Enhancement of phenol biodegradation: Metabolic division of labor in co-culture of Stenotrophomonas sp. N5 and Advenella sp. B9

The evolution of autonomy from two cooperative specialists in fluctuating environments

From microbes to humans, organisms perform numerous tasks for their survival, including food acquisition, migration, and reproduction. A complex biological task can be performed by either an autonomous organism or by cooperation among several specialized organisms. However, it remains unclear how autonomy and cooperation evolutionarily switch. Specifically, it remains unclear whether and how cooperative specialists can repair deleted genes through direct genetic exchange, thereby regaining metabolic autonomy. Here, we address this question by experimentally evolving a mutualistic microbial consortium composed of two specialists that cooperatively degrade naphthalene. We observed that autonomous genotypes capable of performing the entire naphthalene degradation pathway evolved from two cooperative specialists and dominated the community. This evolutionary transition was driven by the horizontal gene transfer (HGT) between the two specialists. However, this evolution was exclusively observed in the fluctuating environment alternately supplied with naphthalene and pyruvate, where mutualism and competition between the two specialists alternated. The naphthalene-supplied environment exerted selective pressure that favors the expansion of autonomous genotypes. The pyruvate-supplied environment promoted the coexistence and cell density of the cooperative specialists, thereby increasing the likelihood of HGT. Using a mathematical model, we quantitatively demonstrate that environmental fluctuations facilitate the evolution of autonomy through HGT when the relative growth rate and carrying capacity of the cooperative specialists allow enhanced coexistence and higher cell density in the competitive environment. Together, our results demonstrate that cooperative specialists can repair deleted genes through a direct genetic exchange under specific conditions, thereby regaining metabolic autonomy.

Design of a two functional permeable reactive barrier for synergistic enzymatic and microbial bioremediation of phenol-contaminated waters: laboratory column evaluation : Enzymatic and microbial bioremediation of phenol in a bilayer permeable reactive barrier

The present study aimed to develop a system using a combination of enzymatic and microbial degradation techniques for removing phenol from contaminated water. In our prior research, the HRP enzyme extracted from horseradish roots was utilized within a core-shell microcapsule to reduce phenolic shock, serving as a monolayer column. To complete the phenol removal process, a second column containing degrading microorganisms was added to the last column in this research. Phenol-degrading bacteria were isolated from different microbial sources on a phenolic base medium. Additionally, encapsulated calcium peroxide nanoparticles were used to provide dissolved oxygen for the microbial population. Results showed that the both isolated strains, WC1 and CC1, were able to completely remove phenol from the contaminated influent water the range within 5 to 7 days, respectively. Molecular identification showed 99.8% similarity for WC1 isolate to Stenotrophomonas rizophila strain e-p10 and 99.9% similarity for CC1 isolate to Bacillus cereus strain IAM 12,605. The results also indicated that columns using activated sludge as a microbial source had the highest removal rate, with the microbial biofilm completely removing 100% of the 100 mg/L phenol concentration in contaminated influent water after 40 days. Finally, the concurrent use of core-shell microcapsules containing enzymes and capsules containing Stenotrophomonas sp. WC1 strain in two continuous column reactors was able to completely remove phenol from polluted water with a concentration of 500 mg/L for a period of 20 days. The results suggest that a combination of enzymatic and microbial degrading systems can be used as a new system to remove phenol from polluted streams with higher concentrations of phenol by eliminating the shock of phenol on the microbial population.

Enhancement of triclocarban biodegradation: Metabolic division of labor in co-culture of Rhodococcus sp. BX2 and Pseudomonas sp. LY-1

Triclocarban (TCC) and its metabolite, 3,4-dichloroaniline (DCA), are classified as emerging organic contaminants (EOCs). Significant concerns arise from water and soil contamination with TCC and its metabolites. These concerns are especially pronounced at high concentrations of up to approximately 20 mg/kg dry weight, as observed in wastewater treatment plants (WWTPs). Here, a TCC-degrading co-culture system comprising Rhodococcus rhodochrous BX2 and Pseudomonas sp. LY-1 was utilized to degrade TCC (14.5 mg/L) by 85.9% in 7 days, showing improved degradation efficiency compared with monocultures. A combination of high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), genome sequencing, transcriptomic analysis, and quantitative reverse transcription-PCR (qRT-PCR) was performed. Meanwhile, through the combination of further experiments involving heterologous expression and gene knockout, we proposed three TCC metabolic pathways and identified four key genes (tccG, tccS, phB, phL) involved in the TCC degradation process. Moreover, we revealed the internal labor division patterns and connections in the co-culture system, indicating that TCC hydrolysis products were exchanged between co-cultured strains. Additionally, mutualistic cooperation between BX2 and LY-1 enhances TCC degradation efficiency. Finally, phytotoxicity assays confirmed a significant reduction in the plant toxicity of TCC following synergistic degradation by two strains. The in-depth understanding of the TCC biotransformation mechanisms and microbial interactions provides useful information for elucidating the mechanism of the collaborative biodegradation of various contaminants.

Competitive mechanism of salt-tolerance/degradation-performance of organic pollutant in bacteria: Na+/H+ antiporters contribute to salt-stress resistance but impact phenol degradation

Phenolic-laden wastewater is typically characterized by its high toxicity and high salinity, imposing serious limits on the application of bioremediation. Although a few halotolerant microorganisms have been reported to degrade phenol, their removal efficiency on high concentrations of phenol remains unsatisfactory. What's more, the deep interaction molecular mechanism of salt-tolerance/phenol-degradation performance has not been clearly revealed. Here, a halotolerant strain Aeribacillus pallidus W-12 employed a meta-pathway to efficiently degrade high concentration of phenol even under high salinity conditions. Investigation of salt-tolerance strategy indicated that four Na+/H+ antiporters, which are widely distributed in bacteria, synergistically endowed the strain with excellent salt adaptability. All these antiporters differentially but positively responded to salinity changes and induction of phenol, forming a synergistic transport effect on salt ions and phenol. In-depth analysis revealed a competitive relationship between salt tolerance and degradation performance, which significantly impaired the degradation efficiency at relatively high salinity. The efficient degradation performance of W-12 under different phenol concentrations and salinity conditions indicated its bioremediation potential for multiple types of phenolic wastewater. Collectively, the competitive mechanism of salt tolerance and degradation performance enlightens a new strategy of introducing or re-constructing Na+/H+ antiporters to further improve bioremediation efficiency of hypersaline organic wastewater.

Controllable chemical redox reactions to couple microbial degradation for organic contaminated sites remediation: A review

Global environmental concern over organic contaminated sites has been progressively conspicuous during the process of urbanization and industrial restructuring. While traditional physical or chemical remediation technologies may significantly destroy the soil structure and function, coupling moderate chemical degradation with microbial remediation becomes a potential way for the green, economic, and efficient remediation of contaminated sites. Hence, this work systematically elucidates why and how to couple chemical technology with microbial remediation, mainly focused on the controllable redox reactions of organic contaminants. The rational design of materials structure, selective generation of reactive oxygen species, and estimation of degradation pathway are described for chemical oxidation. Meanwhile, current progress on efficient and selective reductions of organic contaminants (i.e., dechlorination, defluorination, -NO2 reduction) is introduced. Combined with the microbial remediation of contaminated sites, several consideration factors of how to couple chemical and microbial remediation are proposed based on both fundamental and practical points of view. This review will advance the understanding and development of chemical-microbial coupled remediation for organic contaminated sites.

Synergistic molecular mechanism of degradation in dye wastewater by Rhodopseudomonas palustris intimately coupled carbon nanotube - Silver modified titanium dioxide photocatalytic composite with sodium alginate

The intimately coupled photocatalysis and biodegradation (ICPB), which combined the advantages of high oxidation capacity of photocatalysis and high mineralization rate of biodegradation, has demonstrated excellent removal performance in the degradation of azo dyes with highly toxic, refractory, mutagenic and carcinogenic. In order to explore the metagenomics mechanism of the ICPB system, a novel ICPB was prepared by coupling Rhodopseudomonas palustris (R. Palustris), carbon nanotube - silver modified titanium dioxide photocatalytic composite (CNT-Ag -TiO2, CAT) and sodium alginate (SA) (R. palustris/CAT@SA, R-CAT). Metagenomics sequencing was used to investigate the molecular mechanism of adaptation and degradation of dyes by photosynthetic microorganisms and the adaptive and synergistic interaction between photosynthetic microorganisms and photocatalyst. Experiments on the adaptability and degradability of photosynthetic microorganisms have proved that low concentration azo dyes could be utilized as carbon sources for growth of photosynthetic microorganisms. Metagenomics sequencing revealed that R. palustris was the main degrading bacterium in photosynthetic microorganisms and the functional genes related to carbohydrate metabolism, biological regulation and catalytic activity were abundant. It was found that the addition of photocatalyst significantly up-regulated the functional genes related to the catabolic process, electron transport, oxidoreductase activity and superoxide metabolism of organic matter in the photosynthetic microorganisms. Moreover, many key gene such as alpha-amylase, 1-acyl-sn-glycerol-3-phosphate acyltransferase, aldehyde dehydrogenase enrichment in microbial basal metabolism, such as enoyl-CoA hydratase, malate dehydrogenase, glutathione S-transferase enrichment in degrading azo dyes and electron transport, and many key gene such as undecaprenyl-diphosphatase, carbon storage regulator, DNA ligase enrichment in response to dyes and photocatalysts were discovered. These findings would contribute to a comprehensive understanding of the mechanism of degradation of dye wastewater by ICPB system, a series of genes was produced to adapt to environmental changes, and played synergistic role in terms of intermediate product degradation and electron transfer for degrading azo dyes. The photosynthetic microorganisms might be a promising microorganism for constructing ICPB system.

The trade-off between individual metabolic specialization and versatility determines the metabolic efficiency of microbial communities

In microbial systems, a metabolic pathway can be either completed by one autonomous population or distributed among a consortium performing metabolic division of labor (MDOL). MDOL facilitates the system's function by reducing the metabolic burden; however, it may hinder the function by reducing the exchange efficiency of metabolic intermediates among individuals. As a result, the function of a community is influenced by the trade-offs between the metabolic specialization and versatility of individuals. To experimentally test this hypothesis, we deconstructed the naphthalene degradation pathway into four steps and introduced them individually or combinatorically into different strains with varying levels of metabolic specialization. Using these strains, we engineered 1,456 synthetic consortia and found that 74 consortia exhibited higher degradation function than both the autonomous population and rigorous MDOL consortium. Quantitative modeling provides general strategies for identifying the most effective MDOL configuration. Our study provides critical insights into the engineering of high-performance microbial systems.

Current advances, challenges and strategies for enhancing the biodegradation of plastic waste

Due to its highly recalcitrant nature, the growing accumulation of plastic waste is becoming an urgent global problem. Biodegradation is one of the best possible approaches for the treatment of plastic waste in an environmentally friendly manner, but our current knowledge on the underlying mechanisms, as well as strategies for the development and enhancement of plastic biodegradation are still limited. This review aims to provide an updated and comprehensive overview of current research on plastic waste biodegradation, focusing on enhancement strategies with ongoing research significance, including the mining of highly efficient plastic-degrading microorganisms/enzymes, utilization of synergistic additives, novel pretreatment approaches, modification via molecular engineering, and construction of bacterial/enzyme consortia systems. Studying these strategies can (i) enrich the high-performance microbial/enzymes toolbox for plastic degradation, (ii) provide methods for recycling and upgrading plastics, as well as (iii) enable further molecular modification and functional optimization of plastic-degrading enzymes to realize economically viable biodegradation of plastics. To the best of our knowledge, this is the first review to discuss in detail strategies to enhance biodegradation of plastics. Finally, some recommendations for future research on plastic biodegradation are listed, hoping to provide the best direction for tackling the plastic waste dilemma in the future.

Enhanced biodegradation of phenol by microbial collaboration: Resistance, metabolite utilization, and pH stabilization

Mixed culture of microorganisms is an effective method to remove high concentration of phenol from wastewater. Currently, the mechanism of how microorganisms collaborate to enhance the biodegradation of phenol is still a challenge. In this study, the isolated Bacillus subtilis ZWB1 and Bacillus velezensis ZWB2 were co-cultured to enhance phenol biodegradation, and the mechanism of microbial collaboration was further explored. The co-culture of strains could significantly increase the rate (16.7 mg/L·h, 1000 mg/L) and concentration of phenol degradation (1500 mg/L), comparing with mono-culture of ZWB1 (4.2 mg/L·h, 150 mg/L) and ZWB2 (6.9 mg/L·h, 1000 mg/L), among which the highest degraded concentration of phenol for ZWB1 and ZWB2 was 150 and 1000 mg/L. Further, the mechanism of microbial collaboration to enhance phenol biodegradation was raised: the decrease of antioxidant enzymes, and increase of degrading enzymes and surfactants on content after co-culture, assisted the microorganisms in withstanding phenol; Bacillus subtilis ZWB1 used the metabolites of Bacillus velezensis ZWB2 to promote its growth, and further to degrade phenol rapidly; Bacillus subtilis ZWB1 alleviated the damage, which resulted from the pH drop (5.8) of the fermentation broth during phenol degradation that inhibited the growth and degraded ability of Bacillus velezensis ZWB2, making the pH of fermentation broth stable at 7. Metabolic analysis showed that co-culture of strains could produce more alkaline and buffering compounds and pairs, to stabilize pH and reduce the toxicity of acidity on ZWB2, thus increasing the degradation rate. This study explains the mechanism of microbial collaboration on phenol biodegradation from multiple perspectives, especially pH stabilization, which provides a theoretical basis for the degradation of pollutants by co-culture microorganisms.

Microbial interactions within beneficial consortia promote soil health

By ecologically interacting with various biotic and abiotic agents acting in soil ecosystems, highly diverse soil microorganisms establish complex and stable assemblages and survive in a community context in natural settings. Besides facilitating soil microbiome to maintain great levels of population homeostasis, such microbial interactions drive soil microbes to function as the major engine of terrestrial biogeochemical cycling. It is verified that the regulative effect of microbe-microbe interplay plays an instrumental role in microbial-mediated promotion of soil health, including bioremediation of soil pollutants and biocontrol of soil-borne phytopathogens, which is considered an environmentally friendly strategy for ensuring the healthy condition of soils. Specifically, in microbial consortia, it has been proven that microorganism-microorganism interactions are involved in enhancing the soil health-promoting effectiveness (i.e., efficacies of pollution reduction and disease inhibition) of the beneficial microbes, here defined as soil health-promoting agents. These microbial interactions can positively regulate the soil health-enhancing effect by supporting those soil health-promoting agents utilized in combination, as multi-strain soil health-promoting agents, to overcome three main obstacles: inadequate soil colonization, insufficient soil contaminant eradication and inefficient soil-borne pathogen suppression, all of which can restrict their probiotic functionality. Yet the mechanisms underlying such beneficial interaction-related adjustments and how to efficiently assemble soil health-enhancing consortia with the guidance of microbe-microbe communications remain incompletely understood. In this review, we focus on bacterial and fungal soil health-promoting agents to summarize current research progress on the utilization of multi-strain soil health-promoting agents in the control of soil pollution and soil-borne plant diseases. We discuss potential microbial interaction-relevant mechanisms deployed by the probiotic microorganisms to upgrade their functions in managing soil health. We emphasize the interplay-related factors that should be taken into account when building soil health-promoting consortia, and propose a workflow for assembling them by employing a reductionist synthetic community approach.

Identification of key degraders for controlling toxicity risks of disguised toxic pollutants with division of labor mechanisms in activated sludge microbiomes: Using nonylphenol ethoxylate as an example

Efficient management of disguised toxic pollutants (DTPs), which can undergo microbial degradation and convert into more toxic substances, necessitates the collaboration of diverse microbial populations in wastewater treatment plants. However, the identification of key bacterial degraders capable of controlling the toxicity risks of DTPs through division of labor mechanisms in activated sludge microbiomes has received limited attention. In this study, we investigated the key degraders capable of controlling the risk of estrogenicity associated with nonylphenol ethoxylate (NPEO), a representative DTP, in textile activated sludge microbiomes. The results of our batch experiments revealed that the transformation of NPEO into NP and subsequent NP degradation were the rate-limiting processes for controlling the risk of estrogenicity, resulting in an inverted V-shaped curve of estrogenicity in water samples during the biodegradation of NPEO by textile activated sludge. By utilizing enrichment sludge microbiomes treated with NPEO or NP as the sole carbon and energy source, a total of 15 bacterial degraders, including Sphingbium, Pseudomonas, Dokdonella, Comamonas, and Hyphomicrobium, were identified as capable of participating in these processes, Among them, Sphingobium and Pseudomonas were the two key degraders that could cooperatively interact in the degradation of NPEO with division of labor mechanisms. Co-culturing Sphingobium and Pseudomonas isolates exhibited a synergistic effect in degrading NPEO and reducing estrogenicity. Our study underscores the potential of the identified functional bacteria for controlling estrogenicity associated with NPEO and provides a methodological framework for identifying key cooperators engaged in labor division, contributing to the management of risks associated with DTPs by leveraging intrinsic microbial metabolic interactions.

Improvement of carbon source composition reduces antibiotic resistance genes in the ectopic fermentation system

Effectively reduce antibiotic resistance genes (ARGs) in ectopic fermentation system (EFS) is essential for practical production. In this study, three experiments were performed to explore how to remove ARGs in EFS effectively. Results demonstrated that ARGs were easily enriched in rice-husk-sawdust padding; simultaneous addition of laccase and cellulase suppressed the ARGs, mainly by increasing soluble carbohydrate concentration and promoting humic acid concentration; addition of corn stalks into rice-husk-sawdust decreased the abundance of ARGs by improving the carbon source structure and enhancing cellulase activity. In conclusion, the present study provides a guidance to reduce the threat of ARGs in EFS, which paved a potential pathway to safely utilize manure resources.

Degradation of crude oil in a co-culture system of Bacillus subtilis and Pseudomonas aeruginosa

Microbial remediation has been regarded as one of the most promising decontamination techniques for crude oil pollution. However, there are few studies on the interaction of bacteria in the microbial community during bioremediation. The aim of this work was to research the promotion of defined co-culture of Bacillus subtilis SL and Pseudomonas aeruginosa WJ-1 for biodegradation of crude oil. After 7 days of incubation, the analysis of residual oil, saturated and aromatic fraction in the samples showed that the degradation efficiency of them was significantly improved. The degradation efficiency of crude oil was enhanced from 32.61% and 54.35% in individual culture to 63.05% by the defined co-culture of strains SL and WJ-1. Furthermore, it was found that the defined co-culture system represented relatively excellent performance in bacterial growth, cell surface hydrophobicity (CSH) and emulsification activity. These results indicated that the combination of Bacillus subtilis and Pseudomonas aeruginosa can effectively promote the degradation and utilization of crude oil, which may provide a new idea for the improvement of bioremediation strategies. GRAPHICAL ABSTRACT.

Metaproteomic and gene expression analysis of interspecies interactions in a PAH-degrading synthetic microbial consortium constructed with the key microbes of a natural consortium

Polycyclic Aromatic Hydrocarbons (PAHs) impose adverse effects on the environment and human life. The use of synthetic microbial consortia is promising in bioremediation of contaminated sites with these pollutants. However, the design of consortia taking advantage of natural interactions has been poorly explored. In this study, a dual synthetic bacterial consortium (DSC_AB) was constructed with two key members (Sphingobium sp. AM and Burkholderia sp. Bk), of a natural PAH degrading consortium. DSC_AB showed significantly enhanced degradation of PAHs and toxic intermediary metabolites relative to the axenic cultures, indicating the existence of synergistic relationships. Metaproteomic and gene-expression analyses were applied to obtain a view of bacterial performance during phenanthrene removal. Overexpression of the Bk genes, naph, biph, tol and sal and the AM gene, ahdB, in DSC_AB relative to axenic cultures, demonstrated that both strains are actively participating in degradation, which gave evidence of cross-feeding. Several proteins related to stress response were under-expressed in DSC_AB relative to axenic cultures, indicating that the division of labour reduces cellular stress, increasing the efficiency of degradation. This is the one of the first works revealing bacterial relationships during PAH removal in a synthetic consortium applying an omics approach. Our findings could be used to develop criteria for evaluating the potential effectiveness of synthetic bacterial consortia in bioremediation.

Simultaneous bioremediation of phenol and tellurite by Lysinibacillus sp. EBL303 and characterization of biosynthesized Te nanoparticles

Aromatic compounds and metalloid oxyanions are abundant in the environment due to natural resources and industrial wastes. The high toxicity of phenol and tellurite poses a significant threat to all forms of life. A halotolerant bacterium was isolated and identified as Lysinibacillus sp. EBL303. The remediation analysis shows that 500 mg/L phenol and 0.5 mM tellurite can be remediated entirely in separate cultures within 74 and 56 h, respectively. In addition, co-remediation of pollutants resulted in the same phenol degradation and 27% less tellurite reduction within 98 h. Since phenol and tellurite exhibited inhibitory behavior, their removal kinetics fitted well with the first-order model. In the characterization of biosynthesized tellurium nanoparticles (TeNPs), transmission electron microscopy, dynamic light scattering, FE-SEM, and dispersive X-ray (EDX) showed that the separated intracellular TeNPs were spherical and consisted of only tellurium with 22-148 nm in size. Additionally, investigations using X-ray diffraction and Fourier-transform infrared spectroscopy revealed proteins and lipids covering the surface of these amorphous TeNPs. Remarkably, this study is the first report to demonstrate the simultaneous bioremediation of phenol and tellurite and the biosynthesis of TeNPs, indicating the potential of Lysinibacillus sp. EBL303 in this matter, which can be applied to environmental remediation and the nanotechnology industry.

Novel environmental method for enhanced biodegradation of contaminated wastewater via immobilizing nanoparticles on a new bacterial strain isolated industrial textile

Biological processes comprising bacteria, fungi, yeast, and algae received increasing interest for dye degradation due to their cost-effectiveness and eco-friendly nature. Hence, the current study aims to investigate the ability of the photocatalytic performance of N-S co-doped anatase TiO₂ (NSTO) nanoparticles immobilized on isolated industrial textile bacteria (ITB) for degradation of basic blue 41 (BB 41). To prove the effect of improving the surface area of NSTO, NSTO also was immobilized on glass balls (NSTO-GB). NSTO nanoparticles were synthesized using sol-gel methods, and characterization of NSTO and NSTO-GB were measured using SEM, TEM, XPS, and DLS analysis. The results showed that the average size of NSTO was 50-60 nm. Moreover, the morphology and surface microstructure of ITB and ITB-NSTO were determined by the SEM, XPS technique. According to the results, ITB has a rod structure, NSTO nanoparticles are placed on the surface of ITB. However, NSTO was attached to the surface of ITB with the hydroxyl group. The ITB-NSTO indicated a higher BB 41 degradation yield (99%) than pure NSTO (65%) and ITB (74%). The effect of different factors was evaluated on biodegradation by ITB-NSTO. The high biodegradation was obtained in ITB (10 mg), NSTO (50 mg), BB41 (50 ppm), and pH 11. The GC-Mass, LC-Mass, and FT-IR analysis, which monitored the BB 41 degradation efficiency, proved the degradation efficiency by 99%. In the following, the toxicities of BB 41 solution before and after degradation were accessed through the brine shrimp lethality assay (BSLA) and seed germination assay, which displayed a considerable reduction in BB 41 after degradation. Toxicity results exhibited that ITB-NSTO has potential for industrial application.

Energy recovery from high ash-containing sewage sludge: Focusing on performance evaluation of bio-fuel production

Hydrothermal liquefaction (HTL) has shown great potential to convert sewage sludge (SS) with high moisture into bio-crude. However, the disposal and reutilization of hydrothermal liquefaction wastewater (HTLWW) is a critical issue. Anaerobic digestion (AD) is proven to be an alternative to treat organic wastewater. Therefore, energy recovery from high ash-containing SS was studied by integrating AD with HTL. The effect of temperature on HTL efficiency was investigated and then methane production from HTLWW was conducted by AD with organic loading increasing from 2 g COD/L to 6 g COD/L. Results showed that the maximum bio-crude yield of 23.5 % was obtained at 350 °C. Methane yield of 309.4 mL CH₄/g COD_removed was achieved at 2 g COD/L with COD removal rate of 72.5 %. Meanwhile, the microbial structure and abundance showed great shifts resulting from the adaptation to complex compounds. JGI-000079-D21, Aminicenantales, and Bacteroidetes_ vadinHA17 predominated in the bacterial community. Due to the presence of the toxic substances in HTLWW, such as phenolic and nitrogenous heterocyclic compounds, there was a decrease in methane yield when the organic loading was higher than 4 g COD/L. The organic matters in extracellular polymeric substances (EPS) were rich in fulvic acid-like and humic acid-like substances due to the attack and stimulation of toxicants. Under the condition of unstable fermentation, Advenella and Bacillus first appeared as phenol and pyridine degrading bacteria, respectively. The microbial diversity declined sharply to demonstrate the toxic effect of the refractory organics existing at high organic loading. The enrichment of Methanosaeta in methanogens meant that acetotrophic metabolism is the dominant pathway in methanogenesis. In this study, the profile of bio-fuel production from high ash-containing SS would provide an integrated reference to treat wet biomass and recover energy simultaneously.

Even allocation of benefits stabilizes microbial community engaged in metabolic division of labor

Microbial communities execute metabolic pathways to drive global nutrient cycles. Within a community, functionally specialized strains can perform different yet complementary steps within a linear pathway, a phenomenon termed metabolic division of labor (MDOL). However, little is known about how such metabolic behaviors shape microbial communities. Here, we derive a theoretical framework to define the assembly of a community that degrades an organic compound through MDOL. The framework indicates that to ensure community stability, the strains performing the initial steps should hold a growth advantage (m) over the "private benefit" (n) of the strain performing the last step. The steady-state frequency of the last strain is then determined by the quotient of n and m. Our experiments show that the framework accurately predicts the assembly of our synthetic consortia that degrade naphthalene through MDOL. Our results provide insights for designing and managing stable microbial systems for metabolic pathway optimization.

A study of highly efficient phenol biodegradation by a versatile Bacillus cereus ZWB3 on aerobic condition

As one of the organic pollutants in industrial wastewater, phenol seriously threatens the environment and human health. Among various methods, microbial degradation of phenol possesses the advantages of nontoxicity and no secondary pollution. Therefore, search for microbial resources that can efficiently degrade phenol has become an important issue. In this study, a strain that could efficiently degrade phenol was isolated. The strain was identified as Bacillus cereus based on its morphology, physiological and biochemical features and 16S rRNA sequence analysis. The strain can completely degrade phenol up to 1,500 mg/L within 26 h (57.7 mg·L^-1·h^-1), under the optimum conditions, faster compared with the known degrading bacteria. The strain could efficiently remove phenol at a wide range of temperatures (22-37 °C) and pH (7-9), and Mn²⁺ and Zn²⁺ stress. Interestingly, this strain displayed the potential on microthermal environment, which could degrade 1,200 mg/L phenol within 36 h at 22 °C. Further, the strain had capacity that used a variety of aromatic compounds as the sole carbon source for growth. This study shows a useful biodegradation route on the wastewater treatment under high phenol concentration conditions, providing alternatives for environmental remediation.

Kinetics and molecular mechanism of enhanced fluoranthene biodegradation by co-substrate phenol in co-culture of Stenotrophomonas sp. N5 and Advenella sp. B9

Polycyclic aromatic hydrocarbons (PAHs) and phenol are persistent pollutants that coexist in coking wastewater (CWW). Fluoranthene (Flu) is the predominant PAH species in the CWW treatment system. Our work emphasized on distinguishing the effects of phenol on Flu biodegradation by co-culture of Stenotrophomonas sp. N5 and Advenella sp. B9 and illustrated the molecular mechanisms. Results showed Flu biodegradation by co-culture was enhanced by phenol. According to the first-order degradation kinetic analysis of Flu, phenol significantly increased the biodegradation rate constant and shortened the half-life of Flu. Transcriptome analysis pointed out the up-regulation of DNA repair activity and 3717 significantly differentially expressed genes (DEGs), were triggered by 800 mg/L phenol. GO enrichment analysis suggested these DEGs are mainly concentrated in biochemical processes such as metal ion binding and alpha-amino acid biosynthesis, which are closely associated with Flu biodegradation, indicating that phenol promotes DNA repair activity and reduces Flu genotoxicity. qRT-PCR was performed to detect the gene expression of aromatic ring-opening dioxygenase. Combined with transcriptome analysis, the qRT-PCR results suggested phenol did not induce the expression of related PAHs-degrading enzymes. RNA extraction and microbial growth curves of COC and COC + Ph provided further evidence that phenol serves as co-substrate which increases biomass and the concentration of degrading enzymes, therefore promoting the Flu degradation.

Effect of Nickel as Stress Factor on Phenol Biodegradation by Stenotrophomonas maltophilia KB2

This study focuses on the phenol biodegradation kinetics by Stenotrophomonas maltophilia KB2 in a nickel-contaminated medium. Initial tests proved that a nickel concentration of 33.3 mg·L⁻¹ caused a cessation of bacterial growth. The experiments were conducted in a batch bioreactor in several series: without nickel, at constant nickel concentration and at varying metal concentrations (1.67–13.33 g·m⁻³). For a constant Ni²⁺ concentration (1.67 or 3.33 g·m⁻³), a comparable bacterial growth rate was obtained regardless of the initial phenol concentration (50–300 g·m⁻³). The dependence µ = f (S₀) at constant Ni²⁺ concentration was very well described by the Monod equations. The created varying nickel concentrations experimental database was used to estimate the parameters of selected mathematical models, and the analysis included different methods of determining metal inhibition constant K_IM. Each model showed a very good fit with the experimental data (R² values were higher than 0.9). The best agreement (R² = 0.995) was achieved using a modified Andrews equation, which considers the metal influence and substrate inhibition. Therefore, kinetic equation parameters were estimated: µ_max = 1.584 h⁻¹, K_S = 185.367 g·m⁻³, K_IS = 106.137 g·m⁻³, K_IM = 1.249 g·m⁻³ and n = 1.0706.

Exploring the polyurethanolytic activity and microbial composition of landfill microbial communities

The microbial composition of polyurethane degrading communities has been barely addressed, and it is unknown if microenvironmental conditions modify its composition, affecting its biodegradative capacity. The polyurethanolytic activity and taxonomic composition of five microbial communities, selected by enrichment in the polyether-polyurethane-acrylic (PE-PU-A) coating PolyLack®, from deteriorated PU foams collected at different microenvironments in a municipal landfill (El Bordo Poniente, BP) were explored. All BP communities grew similarly in PolyLack® as the sole carbon source, although BP1, BP4, and BP5 showed better performance than BP2 and BP7. FTIR spectroscopy showed that ester, urethane, ether, aromatic and aliphatic groups, and the acrylate component were targets of the biodegradative activity. Extracellular esterase activity was higher at 5 days of cultivation and decreased at 21 days, while urease activity showed the opposite. Microbial composition analysis, assessed by 16S rDNA V3 region PCR-DGGE, revealed a preponderance of Rhizobiales and Micrococcales. The reported PU-degrading genera Paracoccus, Acinetobacter, and Pseudomonas were identified. In contrast, Advenella, Bordetella, Microbacterium, Castellaniella, and Populibacterium, some of them xenobiotics degraders, can be considered potentially PU-degrading genera. Correspondence analysis identified independent groups for all communities, except the BP4 and BP5. Although partial taxonomic redundancy was detected, unique OTUs were identified, e.g., three members of the Weeksellaceae family were present only in the BP4/BP5 group. These results suggest that the microenvironmental conditions where the landfill microbial communities were collected shaped their taxonomical composition, impacting their PE-PU biodegradative capacities. These BP communities represent valuable biological material for the treatment of PU waste and other xenobiotics. KEY POINTS: • Landfill microbial communities display slightly different capacities for growing in polyether-polyurethane-acrylic. • Ester, urethane, ether, aromatic, aliphatic, and acrylate groups were attacked. • Esterase activity was more significant at early culture times while urease activity at latter. • Landfill microenvironments shape partial taxonomical redundancy in the communities. • Best communities' performance seems to be related to unique members' composition.

Degradation of low-concentration perfluorooctanoic acid via a microbial-based synergistic method: assessment of the feasibility and functional microorganisms

Perfluorooctanoic acid (PFOA) is persistent in the environment. The activities of microorganisms alone are insufficient for the decomposition of PFOA, but microorganisms can contribute positively to the degradation of PFOA in synergistic systems. Herein, a synergistic system combining photocatalytic decay with microbial degradation of the transformation products was applied to degrade 500.0 μg L^-1 PFOA. The microorganisms increased the total removed percentage by 30.7% to a final percentage of 79.7 ± 9.4% in comparison with the photocatalytic method alone. Moreover, an additional 44.2% of removed total organic carbon and additional defluorination percentage of 24.5% were obtained after the synergistic tests. The 16S RNA sequencing analysis indicated that Stenotrophomonas, Bacillus, Pseudomonas, and Brevundimonas were highly enriched in the functional microbial community, which was simultaneously shaped by photocatalysis and substances. This study found it would be feasible to use a synergistic method containing photocatalysis and a microbial community for the degradation of low-concentrations of PFOA, and the results provided a reference to modified the removal efficiency of the synergistic system by looking insight into the relationship between the functional microbial community and PFOA.

Enhanced degradation of different crude oils by defined engineered consortia of Acinetobacter venetianus RAG-1 mutants based on their alkane metabolism

Microbial consortia offer an attractive biodegradation strategy for removing hydrocarbons from oil-contaminated sites. In this study, we explored the degradation properties of Acinetobacter venetianus strain RAG-1 (RAG-1). RAG-1 effectively degrades three crude oils with excellent emulsification activity and cell surface hydrophobicity, while exhibiting broad environmental tolerance. RAG-1 accepts a range of alkane substrates (C₁₀-C₃₈) using three alkane hydroxylases (AlkMa, AlkMb, and AlmA). Bacterial mutant with alkMa or alkMb deletion enhanced degradation of C₁₀-C₂₀ or C₂₂-C₃₂ n-alkanes, respectively. Based on the substrate metabolism of the mutants, adjustable and targeted consortia consisting of ΔalkMa/almA and ΔalkMb were constructed, achieving enhanced degradation (10 days) of light crude oil (73.42% to 88.65%), viscous crude oil (68.40% to 90.05%), and high waxy crude oil (47.46% to 60.52%) compared with the single wild-type strain. The degradation properties of RAG-1 and the engineered consortia strategy may have potential use in microbial biodegradation applications.

Enhancement of PAHs biodegradation in biosurfactant/phenol system by increasing the bioavailability of PAHs

The poor bioavailability of polycyclic aromatic hydrocarbons (PAHs) is the main limiting factor for their biodegradation in contaminated sites. The addition of biosurfactant is an effective method for enhancing the bioavailability of PAHs. Suitable low molecular weight (LMW) organic matters have been shown to increase the bioavailability of PAHs. Therefore, we investigated the effect of phenol, which often co-exists with PAHs, on the biodegradation of PAHs in biosurfactant solution. The results show that the critical micelle concentration (CMC) of the biosurfactant decreased after phenol was added. The formation of mixed micelles resulted in enhancement of PAHs dissolution. The weight solubilization ratio (WSR) values of biosurfactant for Phe, Pyr and BaP in phenol solution are approximately 1.34, 1.40 and 1.67 times that of the control group, respectively. Phenol, therefore, can assist biosurfactant to increase the availability of PAHs by microbes. The bioavailability of PAHs in sludge increased from 27.7% to 43.1% after the biosurfactant was added, and reached a maximum of 49.2%, following the simultaneous addition of phenol and biosurfactant. Phenol also improved the degradation of PAHs by Stenotrophomonas sp. N5 in biosurfactant solution.

Anaerobic biodegradation of phenol in wastewater treatment: achievements and limits

Anaerobic biodegradation of toxic compounds found in industrial wastewater is an attractive solution allowing the recovery of energy and resources but it is still challenging due to the low kinetics making the anaerobic process not competitive against the aerobic one. In this review, we summarise the present state of knowledge on the anaerobic biodegradation process for phenol, a typical target compound employed in toxicity studies on industrial wastewater treatment. The objective of this article is to provide an overview on the microbiological and technological aspects of anaerobic phenol degradation and on the research needs to fill the gaps still hindering the diffusion of the anaerobic process. The first part is focused on the microbiology and extensively presents and characterises phenol-degrading bacteria and biodegradation pathways. In the second part, dedicated to process feasibility, anaerobic and aerobic biodegradation kinetics are analysed and compared, and strategies to enhance process performance, i.e. advanced technologies, bioaugmentation, and biostimulation, are critically analysed and discussed. The final section provides a summary of the research needs. Literature data analysis shows the feasibility of anaerobic phenol biodegradation at laboratory and pilot scale, but there is still a consistent gap between achieved aerobic and anaerobic performance. This is why current research demand is mainly related to the development and optimisation of powerful technologies and effective operation strategies able to enhance the competitiveness of the anaerobic process. Research efforts are strongly justified because the anaerobic process is a step forward to a more sustainable approach in wastewater treatment.Key points• Review of phenol-degraders bacteria and biodegradation pathways.• Anaerobic phenol biodegradation kinetics for metabolic and co-metabolic processes.• Microbial and technological strategies to enhance process performance.