Biodegradation of high molecular weight polycyclic aromatic hydrocarbons by Sarocladium terricola strain PYR-233 isolated from petrochemical contaminated sediment.

Polycyclic aromatic hydrocarbons (PAHs) were frequently found in sediment and were primarily treated through microbial degradation. Thus, efficient management of PAH pollution requires exploring the molecular degradation mechanisms of PAHs and expanding the pool of available microbial resources. A fungus (identified as Sarocladium terricola strain RCEF778) with the remarkable ability to degrade pyrene was screened from sediment near a petrochemical plant, and its growth and pyrene degradation characteristics were comprehensively investigated. The results showed that the fungus exhibited great effectiveness in pyrene degradation, with a degradation ratio of 88.97% at 21 days at the conditions: 35 °C, pH 7, 10 mg L-1 initially pyrene concentration, 3% supplementary salt, and glucose supplementation. The generation and concentration variation of the intermediate products were identified, and the results revealed that the fungus degraded pyrene through two pathways: by salicylic acid and by phthalic acid. Three sediments (M1, M2, M3), each exhibiting different levels of PAH pollution, were employed to examine the effectiveness of fungal degradation of PAHs in practical sediment samples. These data showed that with the fungus, the degradation ratios ranged from 13.64% to 23.50% for 2-3 rings PAHs, 40.93%-49.41% for 4 rings PAHs, and 39.59%-48.07% for 5-6 rings PAHs, which were significantly higher than those for the sediment without the fungus and confirmed the excellent performance of the fungal. Moreover, the Gompertz model was employed to analyze the degradation kinetics of 4-rings and 5-6 rings PAHs in these sediments, and the results demonstrated that the addition of the fungus could significantly increase the maximum degradation ratio, degradation start-up rate and maximum degradation rate of 4-rings and 5-6 rings PAHs and shorten the time required to reach the maximum degradation rate. This study not only supplied fungal materials but also established crucial theoretical foundations for the development of bioremediation technologies aimed at high molecular weight PAH-contaminated sediments.

Research progress and perspective on sludge anaerobic digestion technology: A bibliometric analysis.

Rational disposal of sludge is an ongoing concern. This work is the first attempt for in-depth statistical analysis of anaerobic digestion (AD) research in recent three decades (1986-2022) using both quantitative and qualitative approaches in bibliometrics to investigate the research progress, trends and hot spots. All publications in the Web of Science Core Collection database from 1986 to April 4, 2022 were analyzed. Results showed that the research on AD started in 1999 and the number of papers significantly increased since 2012. The research about the disposal of sewage sludge mainly focuses on energy recovery (e.g. methane and short chain volatile organic acids) by AD. Besides, different pretreatment technologies were studied in this study to eliminate the negative effects on the disposal of sludge caused by hydrolysis (rate-limiting step of AD), water content (increasing the costs) and heavy metal (toxic to the environment) of sludge. Of those, the treatment technologies related to direct interspecies electron transfer were worth further studied in the future. Towards that end, iron conductive material, iron-based advanced oxidation and biological treatment were concluded as the prospective technologies and worth to further study.

How do polystyrene microplastics affect the adsorption of copper in soil?

Microplastics (MPs) commonly coexist with heavy metals in the soil environment. MPs can influence the activity of heavy metals, and the specific mechanisms need to be further explored. Here, different contents of polystyrene (PS) MPs were added to soil to explore their effects on the adsorption and desorption characteristics of copper (Cu2+) in soil. The adsorption process was mainly chemical adsorption and belonged to a spontaneous, endothermic reaction. The hydrophobicity of MPs slowed down the adsorption and desorption rates. The main adsorption mechanisms included complexation by oxygen-containing functional groups, ion exchange (accounting for 33.97-36.04 % of the total adsorption amounts), and electrostatic interactions. MPs lacked oxygen-containing functional groups and were predominantly engaged in ion exchange and electrostatic interactions. MPs diluted, blocked the soil, and covered the active sites of soil, which reduced adsorption (3.56-16.18 %) and increased desorption (0.90-2.07 %) of Cu2+ in soil samples, thus increasing the activity and mobility of Cu2+. These findings provide new insights into the effects of MPs on the fate and risk of heavy metals in soil. ENVIRONMENTAL IMPLICATION: The existing literature concerning the effects of microplastics on the adsorption of heavy metals in soil is insufficient. Our investigation unveiled that the main adsorption mechanisms of different soil samples included complexation by oxygen-containing functional groups, ion exchange (accounting for 33.97-36.04 % of the total adsorption amounts), and electrostatic interactions. MPs lacked oxygen-containing functional groups and were predominantly engaged in ion exchange and electrostatic interactions. MPs diluted, blocked the soil, and covered the active sites of soil, which reduced adsorption (3.56-16.18 %) and increased desorption (0.90-2.07 %) of Cu2+ in soil samples, thus increasing the activity and mobility of Cu2+.

Degradation of pyrene by Xanthobacteraceae bacterium strain S3 isolated from the rhizosphere sediment of Vallisneria natans: active conditions, metabolite identification, and proposed pathways.

Polycyclic aromatic hydrocarbons (PAHs) were typical environmental contaminants that accumulated continuously in sediment. Microbial degradation is the main way of PAH degradation in the natural environment. Therefore, expanding the available pool of microbial resources and investigating the molecular degrading mechanisms of PAHs are critical to the efficient control of PAH-polluted sites. Here, a strain (identified as Xanthobacteraceae bacterium) with the ability to degrade pyrene was screened from the rhizosphere sediment of Vallisneria natans. Response surface analysis showed that the strain could degrade pyrene at pH 5-7, NaCl addition 0-1.5%, and temperature 25-40 °C, and the maximum pyrene degradation (~ 95.4%) was obtained under the optimum conditions (pH 7.0, temperature 28.5 °C, and NaCl-free addition) after 72 h. Also, it was observed that the effect of temperature on the degradation ratio was the most significant. Furthermore, eighteen metabolites were identified by mass spectrometry, among which (2Z)-2-hydroxy-3-(4-oxo-4H-phenalen-3-yl) prop-2-enoic acid, 7-(carboxymethyl)-8-formyl-1-naphthyl acetic acid, phthalic acid, naphthalene-1,2-diol, and phenol were the main metabolites. And the degradation pathway of pyrene was proposed, suggesting that pyrene undergoes initial ortho-cleavage under the catalysis of metapyrocatechase to form (2Z)-2-hydroxy-3-(4-oxo-4H-phenalen-3-yl) prop-2-enoic acid. Subsequently, this intermediate was progressively oxidized and degraded to phthalic acid or phenol, which could enter the tricarboxylic acid cycle. Furthermore, the pyrene biodegradation by the strain followed the first-order kinetic model and the degradation rate changed from fast to slow, with the rate remaining mostly slow in the later stages. The slow biodegradation rate was probably caused by a significant amount of phenol accumulation in the initial stage of degradation, which resulted in a decrease in bacterial activity or death.