ABSTRACT
A simple, selective, and affordable dual fluorescence-colorimetric indicator for hydrogen sulfide was developed based on a complex of copper nanoparticles and N-doped carbon quantum dots (CuNPs/NCQDs). Real-time and visual freshness tracking of fish was done using a colorimetric indicator by incorporating CuNPs/NCQDs into agar hydrogel (AH-CuNPs/NCQDs). The fluorescence response of the CuNPs/NCQDs solution is quenched upon exposure to H2S. The field-emission scanning electron microscopy image of the AH-CuNPs/NCQDs film revealed a unified structure. The prepared indicator exhibited a good and irreversible response to H2S, with a LOD of 91.36 and a LOQ of 276.86 µM, based on the localized surface plasmon resonance (LSPR) mechanism. The X-ray photoelectron spectrometer and Fourier transform infrared spectrometer results confirmed the formation of a CuS bond in the colorimetric indicator exposed to fish spoilage. The prepared indicator demonstrated good stability and remained unaffected by pH or other volatile compounds. Notably, there was a strong correlation between ΔΕ and fish freshness parameters (pH, TV-BN, and TVC). Light green, pale yellow, and dark yellow colors, respectively, indicated freshness, semi-freshness, and spoilage of fish during storage in the refrigerator. Overall, the prepared indicator can be effectively used for detecting spoilage in meat products as a highly sensitive freshness indicator.
Subject(s)
Agar , Colorimetry , Copper , Fishes , Hydrogels , Hydrogen Sulfide , Quantum Dots , Quantum Dots/chemistry , Animals , Colorimetry/methods , Copper/chemistry , Hydrogels/chemistry , Agar/chemistry , Hydrogen Sulfide/analysis , Hydrogen Sulfide/chemistry , Metal Nanoparticles/chemistry , Carbon/chemistry , Seafood/analysis , Limit of DetectionABSTRACT
Multiple researchers are reporting toxic agar, but the ultimate culprit remains unclear.
Subject(s)
Agar , Saccharomyces cerevisiae , Schizosaccharomyces , Agar/supply & distribution , Agar/toxicity , Saccharomyces cerevisiae/drug effects , Saccharomyces cerevisiae/growth & development , Schizosaccharomyces/drug effects , Schizosaccharomyces/growth & development , Laboratories , Seaweed/chemistry , Seaweed/metabolismABSTRACT
Agar gel immunodiffusion assay (AGID) is a laboratory test which detects specific antigen-antibody interactions by the development of visible precipitation lines in a semisolid matrix. Here we describe the preparation of agar gel plates, the method to test serum samples by AGID for the presence of EHDV antibodies, and the interpretation of test results. This test has known cross-reactivity to bluetongue antibodies; therefore positive samples by this assay require additional confirmatory testing; generally, its use should be limited to healthy animal attestations where required.
Subject(s)
Immunodiffusion , Animals , Immunodiffusion/methods , Hemorrhagic Disease Virus, Epizootic/immunology , Agar/chemistry , Antibodies, Viral/immunology , Antibodies, Viral/blood , SheepABSTRACT
Candida albicans is the most common agent in human fungal infections; nevertheless, in the last decades, the closely related yeasts Candida dubliniensis and Candida africana have emerged as pathogens. The purpose of this study was to compare tobacco agar with another five agars prepared from plant extracts (Origanum vulgare, Rosmarinus officinalis, Solanum rudepannum, Solanum oblongifolium and Brugmansia arborea) on the differentiation of C. albicans complex. The hyphae and chlamyconidia formation and the color and margin of the colonies of 200 clinical isolates of C. albicans, C. dubliniensis and C. africana were evaluated. After seven days of incubation at 28 °C, Tobacco agar, S. rudepannum and B. arborea agars allowed the differentiation of 100 % C. dubliniensis. Additionally, 24% of C. africana isolates produced brownish colonies in the medium prepared from Rosmarinus officinalis (rosemary) extract. These results indicate that S. rudepannun, B. arborea and rosemary agar could be used as screening for the phenotypic differentiation between the species of C. albicans complex. Rosemary agar could be used to aid in the differentiation of C. albicans from C. africana. These culture media based on plants, could be used as simple and inexpensive screening methods in the phenotypic differentiation of C. dubliniensis and C. africana.
Subject(s)
Candida albicans , Culture Media , Plant Extracts , Candida albicans/isolation & purification , Candida/classification , Candida/isolation & purification , Agar , Humans , HyphaeABSTRACT
Nanomedicine has the potential to increase the biostability of drugs to treat retinal diseases, improving their performance and decreasing the required number of intravitreal injections. However, accurate pharmacokinetic studies of these nanoparticle-drug conjugates, nanoparticle motion across the vitreous humour and interaction with the retinal cell layers still need to be investigated. Existing nanoparticle tracking techniques require fluorescent labels, which can impact cytotoxicity, nanoparticles' motion, protein interactions, and cell internalization. In this study, a real-time label-free tracking technology, for single nanoparticles in an optical microscope based on the optical phenomena of caustics, was used to characterise the diffusion of nanoparticles in agar-hyaluronic acid hydrogels, previously validated as vitreous humour substitutes for in vitro models. The results demonstrated that the diffusion of nanoparticles through these hydrogels was heterogeneous, and that nanoparticle size had an important role in nanoparticle distribution across and within in vitro vitreous substitutes. These findings suggest that nanoparticle diameter is a critical parameter for designing novel therapeutics for retinal diseases. Moreover, nanoparticle charge did not affect nanoparticle diffusion or distribution in these synthetic hydrogels. The use of caustics in optical microscopy has been demonstrated to be a reproducible, inexpensive technique for screening novel therapeutics in eye in vitro models.
Subject(s)
Hydrogels , Nanoparticles , Vitreous Body , Hydrogels/chemistry , Vitreous Body/metabolism , Nanoparticles/chemistry , Diffusion , Hyaluronic Acid/chemistry , Hyaluronic Acid/pharmacokinetics , Humans , Agar/chemistryABSTRACT
The goal of the current work was to optimize the growth parameters needed to manufacture agarase enzyme from a non-marine PI strain of Bacillus subtilis on an agar-based medium. Using Plackett-Burman design (PBD), nine process parameters were evaluated, and agar, peptone, and yeast-extract were identified as the most significant independent factors influencing agarase production with confidence levels more than 90%. To evaluate the optimal concentrations of the indicated process parameters on agarase production, the Box-Behnken design (BBD) was applied. After optimization, B. subtilis strain PI produced 119.8 U/ml of agarase, representing a 1.36-fold increase. In addition the agar hydrolysate fermented products contain the liberated oligosaccharide acts as strong antioxidant which has 62.4% scavenging activity. Also, the agarase yields increased (1141.12, 1350.253, 1684.854 and 1921.863 U/ml) after substitution the agar with algal biomass of Carolina officinalis at different concentrations (2, 5, 10 and 15%), respectively. After completing the saccharification process, the resulted hydrolysate was used to produce ethanol through fermentation with Pichia pastoris yeast strain as an economical method giving yields (6.68317, 7.09748, 7.75648 and 8.22332 mg/ml), that are higher than using yeast extract peptone dextrose (YPD) medium (4.461 mg/ml).
Subject(s)
Bacillus subtilis , Biomass , Ethanol , Fermentation , Glycoside Hydrolases , Bacillus subtilis/metabolism , Bacillus subtilis/growth & development , Bacillus subtilis/enzymology , Ethanol/metabolism , Glycoside Hydrolases/metabolism , Culture Media/chemistry , Agar/chemistry , Hydrolysis , Antioxidants/metabolismABSTRACT
Previous studies have shown that larvae of the yellow mealworm, Tenebrio molitor L. (Coleoptera: Tenebrionidae), need a source of moisture to grow and perform well. Currently, much research has been oriented towards the effect of dry feed on larval growth and performance. The effect of different wet feeds as moisture source on the performance traits of T. molitor larvae has not been thoroughly investigated yet. This study aims to investigate in laboratory trials the effect of various gelling agents (agar, carrageenans, guar gum, xanthan gum, sodium alginate, modified starch, and pectin) on the growth and performance of T. molitor larvae. A number of 50 newly emerged larvae obtained from the rearings of the LEAZ were inserted in plastic vials together with 4 g of wheat bran as dry feed. Additionally, 1 g of gelling agents was provided 3 times per week as moisture sources. Carrot slices served as control. Larval survival and weight were recorded weekly until the appearance of the first pupa. Dry feed was replenished when depleted. Our data showed that gelling agents efficiently supported the growth of T. molitor larvae, in terms of larval survival and weight, as well as feed utilization expressed as FCR. Interestingly, carrageenans seem to be the most appropriate gelling agent for T. molitor larvae rearing as it can enhance their weight and is also able to reduce their development time and their specific growth rate.
Subject(s)
Daucus carota , Larva , Tenebrio , Animals , Larva/growth & development , Tenebrio/growth & development , Daucus carota/growth & development , Daucus carota/chemistry , Animal Feed , Plant Gums/chemistry , Gels , Carrageenan/chemistry , Galactans/chemistry , Mannans , Polysaccharides, Bacterial/chemistry , Alginates/chemistry , Agar/chemistryABSTRACT
A novel thermoreversible emulsion gel was successfully prepared with citrate agar (CA) as the sole emulsifier. Compared with native agar gel emulsion, CA gel emulsion (CAGE) formed a stable emulsion gel when the CA concentration was increased to 1.25 % (w/w). Results of time-temperature scanning experiments showed that the emulsion gel rapidly transformed into liquid emulsion when heated to 40-50 °C and then solidified into emulsion gel after cooling to the critical temperature of solidification. The emulsion gel had stable sol-gel transformation ability after seven cycles repeated heating-cooling treatment (HCT) at 85 °C and 4 °C. However, the stability of emulsion gels gradually decreased because of the large-droplet formation during heating, which affected the CA molecular-reconfiguration network structure in cooling. The conjunction analysis of microstructure and properties of the emulsion gel indicated that its stability depended primarily on the spatial repulsion and electrostatic repulsion provided by CA gel, and the main factor driving thermal reversibility was the temperature-responsive gelation performance of CA. The retention of quercetin was >90.23 % after seven HCTs because CAGEG enhanced the homogeneity and stability of the droplets.
Subject(s)
Agar , Emulsions , Gels , Temperature , Agar/chemistry , Emulsions/chemistry , Gels/chemistry , Citric Acid/chemistry , Quercetin/chemistryABSTRACT
In the performed study, a novel fabrication of agar-based nanofibers was electrospun in an asymmetric bilayer dressing for biomedical transdermal patches. The optimal parameters for the fabrication of agar-based nanofibers after optimization were a feed rate of 10 µL/min, a 7 cm collector-to-nozzle distance, a 15 kV applied voltage, and a 700-rpm rotating collector speed. Coaxial nanofibers, as a second asymmetric layer, were produced using polyvinyl alcohol (PVA) with cephalexin hydrate, an antibacterial drug, as the core and agar-PCL as the sheath. The morphology of the developed uniaxial and coaxial nanofibrous layers was analysed using a scanning electron microscope and transmission electron microscopy, respectively. For the formation of bilayer asymmetric structures, the agar-PCL uniaxial layer was fabricated over the layer of coaxial PVA and agar-PCL layers for sustained drug release. The agar-based nanofibrous mats exhibited tensile strength of 7 MPa with 40 % elongation failure, 8-fold increased swelling, enhanced wettability (60° contact angle), and a moisture transmission rate of 2174 g/m2/day. The developed coaxial bilayer mats exhibited antimicrobial activity, hemocompatibility, and cytocompatibility. Overall, this novel agar nanofibrous dressing offers promising potential for advanced biomedical applications, particularly as transdermal patches for efficient drug delivery systems.
Subject(s)
Agar , Nanofibers , Transdermal Patch , Agar/chemistry , Nanofibers/chemistry , Polyvinyl Alcohol/chemistry , Biocompatible Materials/chemistry , Anti-Bacterial Agents/pharmacology , Anti-Bacterial Agents/chemistry , Anti-Bacterial Agents/administration & dosage , Humans , Drug Liberation , Tensile StrengthABSTRACT
The potential of Hylocereus polyrhizus peel (HPP) as a new eco-friendly reinforcement for thermoplastic sago starch/agar composite (TPSS/agar) was investigated. The integration of HPP into TPSS/agar composite aimed to enhance its mechanical and thermal characteristics. The study employed Fourier transform-infrared spectroscopy (FT-IR), Scanning electron microscopy (SEM), Thermogravimetric analysis (TGA), and Differential Scanning Calorimetry (DSC), as well as mechanical, physical properties and soil burial testing to analyse the composites. The results showed a favourable miscibility between the matrix and filler, while at higher concentrations of HPP, the starch granules became more visible. The tensile and impact properties of the composites improved significantly after incorporating HPP at 20 wt%, with values of 12.73 MPa and 1.87 kJ/m2, respectively. The glass transition temperature (Tg) and initial decomposition temperature (Ton) decreased with the addition of HPP. The density of the composites reduced from 1.51 ± 0.01 to 1.26 ± 0.01 g/cm3 as the HPP amount increased. The environmental properties indicated that the composites can be composted, with weight loss accelerating from 35 to 60 % and 61 to 91 % by the addition of HPP in 2- and 4-weeks' time, respectively. The study demonstrates the potential of TPSS/agar/HPP composites as eco-friendly materials for various applications.
Subject(s)
Agar , Cactaceae , Fruit , Starch , Agar/chemistry , Starch/chemistry , Cactaceae/chemistry , Fruit/chemistry , Temperature , Thermogravimetry , Biodegradation, Environmental , Spectroscopy, Fourier Transform Infrared , Calorimetry, Differential Scanning , Tensile StrengthABSTRACT
The controllable formation of anisotropic gel structures is presently sought for the development of foods with novel textures. Here, we used unidirectional freezing to generate agar gels consisting of a honeycomb-like porous network of elongated and aligned pores. A custom-built Peltier system allowed for control of the freezing front velocity throughout the agar gels. A higher freezing velocity (10 µm/s) led to smaller pore sizes compared to the slower freezing velocity tested (2 µm/s). Texture analysis highlighted the significantly higher Young's modulus in the gels when compressed in the axial vs. radial direction - a direct consequence of the unidirectional freezing. The proton spin-spin relaxation time revealed greater water mobility in the unidirectionally frozen gel with larger pores. This study serves as the basis for the development of anisotropic hydrocolloid gels with a tunable microstructure and texture.
Subject(s)
Agar , Freezing , Gels , Agar/chemistry , Gels/chemistry , Anisotropy , Elastic Modulus , Porosity , Water/chemistryABSTRACT
Subject(s)
Antitubercular Agents , Microbial Sensitivity Tests , Mycobacterium tuberculosis , Sensitivity and Specificity , Sputum , Tuberculosis, Multidrug-Resistant , Humans , Prospective Studies , Mycobacterium tuberculosis/isolation & purification , Mycobacterium tuberculosis/drug effects , Tuberculosis, Multidrug-Resistant/diagnosis , Tuberculosis, Multidrug-Resistant/drug therapy , Sputum/microbiology , Antitubercular Agents/pharmacology , Agar , Bronchoalveolar Lavage Fluid/microbiology , Female , Adult , Time Factors , Male , Pleural Effusion/microbiology , Pleural Effusion/diagnosis , Culture Media , Middle AgedABSTRACT
AIMS: Staphylococcus aureus is an opportunistic pathogen whose treatment is further complicated by its ability to form biofilms. In this study, we examine the impact of growing S. aureus biofilms on different polymerizing surfaces, specifically agar and agarose, on the pathogen's tolerance to fluoroquinolones. METHODS AND RESULTS: Biofilms of two methicillin-resistant strains of S. aureus were grown on agar or agarose in the presence of the same added nutrients, and their antibiotic susceptibility to two fluoroquinolones, moxifloxacin (MXF) and delafloxacin (DLX), were measured. We also compared the metabolism and extracellular polymeric substances (EPS) production of biofilms that were grown on agar and agarose. CONCLUSIONS: Biofilms that were grown on agarose were consistently more susceptible to antibiotics than those grown on agar. We found that in biofilms that were grown on agar, extracellular protein composition was higher, and adding EPS to agarose-grown biofilms increased their tolerance to DLX to levels that were comparable to agar-grown biofilms.
Subject(s)
Agar , Anti-Bacterial Agents , Biofilms , Fluoroquinolones , Microbial Sensitivity Tests , Sepharose , Staphylococcus aureus , Biofilms/drug effects , Biofilms/growth & development , Fluoroquinolones/pharmacology , Anti-Bacterial Agents/pharmacology , Staphylococcus aureus/drug effects , Staphylococcus aureus/physiology , Staphylococcus aureus/growth & development , Culture Media/chemistry , Moxifloxacin/pharmacology , Methicillin-Resistant Staphylococcus aureus/drug effects , Methicillin-Resistant Staphylococcus aureus/physiologyABSTRACT
The emptying rate of specific nutrients in enteral formulas is poorly understood, despite the importance of controlling the emptying rate in tube-fed patients. Because of their viscosity, thickened formulas are widely used to avoid gastric reflux and reduce the burden on caregivers. This study examined how thickeners in enteral formulas affected the gastric emptying rates of proteins and carbohydrates. A semi-dynamic gastric model was used to prepare and digest test enteral formulas that contained either no thickeners or agar (0.2%). The amounts of protein and carbohydrates in each emptied aliquot were determined, and the emptying rate was calculated. We found that agar accelerated protein emptying, and an exploratory experiment with agar (0.5%) suggested the possibility of concentration dependence. Additionally, experiments using gellan gum (0.08%), guar gum (0.2%), or carrageenan (0.08%, 0.2%) suggested that protein emptying could vary depending on the thickener type and that carrageenan might slow it. These results could help with the appropriate selection of thickeners added to liquid foods based on the patient's metabolic profile to manage nutrition, not only for tube-fed patients but also for those with oropharyngeal dysphagia or diabetes.
Subject(s)
Dietary Proteins , Enteral Nutrition , Food, Formulated , Galactans , Gastric Emptying , Mannans , Plant Gums , Gastric Emptying/drug effects , Enteral Nutrition/methods , Humans , Mannans/pharmacology , Mannans/administration & dosage , Viscosity , Galactans/pharmacology , Dietary Proteins/administration & dosage , Dietary Carbohydrates/administration & dosage , Carrageenan , Agar , Polysaccharides, Bacterial/pharmacology , Models, BiologicalABSTRACT
Two novel Gram-stain-negative, aerobic, and non-motile strains, designated FZY0004T and YYF002T, were isolated from an agar-degrading co-culture, which was obtained from seawater of the intertidal zone of Yancheng City, the Yellow Sea of China. Strain FZY0004T optimally grew at 28 °C, pH 7.0, and 2-6% NaCl, while strain YYF002T optimally grew at 28 °C, pH 7.5, and 2-4% NaCl. Strain FZY0004T possessed Q-9 as the major respiratory quinone, and its major fatty acids (> 10%) were summed feature 8 (C18:1 ω7c), C16:0, and summed feature 3 (C16:1 ω7c/C16:1 ω6c). The polar lipids identified in strain FZY0004T were phosphatidylethanolamine (PE), phosphatidylglycerol (PG), and several unidentified phospholipids (PL) and lipids (L). On the other hand, strain YYF002T had MK-6 as the predominant respiratory quinone and its major fatty acids consisted of iso-C15:0, iso-C15:1 G, and iso-C15:0 3-OH. The polar lipids identified in strain YYF002T were aminolipid (AL), PE, and several unidentified lipids. Strain FZY0004T shared 99.5% 16S rRNA gene sequence similarity and 90.1% average nucleotide identity (ANI) with T. povalilytica Zumi 95T, and strain YYF002T shared 99.2% 16S rRNA gene sequence similarity and 88.2% ANI with W. poriferorum JCM 12885T. The genomic DNA G + C contents of strains FZY0004T and YYF002T were 54.5% and 33.5%, respectively. The phylogenetic, phenotypic, and physiological characteristics permitted the distinction of the two strains from their neighbors, and we thus propose the names Thalassospira aquimaris sp. nov. (type strain FZY0004T = JCM 35895T = MCCC 1K08380T) and Winogradskyella marincola sp. nov. (type strain YYF002T = JCM 35950T = MCCC 1K08382T).
Subject(s)
Agar , DNA, Bacterial , Fatty Acids , Phylogeny , RNA, Ribosomal, 16S , Seawater , RNA, Ribosomal, 16S/genetics , Seawater/microbiology , DNA, Bacterial/genetics , Agar/metabolism , Fatty Acids/metabolism , Base Composition , Bacterial Typing Techniques , China , Phospholipids/metabolism , Coculture Techniques , Sequence Analysis, DNAABSTRACT
Despite the first-line recommendation of fosfomycin for uncomplicated urinary tract infections (UTIs), there are pressing barriers for optimizing its use for the treatment of non-Escherichia coli Enterobacterales UTI. There are no approved breakpoints for oral use against other Enterobacterales, and the recommended agar dilution (AD) reference method for minimal inhibitory concentration (MIC) determination is largely impractical. Using 160 clinical Klebsiella pneumoniae isolates, we sought to understand rates of skipped wells and MIC imprecision in broth microdilution (BMD) and how that compares to rates of error using AD. Though the Clinical and Laboratory Standards Institute refers to the skipped well phenomena in their recommendation against the use of BMD, there is a paucity of data on its frequency. While AD and BMD produced similar MIC50/90 values (32/256 µg/mL for AD and 64/256 µg/mL for BMD), essential agreement was poor. No-growth wells at concentrations below the MIC occurred in up to 10.9% of wells at a given concentration, as the most frequent scientific error. Growth in concentrations above the measured MIC occurred in up to 3.3% of wells and was seen within three dilutions of the MIC for BMD. Observation of single colonies either at or beyond the measured MIC for AD was also common and occurred up to 8.3% and 2.5% of the time, respectively. The frequent scientific error in both testing methods should prompt re-evaluation of AD guidelines and expansion of MIC testing methods for fosfomycin susceptibility testing, as poor agreement with another method prone to scientific error should not be the main detractor from BMD use.IMPORTANCEDespite the recommendation of fosfomycin for uncomplicated urinary tract infections (UTIs), there are barriers for optimizing its use. There are no approved breakpoints for oral use against other Enterobacterales, and the recommended agar dilution (AD) reference method for MIC determination is largely impractical. The use of broth microdilution (BMD) for fosfomycin testing is not recommended by the Clinical and Laboratory Standards Institute due to unsatisfactory precision and skipped wells-occurrence of no-growth in a single well before the minimal inhibitory concentration (MIC)-and trailing endpoints. We sought to understand rates of skipped wells and growth at concentrations above measured MICs in BMD and how that compares to scientific error using AD. No-growth wells at concentrations below the MIC occurred in up to 10.9% of wells for BMD and single colonies at or beyond measured MICs for AD were also common. Frequent scientific error in both methods should prompt re-evaluation of both AD and BMD for fosfomycin susceptibility testing.
Subject(s)
Anti-Bacterial Agents , Fosfomycin , Klebsiella pneumoniae , Microbial Sensitivity Tests , Fosfomycin/pharmacology , Klebsiella pneumoniae/drug effects , Microbial Sensitivity Tests/methods , Anti-Bacterial Agents/pharmacology , Humans , Urinary Tract Infections/microbiology , Urinary Tract Infections/drug therapy , Klebsiella Infections/drug therapy , Klebsiella Infections/microbiology , Agar , Culture Media/chemistryABSTRACT
Introduction. The absence of a gold-standard methodology for the microbiological diagnosis of urinary tract infections (UTI) has led to insufficient standardization of criteria for the interpretation of results and processing methods, particularly incubation time and culture media.Hypothesis. 48-hour incubation time period and use of blood agar enhances the sensitivity of microorganisms isolated significantly.Aim. To determine the sensitivity of blood agar and Brilliance UTI chromogenic agar, incubating for different periods (24-48 hours), for the detection of positive urine cultures.Methodoloy. Comparisons were made between all possible combinations of media and incubation times. As the gold-standard reference, we used the routine methodology of our laboratory, which involves prior screening with available clinical data, flow cytometry, sediment analysis and/or Gram staining. Screened samples were then cultured on blood agar and chromogenic agar and incubated for 48 hours. Also, based on the results of Gram staining, additional media were added in selected cases.Results. The most significant difference was found between chromogenic agar incubated for 24 hours and blood agar incubated for 48 hours, with the latter method allowing the recovery of 10.14â% more microorganisms (P < 0.0001). Furthermore, the value of performing Gram staining to guide processing was demonstrated, as it avoided the loss of at least 5.14â% of isolates.Conclusions. At least in urological and nephrological patients it is essential to include enriched culture media (blood agar) or to extend the incubation times due to the improvement of the diagnostic sensitivity of urine cultures. Gram staining also can help detect the presence of fastidious microorganisms or mixed infections, indicating whether rich and/or selective media should be included to enhance the diagnostic sensitivity of cultures. If this methodology is not followed, it should be noted that besides fastidious species, fastidious strains of Escherichia coli, Proteus mirabilis, Pseudomonas aerugniosa and Stenotrophomonas maltophilia will also be missed.
Subject(s)
Culture Media , Sensitivity and Specificity , Urinary Tract Infections , Urinary Tract Infections/diagnosis , Urinary Tract Infections/microbiology , Humans , Culture Media/chemistry , Time Factors , Bacteriological Techniques/methods , Bacteriological Techniques/standards , Bacteria/isolation & purification , Bacteria/classification , Bacteria/growth & development , Agar , Urine/microbiologyABSTRACT
Ammonia-oxidizing bacteria (AOB) are ubiquitous on the earth and have broad applications in bioremediation. However, the number of their species with standing in nomenclature and deposited in Microbial Culture Collections still remains low. Moreover, only a few novel species have been reported over the last decades. In this study, we sealed agar in serum bottles to develop a kind of solid agar plate with the oxygen concentration in the headspace maintained at low levels. By using these plates, eight AOB isolates including two novel species were obtained. When AOB cells were grown on the sealed solid agar plates, the time to form visible colonies was largely reduced and the maximum diameter of colonies reached 2 mm, which makes the process of AOB isolation rapid and efficient. Based on five AOB isolates, the headspace oxygen concentration had a significant influence on AOB growth either on solid plate or in liquid culture. Especially, when grown under 21 % O2, the number of colonies formed on solid agar plates was very low and sometimes no visible colony formed. Besides the application on AOB isolation, the sealed solid agar plate was also effective for the enumeration and preservation of AOB cells. When preserved under room temperature for more than ten months, the AOB colonies on the plate could still be recovered. This method provides a feasible way to isolate more novel AOB species from the environment and deposit more species in Microbial Culture Collections.
Subject(s)
Agar , Ammonia , Bacteria , Oxidation-Reduction , Ammonia/metabolism , Bacteria/metabolism , Oxygen/metabolism , Culture Media , Chemoautotrophic GrowthABSTRACT
Ti-metal organic framework (Ti-MOF) doped with carbon dots (CDs) with enhanced antibacterial potential was synthesized using solvothermal-assisted mechanical stirring and used for the fabrication of CMC/Agar-based active packaging films. The incorporation of CD@Ti-MOF not only improved the tensile strength of the CMC/Agar film by 17.4% but also exhibited strong antioxidant activity with 100% of ABTS and 57.8% of DPPH radical scavenging using 0.64 cm2/mL of CMC/Agar/CD@Ti-MOF film. Furthermore, water vapor permeability, oxygen permeability, and ultraviolet light-blocking ability (95.7% of UV-B and 84.7% of UV-A) were improved significantly. The CMC/Agar/CD@Ti-MOF film showed strong antibacterial activity and could inhibit the progress of E. coli up to 8.2 Log CFU/mL and completely stopped the growth of L.monocytogenes after 12 h of incubation. Additionally, CMC/Agar/CD@Ti-MOF film extended the shelf life of cherry tomatoes preserved at 4 °C and delayed the quality degradation, maintaining the visual aspects of the packaging.
Subject(s)
Agar , Anti-Bacterial Agents , Carbon , Food Packaging , Fruit , Metal-Organic Frameworks , Food Packaging/instrumentation , Carbon/chemistry , Fruit/chemistry , Anti-Bacterial Agents/pharmacology , Anti-Bacterial Agents/chemistry , Metal-Organic Frameworks/chemistry , Agar/chemistry , Escherichia coli/drug effects , Escherichia coli/growth & development , Titanium/chemistry , Food Storage , Solanum lycopersicum/chemistry , Solanum lycopersicum/growth & development , Food Preservation/methods , Food Preservation/instrumentation , Quantum Dots/chemistry , Antioxidants/chemistry , Antioxidants/pharmacologyABSTRACT
This work focuses on the potential of agar from the seaweed Gracilaria fisheri to modify the properties of starch foam. The effects of different ratios of glycerol and agar on the properties of starch foams were investigated. All formulations used in this study produced easy-to-handle, smooth, single-use foam trays with no visible cracks. The addition of agar slightly affected the off-white color of the foam but red and yellow color values significantly decreased with increments of agar content. As the agar content was increased, the foam became less dense. A foam produced at a glycerol:agar ratio of 3:7 exhibited the highest values of flexural stress at maximum load (3.23 MPa), modulus (194.46 MPa) and hardness (97.50), and the highest temperature at maximum weight loss (Tmax) (337 °C). Therefore, starch foam modified with agar from Gracilaria fisheri showed suitable physical, mechanical and thermal properties for food packaging, and could possibly be used in the place of expanded polystyrene (EPS) foam.