The extracellular electron transfer (EET) efficiency in bioelectrochemical systems has been proven to be dependent on anode potentials. To explore the underlying mechanism, previous studies have ...mainly focused on EET conduit and bacterial biomass but rarely concerned with the role of extracellular polymeric substances (EPS) surrounding electroactive cells. In this study, the response of Geobacter biofilms to anode potentials was investigated with a special emphasis on the mechanistic role of EPS. The electrochemical activities and cell viabilities of Geobacter soli biofilms were simultaneously attenuated at 0.4 and 0.6 V compared to −0.2 and 0 V. It was found that the biofilms (especially the biofilm region closer to electrode surface) grown at −0.2 and 0 V produced relatively more extracellular redox-active proteins and less extracellular polysaccharides, which conferred higher electron accepting/donating capacities to EPS and consequently facilitated EET. Meanwhile, electrically nonconductive extracellular polysaccharide-dominated interior layers were formed in the biofilms grown at 0.4 and 0.6 V, which limited direct EET but might serve as physical barriers for protecting cells in these biofilms from the increasing stress by poised electrodes. These results demonstrated that the production of EPS under different anode potentials might be finely regulated by cells to keep balance between EET efficiency and cell-protection. This study provides a new insight to investigate the Geobacter biofilms coping with various environments, and is useful for optimizing electrochemical activity of anode biofilms.
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•Highest EET and cell viability observed in biofilms grown at −0.2 and 0 V.•Heterogeneity is elucidated in spatial distribution of both viable cells and EPS.•Electrochemical activity of biofilm is positively related to redox activity of EPS.•Polysaccharide-dominated interior layers of EPS in 0.4 and 0.6 V biofilms hinder EET.
l-Asparaginases have the potential to inhibit the formation of acrylamide, a harmful toxin formed during high temperature processing of food. A novel bacterium which produces l-asparaginase was ...screened. Type I l-asparaginase gene from Acinetobacter soli was cloned and expressed in Escherichia coli. The recombinant l-asparaginase had an activity of 42.0 IU mL−1 and showed no activity toward l-glutamine and d-asparagine. The recombinant l-asparaginase exhibited maximum catalytic activity at pH 8.0 and 40°C. The enzyme was stable in the pH ranging from 6.0 to 9.0. The activity of the recombinant enzyme was substantially enhanced by Ba2+, dithiothreitol, and β-mercaptoethanol. The Km and Vmax values of the l-asparaginase for the l-asparagine were 3.22 mmol L−1 and 1.55 IU μg−1, respectively. Moreover, the recombinant l-asparaginase had the ability to mitigate acrylamide formation in potato chips. Compared with the untreated group, the content of acrylamide in samples treated with the enzyme was effectively decreased by 55.9%. These results indicate that the novel type I l-asparaginase has the potential for application in the food processing industry.
•A novel type I l-asparaginase from Acinetobacter soli was characterized.•The recombinant enzyme has high activity over a wide pH range.•AsAsnase exhibited high substrate specificity.•AsAsnase inhibited acrylamide formation in potato chips during frying.
A taxonomic investigation was conducted on four bacterial strains isolated from soil contaminated with polycyclic aromatic hydrocarbons and heavy metals. Phylogenetic analysis revealed that these ...strains belonged to the family Chitinophagaceae. Examination of the 16S rRNA genes indicated that their sequence identities were below 97.6 % compared to any known and validly nominated bacterial species. The genomes of the four strains ranged from 4.12 to 8.76 Mb, with overall G + C molar contents varying from 41.28 % to 50.39 %. Predominant cellular fatty acids included iso-C15:0, iso-C15:1 G, and iso-C17:0 3-OH. The average nucleotide identity ranged from 66.90 % to 74.63 %, and digital DNA-DNA hybridization was 12.5–12.8 %. Based on the genomic and phenotypic features of the new strains, four novel species and two new genera were proposed within the family Chitinophagaceae. The ecological distributions were investigated by data-mining of NCBI databases, and results showed that additional strains or species of the newly proposed taxa were widely distributed in various environments, including polluted soil and waters. Functional analysis demonstrated that strains H1-2-19XT, JS81T, and JY13-12T exhibited resistance to arsenite (III) and chromate (VI). The proposed names for the four novel species are Paraflavitalea pollutisoli (type strain H1-2-19XT = JCM 36460T = CGMCC 1.61321T), Terrimonas pollutisoli (type strain H1YJ31T = JCM 36215T = CGMCC 1.61343T), Pollutibacter soli (type strain JS81T = JCM 36462T = CGMCC 1.61338T), and Polluticoccus soli (type strain JY13-12T = JCM 36463T = CGMCC 1.61341T).
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•Sugar alcohols’ solubility in ionic liquids is modeled by a vast number of models.•Two approaches of activity coefficients and equations of state are examined.•A databank of 13 sugar ...alcohols, 21 ionic liquids, and 653 data points is assessed.•Redlich-Kister model resulted in a 0.82 % (2.77 K) deviation in the entire databank.•Equations of state with temperature-dependent parameters show enhanced precision.
Environmental regulations have recently drawn attention from fossil sources to green materials, among which sugar alcohols (SA) have particular importance due to their vast use in the nutrition, pharmaceutical, and chemical industries. Their properties and equilibrium conditions, including the extraction and solubility behavior utilizing novel solvents such as ionic liquids (ILs), are essential for developing further processes and their optimization. On account of this, the present study aims to develop a comprehensive thermodynamic approach based on simple and accurate tools such as activity coefficient models (ACMs) and equations of state (EoSs), which have not been hitherto addressed. To this end, eleven calculation schemes based on these two approaches were applied to the largest databank investigated thus far (13 SAs, 21 ILs, and 653 data points), and the performance of the models was analyzed. NRTL, free-volume Flory-Huggins (FVFH), and Redlich-Kister (RK) ACMs with different schemes, as well as athermal and ideal solution models, were evaluated and compared against well-known cubic EoSs such as Peng-Robinson (PR) and Valderrama-Patel-Teja (VPT). Benefitting from three adjustable parameters and a simple form, the three-parameter RK model yielded the best results with a 0.82 % (2.77 K) deviation in the entire databank. Moreover, employing temperature-dependent interaction parameters with FVFH ACM (3.55 K, 1.05 %), PR EoS (3.60 K, 1.07 %), and VPT EoS (3.66 K, 1.08 %) improved the accuracy of the calculations remarkably. The results of this contribution prove that thermodynamic models based on NRTL, FVFH, and RK ACMs are the best options for calculating solid–liquid conditions equilibrium of SA-IL systems with a simple and precise calculation procedure, and can therefore be employed for the simulation and optimization tools. This study investigates the most extensive SA-IL databank, a large number of models from different routes, and the nature of SA-IL pairs employing the obtained parameters.
•Preparation of cellulose supported promising magnetic sorbents (CMS) is summarized.•Physical performance of the magnetic nanoparticles is discussed.•Chemical attraction of magnetic nanoparticles ...towards cellulose substrates is summarized.•CMS in the field of heavy metal, organic pollutants, and protein adoption is discussed.•Advantages, challenges, and future of CMS in magnetic solid-phase extraction are provided.
Cellulose with ample hydroxyl groups is considered as a promising supportive biopolymer for fabricating cellulose supported promising magnetic sorbents (CMS) for magnetic solid-phase extraction (MSPE). The easy recovery via external magnetic field, and recyclability of CMS, associated with different types and surface modifications of cellulose has made them a promising sorbent in the field of solid-phase extraction. CMS based sorbent can offer improved adsorption and absorption capabilities due to its high specific surface area, porous structure, and magnetic attraction feature. This review mainly focuses on the fabrication strategies of CMS using magnetic nanoparticles (MNPs) and various forms of cellulose as a heterogeneous and homogeneous solution either in alkaline mediated urea or Ionic liquids (ILs). Moreover, CMS will be elaborated based on their structures, synthesis, physical performance, and chemical attraction of MNPs and their MSPE in details. The advantages, challenges, and prospects of CMS in future applications are also presented.
•Genome analysis of previously unknown strain Acinetobacter soli ANG344B.•Demonstrated 2-PE production that is unprecedented for bacterial strains.•Possibilities for developing environmentally ...friendly strategies for 2-PE production.
A bacterium, Acinetobacter soli ANG344B, isolated from river water, exhibited an exceptional capacity to produce 2-phenylethanol (2-PE) using L-phenylalanine (L-Phe) as a precursor—a capability typically observed in yeasts rather than bacteria. Bioreactor experiments were conducted to evaluate the production performance, using glucose as the carbon source for cellular growth and L-Phe as the precursor for 2-PE production. Remarkably, A. soli ANG344B achieved a 2-PE concentration of 2.35 ± 0.26 g/L in just 24.5 h of cultivation, exhibiting a global volumetric productivity of 0.10 ± 0.01 g/L.h and a production yield of 0.51 ± 0.01 g2-PE/gL-Phe, a result hitherto reported only for yeasts. These findings position A. soli ANG344B as a highly promising microorganism for 2-PE production.
Whole-genome sequencing of A. soli strain ANG344 revealed a genome size of 3.52 Mb with a GC content of 42.7 %. Utilizing the Rapid Annotation using Subsystem Technology (RAST) server, 3418 coding genes were predicted, including genes coding for enzymes previously associated with the metabolic pathway of 2-PE production in other microorganisms, yet unreported in Acinetobacter species. Through gene mapping, 299 subsystems were identified, exhibiting 30 % subsystem coverage. The whole genome sequence data was submitted to NCBI GeneBank with the BioProject ID PRJNA982713. These draft genome data offer significant potential for exploiting the biotechnological capabilities of A. soli strain ANG344 and for conducting further comparative genomic studies.
We report the results of detailed investigations on structural and magnetic properties of polycrystalline GdFeO3 compound. Temperature-dependent magnetization studies support an antiferromagnetic ...transition at TN(Gd3+) ∼ 2.8 K associated with Gd3+ spins. A clear spin-flop type metamagnetic transition associated with Gd3+ sub-lattice is observed in field-dependent magnetization measurements made across TN(Gd3+). The compound also shows a weak hysteresis behaviour linked to canted Fe3+ moments near-zero field region, with a remnant magnetization of ∼0.022 μB.
•Low-temperature magnetization measurements of polycrystalline GdFeO3.•Metamagnetic Transition in GdFeO3.•Plausible ground state spin structure of GdFeO3.•Weak ferromagnetic behaviour due to Dzyaloshinskii–Moriya interaction in GdFeO3.
Background & Objective: The emergence of antibiotic-resistant bacteria and limited treatment options for these infections is a challenging problem in the world. There is increasing interest in ...isolating bioactive molecules from actinobacteria and elucidating their antimicrobial mechanisms at the moment. The current study aimed to investigate the antimicrobial activities of a Nocardia strain (N4) that was previously isolated from the soil samples in Tehran, Iran.
Materials & Methods: The cultural, morphological, and physiological characteristics of the strain were determined and the identity of the strain was confirmed using 16SrRNA gene sequencing. The strain was screened for antimicrobial metabolite production. The in vitro anti-microbial activity of the extracted metabolite was assessed by agar well diffusion and minimum inhibitory concentrations methods. Finally, the structure of the extracted metabolite was confirmed by HPLC and mass spectrometry methods.
Results: The isolate shared 99% sequence similarity with Nocardia soli. The strain showed broad-spectrum antimicrobial activities against some pathogenic bacteria (Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Klebsiella pneumoniae ATCC 700603, Salmonella Typhimurium ATCC 14028 and Shigella sonnei RI366) and fungi (Aspergillus niger ATCC 1015 and Aspergillus fumigatus ATCC 1022) in the agar well diffusion method. The ethyl acetate extract of the strain exhibited the highest antimicrobial activity against E. coli (MIC= 4.67±3.055 μg/mL) and K. pneumoniae (MIC=3.33±1.155 μg/mL). The metabolite showed high similarity with C2 1H28N7 O14.
Conclusions: The current study confirmed the presence of a bioactive metabolite in strain N4, suggesting that this may be a promising candidate for discovering bioactive components with broad antibacterial activities against a variety of pathogens.
