Free Ammonia Research Articles

Exploring the influence of moisture stress on microbial-driven organic acid synthesis in potato waste fermentation

Anaerobic fermentation of potato leaves and stems for organic acid synthesis, serving as food additives, faces impediments due to misconceptions about the effects of moisture stress on the acid-synthesizing microbiome. An ingenious method, avoiding interference from microbiome and nutrient integrations, was employed in the present study. Results showed that increasing the moisture level from 60 % to 75 % significantly improved lactic acid (182.64 %), acetic acid (163.55 %), propionic acid (1960.43 %), nonprotein nitrogen, free amino acid and ammonia levels but reduced pH value and water-soluble carbohydrate and hemicellulose levels. Microbiologically, the high-moisture groups enriched Lactiplantibacillus, Levilactobacillus and Enterobacter, upregulated glycolysis, nitrogen, pyruvate and propanoate metabolisms, and activated genes for acid-producing and ammonia-forming enzymes. Notably, Lactiplantibacillus and Enterobacter prevailed in glycolysis and nitrogen metabolism, respectively, and Levilactobacillus was more prominent in pyruvate and propanoate metabolism under high-moisture conditions. Collectively, a moisture level of 75 % benefited organic acid synthesis from potato waste via anaerobic fermentation.

Drinking water buffer intensity simulator (BIS): Development and practical simulations

AbstractAn established body of research over many decades has identified the importance of both bulk‐water and pipe scale surface microenvironment buffering to meet distribution system pH targets and reduce corrosivity toward metallic piping and components. Buffer intensity quantifies the ability of water to resist pH changes, and the greater the buffer intensity, the more resistant the water is to pH changes. To provide a practical tool for exploring buffer intensity, a buffer intensity simulator (BIS) was implemented in open‐source R code, incorporating typical chemical species (e.g., carbonate and orthophosphate) that contribute to drinking water buffer intensity along with temperature and ionic strength impacts. The BIS was verified against a parallel spreadsheet implementation and is publicly available at https://github.com/USEPA/BIS. Simulations were conducted to illustrate impacts related to buffer intensity using three practical scenarios: carbonate buffering in drinking waters, temperature impacts, and free ammonia presence from chloramine use and/or source water presence.

Evaluation of the efficiency of the hepatoprotector glucuronate in toxic hepatitis of various etiology

The objective was to study the effectiveness of the use of hepatoprotector glucuronate at the early stage of intensive therapy of toxic hepatitis of various etiologies.Materials and methods. We studied 120 patients with toxic hepatitis who were treated at the Republican research center for emergency medicine in 2022–2023. The study was carried out in two groups of patients. Group I – 60 patients admitted in 2023, who, in addition to traditional therapy, received a complex hepatoprotector glucuronate (Jetepar®)*. Group II (comparison group) – 60 patients who applied in 2022 and received only traditional therapy. Biochemical blood parameters were studied upon admission and over time on day 5. The severity of intellectual impairment was assessed using cognitive scales and the Reitan test on days 2 and 5 from the start of treatment.Results. Upon admission, both groups showed signs of toxic liver damage. In dynamics by the 5th day in patients of group I, there was a decrease in ALT by 63.7%, AST by 66.4%, alkaline phosphatase by 54.2% from the initial values, which was 3.9 and 2.6, 2. 1 lower than in the comparison group. The level of free ammonia in patients of group I on the 5th day decreased by 52%, and lactate by 57% from the initial level, almost to the physiological norm, while in the comparison group (II) only by 24.8% and 38.1%, which was 2.2 and 1.5 times worse than in the main group. Screening of the level of intelligence using two cognitive scales and the Reitan test showed that in patients in the comparison group, cognitive function indicators on the 5th day were 1.4, 1.5 and 1.2 times lower than in the main group.Conclusion. The use of the hepatoprotector glucuronate improves liver parameters and cognitive functions in patients with toxic hepatitis.

Urban wastewater treatment at ambient conditions using microalgae-bacteria consortia in a membrane high-rate algal pond (MHRAP): The effect of hydraulic retention time and influent strength

The effects of hydraulic retention time (HRT) and influent wastewater strength on microalgae-bacteria performance were studied in two sets of experiments in a 6-day biomass retention time membrane high-rate algal pond (MHRAP) pilot plant to assess its pollutants removal potential. In the first set of experiments, the MHRAP was continuously fed with effluent from primary settling and operated at 6-, 4- and 2-days HRT and in the second set, the MHRAP was operated at 4-, 2-, and 1-day HRT using pre-treatment effluent. Results showed a complex interaction between algae-bacteria consortium, ambient conditions and MHRAP operation. In set 1, the highest total nitrogen (T-N) and total phosphorus (T-P) removal efficiencies were reached with 6-day HRT (23.6±0.6 % and 32±4 %, respectively), partially due to free ammonia nitrogen stripping and phosphorus precipitation, because of abiotic factors, which reduces the activity of nitrite-oxidizing bacteria and led to partial-nitrification. On the other hand, the 4 and 2-day HRT T-N and T-P removal efficiencies were reduced (below 10 % and 5 %, respectively) because the abiotic factors limited the physicochemical processes, and less biomass was taken up. In set 2, a suitable equilibrium between the microalgae and bacterial communities at 2-days HRT achieved high T-N (91±5 %) and T-P (71±8 %) removal efficiencies. Mass balances indicated that the nitrogen was mostly removed by nitrification-denitrification (87 % of T-N) and T-P predominant removal mechanism was precipitation. The COD removal efficiencies were higher than 86 % in both sets, since the particulate COD and colloids were removed by ultrafiltration. The obtained results showed that MHRAP technology would allow reducing COD and nutrient loads in the effluent under certain operating conditions, demonstrating the potential for resource recovery and wastewater treatment of microalgae-bacteria consortia.

Combined Administration of Metformin and Amprolium to Rats Affects Metabolism of Free Amino Acids in the Brain, Altering Behavior, and Heart Rate.

The risk of developing diabetes and cardiometabolic disorders is associated with increased levels of alpha-aminoadipic acid and disturbances in the metabolism of branched-chain amino acids. The side effects of the widely used antidiabetic drug metformin include impaired degradation of branched-chain amino acids and inhibition of intracellular thiamin transport. These effects may be interconnected, as thiamine deficiency impairs the functioning of thiamine diphosphate (ThDP)-dependent dehydrogenases of 2-oxo acids involved in amino acids degradation, while diabetes is often associated with perturbed thiamine status. In this work, we investigate the action of metformin in rats with impaired thiamine availability. The reduction in the thiamine influx is induced by simultaneous administration of the thiamine transporters inhibitors metformin and amprolium. After 24 days of combined metformin/amprolium administration, no significant changes in the total brain levels of ThDP or activities of ThDP-dependent enzymes of central metabolism are observed, but the affinities of transketolase and 2-oxoglutarate dehydrogenase to ThDP increase. The treatment also significantly elevates the brain levels of free amino acids and ammonia, reduces the antioxidant defense, and alters the sympathetic/parasympathetic regulation, which is evident from changes in the ECG and behavioral parameters. Strong positive correlations between brain ThDP levels and contents of ammonia, glutathione disulfide, alpha-aminoadipate, glycine, citrulline, and ethanolamine are observed in the metformin/amprolium-treated rats, but not in the control animals. Analysis of the obtained data points to a switch in the metabolic impact of ThDP from the antioxidant and nitrogen-sparing in the control rats to the pro-oxidant and hyperammonemic in the metformin/amprolium-treated rats. As a result, metformin administration along with the amprolium-reduced thiamine supply significantly perturb the metabolism of amino acids in the rat brain, altering behavioral and ECG parameters.

Performance Evaluation of Hydroponic Grow-Outs in An Innovative Coldwater Aquaponic System Featuring Rainbow Trout and Lettuce

A 45-day trial was carried out to assess the production performance of different hydroponic media in a novel do-it-yourself (DIY) low-tech re-circulating aquaponic system for temperate regions with rainbow trout (Oncorhynchus mykiss) and lettuce (Lactuca sativa). Rainbow trout juveniles (average weight of 35.59 g) were stocked in the experimental units at 2.8 kg.m-3 and fed with commercial floating pelleted feed at 8 % of their body weight in three treatments and a control. The lettuce saplings were randomly planted in the river stone bed (T1), crushed stone bed (T2), raft/deep water culture (DWC) unit (T3) and control (C) soil bed (fortified with NPK fertiliser) with equivalent planting intervals of 42 saplings.m-2. The system, designed with low-tech simplicity, was managed without alkalinity correction and depended entirely on plant growth and metabolism for biofiltration. The water quality parameters such as temperature, pH, dissolved oxygen (DO), dissolved free CO2, hardness, total alkalinity, ammonium, nitrite, and nitrate varied significantly (P < 0.05) among the treatments compared to the control. The final individual weight, biomass gain, specific growth rate (SGR), and feed conversion ratio (FCR) of rainbow trout were significantly better (P < 0.05) in media beds (crushed stone and river stone) compared to control and DWC systems. The final mean weights of rainbow trout in river stone (12.33 ± 0.002 g and crushed stone (12.39 ± 0.054 g) treatments were significantly higher (P < 0.05) than in DWC (12.1 ± 0.023 g) and control (12.09 ± 0.002 g) treatments. The production of lettuce was significantly greater (P < 0.05) in all three treatments (river stone: 4.33 ± 0.123 g, crushed stone: 4.53 ± 0.09 g and DWC: 4.31 ± 0.163 g) compared to the control (3.31 ± 0.172 g). The DWC including the media bed systems facilitates the improved performance of lettuce saplings in terms of final height and leaf number. These results show that a low-tech media bed system without a supplementary biofiltration unit can achieve sustainable production of both fish and vegetables in temperate hilly terrains.

Numerical simulation of lead-free MASnI3 perovskite/silicon heterojunction for solar cells and photodetectors

Lead free n-type doped methyl ammonium tin iodide (MASnI3) perovskite/p-Silicon heterojunction (HJ) for solar cells and photodetectors are simulated using AFORS-HET automat simulation software. In the earlier work, lead based methyl ammonium lead iodide perovskite/silicon (n-MAPbI3/p-Si) heterojunction devices were studied. In view of the toxicity and environmental concerns related to lead, it is substituted with tin to make lead-free tin based perovskite to make n-MASnI3/p-Si HJ devices. Various parameters associated with the layers of MASnI3 perovskite and silicon wafer like, Band gap, thickness, doping concentration and texturing angle have been optimized. Various transparent conducting oxide (TCO) materials like indium tin oxide (ITO) and zinc oxide (ZnO) are used and its performance with ideal device is compared. Various metals are considered as front and back contact, to obtain best metals for each sides. This study investigates the potential of lead-free perovskite materials in solar cells, achieving a notable efficiency improvement compared to traditional lead-based counterparts. Our numerical simulations demonstrate that the optimized lead-free perovskite with structures, n-MASnI3/p-Si heterojunction can reach efficiencies of 27.2%. These findings suggest that lead-free perovskites could serve as a viable, environmentally friendly alternative in the photovoltaic industry.

Distribution and Characteristics of Ammonia Concentration by Region in Korea

In this study, the characteristics of ammonia and their effects on secondary particulate matter (PM) formation were analyzed by region in Korea in 2020. The NH3 concentration was high in GJ (11.4 ppb), a neighboring agricultural area, followed by DJ (9.0 ppb) and SE (8.6 ppb), which are located in urban areas. On the other hand, BI (2.6 ppb) and JI (4.5 ppb), which are background regions, demonstrated a lower concentration than other areas. Seasonally, ammonia was high in spring and summer, and it generally increased when human activities are active. Therefore, it is believed that the ammonia in the atmosphere not only changes depending on local emissions, but also based on temperature-dependent phase distribution characteristics. For SE and GJ, regions with relatively high ammonia concentrations, investigations into the effect of ammonia on secondary PM formation were conducted. In both regions, the ammonium-to-sulfate mole ratio tended to increase with increasing ammonia or PM2.5 concentration. It can be assumed that the PM2.5 concentration increases as nitrates are formed under the ammonia-sufficient condition. The adjusted gas ratio is generally greater than 4, indicating that there is a lot of free ammonia. Thus, it is estimated that a reduction in ammonia would not be effective to restrain nitrate formation.

Modeling nitrogen behavior in Tigris River using system dynamics approach

Nitrogen behavior across multimedia environment like Tigris River is complex process resulting in a number of interactions of the biogeochemical processes. A solid understanding of the interacted processes is critical to evaluate river system performance. Inorganic nitrogen including ammonium ion (NH4+), free ammonia (NH3), total ammoniacal nitrogen (NHx), nitrite (NO2−), nitrate (NO3−), total oxidized nitrogen (NOx), and total inorganic nitrogen (TIN) in Tigris River were examined from April 2018 to March 2020. A simple system model was implemented to simulate and to help interpret the trend of inorganic N forms based on datasets collected from the river system. It is indicated that the obtained results revealed that the dynamic model was able to represent and predict NHx and NOx behavior in Tigris River. Root mean squared errors between actual and predicted concentrations for NHx and NOx were 0.053 and 0.312 g m−3, respectively. Modeling analysis confirmed the steady-state dynamics of NHx and NOx over the course of the study. Average concentration for NHx was 0.37 ± 0.05 g m−3, while mean value of NOx levels was 2.18 ± 0.33 g m−3 in the Tigris river water. The results from this study also supported by the changes of the water budget, chemical oxygen demand, pH, dissolved oxygen, electrical conductivity, and water temperature in the river system. The results suggest that the microbial mechanisms are the principal N transformation processes in the river system. Findings presented in this research could help to improve conceptual understanding of N behavior in Tigris River, and therefore could assist decision makers to select best management practices and to develop mitigation strategies to sustain water quality in Tigris River.

Rapid achievement of partial nitrification process by adopting the combined strategy of anoxic starvation and free ammonia inhibition

ABSTRACT Partial nitrification (PN) is a prerequisite step for the short-cut nitrogen removal process, which is crucial to provide stable nitrite accumulation for subsequent units. The present study innovatively proposed a new strategy for the rapid establishment of PN by adopting short-term anoxic starvation combined with high free ammonia inhibition. The sludge obtained from the secondary sedimentation tank of a municipal wastewater treatment plant was starved for 7 days under anoxic conditions, and then wastewater with high ammonia nitrogen (400 mg L−1) was introduced. Within 17 days, stable nitrite accumulation was achieved in the sequencing batch reactor, and the nitrite accumulation rate reached more than 95.0%. The activity of ammonia monooxygenase enzyme increased from 0.0364 ± 0.0074 to 0.1275 ± 0.0021 μg NO2 −-N·mg−1 protein min−1, while that of hydroxylamine oxidoreductase enzyme increased from 1.5350 ± 0.0208 to 6.3852 ± 0.0400 EU g−1 SS. The relative abundance of Nitrosomonas increased from 0.10% to 25.90%, while that of Nitrospira consistently remained below 0.04%. And the relative abundance of short-cut denitrifying bacteria, including Truepera, OLB8, and OLB13 all increased. The results proved that the short-term anoxic starvation combined with high free ammonia inhibition was an effective strategy for rapid establishment of PN.

Free Ammonia Strategy for Nitrite-Oxidizing Bacteria (NOB) Suppression in Mainstream Nitritation Start-Up

The partial nitritation (PN)–anammox (PN/A) process offers a sustainable alternative to nitrogen management in wastewater treatment, addressing the high costs and increasing the low eco-friendliness associated with traditional nitrification/denitrification processes. Stable partial nitritation (PN) is critical for effective PN/A operation, and this study specifically focused on the need to suppress nitrite-oxidizing bacteria (NOB) to facilitate the enrichment of ammonia-oxidizing bacteria (AOB). Utilizing two sequencing batch reactors (SBRs), PN1 and PN2 with different free ammonia (FA) concentrations, this study aimed to evaluate the NOB suppression strategy while enriching AOB. The PN2 reactor, which operated with a higher initial FA concentration (50 mg/L), successfully maintained high nitritation activity, with 96.1% ammonium removal efficiency (ARE) and 95.1% nitrite accumulation efficiency (NAE) at reduced influent NH4+-N concentrations (50 mg NH4+-N/L, FA 10 mg/L). In contrast, PN1 showed inadequate NOB suppression due to lower FA concentrations (10 mg/L). These results suggest that initiating the nitritation process with higher FA concentrations can effectively suppress NOB, enhancing the stability and efficiency of PN/A processes in mainstream applications.

Assembly process and co-occurrence network of microbial community in response to free ammonia gradient distribution.

The research presented in this paper explores how varying concentrations of free ammonia impact microbial communities in aquatic ecosystems. By employing advanced gene sequencing techniques, the study reveals significant changes in microbial diversity and network structures in response to increased ammonia levels. Key findings indicate that high ammonia concentrations lead to a decrease in microbial richness and diversity while increasing community dissimilarity. Notably, certain microbial groups, like Actinobacteria, show resilience to ammonia stress. This research enhances our understanding of how pollution affects microbial ecosystems and underscores the importance of maintaining balanced ammonia levels to preserve microbial diversity and ecosystem health.

Deciphering pathogens inactivation mechanism during anaerobic co-digestion of food waste and waste activated sludge: The role of pH

Anaerobic co-digestion of waste activated sludge (WAS) with food waste (FW) represents a viable and effective approach to energy recovery and pollutant elimination. Little is known about the effect of alternating change of acid/alkaline conditions on pathogens inactivation within the co-digestion system of WAS and FW. In this study, pH changes during batch anaerobic co-digestion with WAS/FW ratios varying from 0.4 to 8, and their impact on pathogen inactivation were investigated using Escherichia coli as a model pathogen. At WAS/FW=1 and 2, serious acidification (pH<5.5) was effectively mitigated, and the pH transitioned from 6.4 during the acidogenesis stage to >8.5 during the methanogenesis stage. WAS/FW=1 achieved the highest methane yield (256.7 mL/g VS), which was 38.9 % greater than that in their mono-digestion scenario. A 2.37 − 3.87 log10 reduction in E. coli abundance occurred in all tested conditions during the acidogenesis stage, and a further reduction to an undetectable level was achieved only in WAS/FW reaching 1 subsequently. Low pH induced free volatile fatty acids dominated E. coli inactivation during the acidogenesis stage. During the methanogenesis stage, the combined action of OH− and the resultant free ammonia contributed to E. coli inactivation with free ammonia being more efficient in its action. This research contributes to the advancement of sustainable and secure management of organic wastes.

Achieving nitrite shunt using in-situ free ammonia enriched by natural zeolite: Pilot-scale mainstream anammox with flexible nitritation strategy

The mainstream partial nitritation/anammox (PN/A) process represents a significant innovation in decarbonizing municipal wastewater treatment. However, its implementation is considerably hampered by the challenge of stable nitrite supply. In this study, a pilot-scale PN/A system receiving real sewage (20 m3) was operated at room temperature for nearly one year. Remarkable PN performance with relatively high nitrite accumulation ratio of 75.04 ± 10.05 % was obtained via in-situ free ammonia (FA) strategy. The ammonium concentration enriched in the zeolite increased significantly by 548.8 times compared to that in the aqueous phase by ion exchange. This substantial increase robustly inhibited nitrite-oxidizing bacteria (NOB), resulting in high relative abundance ratio of ammonia-oxidizing bacteria (AOB) to NOB of 37.93 ± 12.61 in the zeolite biofilm, compared to 10.22 ± 1.67 in suspended floc sludge. The significant differences in FA concentrations between zeolite biofilm and suspended floc sludge resulted in distinct spatial distribution disparities of AOB and NOB, which were central to achieving stable nitrite accumulation without complex multiple selective pressures. Consequently, compliant effluent with total nitrogen of 10.91 ± 4.23 mg N/L was achieved at 10.4-31.1 °C without external carbon source addition. The biocarriers in the anammox process played a key role in enhancing functional genes and electron flow, supporting anammox-dominated nitrogen removal. This study presents a flexible and adaptable strategy for mainstream nitrite shunting, highlighting its potential for large-scale implementation of mainstream anammox treatment.

Nanoarchitectonics of in Situ Antibiotic-Releasing Acicular Nanozymes for Targeting and Inducing Cuproptosis-like Death to Eliminate Drug-Resistant Bacteria.

A series of progress has been made in the field of antimicrobial use of nanozymes due to their superior stability and decreased susceptibility to drug resistance. However, catalytically generated reactive oxygen species (ROS) are insufficient for coping with multidrug-resistant organisms (MDROs) in complex wound environments due to their low targeting ability and insufficient catalytic activity. To address this problem, chemically stable copper-gallic acid-vancomycin (CuGA-VAN) nanoneedles were successfully constructed by a simple approach for targeting bacteria; these nanoneedles exhibit OXD-like and GSH-px-like dual enzyme activities to produce ROS and induce bacterial cuproptosis-like death, thereby eliminating MDRO infections. The results of in vitro experiments showed that the free carboxylic acid of GA could react with the free ammonia of teichoic acid in the methicillin-resistant Staphylococcus aureus (MRSA) cell wall skeleton. Thus, CuGA-VAN nanoneedles can rapidly "capture" MRSA in liquid environments, releasing ROS, VAN and Cu2+ on bacterial surfaces to break down the MRSA barrier, destroying the biofilm. In addition, CuGA-VAN effectively promoted wound repair cell proliferation and angiogenesis to facilitate wound healing while ensuring biosafety. According to transcriptome sequencing, highly internalized Cu2+ causes copper overload toxicity; downregulates genes related to the bacterial glyoxylate cycle, tricarboxylic acid cycle, and oxidative respiratory chain; and induces lipid peroxidation in the cytoplasm, leading to bacterial cuproptosis-like death. In this study, CuGA-VAN was cleverly designed to trigger a cascade reaction of targeting, drug release, ROS-catalyzed antibacterial activity and cuproptosis-like death. This provides an innovative idea for multidrug-resistant infections.

Performance evaluation and microbial community analysis of a continuous stirred tank reactor–anaerobic ceramic membrane bioreactor system for practical swine wastewater treatment

To treat swine wastewater from a practical piggery, a continuous stirred tank reactor (CSTR)–anaerobic ceramic membrane bioreactor (AnCMBR) was operated for 201 days. A high chemical oxygen demand (COD) removal efficiency of 95 % and biogas production rate of 0.31 L/L·d were achieved at an organic loading rate (OLR) of 1.19 g-COD/L·d. Although the free ammonia concentration reached a maximum of 200 mg/L during the last operational phase, no evident inhibitory effect on AnCMBR performance was observed. Microbial community analyses indicated that six bacterial phyla were responsible for the hydrolysis, acidification, and fermentation of organics and environmental stabilization. Hydrotrophic methanogenic archaea were dominant, indicating that the main methane production pathway involved the use of H2 and CO2 as substrates. The results demonstrated that CSTR–AnCMBR systems exhibit excellent organics removal performance and energy recovery at high organic concentrations and possess strong anti-shock ability. Thus, they represent alternative green and sustainable anaerobic technologies for practical swine wastewater treatment.

Rapid start-up and stable operation of pilot scale denitrification-partial nitritation/anammox process for treating electroplating tail wastewater

This study explored a novel economical and efficient process for treating actual low-ammonia nitrogen electroplating tail wastewater. A pilot scale system of denitrification-partial nitrification/anaerobic ammonium oxidation (DN-PN/A) was constructed and operated for 190 days. The partial nitrification (PN) reactor, filled with zeolite, increased free ammonia concentration beyond the nitrite oxidizing bacteria threshold and successfully supplied NO2−-N, with nitrite accumulation rate exceeding 90 %. Over 109 days, the total nitrogen removal rate achieved was 80.2 ± 7.41 %, and the chemical oxygen demand removal rate reached 79.68 ± 9.53 %. The dominant functional bacteria were Nitrosomonas (5.45 %) and Candidatus Anammoxoglobus (28.84 %) in PN reactor and anaerobic ammonium oxidation (Anammox) reactor. This process, characterized by rapid start-up, strong shock resistance, and low cost, alleviates the pressure of ammonium pollution control, promotes the sustainable development of the electroplating industry and has the potential for application in the treatment of other industrial wastewater.

Proteomic Analysis of the Characteristic Flavor Components in Bacillus subtilis BSNK-5-Fermented Soymilk.

Fermentation with Bacillus subtilis significantly enhances the physiological activity and bioavailability of soymilk, but the resulting characteristic flavor seriously affects its industrial promotion. The objective of this study was to identify key proteins associated with characteristic flavors in B. subtilis BSNK-5-fermented soymilk using tandem mass tag (TMT) proteomics. The results showed that a total of 765 differentially expressed proteins were identified. Seventy differentially expressed proteins related to characteristic flavor were screened through Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. After integrating metabolomics data, fifteen key proteases of characteristic flavor components in BSNK-5-fermented soymilk were further identified, and free ammonia was added. In addition, there were five main formation mechanisms, including the decomposition of urea to produce ammonia; the degradation of glutamate by glutamate dehydrogenase to produce ammonia; the degradation of threonine and non-enzymatic changes to form the derivative 2,5-dimethylpyrazine; the degradation of valine, leucine, and isoleucine to synthesize isovalerate and 2-methylbutyrate; and the metabolism of pyruvate and lactate to synthesize acetate. These results provide a theoretical foundation for the improvement of undesirable flavor in B. subtilis BSNK-5-fermented soy foods.

Metagenomic insights into the influence of pH on antibiotic removal and antibiotic resistance during nitritation: Regulations on functional genus and genes

The changes in pH and the resulting presence of free nitrous acid (FNA) or free ammonia (FA) often inhibit antibiotic biodegradation during nitritation. However, the specific mechanisms through which pH, FNA and FA influence antibiotic removal and the fate of antibiotic resistance genes (ARGs) are not yet fully understood. In this study, the effects of pH, FNA, and FA on the removal of cefalexin and amoxicillin during nitritation were investigated. The results revealed that the decreased antibiotic removal under both acidic condition (pH 4.5) and alkaline condition (pH 9.5) was due to the inhibition of the expression of amoA in ammonia-oxidizing bacteria and functional genes (hydrolase-encoding genes, transferase-encoding genes, lyase-encoding genes, and oxidoreductase-encoding genes) in heterotrophs. Furthermore, acidity was the primary inhibitor of antibiotic removal at pH 4.5, followed by FNA. Antibiotic removal was primarily inhibited by alkalinity at pH 9.5, followed by FA. The proliferation of ARGs mediated by mobile genetic element was promoted under both acidic and alkaline conditions, attributed to the promotion of FNA and FA, respectively. Overall, this study highlights the inhibitory effects of acidity and alkalinity on antibiotic removal during nitritation.

A sustainable, zero-waste approach for production of biohydrogen from chicken manure slurry by hybrid recycling of digestate

This study provides a sustainable approach to produce biohydrogen through the long-term hydrogenic fermentation of chicken manure (CM) in a semi-continuous stirred tank reactor (CSTR) under different organic loading rates (OLRs). To ensure the zero-waste route and sustainability, the total digestate was mechanically separated into liquid and solid fractions. The solid digestate fraction was thermally treated to produce biochar, while the liquid digestate fraction was biologically treated through bioaugmentation with a novel heterotrophic nitrification-aerobic denitrification (HD-AN (bacterial strain (Alcaligenes sp. ME-1). The results showed that the high concentration of free ammonia nitrogen (FAN) contents of CM could inhibit methanogenesis and induce hydrogen production. The ORLs of 2.5, 3.5, 4.5, and 5.5 gVS/L.d imposed to the CSTR resulted in volumetric hydrogen production (VHP) of 643.3 ± 37, 908.8 ± 64.5, 1077.8 ± 95.17, and 1383.3 ± 156.8 mL/L.d, respectively. The microbial community structures indicated the long-term adaptation of hydrogen-producing bacteria and methanogenesis inhibition. The bioaugmentation process removed 83.3 % of total ammonia and 66.2 % of the chemical oxygen demand (COD) from the liquid digestate fraction. The characteristics of the biochar derived solid digestate is suitable for land applications as fertilizer. The hybrid approach combining biohydrogenation, pyrolysis, and bioaugmentation, maximizes the utilization of chicken manure slurry while conforming to the sustainable development goals.