Fungal biodegradation of anthracene-polluted cork: A comparative study

Anthracene detoxification by Laccases from indigenous fungal strains Trichoderma lixii FLU1 and Talaromyces pinophilus FLU12

The persistence and ubiquity of polycyclic aromatic hydrocarbons (PAHs) in the environment necessitate effective remediation strategies. Hence, this study investigated the potential of purified Laccases, TlFLU1L and TpFLU12L, from two indigenous fungi Trichoderma lixii FLU1 (TlFLU1) and Talaromyces pinophilus FLU12 (TpFLU12), respectively for the oxidation and detoxification of anthracene. Anthracene was degraded with vmax values of 3.51 ± 0.06 mg/L/h and 3.44 ± 0.06 mg/L/h, and Km values of 173.2 ± 0.06 mg/L and 73.3 ± 0.07 mg/L by TlFLU1L and TpFLU12L, respectively. The addition of a mediator compound 2,2-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) to the reaction system significantly increased the degradation of anthracene, with up to a 2.9-fold increase in vmax value and up to threefold decrease in Km values of TlFLU1L and TpFLU12L. The GC-MS analysis of the metabolites suggests that anthracene degradation follows one new pathway unique to the ABTS system-hydroxylation and carboxylation of C-1 and C-2 position of anthracene to form 3-hydroxy-2-naphthoic acid, before undergoing dioxygenation and side chain removal to form chromone which was later converted into benzoic acid and CO2. This pathway contrasts with the common dioxygenation route observed in the free Laccase system, which is observed in the second degradation pathways. Furthermore, toxicity tests using V. parahaemolyticus and HT-22 cells, respectively, demonstrated the non-toxic nature of Laccase-ABTS-mediated metabolites. Intriguingly, analysis of the expression level of Alzheimer's related genes in HT-22 cells exposed to degradation products revealed no induction of neurotoxicity unlike untreated cells. These findings propose a paradigm shift for bioremediation by highlighting the Laccase-ABTS system as a promising green technology due to its efficiency with the discovery of a potentially less harmful degradation pathway, and the production of non-toxic metabolites.

Biodegradation mechanisms of polycyclic aromatic hydrocarbons: Combination of instrumental analysis and theoretical calculation

Polycyclic aromatic hydrocarbons (PAHs) are a common class of petroleum hydrocarbons, widely encountered in both environment and industrial pollution sources. Owing to their toxicity, environmental persistence, and potential bioaccumulation properties, a mounting interest has been kindled in addressing the remediation of PAHs. Biodegradation is widely employed for the removal and remediation of PAHs due to its low cost, lack of second-contamination and ease of operation. This paper reviews the degradation efficiency of degradation and the underlying mechanisms exhibited by algae, bacteria, and fungi in remediation. Additionally, it delved into the application of modern instrumental analysis techniques and theoretical investigations in the realm of PAH degradation. Advanced instrumental analysis methods such as mass spectrometry provide a powerful tool for identifying intermediates and metabolites throughout the degradation process. Meanwhile, theoretical calculations could guide the optimization of degradation processes by revealing the reaction mechanisms and energy changes in PAH degradation. The combined use of instrumental analysis and theoretical calculations allows for a comprehensive understanding of the degradation mechanisms of PAHs and provides new insights and approaches for the development of environmental remediation technologies.

Enhanced biodegradation of phenanthrene and anthracene using a microalgal-bacterial consortium

Polycyclic aromatic hydrocarbons (PAHs) are chemicals that are released into the environment during activities of the petroleum industry. The bioaccumulation, carcinogenic and mutagenic potential of PAHs necessitates the bioremediation of these contaminants. However, bioremediation of PAHs has a number of limitations including the inability of a single microbe to degrade all of the PAH fraction's environmental constituents. Therefore, a different paradigm, employing microalgal-bacterial consortium (MBC), may be used to effectively remove PAHs contaminants. In this type of interaction, the microalgae and bacteria species in the consortium work together in a way that enhances the overall performance of the MBC. Bacterial species in the consortium provide essential nutrients or growth factors by degrading toxic substances and provide these to microalgae, while the microalgae species provide organic carbon for the bacterial species to grow. For the first time, the ability of Gonium pectorale (G. pectorale) microalgae to break down phenanthrene (PHE) and anthracene (ANT) was investigated. Phenanthrene was shown to be more effectively degraded by G. pectorale (98%) as compared to Bacillus licheniformis (B. licheniformis) 19%. Similarly, G. pectorale has effectively degrade anthracene (98%) as compared with B. licheniformis (45%). The consortia of G. pectorale and B. licheniformis has shown a slight increase in the degradation of PHE (96%) and ANT (99%). Our findings show that B. licheniformis did not inhibit the growth of G. pectorale and in the consortia has effectively eliminated the PAHs from the media. Therefore G. pectorale has a tremendous potential to remove PAHs from the polluted environment. Future research will be conducted to assess Gonium's capacity to eliminate PAHs that exhibit high molar masses than that of PHE and ANT.

Endophytic, extremophilic and entomophilic fungi strains biodegrade anthracene showing potential for bioremediation

Anthropogenic activities have been increasing Polycyclic Aromatic Hydrocarbons (PAHs) release, promoting an urgent need for decontamination methods. Therefore, anthracene biodegradation by endophytic, extremophilic, and entomophilic fungi was studied. Moreover, a salting-out extraction methodology with the renewable solvent ethanol and the innocuous salt K₂HPO₄ was employed. Nine of the ten employed strains biodegraded anthracene in liquid medium (19-56% biodegradation) after 14 days at 30 °C, 130 rpm, and 100 mg L^-1. The most efficient strain Didymellaceae sp. LaBioMMi 155, an entomophilic strain, was employed for optimized biodegradation, aiming at a better understanding of how factors like pollutant initial concentration, pH, and temperature affected this process. Biodegradation reached 90 ± 11% at 22 °C, pH 9.0, and 50 mg L^-1. Futhermore, 8 different PAHs were biodegraded and metabolites were identified. Then, experiments with anthracene in soil ex situ were performed and bioaugmentation with Didymellaceae sp. LaBioMMi 155 presented better results than natural attenuation by the native microbiome and biostimulation by the addition of liquid nutrient medium into soil. Therefore, an expanded knowledge about PAHs biodegradation processes was achieved with emphasis to the action of Didymellaceae sp. LaBioMMi 155, which can be further employed for in situ biodegradation (after strain security test), or for enzyme identification and isolation aiming at oxygenases with optimal activity under alkaline conditions.

Contaminants from a former Croatian coal sludge dictate the structure of microbiota in the estuarine (Raša Bay) sediment and soil

Introduction

Croatian superhigh-organic-sulfur Raša coal had been mined for nearly 400 years. The release of hazardous trace elements (HTEs) and toxic organic pollutants (TOPs) into the local environment by coal mining, preparation, and combustion activities has resulted in pollution.

Methods

In this study, the diversity and composition of microbial communities in estuarine sediment and soil samples as well as community function responses to the pollutants were investigated.

Results

The results showed that PAH degradation does occur following 60 years of natural attenuation, the location is still heavily polluted by polycyclic aromatic hydrocarbons (PAHs) and HTEs. Microbial analyses have shown that high concentrations of PAHs have reduced the diversity and abundance of microbial communities. The pollution exerted an adverse, long-term impact on the microbial community structure and function in the brackish aquatic ecosystem. Microorganisms associated with the degradation of PAHs and sulfur-containing compounds have been enriched although the diversity and abundance of the microbial community have reduced. Fungi which are believed to be the main PAH degrader may play an important role initially, but the activity remains lower thereafter. It is the high concentrations of coal-derived PAHs, rather than HTEs, that have reduced the diversity and abundance of microbial communities and shaped the structure of the local microbiota.

Discussion

This study could provide a basis for the monitoring and restoration of ecosystems impacted by coal mining activities considering the expected decommission of a large number of coal plants on a global scale in the coming years due to growing global climate change concerns.

Diversity and Metabolic Potential of a PAH-Degrading Bacterial Consortium in Technogenically Contaminated Haplic Chernozem, Southern Russia

Polycyclic aromatic hydrocarbons (PAHs) are chemically recalcitrant carcinogenic and mutagenic compounds with primarily anthropogenic origin. The investigation of the effects of emissions from energy enterprises on soil microbiomes is of a high priority for modern soil science. In this study, metagenomic profiling of technogenic contaminated soils was carried out based on bioinformatic analysis of shotgun metagenome data with PAH-degrading genes identification. The use of prokaryotic consortia has been often used as one of the bio-remediation approaches to degrade PAHs with different molecular weight. Since the process of PAH degradation predominantly includes non-culturable or yet-to-be cultured species, metagenomic approaches are highly recommended for studying the composition and metabolic abilities of microbial communities. In this study, whole metagenome shotgun sequencing of DNA from two soils with varying PAH levels was performed. In the control site, the total content of 12 priority PAHs was 262 µg kg−1. The background soil levels in the polluted site for PAHs with 3 or more rings exceeded this, at 800 µg kg−1. The abundance of genes and taxa associated with PAH degradation in these two sites were estimated. Despite differences in PAH concentrations up to 1200 µg kg−1, individual and operon-organized PAH degradation genes were almost equally abundant and diverse in pristine and highly contaminated areas. The most numerous taxa in both spots were actinobacteria from Terrabacteria group. In addition to well-known PAH degraders such as Gordonia and Rhodococcus, genes corresponding to the PAH degradation were found in Azoarcus, Burkholderia and Variovorax. The data shows non-specificity and multifunctionality of metabolic pathways encoded in the genes of PAH-degrading microorganisms.

Use of green light to improve the production of lignocellulose-decay enzymes by Pleurotus spp. in liquid cultivation

The influence of green light on mycelium biomass growth and extracellular enzyme activities of edible mushrooms from the Pleurotus genus, which is popularly cultivated all over the world, were investigated. The mycelium of seven strains of five species of Pleurotus (P. citrinopileatus, P. djamor, P. eryngii, P. ostreatus, and P. pulmonarius) was grown in liquid medium at 28 °C in the dark or under green light (515-530 nm). The light source was light-emitting diodes (LED) with photon flux density adjusted to 20 μmol m^-2 s^-1 that was kept on throughout the cultivation period. After 12 days of growth, the mycelium was recovered and used for biomass determination and the cultivation medium was used to total cellulase, endoglucanase, xylanase, and laccase activities determination. Green light reduced the mycelial biomass growth of Pleurotus spp. but increased the cellulolytic and xylanolytic activities. The cellulolytic activity of most strains increased in the presence of green light with increases ranging from 1.5 times (P. ostreatus endoglucanase) to 8 times (P. citrinopileatus total cellulase and endoglucanase). Green light reduced laccase activity for most strains with the greatest reduction for P. eryngii (2.2 times lower). The specific enzymatic activity of cellulase and endoglucanase from P. citrinopileatus, increased by 31 times and 30 times, respectively, compared to the dark. Also, the specific laccase and xylanase activities of P. pulmonarius increased 4.4 times and 6.8 times, respectively, under green light. The use of light at particular wavelengths can be a viable strategy to increase the production of enzymes for different biotechnological applications and species of Pleurotus are particularly interesting for this purpose.

Acute effects of PAH contamination on microbial community of different forest soils

Polycyclic aromatic hydrocarbons (PAHs) are hazardous organic compounds with mutagenic, genotoxic and carcinogenic properties. Although PAHs in soil can cause toxicity to microorganisms, the microbial community is able to degrade these compounds. For this reason, it is important to study acute and short-term effects of PAH contamination on soil microbial community, also to shed light on its possible exploitation in soil restoration. The effects of acute PAH contamination on the structure and metabolic activity of microbial communities in three forest (beech, holm oak, black pine) soils were studied. The soils were spiked with phenanthrene, pyrene or benzo[a]pyrene and incubated in experimental mesocosms, under controlled conditions. Enzymatic activities (laccase, total peroxidase and hydrolase), as well as microbial biomass and community structure (through phospholipid fatty acid and ergosterol analyses), were evaluated in the three soil systems 4 days after contamination and compared to no-spiked soils. In soil under holm oak, there was a stimulation of Gram+ bacteria after contamination with all the 3 PAHs, whereas in soil under pine, pyrene and phenanthrene additions mainly stimulated fungi and actinomycetes.

Green potential of Pleurotus spp. in biotechnology

BACKGROUND

The genus Pleurotus is most exploitable xylotrophic fungi, with valuable biotechnological, medical, and nutritional properties. The relevant features of the representatives of this genus to provide attractive low-cost industrial tools have been reported in numerous studies to resolve the pressure of ecological issues. Additionally, a number of Pleurotus species are highly adaptive, do not require any special conditions for growth, and possess specific resistance to contaminating diseases and pests. The unique properties of Pleurotus species widely used in many environmental technologies, such as organic solid waste recycling, chemical pollutant degradation, and bioethanol production.

METHODOLOGY

The literature study encompasses peer-reviewed journals identified by systematic searches of electronic databases such as Google Scholar, NCBI, Springer, ResearchGate, ScienceDirect, and ISI Web of Knowledge. The search scheme was divided into several steps, as described below.

RESULTS

In this review, we describe studies examining the biotechnological feasibility of Pleurotus spp. to elucidate the importance of this genus for use in green technology. Here, we review areas of application of the genus Pleurotus as a prospective biotechnological tool.

CONCLUSION

The incomplete description of some fungal biochemical pathways emphasises the future research goals for this fungal culture.

Degradation of bisphenol A and acute toxicity reduction by different thermo-tolerant ascomycete strains isolated from arid soils

Four different laccase-producing strains were isolated from arid soils and used for bisphenol A (BPA) degradation. These strains were identified as Chaetomium strumarium G5I, Thielavia arenaria CH9, Thielavia arenaria HJ22 and Thielavia arenaria SM1(III) by internal transcribed spacer 5.8 S rDNA analysis. Residual BPA was evaluated by HPLC analysis during 48 h of incubation. A complete removal of BPA was observed by the whole cell fungal cultures within different times, depending on each strain. C. strumarium G5I was the most efficient degrader, showing 100% of removal within 8 h of incubation. The degradation of BPA was accompanied by the production of laccase and dye decolorizing peroxidase (DyP) under degradation conditions. The presence of aminobenzotriazole (ABT) as an inhibitor of cytochrome P450s monooxygenases (CYP) demonstrated a slight decrease in BPA removal rate, suggesting the effective contribution of CYP in the conversion. The great involvement of laccase in BPA transformation together with cell-associated enzymes, such as CYP, was supported by the identification of hydroxylated metabolites by ultra-high performance liquid chromatography-mass spectroscopy (UHPLC-MS). The metabolic pathway of BPA transformation was proposed based on the detected metabolites. The acute toxicity of BPA and its products was investigated and showed a significant reduction, except for T. arenaria SM1(III) that did not caused reduction of toxicity (IC₅₀ < 8%), possibly due to the presence of toxic metabolites. The results of the present study point out the potential application of the isolated ascomycetes in pollutant removal processes, especially C. strumarium G5I as an efficient degrader of BPA.

Biodegradation of asphaltene and petroleum compounds by a highly potent Daedaleopsis sp

Petroleum, as the major energy source, is indispensable from our lives. Presence of compounds resistant to degradation can pose risks for human health and environment. Basidiomycetes have been considered as powerful candidates in biodegradation of petroleum compounds via secreting ligninolytic enzymes. In this study a wood-decaying fungus was isolated by significant degradation ability that was identified as Daedaleopsis sp. by morphological and molecular identification methods. According to GC/MS studies, incubation of heavy crude oil with Daedaleopsis sp. resulted in increased amounts of <C24 hydrocarbons and decreased amounts of >C24 compounds. Degradation of asphaltene, anthracene, and dibenzofuran by the identified fungal strain was determined to evaluate its potential in biodegradation. After 14 days of incubation, Daedaleopsis sp. could degrade 93.7% and 91.2% of anthracene and dibenzofuran, respectively, in pH 5 and 40 °C in optimized medium, as revealed by GC/FID. Notably, analysis of saturates, aromatics, resins, and asphaltenes showed a reduction of 88.7% and 38% in asphaletene and aromatic fractions. Laccase, lignin peroxidase, and manganese peroxidase activities were enhanced from 51.3, 145.2, 214.5 U ml^-1 in the absence to 121.5, 231.4, and 352.5 U ml^-1 in the presence of heavy crude oil, respectively. This is the first report that Daedaleopsis sp. can degrade asphaltene and dibenzofuran. Moreover, compared to the reported results of asphaltene biodegradation, this strain was the most successful. Thus, Daedaleopsis sp. could be a promising candidate for biotransformation of heavy crude oil and biodegradation of recalcitrant toxic compounds.

Biodegradation of anthracene and several PAHs by the marine-derived fungus Cladosporium sp. CBMAI 1237

The biodegradation of polycyclic aromatic hydrocarbons (PAHs) by marine-derived fungi was reported in this work. Marine-derived fungi (Trichoderma harzianum CBMAI 1677, Cladosporium sp. CBMAI 1237, Aspergillus sydowii CBMAI 935, Penicillium citrinum CBMAI 1186 and Mucor racemosus CBMAI 847) biodegraded anthracene (14days, 130rpm, 50mgmL^-1 initial concentration in malt 2% medium). Cladosporium sp. CBMAI 1237 was the most efficient strain and biodegraded more anthracene in the presence (42% biodegradation) than in the absence (26%) of artificial seawater, suggesting that the biodegradation of PAHs may be faster in seawater than in non-saline environment. After 21days, Cladosporium sp. CBMAI 1237 biodegraded anthracene (71% biodegradation), anthrone (100%), anthraquinone (32%), acenaphthene (78%), fluorene (70%), phenanthrene (47%), fluoranthene (52%), pyrene (62%) and nitropyrene (64%). Previous undocumented metabolites were identified and, anthraquinone was a common product of different PAHs biodegradation. The marine-derived fungus Cladosporium sp. CBMAI 1237 showed potential for bioremediation of PAHs.

The degradation of three-ringed polycyclic aromatic hydrocarbons by wood-inhabiting fungus Pleurotus ostreatus and soil-inhabiting fungus Agaricus bisporus

The degradation of two isomeric three-ringed polycyclic aromatic hydrocarbons by the white rot fungus Pleurotus ostreatus D1 and the litter-decomposing fungus Agaricus bisporus F-8 was studied. Despite some differences, the degradation of phenanthrene and anthracene followed the same scheme, forming quinone metabolites at the first stage. The further fate of these metabolites was determined by the composition of the ligninolytic enzyme complexes of the fungi. The quinone metabolites of phenanthrene and anthracene produced in the presence of only laccase were observed to accumulate, whereas those formed in presence of laccase and versatile peroxidase were metabolized further to form products that were further included in basal metabolism (e.g. phthalic acid). Laccase can catalyze the initial attack on the PAH molecule, which leads to the formation of quinones, and that peroxidase ensures their further oxidation, which eventually leads to PAH mineralization. A. bisporus, which produced only laccase, metabolized phenanthrene and anthracene to give the corresponding quinones as the dominant metabolites. No products of further utilization of these compounds were detected. Thus, the fungi's affiliation with different ecophysiological groups and their cultivation conditions affect the composition and dynamics of production of the ligninolytic enzyme complex and the completeness of PAH utilization.

Removal of phenanthrene in contaminated soil by combination of alfalfa, white-rot fungus, and earthworms

The aim of this study was to investigate the removal of phenanthrene by combination of alfalfa, white-rot fungus, and earthworms in soil. A 60-day experiment was conducted. Inoculation with earthworms and/or white-rot fungus increased alfalfa biomass and phenanthrene accumulation in alfalfa. However, inoculations of alfalfa and white-rot fungus can significantly decrease the accumulation of phenanthrene in earthworms. The removal rates for phenanthrene in soil were 33, 48, 66, 74, 85, and 93% under treatments control, only earthworms, only alfalfa, earthworms + alfalfa, alfalfa + white-rot fungus, and alfalfa + earthworms + white-rot fungus, respectively. The present study demonstrated that the combination of alfalfa, earthworms, and white-rot fungus is an effective way to remove phenanthrene in the soil. The removal is mainly via stimulating both microbial development and soil enzyme activity.

Biodegradation of polycyclic aromatic hydrocarbons (PAHs) by fungal enzymes: A review

Polycyclic aromatic hydrocarbons (PAHs) are a large group of chemicals. They represent an important concern due to their widespread distribution in the environment, their resistance to biodegradation, their potential to bioaccumulate and their harmful effects. Several pilot treatments have been implemented to prevent economic consequences and deterioration of soil and water quality. As a promising option, fungal enzymes are regarded as a powerful choice for degradation of PAHs. Phanerochaete chrysosporium, Pleurotus ostreatus and Bjerkandera adusta are most commonly used for the degradation of such compounds due to their production of ligninolytic enzymes such as lignin peroxidase, manganese peroxidase and laccase. The rate of biodegradation depends on many culture conditions, such as temperature, oxygen, accessibility of nutrients and agitated or shallow culture. Moreover, the addition of biosurfactants can strongly modify the enzyme activity. The removal of PAHs is dependent on the ionization potential. The study of the kinetics is not completely comprehended, and it becomes more challenging when fungi are applied for bioremediation. Degradation studies in soil are much more complicated than liquid cultures because of the heterogeneity of soil, thus, many factors should be considered when studying soil bioremediation, such as desorption and bioavailability of PAHs. Different degradation pathways can be suggested. The peroxidases are heme-containing enzymes having common catalytic cycles. One molecule of hydrogen peroxide oxidizes the resting enzyme withdrawing two electrons. Subsequently, the peroxidase is reduced back in two steps of one electron oxidation. Laccases are copper-containing oxidases. They reduce molecular oxygen to water and oxidize phenolic compounds.