Biodegradation can achieve complete and cost-effective elimination of aromatic pollutants through harnessing diverse microbial metabolic processes. Aromatics biodegradation plays an important role in environmental cleanup and has been extensively studied since the inception of biodegradation. These studies, however, are diverse and scattered; there is an imperative need to consolidate, summarize, and review the current status of aromatics biodegradation. The first part of this review briefly discusses the catabolic mechanisms and describes the current status of aromatics biodegradation. Emphasis is placed on monocyclic, polycyclic, and chlorinated aromatic hydrocarbons because they are the most prevalent aromatic contaminants in the environment. Among monocyclic aromatic hydrocarbons, benzene, toluene, ethylbenzene, and xylene; phenylacetic acid; and structurally related aromatic compounds are highlighted. In addition, biofilms and their applications in biodegradation of aromatic compounds are briefly discussed. In recent years, various biomolecular approaches have been applied to design and understand microorganisms for enhanced biodegradation. In the second part of this review, biomolecular approaches, their applications in aromatics biodegradation, and associated biosafety issues are discussed. Particular attention is given to the applications of metabolic engineering, protein engineering, and “omics” technologies in aromatics biodegradation.

Biodegradation of aromatic compounds: current status and opportunities for biomolecular approaches

Activated sludge model (ASM) based modelling of membrane bioreactor (MBR) processes: a critical review with special regard to MBR specificities.

https://hal.archives-ouvertes.fr/hal-01664754/document

Alkylphenol and alkylphenol polyethoxylates in water and wastewater: A review of options for their elimination

A critical review on saline wastewater treatment by membrane bioreactor (MBR) from a microbial perspective.

Bacterial diversity, organic pollutants and their metabolites in two aeration lagoons of common effluent treatment plant (CETP) during the degradation and detoxification of tannery wastewater

Process efficiency and microbial monitoring in MBR (membrane bioreactor) and CASP (conventional activated sludge process) treatment of tannery wastewater.

Nonylphenol polyethoxylate degradation in aqueous waste by the use of batch and continuous biofilm bioreactors.

An aerobic bacterium (BCc6), isolated from nonylphenol polyethoxylates (NPEOs)-contaminated sludge, was shown to be capable of degrading low-ethoxylated NPEO mixtures. Sequencing of 16S rRNA gene (rDNA) showed that it clustered with Stenotrophomonas nitritireducens. Fluorescent in situ hybridization (FISH), performed on BCc6 strain and on the previously isolated Stenotrophomonas BCaL2, also involved in NPEO degradation but clustering with S. maltophilia, showed that strain BCc6 did not hybridize with the S. maltophilia-specific probe, and neither of the two strains hybridized with probes targeted to the Gammaproteobacteria site, rDNA analyses performed on the two strains evidenced two new polymorphisms, the first one at the 23S rRNA Gammaproteobacteria site, characterizing the known members of the Stenotrophomonas genus, and the other one at the 16S rRNA level, characteristic of S. nitritireducens. Two new FISH probes were designed accordingly, tested on control bacterial cultures, and employed for in situ monitoring of Stenotrophomonas representatives.

Degradation of Low-Ethoxylated Nonylphenols by a Stenotrophomonas Strain and Development of New Phylogenetic Probes for Stenotrophomonas spp. Detection

4-Nonylphenol (4-NP) isomers are toxic and recalcitrant compounds often resulting, together with short-chain ethoxylated nonylphenol (NPnEO, where n is the number of ethylene oxide units), from NPnEO biodegradation in conventional activated sludge plants. In this work, a microbial consortium, defined as Consortium A, capable of removing 100 mg/L of 4-NP with no accumulation of metabolites with aromatic moiety was isolated from textile wastewaters after enrichment with 4-NP. The consortium showed remarkable degradation activities toward several short-chain NPnEO congeners. Culture-dependent techniques were used to isolate from the consortium twenty-six strains assigned to seven different amplified ribosomal DNA restriction analysis groups. Two- and three-member cocultures were prepared with the strains showing highest 4-NP-degrading capabilities, but neither the single strains nor the cocultures were as efficient in 4-NP degradation as Consortium A. FISH was used to characterize the microbial composition of Consortium A: it evidenced a strong occurrence of Proteobacteria and, in particular, of Gammaproteobacteria along with a relevant stability of the culture. Therefore, the isolated consortium has the potential of being used in the development of a biotechnological process for the tertiary treatment of effluents of activated sludge plants fed with NPnEO-contaminated wastewaters.

Laura Salvadori

Papers

Process efficiency and microbial monitoring in MBR (membrane bioreactor) and CASP (conventional activated sludge process) treatment of tannery wastewater.

Nonylphenol polyethoxylate degradation in aqueous waste by the use of batch and continuous biofilm bioreactors.

Degradation of Low-Ethoxylated Nonylphenols by a Stenotrophomonas Strain and Development of New Phylogenetic Probes for Stenotrophomonas spp. Detection

Characterization of 4-nonylphenol-degrading bacterial consortium obtained from a textile wastewater pretreatment plant.