-100u202fmV promoted the conversion of pyruvate to l-lactate by 77.9% compared to the Blank, which triggered the generation of l-lactic acid to occur rapidly even at low concentration of pyruvate. The significant variation of microbial community in family- and genus-level distributions were observed in CEF system. Furthermore, the open-circuit operation test demonstrated that the cathode providing in-situ electron supply was essential to achieve high efficient bioconversion of organic wastes to lactic acid. Our work highlights the feasibility of CEF to steer high value-added fermentation products deriving from organic wastes by the mixed microbial consortium.

Evaluation of pulsed corona discharge plasma for the treatment of petroleum-contaminated soil

Petroleum hydrocarbons released to the environment caused by leakage or illegal dumping pose a threat to human health and the natural environment. In this study, the potential of a pulsed corona discharge plasma system for treating petroleum-polluted soils was evaluated. This system removed 76.93xa0% of the petroleum from the soil in 60xa0min with an energy efficiency of 0.20xa0mg/kJ. Furthermore, the energy and degradation efficiencies for the remediation of soil contaminated by single polyaromatic hydrocarbons, such as phenanthrene and pyrene, were also compared, and the results showed that this technology had potential in organic-polluted soil remediation. In addition, the role of water molecules was investigated for their direct involvement in the formation and transportation of active species. The increase of soil moisture to a certain extent clearly benefitted degradation efficiency. Then, treated soils were analyzed by FTIR and GC-MS for proposing the degradation mechanism of petroleum. During the plasma discharging processes, the change of functional group and the detection of small aromatic hydrocarbons indicated that the plasma active species attached petroleum hydrocarbons and degradation occurred. This technique reported herein demonstrated significant potential for the remediation of heavily petroleum-polluted soil, as well as for the treatment of organic-polluted soils.

Degradation of Phenol in Water Using a Novel Gas-Liquid Two-Phase Dielectric Barrier Discharge Plasma Reactor

Phenol is toxic to human and persistent in the environment. Traditional treatment methods have the disadvantages of long treatment time, large amount of agents, and secondary pollution. In this study, a novel gas-liquid two-phase dielectric barrier discharge reactor was designed to remove phenol in aqueous solution. The effects of operating conditions (applied voltage, discharge spacing, pH, and conductivity), different water matrix (deionized water, groundwater, surface water, tap water), and inorganic ions were investigated. Moreover, the reaction mechanisms and the possible degradation pathway were proposed. The removal efficiency of phenol achieved 95.5% under the optimal operating conditions (discharge voltage of 17.6xa0kV, discharge gap of 1xa0mm, air flow rate of 60xa0mLxa0min−1) coupling with H2O2 at 10xa0mM. The presence of different concentrations of inorganic ions (0.1, 1, 10, and 20xa0mM) could inhibit the phenol removal efficiencies. Specially, Cl− had different effects on phenol removal efficiency. The inhibition of Cl− on phenol removal was weakened when Cl− concentration was greater than 1xa0mM, which allows the technology that has certain advantages in treating high-salt wastewater containing high chloride concentration. In addition, ˙OH was verified as the main active species in phenol removal. The possible degradation pathway was proposed according to theoretical calculation and GC-MS measurement.

Copper (II) addition to accelerate lactic acid production from co-fermentation of food waste and waste activated sludge: Understanding of the corresponding metabolisms, microbial community and predictive functional profiling

Bio-refinery of food waste and waste activated sludge to high value-added chemicals, such as lactic acid, has attracted particular interest in recent years. In this paper, the effect of copper (II) dosing to the organic waste fermentation system on lactic acid production was evaluated, which proved to be a promising method to stimulate high yield of lactic acid (77.0% higher than blank) at dosage of 15u202fμM-Cu2+/g VSS. As mechanism study suggested, copper addition enhanced the activity of α-glycosidase and glycolysis, which increased the substrate for subsequent acidification; whereas, the high dosage (70u202fμM-Cu2+/g VSS) inhibited the conversion of lactic acid to VFA, thus stabilized lactic acid concentration. Microbial community study revealed that small amount of copper (II) at 15u202fμM/g VSS resulted in the proliferation of Lactobacillus to 82.6%, which mainly produced lactic acid. Finally, the variation of functional capabilities implied that the proposed homeostatic system II was activated at relatively low concentration of copper. Meanwhile, membrane transport function and carbohydrate metabolism were also strengthened. This study provides insights into the effect of copper (II) on the enhancement of lactic acid production from co-fermentation of food waste and waste activated sludge.