Deciphering the Fenton-reaction-aid lignocellulose degradation pattern by Phanerochaete chrysosporium with ferroferric oxide nanomaterials: Enzyme secretion, straw humification and structural alteration

Exploring the promoting effect of nitrilotriacetic acid on hydroxyl radical and humification during magnetite-amended composting of sewage sludge

The OH production by adding magnetite (MGT) alone has been reported in composting. However, the potential of nitrilotriacetic acid (NTA) addition for magnetite-amended sludge composting remained unclear. Three treatments with different addition [control check (CK); T1: 5 % MGT; T2: 5 % MGT + 5 % NTA] were investigated to characterize hydroxyl radical, humification and bacterial community response. The NTA addition manifested the best performance, with the peak OH content increase by 52 % through facilitating the cycle of Fe(Ⅱ)/Fe(Ⅲ). It led to the highest organic matters degradation (22.3 %) and humic acids content (36.1 g/kg). Furthermore, NTA addition altered bacterial community response, promoting relative abundances of iron-redox related genera, and amino acid metabolism but decreasing carbohydrate metabolism. Structural equation model indicated that temperature and Streptomyces were the primary factors affecting OH content. The study suggests that utilizing chelators is a promising strategy to strengthen humification in sewage sludge composting with adding iron-containing minerals.

Straw from Different Crop Species Recruits Different Communities of Lignocellulose-Degrading Microorganisms in Black Soil

The biological degradation of plant residues in the soil or on the soil surface is an integral part of the natural life cycle of annual plants and does not have adverse effects on the environment. Crop straw is characterized by a complex structure and exhibits stability and resistance to rapid microbial decomposition. In this study, we conducted a microcosm experiment to investigate the dynamic succession of the soil microbial community and the functional characteristics associated with lignocellulose-degrading pathways. Additionally, we aimed to identify lignocellulose-degrading microorganisms from the straw of three crop species prevalent in Northeast China: soybean (Glycine max Merr.), rice (Oryza sativa L.), and maize (Zea mays L.). Our findings revealed that both the type of straw and the degradation time influenced the bacterial and fungal community structure and composition. Metagenome sequencing results demonstrated that during degradation, different straw types assembled carbohydrate-active enzymes (CAZymes) and KEGG pathways in distinct manners, contributing to lignocellulose and hemicellulose degradation. Furthermore, isolation of lignocellulose-degrading microbes yielded 59 bacterial and 14 fungal strains contributing to straw degradation, with fungi generally exhibiting superior lignocellulose-degrading enzyme production compared to bacteria. Experiments were conducted to assess the potential synergistic effects of synthetic microbial communities (SynComs) comprising both fungi and bacteria. These SynComs resulted in a straw weight loss of 42% at 15 days post-inoculation, representing a 22% increase compared to conditions without any SynComs. In summary, our study provides novel ecological insights into crop straw degradation by microbes.

Harnessing recalcitrant lignocellulosic biomass for enhanced biohydrogen production: Recent advances, challenges, and future perspective

Biohydrogen (Bio-H2) is widely recognized as a sustainable and environmentally friendly energy source, devoid of any detrimental impact on the environment. Lignocellulosic biomass (LB) is a readily accessible and plentiful source material that can be effectively employed as a cost-effective and sustainable substrate for Bio-H2 production. Despite the numerous challenges, the ongoing progress in LB pretreatment technology, microbial fermentation, and the integration of molecular biology techniques have the potential to enhance Bio-H2 productivity and yield. Consequently, this technology exhibits efficiency and the capacity to meet the future energy demands associated with the valorization of recalcitrant biomass. To date, several pretreatment approaches have been investigated in order to improve the digestibility of feedstock. Nevertheless, there has been a lack of comprehensive systematic studies examining the effectiveness of pretreatment methods in enhancing Bio-H2 production through dark fermentation. Additionally, there is a dearth of economic feasibility evaluations pertaining to this area of research. Thus, this review has conducted comparative studies on the technological and economic viability of current pretreatment methods. It has also examined the potential of these pretreatments in terms of carbon neutrality and circular economy principles. This review paves the way for a new opportunity to enhance Bio-H2 production with technological approaches.

Effects of Fe3O4 NMs based Fenton-like reactions on biodegradable plastic bags in compost: New insight into plastisphere community succession, co-composting efficiency and free radical in situ aging theory

Biodegradable plastic bags (BPBs), meant for eco-friendly, often inadequately degrade in compost, leading to microplastic pollution. In this study, the effect of Fenton-like reaction with Fe3O4 nanoparticles (NMs) on the plastisphere microorganisms' evolution and the BPBs' aging mechanism was revealed by co-composting of food waste with BPBs for 40 days. The establishment of the Fenton-like reaction was confirmed, with the addition of Fenton-like reagent treatments resulting in an increase of 57.67% and 37.75% in H2O2 levels during the composting, compared to the control group. Moreover, the structural characterization reveals that increasing oxygen content continuously generates reactive free radicals on the surface, leading to the formation of oxidative cavities. This process results in random chain-breaking, significantly reducing molecular weights by 39.27% and 38.81%, thus showcasing a deep-seated transformation in the plastic's molecular structure. Furthermore, the microbial network suggested that the Fenton-like reaction enriched plastisphere keystone species, thus accelerating the BPBs' aging. Additionally, the Fenton-like reaction improved compost maturity and reduced greenhouse gas emissions. These results reveal the bio-chemical mechanisms of BPBs aging and random chain-breaking by the Fenton-like reaction, under alternating oxidative/anoxic conditions of composting and provide a new insight to resolve the BPBs' pollutions.

Elucidating polyethylene microplastic degradation mechanisms and metabolic pathways via iron-enhanced microbiota dynamics in marine sediments

The extensive use of plastics has given rise to microplastics, a novel environmental contaminant that has sparked considerable ecological and environmental concerns. Biodegradation offers a more environmentally friendly approach to eliminating microplastics, but their degradation by marine microbial communities has received little attention. In this study, we used iron-enhanced marine sediment to augment the natural bacterial community and facilitate the decomposition of polyethylene (PE) microplastics. The introduction of iron-enhanced sediment engendered an augmented bacterial biofilm formation on the surface of polyethylene (PE), thereby leading to a more pronounced degradation effect. This novel observation has been ascribed to the oxidative stress-induced generation of a variety of oxygenated functional groups, including hydroxyl (-OH), carbonyl (-CO), and ether (-C-O) moieties, within the microplastic substrate. The analysis of succession in the community structure of sediment bacteria during the degradation phase disclosed that Acinetobacter and Pseudomonas emerged as the principal bacterial players in PE degradation. These taxa were directly implicated in oxidative metabolic pathways facilitated by diverse oxidase enzymes under iron-facilitated conditions. The present study highlights bacterial community succession as a new pivotal factor influencing the complex biodegradation dynamics of polyethylene (PE) microplastics. This investigation also reveals, for the first time, a unique degradation pathway for PE microplastics orchestrated by the multifaceted marine sediment microbiota. These novel insights shed light on the unique functional capabilities and internal biochemical mechanisms employed by the marine sediment microbiota in effectively degrading polyethylene microplastics.

Enhanced ammonia nitrogen and phenol removal by immobilized bacteria through composite mycelium pellet-driven quinone redox cycle

The composite mycelium pellet (CMP) was coupled with Pseudomonas sp. Y1 (CMP-Y1) to remove phenol and ammonia nitrogen (NH4+-N). The CMP was formed by the self-assembly of fungal mycelium with sponge iron (SIO), gallic acid (GA), and oxalic acid. The results showed that CMP with abundant pore size and successful internal loading of sponge iron containing iron nanoparticles. CMP could induce GA redox cycle to form Fenton-like reaction and thus achieve efficient phenol removal (93.32%, 24 h). Meanwhile, the removal efficiencies of phenol, NH4+-N, and chemical oxygen demand (COD) using CMP-Y1 at 12 h were 93.71, 92.40, and 89.00%, respectively. The increase in the electron transfer activity of strain Y1 by the addition of CMP could facilitate the nitrogen removal processes. In addition, high-throughput sequencing results indicated the abundance of antioxidant and repair genes was increased, which might be a strategy of strain Y1 to cope with oxidative stress. This strategy provided the possibility for the practical application of the combination of advanced oxidation and biological treatment, and offered new insights into the symbiotic system of fungi and bacteria.

Strengthening Fenton-like reactions to improve lignocellulosic degradation performance by increasing lignocellulolytic enzyme core microbes during rice straw composting

This study aimed to explore the effect of Fenton-like reactions on lignocellulosic degradation performance and identify their driving factors during composting. Rice straw was pretreated by inoculating Aspergillus fumigatus Z1 and then adding Fe (II), which resulted in Fenton-like reactions. The treatment groups included CK (control), Fe (addition of Fe (II)), Z1 (inoculation of A. fumigatus Z1), and Fe + Z1 (inoculation of A. fumigatus Z1 and addition of Fe (II)). The results suggested that Fenton-like reactions can produce lignocellulolytic enzymes and degrade lignocellulose, due to the variation in microbial community composition and diversity. In addition, functional modular microbes were identified by network analysis, which can produce endoglucanase and xylanase. Regarding ligninase, bacteria were more favorable for producing manganese peroxidase, and fungi were more favorable for producing laccase. Additionally, reducing sugars, organic matter, total nitrogen and amino acids were key microhabitat factors of functional modular bacteria, while organic matter, reducing sugars, amino acids and C/N were key microhabitat factors of functional modular fungi, thereby promoting the degradation of lignocellulose. This study provides technical support for lignocellulosic degradation based on Fenton-like reactions.

Coupling of Fenton reaction and white rot fungi for the degradation of organic pollutants

Advanced oxidation processes (AOPs) are a class of highly efficient pollution remediation technologies that produce oxidising radicals under specific conditions to degrade organic pollutants. The Fenton reaction is a commonly applied AOP. To combine the advantages of AOPs and biodegradation in the remediation of organic pollutants, some studies have developed coupled systems between Fenton AOPs and white rot fungi (WRF) for environmental organic pollutant remediation and have achieved some success. Moreover, a promising system, termed as advanced bio-oxidation processes (ABOPs), mediated by the quinone redox cycling of WRF, has attracted increasing attention in the field. In this ABOP system, the radicals and H₂O₂ produced through the quinone redox cycling of WRF can strengthen Fenton reaction. Meanwhile, in this process, the reduction of Fe³⁺ to Fe²⁺ ensures the maintenance of Fenton reaction, leading to a promising application potential for the remediation of environmental organic pollutants. ABOPs combine the advantages of bioremediation and advanced oxidation remediation. Further understanding the coupling of Fenton reaction and WRF in the degradation of organic pollutants will be of great significance for the remediation of organic pollutants. Therefore, in this study, we reviewed recent remediation techniques for organic pollutants involving the coupled application of WRF and the Fenton reaction, focusing on the application of new ABOPs mediated by WRF, and discussed the reaction mechanism and conditions of ABOPs. Finally, we discussed the application prospects and future research directions of the joint application of WRF and advanced oxidation technologies for the remediation of environmental organic pollutants.

Lignocellulose dissociation with biological pretreatment towards the biochemical platform: A review

Lignocellulose utilization has been gaining great attention worldwide due to its abundance, accessibility, renewability and recyclability. Destruction and dissociation of the cross-linked, hierarchical structure within cellulose hemicellulose and lignin is the key procedure during chemical utilization of lignocellulose. Of the pretreatments, biological treatment, which can effectively target the complex structures, is attractive due to its mild reaction conditions and environmentally friendly characteristics. Herein, we report a comprehensive review of the current biological pretreatments for lignocellulose dissociation and their corresponding degradation mechanisms. Firstly, we analyze the layered, hierarchical structure of cell wall, and the cross-linked network between cellulose, hemicellulose and lignin, then highlight that the cracking of β-aryl ether is considered the key to lignin degradation because of its dominant position. Secondly, we explore the effect of biological pretreatments, such as fungi, bacteria, microbial consortium, and enzymes, on substrate structure and degradation efficiency. Additionally, combining biological pretreatment with other methods (chemical methods and catalytic materials) may reduce the time necessary for the whole process, which also help to strengthen the lignocellulose dissociation efficiency. Thirdly, we summarize the related applications of lignocellulose, such as fuel production, chemicals platform, and bio-pulping, which could effectively alleviate the energy pressure through bioconversion into high value-added products. Based on reviewing of current progress of lignocellulose pretreatment, the challenges and future prospects are emphasized. Genetic engineering and other technologies to modify strains or enzymes for improved biotransformation efficiency will be the focus of future research.

Recent Update on anaerobic digestion of paddy straw for biogas production: Advancement, limitation and recommendations

At present, development and production of advanced green energy sources are highly demanded, and this may offer a clean and sustainable environment to our modern society. In this reference, biogas is emerging as a promising green energy source and seems to have high potential to replace fossil-fuel based energy sources in the coming future. Further, lignocellulosic biomass (LCB) based biogas production technology has been found to be highly promising owing to several advantages associated therewith. Rich inorganic content, renewable nature, huge availability and low-cost are the key beneficial factors of LCB-based feedstock l to produce biogas. Among the varieties of LCB, paddy straw is one of the most demanding feedstocks and is highly rich in organic compounds that are imperative to producing biogas. Nevertheless, it is noticed that paddy straw as a waste material is usually disposed-off by direct burning, whereas it exhibits low natural digestibility due to the presence of high lignin and silica content which causes severe environmental pollution. On the other hand, paddy straw can be a potential feedstock to produce biogas through anaerobic digestion. Therefore, based on the current ongoing research studies worldwide, this review evaluates the advancements made in the AD process. Meanwhile, existing limitations and future recommendations to improve the yield and productivity of the biogas using paddy straw have been discussed. The emphasis has also been given to various operational parameters developments, related shortcomings, and strategies to improve biogas production at pilot scale.

Improved production of biogas via microbial digestion of pressmud using CuO/Cu2O based nanocatalyst prepared from pressmud and sugarcane bagasse waste

Biogas production through anaerobic digestions of organic wastes using microbes is a potential alternative to maintain the long term sustainability of the environment and also to full-fill the energy demands and waste management issues. In this context, pressmud can be a vital substrate which is generated from sugarcane industries and found to be broadly available. In this work, biogas improvement has been investigated in presence of CuO/Cu₂O based nanocatalyst wherein pressmud is employed as a substrate in anaerobic digestion. Herein, CuO/Cu₂O based nanocatalyst has been prepared using the aqueous extract prepared from the combination of PM and SCB which is employed as a reducing agent. The physicochemical properties of CuO/Cu₂O nanocatalyst have been probed through different techniques and it is noticed that using 1.0 % CuO/Cu₂O based nanocatalyst employed in AD process, cumulative biogas 224.7 mL CH₄ /g VS could be recorded after 42 days.

Nanomaterials for biogas augmentation towards renewable and sustainable energy production: A critical review

Nanotechnology is considered one of the most significant advancements in science and technology over the last few decades. However, the contemporary use of nanomaterials in bioenergy production is very deficient. This study evaluates the application of nanomaterials for biogas production from different kinds of waste. A state-of-the-art comprehensive review is carried out to elaborate on the deployment of different categories of nano-additives (metal oxides, zero-valent metals, various compounds, carbon-based nanomaterials, nano-composites, and nano-ash) in several kinds of biodegradable waste, including cattle manure, wastewater sludge, municipal solid waste, lake sediments, and sanitary landfills. This study discusses the pros and cons of nano-additives on biogas production from the anaerobic digestion process. Several all-inclusive tables are presented to appraise the literature on different nanomaterials used for biogas production from biomass. Future perspectives to increase biogas production via nano-additives are presented, and the conclusion is drawn on the productivity of biogas based on various nanomaterials. A qualitative review of relevant literature published in the last 50 years is conducted using the bibliometric technique for the first time in literature. About 14,000 research articles are included in this analysis, indexed on the Web of Science. The analysis revealed that the last decade (2010–20) was the golden era for biogas literature, as 84.4% of total publications were published in this timeline. Moreover, it was observed that nanomaterials had revolutionized the field of anaerobic digestion, methane production, and waste activated sludge; and are currently the central pivot of the research community. The toxicity of nanomaterials adversely affects anaerobic bacteria; therefore, using bioactive nanomaterials is emerging as the best alternative. Conducting optimization studies by varying substrate and nanomaterials’ size, concentration and shape is still a field. Furthermore, collecting and disposing nanomaterials at the end of the anaerobic process is a critical environmental challenge to technology implementation that needs to be addressed before the nanomaterials assisted anaerobic process could pave its path to the large-scale industrial sector.

Effects of CaO2 based Fenton - like reaction on heavy metals and microbial community during co-composting of straw and sediment

In this study, a Fenton-like system was constructed by CaO₂ and nano-Fe₃O₄ in the co-composting system of straw and sediment. Its effect on the passivation of heavy metals and the evolution of microbial community were investigated. The results showed that the establishment of CaO₂-Fenton-like system increased the residual Cu and residual Zn by 27.62% and 16.80%, respectively. In addition, the CaO₂-Fenton-like system facilitated the formation of humic acid (HA) up to 20.84 g·kg^-1. Redundancy analysis (RDA) showed that the CaO₂-Fenton-like system accelerated bacterial community succession and promoted the passivation of Cu and Zn. Structural equation models (SEMs) indicated that Fenton reaction affected Cu and Zn passivation by affecting pH, bacterial communities, and HA. This study shows that the CaO₂-Fenton-like system could promote the application of composting in the remediation of heavy metals contamination in sediment.

Oxygen Limitation Accelerates Regeneration of Active Sites on a MnO2 Surface: Promoting Transformation of Organic Matter and Carbon Preservation

Birnessite (δ-MnO₂) is a layered manganese oxide widely present in the environment and actively participates in the transformation of natural organic matter (NOM) in biogeochemical processes. However, the effect of oxygen on the dynamic interface processes of NOM and δ-MnO₂ remains unclear. This study systematically investigated the interactions between δ-MnO₂ and fulvic acid (FA) under both aerobic and anaerobic conditions. FA was transformed by δ-MnO₂ via direct electron transfer and the generated reactive oxygen species (ROS). During the 32-day reaction, 79.8% of total organic carbon (TOC) in solution was removed under anaerobic conditions, unexpectedly higher than that under aerobic conditions (69.8%), suggesting that oxygen limitation was more conducive to the oxidative transformation of FA by δ-MnO₂. The oxygen vacancies (O_V) on the surface of δ-MnO₂ were more exposed under anaerobic conditions, thus promoting the adsorption and transformation of FA as well as regeneration of the active sites. Additionally, the reaction of FA with δ-MnO₂ weakened the strongly bonded lattice oxygen (O_latt), and the released O_latt was an important source of ROS. Interestingly, a part of organic carbon (OC) was preserved by forming MnCO₃, which might be a novel mechanism for carbon preservation. These findings contribute to an improved understanding of the dynamic interface processes between MnO₂ and NOM and provide new insights into the effects of oxygen limitation on the cycling and preservation of OC.

Microbially-mediated synthesis of activated carbon derived from cottonseed husks for enhanced sulfanilamide removal

This study provided a novel pathway to develop activated carbon with enhanced adsorption performance via feedstock pretreatment by fungi. The growth of Pleurotus ostreatus on cottonseed husks offered this feedstock an advantageous pore size for porous carbon making. The prepared activated carbons derived from cottonseed husks (CSH-ACs) during different fungal growth periods exhibited extraordinary performance than commercial activated carbon for sulfanilamide adsorptive removal. Their experimental data of adsorption capacities for sulfanilamide were 139.43, 146.15, and 146.16 mg g^-1, respectively. The adsorption behaviors of sulfanilamide on CSH-ACs were evaluated by kinetic, isotherm and thermodynamic models. Pore filling, hydrogen-bond forming and π-π staking interactions all contributed to the rapid sulfanilamide removal. The microporous-mesoporous structure, stronger hydrophilicity, and richer functional groups moieties owing to the lignocellulose decomposition in the plant wall significantly strengthened the adsorption process on the microbial-mediated activated carbon. The effects of pH and water impurities (H₂PO₄^-, CO₃^2-, SO₄^2-, Cl^-, and humic acid) on sulfanilamide removal were investigated by a single factor experimental design. Results indicated that CSH-ACs were suitable for sulfanilamide removal in actual wastewater treatment with wide pH adaptability and resilience to interference.

Effect of Fenton pretreatment combined with bacterial inoculation on humification characteristics of dissolved organic matter during rice straw composting

The main purpose of this study was to explore the effects of Fenton pretreatment combined with bacterial inoculation on humification characteristics of dissolved organic matter (DOM) during rice straw composting. Three treatment groups (Fenton pretreatment: FeW, Fenton pretreatment and bacterial inoculation: FeWI, control: CK) were carried out during composting. The results showed that total organic carbon concentration of DOM and HIX showed an increase trend in all treatments in the composting process. The fungi that affect DOM conversion showed remarkable effects, meanwhile, fungal numbers of influencing DOM conversion were higher for FeWI than CK and FeW. The contribution rate of fungi to DOM was greater than that of environmental factors in FeWI composting, while environmental factors accounted for a large proportion in FeW and CK composting. This study exhibits referential significance for the effective degradation of agricultural wastes.

Humification process and mechanisms investigated by Fenton-like reaction and laccase functional expression during composting

This study aims to explore the impacts of the Fenton-like reaction on hydrogen peroxide, hydroxyl radicals, humic substance (HS) formation, laccase activity and microbial communities during composting to optimize composting performances. The results indicated that the activity of laccase in the presence of the Fenton-like reaction (HC) (35.92 U/g) was significantly higher than that in the control (CP) (29.56 U/g). The content of HS in HC (151.91 g/kg) was higher than that in CP (131.73 g/kg), and amides, quinones, aliphatic compounds and aromatic compounds were promoted to form HS in HC by 2D-FTIR-COS analysis. Proteobacteria contributed most greatly to AA1 at phylum level, Pseudomonas and Sphingomonas abundances increased in HC. Redundancy analysis indicated that there was a strong positive correlation among the Fenton-like reaction, laccase and HS. Conclusively, the Fenton-like reaction improved the activity of laccase, promoted the formation of HS and enhanced the quality of compost.

Efficient decomposition of lignocellulose and improved composting performances driven by thermally activated persulfate based on metagenomics analysis

In this study, fresh dairy manure and bagasse pith were used as raw materials to study the effect of potassium persulfate in the aerobic composting process. The influence of sulfate radical anion (SO₄^-·) generated by thermally activated persulfate on physicochemical parameters, lignocellulose degradation, humic substance (HS) formation, microbial community succession, and carbohydrate-active enzymes (CAZymes) composition were assessed during composting. Experimental results showed that the degradation rates of cellulose, hemicellulose and lignin in the treatment group with potassium persulfate (PS) (61.47%, 74.63%, 73.1%) were higher than that in blank control group (CK) (59.98%, 71.47%, 70.89%), respectively. Additionally, persulfate additive promoted dynamic variation of dissolved organic matter (DOM) and accelerated the formation of HS. Furthermore, metagenomics analysis revealed that persulfate changed the structure of the microbial community, and the relative abundances of Actinobacteria and Proteobacteria increased by 17.64% and 34.09% in PS, whereas 12.09% and 29.96% in CK. Glycoside hydrolases (GHs) and auxiliary activities (AAs) families were crucial to degrade lignocellulose, and their abundances were more in PS. Redundancy analysis (RDA) manifested that Actinobacteria and Proteobacteria were closely associated with lignocellulosic degradation. In brief, persulfate could accelerate the degradation of organic components, promote the formation of HS, optimize the structure of microbial community, and improve the compost quality.

Identifying driving factors of humic acid formation during rice straw composting based on Fenton pretreatment with bacterial inoculation

The aims of this study were to identify the driving factors of humic acid (HA) during rice straw composting based on Fenton pretreatment with bacterial inoculation. Rice straw was pretreated by Fenton reactions and then inoculated during composting, which was set up CK (control), FeW (Fenton pretreatment) and FeWI (Fenton pretreatment + functional bacterial agents). Results indicated that Fenton pretreatment and inoculation of functional bacteria increased the concentration of HA components, which was due to that bacterial composition was changed and bacterial diversity was decreased. Moreover, Fenton pretreatment and inoculation of functional bacteria increased the bacterial amounts of shikimic acid metabolism genes and the correlation between HA components and shikimic acid metabolism genes. Therefore, the functional bacteria were core driving factors, and NH₄^--N, pH, cellulose and bacterial diversity as key environmental factors to promote the formation of HA components.

Hydrogen peroxide plus ascorbic acid enhanced organic matter deconstructions and composting performances via changing microbial communities

This work aims to investigate the influence of hydrogen peroxide (H₂O₂) and ascorbic acid (ASCA) on the physicochemical characteristics, organic matter (OM) deconstructions, humification degree and succession of bacterial communities for co-composting of bagasse pith and dairy manure. The results indicated that H₂O₂ and ASCA accelerated the degradation of lignocellulose, improved the transformation of dissolved organic matter (DOM), and enhanced the content of humic substance (HS) and the degree of its aromatization. The bacterial communities were significantly changed in the presence of additives, in which the relative abundances of Firmicutes and Actinobacteria significantly increased. Redundancy analysis (RDA) indicated that the degradation of OM and lignocellulose more influenced the bacterial community compositions. Conclusively, adding H₂O₂ and ASCA accelerated lignocellulose degradation efficiency, and improved the composting process, which provided an optimized method to dispose of lignocellulose wastes and livestock manure.

Evolution of humic substances and the forms of heavy metals during co-composting of rice straw and sediment with the aid of Fenton-like process

The Fenton-like process was established by Fe₃O₄ nanomaterials (NMs) and Phanerochaete chrysosporium or oxalate, and applied to the co-composting of rice straw and sediment to study its effect on the formation of humic substance and the bioavailability of Cd, Cu, and Pb. Results shown that the application of Fenton-like process significantly promoted the passivation of Cd and Cu, while not shown obvious enhancement for Pb. The decrease of exchangeable fraction Cd (EXC-Cd) and the humic acid (HA) content in pile B with Fe₃O₄ NMs and oxalate were highest, which were 22.35% and 20.3 g/kg, respectively. Redundancy analyses (RDA) manifested that the Fenton-like process enhanced the influence of humus substance on the bioavailability of Cd, Cu, and Pb. Excitation-emission matrix (EEM) fluorescence spectra analysis suggested that Fenton-like process could obviously enhance the generation of humic substance. This research provides a new perspective and way for composting to remediate heavy metals pollution.

Renewable biohydrogen production from lignocellulosic biomass using fermentation and integration of systems with other energy generation technologies

Biohydrogen is a clean and renewable source of energy. It can be produced by using technologies such as thermochemical, electrolysis, photoelectrochemical and biological, etc. Among these technologies, the biological method (dark fermentation) is considered more sustainable and ecofriendly. Dark fermentation involves anaerobic microbes which degrade carbohydrate rich substrate and produce hydrogen. Lignocellulosic biomass is an abundantly available raw material and can be utilized as an economic and renewable substrate for biohydrogen production. Although there are many hurdles, continuous advancements in lignocellulosic biomass pretreatment technology, microbial fermentation (mixed substrate and co-culture fermentation), the involvement of molecular biology techniques, and understanding of various factors (pH, T, addition of nanomaterials) effect on biohydrogen productivity and yield render this technology efficient and capable to meet future energy demands. Further integration of biohydrogen production technology with other products such as bio-alcohol, volatile fatty acids (VFAs), and methane have the potential to improve the efficiency and economics of the overall process. In this article, various methods used for lignocellulosic biomass pretreatment, technologies in trends to produce and improve biohydrogen production, a coproduction of other energy resources, and techno-economic analysis of biohydrogen production from lignocellulosic biomass are reviewed.

Biodegradation mechanisms of sulfonamides by Phanerochaete chrysosporium - Luffa fiber system revealed at the transcriptome level

The overuse of antibiotics and subsequent enrichment of antibiotic resistant microbes in the natural and built environments is a severe threat to global public health. In this study, a Phanerochaete chrysosporium fungal-luffa fiber system was found to efficiently biodegrade two sulfonamides, sulfadimethoxine (SDM) and sulfadizine (SDZ), in cow urine wastewater. Biodegradation pathways were proposed on the basis of key metabolites identified using high performance liquid chromatography coupled with quadrupole-time-of-flight mass spectrometry (HPLC-QqTOF-MS). Transcriptomic, metabolomic, and free radical analyses were performed to explore the functional groups and detailed molecular mechanisms of SDM and SDZ degradation. A total of 27 UniGene clusters showed significant differences between luffa fiber and luffa fiber-free systems, which were significantly correlated to cellulose catabolism, carbohydrate metabolism, and oxidoreductase activity. Carbohydrate-active enzymes and oxidoreductases appear to play particularly important roles in SDM and SDZ degradation. Electron paramagnetic resonance (EPR) spectroscopy revealed the generation and evolution of OH and R during the biodegradation of SDM and SDZ, suggesting that beyond enzymatic degradation, SDM and SDZ were also transformed through a free radical pathway. Luffa fiber also acts as a co-substrate to improve the activity of enzymes for the degradation of SDM and SDZ. This research provides a potential strategy for removing SDM and SDZ from agricultural and industrial wastewater using fungal-luffa fiber systems.

White rot fungi can be a promising tool for removal of bisphenol A, bisphenol S, and nonylphenol from wastewater

Endocrine-disrupting chemicals (EDC) are a wide group of chemicals that interfere with the endocrine system. Their similarity to natural steroid hormones makes them able to attach to hormone receptors, thereby causing unfavorable health effects. Among EDC, bisphenol A (BPA), bisphenol S (BPS), and nonylphenol (NP) seem to be particularly harmful. As the industry is experiencing rapid expansion, BPA, BPS, and NP are being produced in growing amounts, generating considerable environmental pollution. White rot fungi (WRF) are an economical, ecologically friendly, and socially acceptable way to remove EDC contamination from ecosystems. WRF secrete extracellular ligninolytic enzymes such as laccase, manganese peroxidase, lignin peroxidase, and versatile peroxidase, involved in lignin deterioration. Owing to the broad substrate specificity of these enzymes, they are able to remove numerous xenobiotics, including EDC. Therefore, WRF seem to be a promising tool in the abovementioned EDC elimination during wastewater treatment processes. Here, we review WRF application for this EDC removal from wastewater and indicate several strengths and limitations of such methods.

Recognition of core microbial communities contributing to complex organic components degradation during dry anaerobic digestion of chicken manure

Microbial metabolism of complex organic components can drive different microbial communities, which is significant to the process of dry anaerobic digestion (AD). However, possible mechanisms between organic components and the corresponding microbial communities during the process of dry AD is poorly investigated. Results showed that the microbial species affecting the degradation of organic components were 69 nodes (13.3%) in the hydrolysis stage, hemicellulose was mainly degraded by Methanobacterium (2.3%), with a degradation rate of 35.0%. In the acetogenesis stage, the microbial species were 27 nodes (10.3%), hemicellulose was mainly degraded by LK-44f (0.1%) and Treponema (0.3%), with a degradation rate of 52.2%. In the methanogenesis stage, the microbial species were 10 nodes (4.8%), polysaccharide was mainly degraded by Ureibacillus (0.1%), with a degradation rate of 46.9%. The study provides theoretical support for the rapid degradation of complex components by segment-oriented regulation.

Advances in nanomaterials induced biohydrogen production using waste biomass

Recent advances on biohydrogen production using different types of waste biomass with the implementation of nanomaterials are summarized. Inspired by exceptional physicochemical and catalytic properties of nanomaterials, the present review focuses on several approaches including impact of nanomaterials on cellulosic biohydrogen production, possible pretreatment technology, as well as improved enzyme & sugar production in order to enhance the biohydrogen yield. Particularly, impacts of nanomaterial are elaborated in detail on different pathways of biohydrogen production (e.g. dark fermentation, photo-fermentation and hybrid-fermentation) using variety of waste biomass. Additionally, emphases are made on the feasibility of nanomaterials for making the biohydrogen production process more economical and sustainable and hence to develop advanced techniques for biohydrogen production using waste biomass.

Improved lignocellulose degradation efficiency based on Fenton pretreatment during rice straw composting

This study aims to explore the effect of Fenton pretreatment on organic fractions, enzymes activities and microbial communities during composting. In this study, rice straw was chosen to be composted after pretreatment. The results indicated that Fenton pretreatment significantly increased the degradation of organic matter and coarse fiber contents, which might be the reason that Fenton pretreatment enhanced lignocellulose-degrading enzymes activities during composting, including CMCase, FPase, xylanase, manganese peroxidase, lignin peroxidase and laccase. Additionally, Fenton pretreatment reshaped bacteria community. The key enzymes and environmental factors, which affected organic fractions degradation were identified by redundancy analysis. Furthermore, structural equation modeling and variation partitioning analysis further revealed possible mechanisms of organic fractions degradation in different treatments during composting. In summary, the combined application Fenton pretreatment and composting improved lignocellulose degradation efficiency, which provided for an effective and environment-friendly way to manage lignocellulose wastes.

Impact of adding metal nanoparticles on anaerobic digestion performance - A review

Anaerobic digestion is the most widely adopted biological waste treatment processes with renewable energy production. The effects of adding metal nanoparticles (NPs) on improving digestion performance are well noted. This paper reviewed the traditional view on the cytotoxicity of NPs to living organisms and the contemporary view of mechanisms for enhancement in anaerobic digestion performance in the presence of metal NPs. The complicated interactions acquire further studies for comprehending the physical and chemical interactions of metal NPs to the constituent compounds and to the living cells, and the involvement of mechanisms such as direct interspecies electron transfer for better design and control of the "NP strategy" for anaerobic digestion performance enhancement.

Comparison of Fenton and bismuth ferrite Fenton-like pretreatments of sugarcane bagasse to enhance enzymatic saccharification

This study compared enzymatic saccharification of sugarcane bagasse (SCB) after application of two different pretreatment methods, Fenton pretreatment (FP) and BiFeO₃ Fenton-like pretreatment (BFP). The composition, morphology and structural properties of SCB with different pretreatments were analyzed. Results showed that, after BFP, the yield of reducing sugar of SCB under enzymatic saccharification for 72 h was 25.8%, and the sugar conversion rate was 36.6%, which were 2.2 and 2.4-fold those of the FP, respectively. Moreover, the removal of hemicellulose and delignification in the BFP was more severe than that in the FP. The determination of hydroxyl radical (OH) in the two different Fenton processes revealed that the OH generated in the BiFeO₃ Fenton-like system was higher in concentration and longer in action time than that in the Fenton system, which was likely key to the stronger effect of BFP than FP on the enzymatic saccharification of SCB.