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The increasing use of antibiotics in livestock poses environmental risks, leading to contamination of agricultural soils and propagation of microbial antibiotic-resistant genes (ARGs). This study examined the impacts of wood- and manure-derived biochar (BC) on antibiotic residues, ARGs, and microbial communities in sandy loam and clay loam soils amended with manure in Cynodon dactylon pastures. We hypothesized that BC amendments would influence the degradation of antibiotics and the structure of microbial communities based on their physicochemical properties and soil types. Our results demonstrated that wood BC reduced the concentrations of tetracycline and sulfonamides, particularly in sandy loam soil, due to its larger surface area and hydrophobic properties. In contrast, manure BC provided additional nutrients and supported atmospheric nitrogen-fixing microbial groups, especially in clay loam soil, while exhibiting variable efficiency in reducing antibiotic residues due to its lower surface area and higher ash content. These findings underscore the differential impacts of each BC type, emphasizing the need for tailored BC applications based on soil type to effectively mitigate antibiotic contamination and promote sustainable agricultural practices. In conclusion, wood BC was more effective in enhancing soil health by reducing antibiotic residues and improving microbial diversity, particularly in sandy loam soils, while manure BC was beneficial for nutrient cycling in clay loam soils. [ABSTRACT FROM AUTHOR]

Improving a functional property of an enzyme via mutagenesis is still a challenging problem due to vast search space and difficulty of predicting the effects of mutation(s). Machine learning has proven to be proficient in solving similar problems with unprecedented speed owing to the latest advances in computing power and analytical algorithms. In this study, we investigate the performance of machine learning methods in predicting the H2 production activity and O2 tolerance of the hydrogenase variants. Experimentally measured activities and tolerance of 377 variants having single or double amino acid replacements are used to train and test seven types of machine learning models. Binary representation of amino acid sequence as well as the series of vectors quantifying physicochemical properties of amino acids, namely VHSE, are employed as features representing each variant. The results show that the VHSE enable higher performance, especially with respect to correlation coefficient and coefficient of determination in addition to the root mean square error. Next, the analysis of model performance with respect to changes in the data size and heterogeneity is conducted to provide insights on designing effective mutagenesis library for applying machine learning. The best performance was obtained when support vector machine or ridge regression was trained using a large, homogeneous data. In this manner, our study reveals the factors affecting the performance of machine learning in identifying the enzyme variants with enhanced function. [ABSTRACT FROM AUTHOR]

The main objective of this research was to evaluate the impacts of FeCl 3 -activated biochar (FA-BC) on anaerobic digestion (AD) treating cow manure. The study focused on improving AD performance and understanding microbial community structure with the addition of FA-BC, while comparing FA-BC with other conductive additives, such as pristine biochar (P-BC), NaOH-activated biochar (NA-BC), and magnetite. Key findings indicated that FA- BC significantly enhanced the AD performance, supported by an increase in CH 4 yield of 11–16% and a reduction in the lag phase by 51%. The high surface area and electrical conductivity of FA-BC synergistically facilitated direct interspecies electron transfer (DIET), leading to these improvements. On contrast, P-BC and NA-BC were not efficient in enhancing the AD performance due to relatively low electrical conductivity. P-BC also improved the CH 4 yield, but less effectively than FA-BC. The effects of NA-BC varied with its dosage, showing inhibition at higher dosages due to excessive surface area. Magnetite, despite its high conductivity, made the limited enhancement in CH 4 yield owing to its low surface area. Additionally, the statistical analyses revealed that each additive differently affected specific bacterial and archaeal groups depending on their physical and chemical properties. Thus, these findings suggest that FA-BC would be a highly promising additive for enhan cing AD systems, with potential applications in waste management and renewable energy production. [Display omitted] • FA-BC possesses both a large surface area and high electrical conductivity feature. • FA-BC showed the highest AD performance by facilitating DIET efficiently. • High dose levels of NA-BC inhibited the AD performance by reducing mass transfer. • Magnetite only marginally improved the AD efficiency due to its low surface area. • Each additive's inherent characteristics impacted distinctive AD parameters. [ABSTRACT FROM AUTHOR]

[Display omitted] • Increase of PFAS level adversely affected the AD system and microbial activity. • PFOA led to higher impacts on AD performance and microbial activity than PFOS. • Archaeal group was more vulnerable to both PFOA and PFOS than bacterial group. • PFOA induced changes in microbial community by their toxicity. • PFOS induced changes in microbial community by their toxicity and functional group. Per- and polyfluoroalkyl substances (PFASs) are recalcitrant organic pollutants, which accumulate widely in aquatic and solid matrices. Anaerobic digestion (AD) is one of possible options to manage organic wastes containing PFASs, however, the impacts of different types of PFAS on AD remains unclear. This study aimed to critically investigate the effects of two representative PFAS compounds, i.e., perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), on the AD performance and microbial community structure. 100 mg/L of both PFOA and PFOS considerably inhibited the AD performance and changed the microbial community structure. Especially, PFOA was more toxic to bacterial and archaeal activity than PFOS, which was reflected in AD performance. In addition, the sulfonic acid group in PFOS affected the changes in microbial community structure by inducing abundant sulfate reducing bacteria (i.e., Desulfobacterota). This study provides a significant reference to the response of AD system on different PFAS types and dosage. [ABSTRACT FROM AUTHOR]

Thermal hydrolysis (TH) pretreatment was investigated for the anaerobic digestion (AD) of a mixture of high-strength organic wastes (i.e., dewatered human feces, dewatered sewage sludge, and food wastewater) at laboratory scale to simulate a full-scale plant and evaluate its feasibility. The reactors maintained efficient and stable performance at a hydraulic retention time of 20 days, which may be not sufficient for the mesophilic AD of high-suspended-solid wastes, despite the temporal variations in organic load. The addition of FeCl 3 was effective in controlling H 2 S and resulted in significant changes in the microbial community structure, particularly the methanogens. The temporary interruption in feeding or temperature control led to immediate performance deterioration, but it recovered rapidly when normal operations were resumed. The overall results suggest that the AD process coupled with TH pretreatment can provide an efficient, robust, and resilient system to manage high-suspended-solid wastes, supporting the feasibility of its full-scale implementation. [ABSTRACT FROM AUTHOR]

Mixed-culture fermentation that does not require an energy-intensive sterilization process is a viable approach for the economically feasible production of lactic acid (LA) due to the potential use of organic waste as feedstock. This study investigated mixed-culture LA fermentation of whey, a high-strength organic wastewater, in continuous mode. Variations in the hydraulic retention time (HRT) from 120 to 8 h under different pH regimes in two thermophilic reactors (55 °C) were compared for their fermentation performance. One reactor was maintained at a low pH (pH 3.0) during operation at HRTs of 120 to 24 h and then adjusted to pH 5.5 in the later phases of fermentation at HRTs of 24 to 8 h (R1), while the second reactor was maintained at pH 5.5 throughout the experiment (R2). Although the LA production in R1 was negligible at low pH, it increased dramatically after the pH was raised to 5.5 and exceeded that in R2 when stabilized at HRTs of 8 and 12 h. The maximum yield (0.62 g LA/g substrate fed as the chemical oxygen demand (COD) equivalent), the production rate (11.5 g/L day), and the selectivity (95 %) of LA were all determined at a 12-h HRT in R1. Additionally, molecular and statistical analyses revealed that changes in the HRT and the pH significantly affected the bacterial community structure and thus the fermentation characteristics of the experimental reactors. Bacillus coagulans was likely the predominant LA producer in both reactors. The overall results suggest that low pH start-up has a positive effect on yield and selectivity in mixed-culture LA fermentation. [ABSTRACT FROM AUTHOR]

• External voltage application affects the development of dynamic membrane (DM). • DM fouling was delayed by applying negative voltages of –0.6 to –1.2 V. • DM development was accelerated by applying positive voltages of + 0.2 to + 0.6 V. • Too large applied voltages caused electrochemical corrosion and chemical fouling. • Applying an external voltage of appropriate magnitude is key to effective DM control. Maintaining proper dynamic membrane (DM) thickness and structure is the key factor for effective filtration and biomass retention in DM bioreactors. This study investigated the effects of negative and positive applied voltages on the development and characteristics of anaerobic DM under high suspended solids conditions. The DM filtration experiments with anaerobic sludge were performed using submerged DM modules with stainless steel support material at applied voltages of –1.2 to +1.2 V. Negative applied voltage (i.e., cathodic DM) delayed the DM fouling, while positive applied voltage (i.e., anodic DM) accelerated the DM growth, within certain voltage ranges by the combined effect of electrostatic forces and electrochemical reactions. Too large negative or positive voltages caused electrochemical corrosion of support material and precipitation of mineral scales, resulting in serious chemical fouling. The cathodic and anodic DMs formed at different applied voltages achieved high suspended solids rejection efficiencies of 86.4–89.6%. The applied voltage had a significant effect not only on the DM growth and filtration resistance but also the surface morphology, cell viability (live/dead cell ratio), and extracellular polymeric substances distribution of DM. Cell damage by electrochemically formed reactive species was observed at high electrode potentials. The overall results suggest that applying external voltage within an appropriate range can be an effective way to control the DM development. Although much more research is needed, the findings of this study offer a new possibility to improve the feasibility of DM technology and its applicability in anaerobic DM bioreactors. [ABSTRACT FROM AUTHOR]

Two parallel anaerobic digesters (8500 m3 capacity each), combined with thermal hydrolysis (TH) pretreatment, co-digesting dewatered sewage sludge, dewatered human feces, and food wastewater were monitored over a 12-month period from start-up to explore the feasibility of field application of the combined process. The waste mixtures before and after pretreatment and the feed and digestate of each digester were taken semimonthly (i.e., 48 samples in total) for analysis of the feed characteristics, process parameters, and digester microbial community structure. The TH pretreatment proved effective in improving the bioavailability of the waste mixture. The solubilization efficiency tended to increase with the particulate organic fraction in the raw mixture. Although fluctuations in the feed characteristics and loading significantly influenced the process and microbial behaviors, the digesters maintained stable performance during the study period. Our results demonstrate that the TH-anaerobic digestion process can achieve an effective and robust treatment of the waste mixture. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fused aromatic networks are unique subclasses of porous organic polymers. • Fused aromatic networks were examined as kinetic hydrate inhibitors (KHIs). • The V2D-BBL structure showed remarkable performances as a KHI for gas hydrates. • The designed perinone moiety enabled synergistic interactions with host and guest. Fused aromatic networks (FANs) are attracting considerable interest in the scientific community because of their intriguing electronic properties and superior physiochemical stability due to their fully fused aromatic systems. Here, a three-dimensional (3D) cage-like organic network (3D-CON) and a vertical two-dimensional (2D) layered ladder structure (designated as V2D-BBL structure) were studied as materials for gas hydrate inhibitors because of their outstanding stability in high-pressure/low-temperature and periodically incorporated molecular building blocks. The V2D-BBL structure demonstrated remarkable performance, inhibiting the formation of both methane (CH 4) and carbon dioxide (CO 2) hydrates, comparable to conventional lactam-based polymers. It was determined that the designed perinone moiety in the V2D-BBL structure enables synergistic interactions with the host (water) and guest (CH 4) molecules involved in hydrate nucleation. Given their pre-designability and inherent stability, the FANs hold enormous potential as gas hydrate inhibitors for industrial applications. [ABSTRACT FROM AUTHOR]