Energy-efficient wastewater treatment plants (WWTPs) utilize systems like high-rate activated sludge (A-stage) system to redirect organics from wastewater are redirected into energy-rich sludge (A-sludge). Anaerobic membrane bioreactors (AnMBRs) offer lower footprint and higher effluent quality compared to conventional digesters. In this study, the biological treatment and the filtration performances of AnMBRs for A-sludge digestion under mesophilic and thermophilic conditions were comparatively evaluated through lab-scale experiments, mass balancing and dynamic modeling. Under thermophilic conditions, a higher COD fraction of the influent sludge was converted into methane gas than under mesophilic conditions (65% versus 57%). The energy balance indicated that the surplus energy recovery under thermophilic conditions was less than the additional energy required for heating the AnMBR, resulting in a more than three-fold higher net energy recovery under mesophilic conditions. Therefore, operating an AnMBR for sludge digestion under mesophilic conditions has a higher potential to improve the energy balance in WWTPs.

In this study, the effects of fermentation pH and redox potential on the performance of the lactate platform were comprehensively evaluated. The results indicated that the type of acidogenic fermentation was influenced by redox potential, while pH was correlated with volatile fatty acid yield. The highest propionate yield was achieved under anaerobic conditions at a pH of9, with the dominant genus Serpentinicella producing propionate through the acrylate pathway. The highest acetate yield was produced under facultative conditions at a pH of 6. This production was primarily facilitated by the dominant genera unclassified_f__Enterobacteriaceae and Desulfovibrio, which exhibited significant upregulation of the expression of related genes. Furthermore, ecological processes were employed to establish the relationship between environmental factors and microbial communities. This study emphasized the process of converting lactate into volatile fatty acid, providing a theoretical basis for future strategies aimed at regulating targeted acid production.

Dimethyl disulfide (DMDS) is an odor compound characterized by the lowest olfactory threshold and high toxicity. It is indispensable to explore the bacteria with high resistance and degradation efficiency to DMDS. Acinetobacter lwoffii, Pseudomonas mendocina, and Myroides odoratus were isolated from kitchen waste. After 6 days of individual treatment, the removal rates were 34.22 %, 40.95 %, and 41.94 % respectively. The DMDS metabolic pathways based on metagenomic assays were discovered to be incomplete due to the insufficient annotation of some key genes in the current database. Following 3 days of treatment with bacterial consortia at ratios of 5:1 for A. lwoffii C2/ M. odoratus C7 and 1:1:1 for the three strains achieved 100 % DMDS removal. Additionally, the consortia reduced hydrogen sulfide (HS) and dimethyl sulfide (DMS).This discovery broadens the spectrum of bacteria exhibiting high tolerance and efficient degradation of DMDS, with significant implications for DMDS removal and odor treatment.

Although prokaryotic microbes in coking wastewater (CWW) treatment have been comprehensively studied, the ecological functions of viruses remain unclear. A full-scale CWW biological treatment AOHO combination was studied for the virus-bacterium interactions involved in element cycles by metaviromics, metagenomics and physicochemical characteristics. Results showed the unique viromic profile with Cirlivirales and Petitvirales as the dominant viruses infecting functional bacteria hosts. The auxiliary metabolic genes (AMGs) focused on element cycles, including metabolisms of carbon (fadA), nitrogen (glnA), sulfur (mddA and cysK) and phosphorus (phoH). Other AMGs were involved in toxic tolerance of hosts, improving their cell membrane and wall robustness, antioxidant, DNA repair and cobalamin biosynthesis. Vice versa, the bloomed host provided fitness advantages for viruses. Dissolved oxygen was found to be the key factor shaping the distributions of viral community and AMGs. Summarizing, the study exposed the mutual virus-bacterium interaction in the AOHO combination providing stable treatment efficiency.

This study addressed a less-reported issue: the insufficient alkalinity encountered when anaerobic membrane bioreactors (AnMBRs) are used to treat municipal wastewater (MWW). In the present study, a 20-L AnMBR was initiated at an MWW treatment plant. During the initial startup, a continuous decrease in pH was observed. Through the analyses of the balance between HCO/CO in the biogas and alkalinity in the reactor, the cause of pH instability was determined to be that the alkalinity could not balance the acidity induced by the continuous dissolution of CO from biogas in the liquid phase. Therefore, this study employed the in-situ removal of CO from biogas using soda lime to reduce the CO partial pressure, thereby achieving stable control of the pH in the reactor. This study provides valuable experience and technical support for anaerobic processes for treating low-alkalinity MWW in the future applications.

In this study, total nitrogen (N) removal efficiency of Pontederia cordata and Myriophyllum elatinoides in surface flow constructed wetlands (SFCWs) with Bellamya aeruginosa were 6.43% and 3.54% higher, respectively, than those in non-B. aeruginosa SFCWs. Further, bioturbation could promote N uptake by plants and release from sediment. In summer and autumn, potential nitrification rate was significantly higher in SFCWs with snails than that in SFCWs without snails. In each season, potential denitrification rate was significantly higher in SFCWs with snails than that in SFCWs without snails. Additionally, ammonia oxidizing archaea, narG, nirS, nirK and nosZ gene abundances were significantly higher in SFCWs with snails than those in SFCWs without snails. Structural equation model analysis revealed a strong positive correlation between nitrifiers and denitrifiers in SFCWs with snails, suggesting that bioturbation enhanced N removal by increasing synergistic effect of nitrifying and denitrifying bacteria.

Crude sugarcane molasses (SCM) was successfully applied for the first time as a bio-feedstock for producing biochar catalysts for glycerol upgrading. Preparation methods were developed, including partial or hydrothermal carbonization (abbr. PC and HTC) and chemical activation. After functionalization with -SOH groups, the catalysts were tested for the esterification of glycerol to acetins. The materials varied in their textural and chemical features, particularly in the -SOH content, giving the single-step PC method a distinct advantage. The best catalyst yielded approximately 74 % of di- and tri-acetins with 97 % glycerol conversion within only 2 h of the reaction and demonstrated great stability over three consecutive cycles. The formation of the desired TA product was correlated with the concentration of -SOH groups. Despite being non-porous, the most active PC catalyst possessed a compact structure with a high abundance and easy accessibility of -SOH, COOH, and -OH groups on its surface.

Batch fermentations of the wild type Yarrowia lipolytica MUCL 28849 were performed in a bench-top bioreactor to assess crucial operating conditions. A setup of carbon to nitrogen (mol/mol) ratio equal to 34, pH = 6.0 and 52 g/L of crude glycerol showed increased lipid production and complete glycerol consumption at t = 24 h, thus, selected for further process improvement. Α semi-continuous process was implemented, where a pH drop to 4.0 at 24 h, interrupted citric acid secretion without affecting lipid production. An in-situ membrane module was employed for membrane bioreactor fermentations, where yeast cells were successfully retained with minimum fouling. The membrane bioreactor fed-batch process, resulted in a high-cell-density culture reaching 49.8 g/L of dry biomass and 4.9 g/L of lipids. An unstructured model was developed and successfully simulated operation under all fermentation modes, distinguishing diverse physiological shifts.

A coupled thiosulfate-driven denitrification and anammox (TDDA) process was established to remove nitrogen from wastewater. It was optimized in an up-flow anaerobic sludge blanket reactor using synthetic wastewater, and its reliability was then verified with actual wastewater. The results demonstrated that nitrate, nitrite, and ammonium could be synergistically removed, and the highest total nitrogen removal efficiency reached 97.8% at a loading of 1.39 kgN/(m·d). Anammox bacteria, primarily Candidatus_Brocadia, were the main contributors to nitrogen removal, while sulfur-oxidizing bacteria such as Thiobacillus and Rhodanobacter played a supportive role. By optimizing substrate conditions to enhance the anammox process, the coupled system attained higher abundances of functional genes such as napA, nirS, hzs, soxXA, and soxYZ, along with the corresponding microbial species. The data suggested that microbial cross-feeding and self-adaptation strategies were key to efficient nitrogen removal by TDDA.

Solving the plastic crisis requires high recycling quotas and technologies that allow open loop recycling. Here a biological plastic valorization approach consisting of tandem enzymatic hydrolysis and monomer conversion of post-consumer polyethylene terephthalate into value-added products is presented. Hydrolysates obtained from enzymatic degradation of pre-treated post-consumer polyethylene terephthalate bottles in a stirred-tank reactor served as the carbon source for a batch fermentation with an engineered Pseudomonas putida strain to produce 90mg/L of the biopolymer cyanophycin. Through fed-batch operation, the fermentation could be intensified to 1.4 g/L cyanophycin. Additionally, the upcycling of polyethylene terephthalate monomers to the biosurfactants (hydroxyalkanoyloxy)alkanoates and rhamnolipids is presented. These biodegradable products hold significant potential for applications in areas such as detergents, building blocks for novel polymers, and tissue engineering. In summary, the presented bio-valorization process underscores that addressing challenges like the plastic crisis requires an interdisciplinary approach.

This study explored the use of algae to supply oxygen in situ as an alternative to mechanical aeration for anaerobic effluent treatment in a photo-sequencing batch biofilm reactor (PSBBR). By establishing alternating aerobic (dissolved oxygen (DO) > 2 mg /L)/anoxic conditions (<0.5 mg-DO/L) through a 6-h off/6-h on biogas sparging cycle and continuous illumination (1500-3000 lx), the PSBBR achieved a significant ammonia removal rate of 15-25 mg N Ld. This system demonstrated robust partial nitrification and nitrite reduction activities, coupled with aerobic methane oxidation. Metagenomic analysis revealed the enrichment of key microbial groups, including Leptolyngbyaceae, Methylocystis, Nitrosomonas and Hyphomicrobium. The key functional genes of methane (mmo, mdh, gfa, frm and fdh) and nitrogen (amo, hao, narGHI, and napAB) metabolisms were identified, while notably lacking nitrite oxidation genes. In conclusion, this study provides a promising post-treatment approach for anaerobic effluent through integrating biogas utilization with efficient nitrogen removal.

Dopamine (DA) has attracted attention because of its effects on Haematococcus lacustris biomass, astaxanthin production, and physiological responses. The alga treated with 25 μM DA combined with 1 g L sodium chloride exhibited 7.63 %, 41.25 %, and 52.04 % increases in biomass (1.41 g L), astaxanthin content (32.37 mg/g), and astaxanthin productivity (3.51 mg L d) respectively, compared with the salinity stress and high light. Exogenous DA treatment promoted lipid synthesis while reducing carbohydrate and protein contents. Moreover, carotenogenesis and lipogenesis-associated genes were upregulated under DA induction. Inhibition of reactive oxygen species and autophagy, along with mitogen-activated protein kinase activation, promoted astaxanthin accumulation under DA. Furthermore, DA application boosted astaxanthin biosynthesis by regulating the levels of respiratory metabolic intermediates, the γ-aminobutyric acid shunt, and important phytohormones. These findings present a potential and successful biotechnological approach for enhancing biomass and astaxanthin production in H. lacustris under stressful conditions.

Polyhydroxyalkanoates (PHA) are promising eco-friendly alternatives to petrochemical plastics. This study investigated the impact of the main fatty acids present in waste and fresh oils -palmitic, stearic, oleic, and linoleic acid-on PHA production using Cupriavidus necator H16, focusing on production yield, polymer composition, thermal properties, and microbial viability. Experiments were conducted with low (5 g/L) and high (15 g/L) carbon content for 168 h. Oleic acid was the most effective carbon source, yielding higher PHA production rates, especially noticeable at higher concentrations. The monomer composition and thermal properties of PHAs varied with the type and concentration of fatty acid used. Stearic acid produced PHAs with more 3-hydroxyvalerate and medium-chain length monomers. Microbial viability was consistent across all conditions, except for linoleic acid, which had a detrimental effect. These findings provide key insights into optimizing fatty acid selection to enhance PHA production and tailor polymer properties for industrial applications.

Microbial electrosynthesis is a promising technology that recovers energy from wastewater while converting CO into CH. Constructing a biocathode with both strong H-mediated and direct electron transfer capacities is crucial for efficient startup and long-term stable CH production. This study found that introducing carboxyl groups onto the cathode effectively enhanced both electron transfer pathways, improving the reduction rate and coulombic efficiency of CH production and increasing the CH yield by 2-3 times. Carboxyl groups decreased the overpotential for H evolution and increased current density, thereby enhancing H-mediated electron transfer. Additionally, carboxyl groups increased the relative abundance of Methanosaeta by 3%-10%, doubled the protein content in extracellular polymeric substances, and boosted the expression of cytochrome c-related genes, thereby enhancing direct electron transfer capacity. These findings present a novel and efficient approach for constructing a stable, high-performance biocathode, contributing to energy recovery and CO fixation.

The impact of carbon/nitrogen (C/N) ratio on sequencing batch biofilm reactor (SBBR) initiated with different seed sludges for treating actual mariculture effluent was explored. Increasing the C/N ratio significantly enhanced the nitrogen removal efficiency, achieving average removal efficiency of 95% for ammonia nitrogen and 73% for total nitrogen at ratio of 30, while the impact of seed sludge was minimal. High C/N ratio promoted the secretion of tightly bound extracellular polymeric substances (TB-EPS), which showed significant correlation with nitrogen removal. Interactions between bacteria and archaea were enhanced and conditionally rare or abundant taxa were the keystone taxa. High C/N ratio inhibited the relative abundance of ammonia-oxidizing archaea (Candidatus_Nitrosopumilus) and bacteria (Nitrosomonas), but promoted the heterotrophic nitrification-aerobic denitrification bacteria (Halomonas). The expression of nitrogen removal functional genes significantly correlated with functional genera. This study emphasized the crucial role of high C/N ratios in biological nitrogen removal from actual mariculture effluent.

Plastics and paper are common components of municipal solid waste (MSW), making an in-depth understanding of their interactions essential for MSW thermal conversion. In this study, the co-pyrolysis behavior of plastic and paper was investigated. Firstly, the thermal decomposition characteristics were analyzed. Secondly, the pyrolytic behavior was elucidated in a fixed-bed reactor. Thirdly, the impact of plastic melting on co-pyrolysis was clarified. Results indicated that the thermal decomposition was accelerated between 250 °C and 283 °C, while temperatures above 400 °C resulted in inhibition. During fixed-bed pyrolysis, char yields (70.7-16.9 %) were increased by 4.0 %-12.7 %. This increase was mainly due to plastic melting, which contributed 8.6 % and increased aliphatic carbon content. Besides, PVC and PET exhibited a broader melting range > 500 °C. Bio-oil yields (25.5-70.6 %) were reduced by 3.4 %-12.4 %, primarily affecting aliphatic compositions. Gas yields (3.8-6.5 %) were reduced < 400 °C but increased with temperature, involving primarily H, CH, CH, and CH.

A novel mixotrophic denitrification biofilter for nitrate removal using polycaprolactone and thiosulfate (MD-PT) as electron donors was investigated. MD-PT achieved high nitrate removal efficiency of approximately 99.8 %. The nitrate removal rates of MD-PT reached 1820 g N/m/d, which was 304 g N/m/d higher than that of autotrophic denitrification biofilter using thiosulfate (AD-T). Autotrophic and heterotrophic denitrification pathways in MD-PT were responsible for 67.6-94.5 % and 4.7-32.4 % of the nitrate removal, respectively. The production of SO in MD-PT was lower than that in AD-T, and the effluent pH was maintained at approximately 7.3 without acid-base neutralization. The abundance of key genes involved in carbon, nitrogen, and sulfur transformation was enhanced, which improved the nitrate removal of MD-PT. Alicycliphilus and Simplicispira related to organic compounds degradation were enriched after the addition of polycaprolactone. This research provided new insights into mixotrophic denitrification systems.

It is feasible to integrate an anaerobic membrane bioreactor with a membrane aerated biofilm reactor to efficiently implement the sulfate reduction, simultaneous nitrification and autotrophic denitrification process. However, the effect of parameters on nutrient removal and environmental impacts of the process are unclear. In this study, the reactor performance was mainly influenced by the chemical oxygen demand to sulfate (COD/S) ratio and the ammonium to sulfate (N/S) ratio in long-term operation. Significant models were developed to optimize the two factors using the response surface methodology. Under optimal conditions (COD/S ratio of 2.5 and N/S ratio of 0.3), the system could remove above 86 % COD, 99 % ammonium, and 92 % total inorganic nitrogen. Moreover, this process could reduce energy consumption by 30 % and global warming potential by 50 % compared with traditional anaerobic/oxic activated sludge process. These findings provide guidance for the application of this technology in sulfate-containing municipal sewage treatment.

NAD/NADH-dependent CO reductase (CR) adapted from Candida boidinii (PDB ID: 5DNA) was introduced with a non-native graphite-specific peptide (Gr; IMVTESSDYSSY) as molecular binder to modify the native enzyme (CR-WT) with peptide insertion at N, C and NC terminus (CR-GrN, CR-GrC and CR-GrNC) to assess the influence of site-specific fusion on electrode binding. Graphite surface-binding activity relative to the electrode topography was evaluated for both native and synthetic CRs to establish the enzyme-electrode interfacing potentiality for efficient electron channelling. Impact of site-specific peptide fusion and amino-acids positioning was assessed for the active site availability/binding and adsorption/desorption ability towards efficient CO-based redox catalysis. Solid-binding peptide and graphite surface interactive ability on direct electron transfer was studied with structural, enzymatic and electrochemical characterizations towards efficient CO electrosynthesis. Overall, enzymatic CO reduction to formate based on interactive ability of enzyme-electrode complex with peptide modifications and graphite surface towards possibility of bioelectronics upscaling was depicted.

Recent research has discussed the positive impacts of metal-based nanoparticles (NPs) on bioprocesses producing either hydrogen (H) or methane (CH). The enhancement has been explained by mechanisms such as direct interspecies electron transfer (DIET), metal corrosion, and dissimilatory reduction. Such interactions could induce further benefits, such as controlling oxidation-reduction potential (ORP), mitigating toxicants, promoting enzymatic activity, and altering the microbiome, which have not yet been comprehensively discussed. Factors like metal type, oxidation state, and size of NPs are crucial for their reactivity and corresponding responses. This review discusses how different redox potentials of metals can regulate metabolic pathways and how NPs and their reactive ions can eliminate toxicants (e.g., sulfate) and enhance the activity of intra- and extracellular enzymes. The enrichment of responsive microorganisms in correlation with NPs is further discussed. A better understanding of the multifaceted role of metal-based NPs can guide potential new incorporation strategies to improve bioprocesses.

Syngas from the gasification of organic wastes represents a promising feedstock for fostering a sustainable bioeconomy. However, its potential is currently constrained by the low-value products generated. Osmolytes, such as hydroxyectoine, are high-value compounds, however, their biological production as isolated osmolytes is not yet cost-effective. This study utilized shotgun genomics and laboratory validation to find a carboxydotrophic, halotolerant bacterium, Hydrogenibacillus schlegelii, that could produce hydroxyectoine using H, CO and CO as the sole source of energy and carbon. Subsequently, NaCl concentration, temperature and syngas composition were optimized in semi-continuous bioreactors. Optimal conversion of CO into hydroxyectoine occurred at a gas composition of 70 %:10 % CO:H (v/v) (44.8 ± 10.1 mg·g). NaCl concentrations of 5 % significantly enhanced hydroxyectoine content (46.7 ± 9.5 mg·g), but negatively affected gas consumption. This study opens new perspectives for the valorisation of syngas into hydroxyectoine, and for new cell platforms for pharmaceutical production based on syngas.