Effective remediation of fish processing waste using mixed culture biofilms capable of simultaneous nitrification and denitrification

Glycerol/organic acid-based ternary deep eutectic solvents as a green approach to recover chitin with different molecular weight from seafood waste

In this study, we designed a green and efficient approach for the fractionation of high-purity chitin with tunable molecular weights from seafood waste. This was achieved by using ternary deep eutectic solvents (TDESs) composed of choline chloride as a hydrogen bond acceptor, glycerol as the polyol-based hydrogen bond donor, together with lactic acid or malic acid. Two binary DESs and four TDESs were evaluated for their ability to recover chitin. The extracted chitin exhibited not only high yield with excellent protein and mineral removal, but also high purity with similar crystallinity patterns as standard chitin. However, the average molecular weights, viscosity behavior and morphology of chitin extracted by DESs were varied and influenced by organic acid to glycerol molar ratios. The molecular weights of chitin extracted by lactic acid-based TDES ranged from 264 kDa to 541 kDa, but malic acid-based TEDS displayed a stronger depolymerization effect, resulting in chitin with a smaller molecular weight of less than 300 kDa. Lactic acid-based TDES revealed that the purity of chitin remained higher than 92 % after three cycles. This sustainable and environmentally friendly extraction system holds great potential to recover chitin from seafood waste, opening a new era for chitin extraction and applications.

Multifaceted Impacts of Plant-Beneficial Pseudomonas spp. in Managing Various Plant Diseases and Crop Yield Improvement

The modern agricultural system has issues with the reduction of agricultural productivity due to a wide range of abiotic and biotic stresses. It is also expected that in the future the entire world population may rapidly increase and will surely demand more food. Farmers now utilize a massive quantity of synthetic fertilizers and pesticides for disease management and to increase food production. These synthetic fertilizers badly affect the environment, the texture of the soil, plant productivity, and human health. However, agricultural safety and sustainability depend on an ecofriendly and inexpensive biological application. In contrast to synthetic fertilizers, soil inoculation with plant-growth-promoting rhizobacteria (PGPR) is one of the excellent alternative options. In this regard, we focused on the best PGPR genera, Pseudomonas, which exists in the rhizosphere as well as inside the plant's body and plays a role in sustainable agriculture. Many Pseudomonas spp. control plant pathogens and play an effective role in disease management through direct and indirect mechanisms. Pseudomonas spp. fix the amount of atmospheric nitrogen, solubilize phosphorus and potassium, and also produce phytohormones, lytic enzymes, volatile organic compounds, antibiotics, and secondary metabolites during stress conditions. These compounds stimulate plant growth by inducing systemic resistance and by inhibiting the growth of pathogens. Furthermore, pseudomonads also protect plants during different stress conditions like heavy metal pollution, osmosis, temperature, oxidative stress, etc. Now, several Pseudomonas-based commercial biological control products have been promoted and marketed, but there are a few limitations that hinder the development of this technology for extensive usage in agricultural systems. The variability among the members of Pseudomonas spp. draws attention to the huge research interest in this genus. There is a need to explore the potential of native Pseudomonas spp. as biocontrol agents and to use them in biopesticide development to support sustainable agriculture.

Pangenome-driven insights into nitrogen metabolic characteristics of Citrobacter portucalensis strain AAK_AS5 associated with wastewater nitrogen removal

Nitrogen metabolism in the genus Citrobacter is very poorly studied despite its several implications in wastewater treatment. In the current study, Citrobacter portucalensis strain AAK_AS5 was assessed for remediation of simulated wastewater supplemented with different inorganic nitrogen sources. Combination of (NH₄)₂SO₄ with KNO₃ was the most preferred for achieving high growth density followed by (NH₄)₂SO₄ and KNO₃ alone. This was in agreement with highest ammonical nitrogen removal of 92.9% in the presence of combined nitrogen sources and the corresponding nitrate nitrogen removal of 93% in the presence of KNO₃. Furthermore, these removal capacities were validated by investigating the uniqueness and the spread of metabolic features through pan-genomic approach that revealed the largest number of unique genes (2097) and accessory genes (705) in strain AAK_AS5. Of the total 44 different types of nitrogen metabolism-related genes, 39 genes were associated with the core genome, while 5 genes such as gltI, nasA, nasR, nrtA, and ntrC uniquely belonged to the accessory genome. Strain AAK_AS5 possessed three major nitrate removal pathways viz., assimilatory and dissimilatory nitrate reduction to ammonia (ANRA & DNRA), and denitrification; however, the absence of nitrification was compensated by ammonia assimilation catalyzed by gene products of the GDH and GS-GOGAT pathways. narGHIJ encoding the respiratory nitrate reductase was commonly identified in all the studied genomes, while genes such as nirK, norB, and nosZ were uniquely present in the strain AAK_AS5 only. A markedly different genetic content and metabolic diversity between the strains reflected their adaptive evolution in the environment thus highlighting the significance of C. portucalensis AAK_AS5 for potential application in nitrogen removal from wastewater.

Low temperature Moving Bed Bioreactor denitrification as mitigation measure to reduce agricultural nitrate losses

The negative impact of agriculture on the quality of local water streams is widely recognized. Fertilizer residues not taken up by the crops leach into the drainage water and enter the surface water, resulting in eutrophication. Despite various initiatives to prevent this leaching by optimizing fertilizer schemes, the desired effect was not achieved, and the focus has shifted to denitrifying end-of-pipe techniques. Because the available area for installing such treatment systems is often limited, the development of intensified systems is a trend that has emerged recently. In this scope, the main goal of this study was therefore to investigate the suitability of a denitrifying Moving Bed Bioreactor (MBBR) as a low footprint technology, which can compete with conventional technologies. Two parallel lab-scale pilot MBBRs, one at low temperature and one at ambient temperature, were operated for 850 days to investigate the effectiveness and robustness under changing process parameters (hydraulic retention time (HRT), temperature, shutdown). Eventually, the system was scaled up to a full-scale installation and monitored during a full drainage season in the field. The pilot-scale MBBRs achieved removal efficiencies above 90% under optimal conditions (high C/N ratio and minimal HRT of 8 h), even while operating at low temperatures. The robustness of the system was also demonstrated by the immediate start-up after a shutdown period of 220 days. Overall, the full-scale MBBR treated 2910.1 m³ drainage water and removed approximately 59 kg NO₃-N. Unfortunately, the average removal efficiency, i.e., 70%, was lower than the lab-scale system, but by intensifying the mixing in the MBBR, improved results were obtained. Nitrite accumulation was furthermore also prevented.

Role of heterotrophic nitrifiers and aerobic denitrifiers in simultaneous nitrification and denitrification process: A non-conventional nitrogen removal pathway in wastewater treatment

Bacterial species capable of performing both nitrification and denitrification in a single vessel under similar conditions have gained significance in the wastewater treatment scenario considering their unique character of performing the above reactions under heterotrophic and aerobic conditions respectively. Such a novel strategy often referred to as simultaneous nitrification and denitrification (SND) has a tremendous potential in dealing with various wastewaters having low C:N content, considering that the process needs very little or no external carbon source and oxygen supply thus adding to its cost-effective and environmentally friendly nature. Though like other microorganisms, heterotrophic nitrifiers and aerobic denitrifiers convert inorganic or organic nitrogen-containing substances into harmless dinitrogen gas in the wastewater, their ecophysiological role in the global nitrogen cycle is still not yet fully understood. Attempts to highlight the role played by the heterotrophic nitrifiers and aerobic denitrifiers in dealing with nitrogen pollution under various environmental operating conditions will help in developing a mechanistic understanding of the SND process to address the issues faced by the traditional methods of aerobic autotrophic nitrification-anaerobic heterotrophic denitrification.

Simultaneous electricity generation and eutrophic water treatment utilizing iron coagulation cell with nitrification and denitrification biocathodes

Anthropogenic nutrients released into water induce eutrophication and threaten aquatic life and human health. In this study, an Fe anode coagulation cell with nitrification and denitrification biocathodes was constructed for power generation and algae and nutrient removal. The nitrification and denitrification biocathodes achieved maximum power densities of 6.0 and 6.6 W/m³, respectively. The algae (99.2 ± 0.5%), phosphate (97.4 ± 0.6%), and ammonia (23.1 ± 0.2%) were removed by a spontaneous electrocoagulation process in the anode chamber. In the nitrification biocathode chamber, 95.3 ± 1.4% of the ammonia was oxidized within 6 h, and 88.2 ± 2.5% of the nitrate was removed in 10 h in the denitrification biocathode chamber. The microbial community analysis revealed that ammonia removal was attributed to nitrifying bacteria, including Acinetobacter sp., Phycisphaera sp., and Nitrosomonas sp., and the dominant denitrifying bacteria in the denitrifying biocathode chamber were Planococcus sp., Exiguobacterium sp., and Lysinibacillus sp. In this study, the combination of Fe anodes and biocathodes is shown to afford an efficient method for the simultaneous algae and nutrient removal and power generation.