Increasing Incubation Time Research Articles

Stabilizing effects on a Cd polluted coastal wetland soil using calcium polysulphide

In this study, different dosages of calcium polysulphide (CaSx) were used as an amendment to investigate effects on the immobilizing of Cd in a wetland soil by pot experiment. In addition to chemical analysis (pH and bioavailable Cd concentration), changes in soil enzyme activities, microbial carbon utilization capacity, metabolic and community diversity were examined to assess dynamic impacts on soil environmental quality and toxicity of Cd resulting from ameliorant dosing. Soil pH increased immediately upon CaSx amendment compared to the unamended control (CK), and then declined slowly to a level lower than CK. Diethylenetriamine pentaacetic acid (DTPA) extractable Cd concentration was determined to characterize the bioavailability of Cd in the soil. The CaSx dose-dependent effect observed that with increasing CaSx dosage, the immobilizing efficiency decreased. Soil urease and catalase activity assays and Biolog EcoPlate assay indicated that early stage addition of CaSx significantly inhibited soil microbial activities. However, mid and late stage time periods showed the inhibition effects were alleviated, and the microbial activities could be recovered in 1% and 2% CaSx treatments. Moreover, with increasing incubation time, microbial community diversity and richness were significantly recovered in 1% and 2% CaSx treatments compared to the CK. No considerable changes were observed in the 5% CaSx treatment. Conclusively, the 1% CaSx amendment was an efficient and safe dosage for the stabilization of Cd contaminated wetland soil. This study contributes to the development of in situ remediation ameliorants and technologies for heavy metal polluted wetland soils.

Crosslinked pectin nanofibers with well-dispersed Ag nanoparticles: Preparation and characterization

Nanofibers with well-dispersed Ag nanoparticles (AgNPs) are promising for some applications. Dispersion electrospinning is a straightforward preparation method but is suffered from the negative effects that the further treatments of nanofibers after electrospinning may bring to the dispersed AgNPs. In this study, we report a post reduction method to fabricate nanofibers with well-dispersed AgNPs. Crosslinked nanofibers of a hydrophilic polysaccharide, pectin, are used. When being immersed in the aqueous solution of AgNO3, the crosslinked pectin nanofibers swell, allowing Ag+ ions enter inside. The surrounding crosslinked pectin macromolecules functionalize as in situ reducing reagents to reduce Ag+ ions, nucleating the crystallization of AgNPs locally. X-ray diffraction characterizations indicate that the formed AgNPs are face-centered cubic crystalline. Results of optical imaging, UV–vis spectroscopy, scanning electron microscopy (SEM), electron dispersive spectrometry as well as transmission electron microscopy (TEM) indicate that the content and size of AgNPs increase with the increase of AgNO3 concentration and incubation time. SEM and TEM results show that the dispersion of the AgNPs does not affect the nanofibrous structure and size of the crosslinked pectin nanofibers. TEM results also demonstrate that AgNPs distribute homogeneously along both the length and diameter direction of nanofibers. The composite nanofibers can sustainably release silver for 4 weeks and inhibit the growth of Escherichia coli for 7 days, showing great potential as long-term antibacterial materials. The method may also be used to disperse AgNPs in other hydrophilic nanofibers which need further treatments after electrospinning.

Abstract 608: IFN-γ elicits stimulatory MHC class I isotypes in human colorectal carcinoma cell lines with genetic features of microsatellite stable

Abstract Background: Immunotherapy, especially anti-programmed cell death protein 1 (PD-1) antibodies, has yielded significant and durable tumor response in melanoma, renal cell carcinoma, and other cancer types. In contrast, immunotherapy applied major breakthrough achievement only on patients with microsatellite instability high (MSI-H) metastatic colorectal cancer (mCRC). However, MSI-H mCRC comprised only 1.8-4% of total mCRC patients. It is crucial to investigate immune pathways to develop a new strategy for immunotherapy in treatment of microsatellite stable (MSS) mCRC. Recently, some evidences indicate that interferon (IFN)-γ pathway is critical for anti-PD-1 therapy. In this study, we emphasized on evaluating the response of MSS CRC cell lines to IFN-γ. Methods: We characterized two MSS CRC cell lines, namely SW480 (KRAS G12V mutation, BRAF wild type) and COLO320 (KRAS wild type, BRAF wild type) for our studies. The impacts of interferon-γ (IFN-γ) on cell surface expressions of different isotypes of major histocompatibility complex (MHC) class I and MHC class 1 related molecule A/B (MICA/B, the NK cell ligand) were explored. Different concentration of IFN-γ with different incubation time were also examined. Results: Both cell lines demonstrated low baseline human leukocyte antigen (HLA)-ABC and HLA-BC expression and the expression significantly increased in response to IFN-γ stimulation. We further focused on the SW480 cell line. The SW480 demonstrated low expression of all MHC class I isotypes, including HLA-ABC, HLA-BC, HLA-A, HLA-C, HLA-E, HLA-F, HLA-G and NK cell ligand MICA/B. The IFN-γ specifically stimulated the expression of HLA-A, but all other isotypes were not responsive to IFN-γ stimulation. In summary, IFN-γ significantly stimulates the expression of HLA-ABC, HLA-BC and HLA-A without stimulating HLA-C. The NK cell ligand MIC A/B was also not responsive to IFN-γ stimulation. The stimulatory effect of HLA-ABC and HLA-A in response to IFN-γ stimulation was positively correlated with IFN-γ dosage, which demonstrated highest expression level in response to 800U/ml IFN-γ stimulation. The stimulatory effect in response to IFN-γ stimulation was also positively correlated with increased incubation time with IFN-γ. Conclusion: These findings reveal that regardless of their KRAS mutation status, both MSS CRC cell lines possess a phenotype that may be not responsive to anti-PD-1 therapy due to low expression of MHC class I molecules. The IFN-γ specifically elicits the expression of stimulatory isotype, HLA-A and HLA-B, without eliciting all other inhibitory MHC class I isotypes. These results indicated that IFN-γ demonstrated pure adaptive immune stimulatory effect on CRC cell lines. Analysis of T- and NK cell-responsive immune markers along with IFN-γ signaling pathway may help us to survey possible combination therapy with anti-PD-1 treatment in CRC. Citation Format: Yi-Hsin Liang, Kuan-Yu Chan, Chang-Cheng Lee, Te-Jung Chen, Ann-Lii Cheng, Kun-Huei Yeh. IFN-γ elicits stimulatory MHC class I isotypes in human colorectal carcinoma cell lines with genetic features of microsatellite stable [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 608.

The regulation of DLTA gene in bacterial growth and biofilm formation by Parvimonas micra.

To evaluate the effect of dltA-deficient mutant on the bacterial growth and biofilm formation by P. micra ATCC 33270. Parvimonas micra contributes to many human polymicrobial infections, and is common in dental plaque biofilms of patients with periodontal and endodontic conditions. Lipoteichoic acid (LTA) performs several functions in gram-positive bacteria, including maintenance of cationic homeostasis and modulation of autolytic activities. The activation of dltA gene expression protects LTA expressing gram-positive bacteria from innate immune anti-microbial defense. Deficient mutant of the dltA gene was created from P. micra ATCC 33270 by homologous recombination. Colony-forming units (CFUs) and turbidity helped estimate the growth of P. micra. Crystal violet staining, Confocal Scanning Laser Microscopy (CSLM) and Scanning Electron Microscopy (SEM) evaluated biofilm mass and structure. P. micra ATCC 33270 with dltA-deficient mutant was successfully established. CFUs of the wild-type strains were significantly higher than that of the dltA-deficient mutant strains after 24 h, 48 h, 72 h and 7 d culture (all p < 0.05). The growth rate of dltA-deficient mutant strains was significantly lower than their wild-type counterparts. Furthermore, crystal violet staining showed that the dltA mutant formed significantly less biofilm as compared to wild-type strains. The dltA-deficient mutant synthesized a thin and incomplete biofilm after incubation for 48 h. With increasing incubation time, all biofilm units were seen to shrink, and this structure almost disappeared after 7 days of culture as observed by CSLM and SEM. The dltA gene is associated with bacterial growth and biofilm formation by P. micra ATCC 33270.

The anti-tumor effect of regorafenib in lung squamous cell carcinoma in vitro

Lung squamous cell carcinoma (LSCC) is a common type of non-small-cell lung cancer (NSCLC) and lacks effective treatment. Regorafenib, an oral multikinase inhibitor, has demonstrated promising anti-tumor activity in various solid tumors. To study whether regorafenib inhibits LSCC cells, we investigate the compound in several LSCC cell lines and explore the possible mechanism. In this study, we confirmed that regorafenib had anti-proliferation effect on LSCC cell lines by inducing G0/G1 arrest. In addition, glycogen synthase kinase 3β (GSK3β) remained at the same level and Ser9 phosphorylation of GSK3β decreased with increasing incubation time and increasing regorafenib concentration in LSCC cells. GSK3β inhibition enhanced the anti-tumor activity of regorafenib. Thus, GSK3β activation restricted the anti-cancer effect of regorafenib on LSCC. In conclusion, regorafenib might be a promising drug for LSCC therapy. GSK3β might be a potential target to increase the anti-tumor effect of regorafenib in LSCC cells.

Degradation of Chrysene by Enriched Bacterial Consortium.

Chrysene is a high molecular weight (HMW), polycyclic aromatic hydrocarbon (PAH) known for its recalcitrance and carcinogenic properties and sparsely soluble (0.003 mg/L) in aqueous medium. Due to these refractory properties, bioavailability of chrysene is very low and therefore is persistence in the environment escaping the metabolism by microorganisms. However, few bacterial and fungal strains are reported to degrade chrysene, but with lower efficiency, requiring additional/extraneous carbon sources (co-substrates) for it’s complete mineralization. In this study, development, enrichment and characterization of bacterial consortium ASDC, consisting of Rhodococcus sp., ASDC1; Bacillus sp. ASDC2; and Burkholderia sp. ASDC3 were reported. Chrysene was utilized as a sole source of carbon and energy by the consortium, having maximum degradation rate of 1.5 mg/L/day and maximum growth rate of 0.125/h, under optimized conditions of pH 7.0, 37°C under aeration of 150 rpm on gyrating shaking. Chrysene degradation was unaffected in presence of other PAHs like pyrene, fluoranthene, naphthalene, phenanthrene, benzene, toluene and xylene, individually as well as in mixture. The results revealed that peptone, ammonium nitrate, sodium succinate have enhanced the chrysene degradation rate during first 24 h of experimentation, which was later on inhibited with increase in incubation time. The chrysene degradation was inhibited by mercury even at lower concentration (1 mM). The results also revealed that SDS has enhanced its degradation by 5.2-fold for initial 24 h of growth, but with increasing in the incubation period, it decreases by 1.2-fold on 7th day of experimentation. The HPLC studies suggested that chrysene was degraded through phthalic acid pathway by the consortium ASDC and the stoichiometric measurements indicated the complete mineralization of chrysene. The flask scale results were validated at simulated microcosm models, where enriched consortium ASDC exhibited maximum degradation (96%) in polluted, non-sterile soil sediment, indicating that consortial strains along with indigenous metabolism showed synergistic metabolism for degradation of chrysene. Thus, the above study revealed the useful enrichment of bacterial community for synergistic degradation of PAHs (chrysene) which could be further exploited for in situ remediation of PAH contaminated sites.

A novel technique for aflatoxin M1 detoxification using chitin or treated shrimp shells: in vitro effect of physical and kinetic parameters on the binding stability.

This study aimed to investigate the ability of chitin and heat-treated shrimp shells to bind aflatoxin M1 (AFM1) in liquid matrix. Several concentrations of chitin or shrimp shells (grinded and ungrinded) were incubated in AFM1-contaminated phosphate-buffered saline (PBS) at different incubation times. The stability of the formed adsorbent-AFM1 complex was also tested in milk at different incubation times and temperatures. The unbound AFM1 was quantified by HPLC. Thereby, the percentages of the initial bounded AFM1 varied between 14.29 and 94.74%. Interestingly, in milk, an increase in incubation time coupled with a decrease in temperature affected positively the amount of bounded AFM1 to chitin and negatively those bounded to ungrinded shells. Results also revealed a partial reversibility in the binding of AFM1 to these adsorbents. These findings provided strong evidence on ability of chitin or shrimp shells by-product to bind AFM1 in milk and in PBS.

Probing DNA damage induced by common antiviral agents using multiple analytical techniques

Hepatocellular carcinoma is one of the most common malignant tumors in the world. Chronic hepatitis B and C infections are the most common etiologies of hepatocellular carcinoma worldwide. In this study, we explore the potential DNA damaging effect of some FDA-approved antiviral drugs which may be able to serve as anticancer agents for hepatocellular carcinoma, in order to better elucidate their mode of action. Five antiviral drugs were selected; ribavirin, sofosbuvir, tenofovir disoproxil fumerate, daclatasvir and ledipasvir. Several methods, including absorption spectroscopy, MALDI-TOF mass spectrometry and fluorimetric analysis using the EvaGreen (EG) intercalating dye, were used to probe the drug-induced DNA damage. Results show that only daclatasvir and ledipasvir induced DNA damage. Absorption spectroscopy showed hyperchromicity in the 260-nm DNA absorption band of DNA samples incubated with each drug, indicating disruption of the double-strand structure. Mass spectra for DNA samples incubated with each of the two drugs showed a disappearance of the DNA molecular ion peak with a concomitant appearance of peaks with smaller m/z, indicating DNA strand breaks. EG fluorescence was observed to decrease with increasing incubation time of daclatasvir and ledipasvir with DNA, indicating that the EG detaches from the DNA, likely due to DNA damage. All of these results are consistent with DNA damage, proposed as oxidative damage to both nucleobase and deoxyribose moieties of DNA as the mode of action for these two drugs. Moreover, these results are dependent on the antiviral drug concentration and show that DNA regions rich in guanine are affected more than other regions by these two drugs. Therefore, such antiviral drugs may present a promising therapeutic alternative to the currently used anticancer agents, especially for hepatitis B and C patients with hepatocellular carcinoma resistant to conventional treatment approaches.

Effect of Surface Tension Anisotropy and Welding Parameters on Initial Instability Dynamics During Solidification: A Phase-Field Study

The effects of surface tension anisotropy and welding parameters on initial instability dynamics during gas tungsten arc welding of an Al-alloy are investigated by a quantitative phase-field model. The results show that the surface tension anisotropy and welding parameters affect the initial instability dynamics in different ways during welding. The surface tension anisotropy does not influence the solute diffusion process but does affect the stability of the solid/liquid interface during solidification. The welding parameters affect the initial instability dynamics by varying the growth rate and thermal gradient. The incubation time decreases, and the initial wavelength remains stable as the welding speed increases. When welding power increases, the incubation time increases and the initial wavelength slightly increases. Experiments were performed for the same set of welding parameters used in modeling, and the results of the experiments and simulations were in good agreement.

Visualization of Mechanochemically-Assisted Degrafting of Surface-Tethered Poly(Acrylic Acid) Brushes.

We report visualization of mechanochemically assisted degrafting of surface-tethered poly(acrylic acid) (PAA) brushes in a basic aqueous buffer at nanometer to micrometer length scale by monitoring changes in local etching of silicon substrates. PAA brushes were prepared by surface-initiated atom transfer radical polymerization and incubated in 0.1 M ethanolamine buffer (pH 9.0) with 0.5 M NaCl. Morphological changes of the underlying substrates were monitored by scanning electron microscopy and atomic force microscopy. The appearance of regular-shaped pits indicated etching of the substrate, and both their number and size grew with increasing incubation time. We compared the etching behaviors for PAA, poly(methyl methacrylate) (PMMA), and poly(poly(ethylene glycol) methacrylate) (PPEGMA) brushes grafted on silicon substrates. After incubation for 7 days, the substrate of PMMA brush remained intact. In PAA brush systems, we detected the formation of a few large pits whose size grew in time. Many pits showed up on the substrate of PPEGMA brush but with substantially smaller size compared to PAA. Our findings suggest that hydrophobicity and stability of the grafted polymers play an important role in the morphological changes of the underlying silicon substrates under given incubation conditions.

Effects of incubation conditions on nutrient mineralisation rates in fish and shrimp

Abstract Consumer mineralisation of nutrients can affect ecosystem processes, such as primary productivity, community respiration and biogeochemical cycling. Researchers have not tested, however, the influence of standard incubation methods on mineralisation rates. Therefore, the influence of varied incubation methods on consumer mineralisation rates is poorly understood. Here, we investigated how incubation conditions affected the mineralisation rates of ammonium and phosphate of two species of fish and two species of shrimp. For each species, we measured mineralisation rates during the day and at night in two incubation environments (standard and modified to reduce stress). We also estimated the effect of conspecific density (1, 3 or 5 individuals) and the duration of incubation (after 15, 30, 45, 60 and 75 min) on mineralisation for a species of shrimp. Our results indicated mass‐specific N mineralisation by three species was influenced by the time of day, and for two of the species, mass‐specific N mineralisation was also influenced by incubation conditions. Mass‐specific mineralisation rates for both N and P by a species of shrimp decreased significantly with increasing incubation time, but we did not detect significant differences in mineralisation among incubation durations or densities for either element. Mass‐specific mineralisation rates for P were negatively correlated with body size for all studied species, as previously reported. Only the two species of shrimp showed the expected negative relationship between mass‐specific N mineralisation rates and body size. Our results suggest that the mechanisms by which organisms excrete elements are differentially influenced by incubation conditions. Our study highlights the need to develop methods specific to the organisms of interest, especially the duration and the time of day of the incubation. Additionally, our attempt to influence mineralisation rates by modifying chamber design was mostly ineffective, indicating that this measure may not be a priority for future studies.

Quantification of ascorbyl adducts of epigallocatechin gallate and gallocatechin gallate in bottled tea beverages

Catechins are the major bioactive compounds existing in tea leaves (Camellia sinensis). Dehydroascorbic acid is (DHAA) a reactive dicarbonyl species and previous studies have demonstrated that catechins could effectively trap DHAA to form ascorbyl adducts of catechins, especially epigallocatechin gallate (EGCG). Since catechins in the aqueous solution are unstable due to their structural features, ascorbic acid (AA) is usually added to bottled tea beverages to protect catechins. However, whether ascorbyl adducts of catechins are formed in bottled tea beverages remains unclear. In this study, formation of ascorbyl adducts of EGCG increased along with increased incubation time when EGCG and AA were dissolved in the aqueous solution. Next, 6C-DHAA-EGCG and 8C-DHAA-EGCG were detected in both green tea and oolong tea beverages, and their concentrations ranged from 0.23 to 1.95 µM and 0.28 to 1.97 µM, respectively. Furthermore, an 8C-ascorbyl adduct derived from gallocatechin gallate was also found in some tea beverages.

Fiber length and concentration: Synergistic effect on mechanical and cellular response in wet-laid poly(lactic acid) fibrous scaffolds.

In the area of biomaterials, fibers not only offer increased mechanical response, but also serve as an extracellular matrix mimicking morphology to direct cellular attachment and proliferation. While biologically similar in morphology, soft, and flexible hydrogel materials have low mechanical properties. For applications in tissue engineering, the lack of directional cues and attachment regions within the biogels is undesired as cells require a guide for adequate attachment and organized proliferation. In this work, we have investigated the role of poly(lactic acid) (PLA) fiber length and concentration as a reinforcement phase in a gelatin hydrogel matrix and the resultant mechanical and cellular responses. With increasing fiber length and concentration, the ultimate tensile strength, modulus, and toughness increased for the samples. Similarly, for shorter fiber lengths, the loss and storage modulus increased with fiber concentration. After seeding human mesenchymal stem cells (hMSCs) onto the neat fibrous scaffolds it was found that the fabrication process imparted no cytotoxicity. Furthermore, it was the concentrations and lengths of fiber both caused discernable differences in cell viability at the extreme values. Fibers of all lengths, when in a 4.0 wt % concentration, had a decrease in cell viability after 10 days while the 12.7 mm fibers showed a similar response at 2.0 wt %, but all stayed about 90% viability. With increased incubation time, hMSCs became elongated with increased proliferation. These results indicate that the wet-lay process is a rapid and scalable method by which fibrous 3D-scaffolds can be produced to reinforce hydrogel matrices. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 107B: 332-341, 2019.

Immunochemical studies on native and glycated LDL – An approach to uncover the structural perturbations

Glycation initiates with the non-enzymatic reaction of amino group of proteins and lipoproteins by carbonyl group of sugar moiety and intermediates of glycative stress such as methylglyoxal (MG). The initial glycation leads to the formation of early glycation products (Amadori products) which undergo rearrangement, cyclization and dehydration to form advanced glycation end products (AGEs). The main objective of the present study is to investigate the non-enzymatic glycation of low density lipoprotein (LDL) by MG at different concentration and at increasing incubation time period in vitro. This modification may increase the formation of Amadori products and AGEs which are physico-chemically characterized with respect to the extent of LDL modification. Additionally, immunogenicity of native and MG modified LDL (MG-LDL) was probed in female rabbits in vivo. Immunogenicity of MG-LDL was found to be highly immunogenic, eliciting high titer immunogen-specific antibodies while native form of LDL is less immunogenic. Furthermore, the histopathology and immune-fluorescence studies suggest that the kidney section of immunized rabbits exhibit the presence of immune complex (MG-LDL-IgG) deposition in the glomerular basement membrane (GBM).

Evaluation of Carbazeran as an Enzyme‐Selective Substrate of Human Aldehyde Oxidase: Evidence for Regiospecific Oxidation of Carbazeran by CYP1A2, CYP2D6, CYP3A4, and CYP3A5

Aldehyde oxidase‐1 (AOX‐1) is a cytosolic xenobiotic‐metabolizing enzyme that has gained increasing interest because of its emerging role in drug metabolism and toxicity. It is a catalyst of carbazeran 4‐oxidation, resulting in the formation of 4‐oxo‐carbazeran. However, cytochrome P450 is also a catalyst of oxidative reactions. Therefore, we tested the hypothesis that cytochrome P450 and AOX‐1 catalyze carbazeran 4‐oxidation in the endoplasmic reticulum and cytosol, respectively. Incubations containing human liver microsomes with or without NADPH yielded 4‐oxo‐carbazeran, but to a lesser extent than that in incubations containing human liver cytosol. Cytochrome P450 inhibitors (1‐aminobenzotriazole and ketoconazole) did not decrease the extent of carbazeran 4‐oxidation in liver microsomes, whereas an AOX‐1 inhibitor (hydralazine) decreased it in liver cytosol. Human recombinant CYP1A2, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP3A4, and CYP3A5 did not catalyze carbazeran 4‐oxidation, in contrast to the catalysis by recombinant AOX‐1. The extent of carbazeran 4‐oxidation in incubations containing liver microsomes was attributed to the presence of AOX‐1 in the microsomal preparations, as indicated by the decrease in carbazeran 4‐oxidation by an AOX‐1 inhibitor (hydralazine) and the detection of AOX‐1 protein in liver microsomes (at a level that was up to one‐third of that in liver cytosol). Cytosolic sulfotransferases‐catalyzed dehydroepiandrosterone sulfation increased with increasing amount of microsomes, indicating that the two lots of hepatic microsomes are contaminated with not only AOX‐1, but also other cytosolic enzymes. An isomer of 4‐oxo‐carbazeran, putatively identified as 5‐hydroxy‐carbazeran or 8‐hydroxy‐carbazeran, was detected in incubations containing carbazeran and CYP1A2, CYP2D6, CYP3A4, or CYP3A5. The 5‐hydroxy‐carbazeran or 8‐hydroxy‐carbazeran peak was detected in human liver microsomal incubation and the peak area increased with increasing incubation time. The 5‐hydroxy‐carbazeran or 8‐hydroxy‐carbazeran peak was decreased by a pan‐CYP inhibitor (1‐aminobenzotriazole), but not by an AOX‐1 inhibitor (hydralazine). The addition of 1‐aminobenzotriazole increased the 4‐oxo‐carbazeran formation, indicating a shunting of carbazeran metabolism to AOX‐1 in the presence of the CYP inhibitor. In conclusion, carbazeran is a dual substrate of AOX‐1 and cytochrome P450. However, AOX‐1, but not cytochrome P450, catalyzes carbazeran 4‐oxidation.Support or Funding InformationSingapore Ministry of Education Academic Research Fund Tier 1 [Grant R‐148‐000‐218‐112 to AJL]This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

A study on 3-mercaptopyruvate sulphurtransferase (3-MST) produced under submerged fermentation by &lt;i&gt;Pseudomonas putida&lt;/i&gt; KT12440 isolated from an industrial effluent

Effluents from an Iron and Steel company were collected, the cyanide level was determined and screening for cyanide degrading bacterial isolates on modified Bushnell Haas agar media was done. The amount of cyanide present in the industrial effluent was 1.06 mg/L. The 16S rRNA gene sequencing identified Pseudomonas putida KT12440 as the isolate with highest activity for 3-MST production. The cell growth was optimal at 30 h incubation time and a decrease in cell growth was observed with the increase of incubation time after the optimum. The highest 3-MST production was observed when mannitol was used as the sole carbon source while fructose is the least source of carbon. Casein showed the highest production for 3-MST when used as an alternative nitrogen source while NH 4 NO 3 was the least. The optimal pH for 3-MST production was 9.0 and a sharp decrease in the enzyme production was observed thereafter. The incubation temperature for the production of 3-MST in the culture medium peaked at 30oC and a sharp decline in temperature was observed afterward. The bacterial isolate screened in this study showed degradation potential that can be harnessed to remediate effluents containing cyanide. Keywords : Cyanide, Industrial Effluent, Pseudomonas putida KT12440, 3-MST

Influence of incubation time and action of fluid flow on SPEV cell adhesion strength to a glass substrate

The results of study of SPEV cell adhesion to the glass substrate that were obtained with a radial-flow chamber shown that in some cases the cells which were incubated on the substrate for a longer time were more strongly attached to it, and under certain conditions such cells detached easier than cells with a shorter incubation time. For example, when the channel height was decreased more of cells were detached from substrate with increasing incubation time. Besides an increase of flow action time on the cells increased an amount of detached cells, and an increase of initial shear stress resulted in decrease an amount of cells which detached from the surface regardless of incubation time. During each experiment more spread cells detached from the substrate earlier than the more spherical one. When both the flow rate and channel height were reduced in the radial-flow chamber, but the initial shear stress was the same as before the changes of these parameters, then the critical radius, the critical shear stress and the time of reach these critical values sharply decreased. In addition, in this case, the area of the projection of cells remaining on the substrate also decreased.

Characteristics of soil organic carbon mineralization in low altitude and high altitude forests in Wuyi Mountains, southeastern China

Examining the variations of soil organic carbon mineralization at different altitudes is crucial for better understanding of soil organic carbon (SOC) dynamics. We selected the low altitude and high altitude broad-leaved forest soils in Wuyi Mountains as the research object, and incubated them under particular annual average temperature (17 and 9 ℃, respectively) in laboratory to investigate the difference of SOC mineralization characteristics. The results showed that the cumulative SOC mineralization had no significant difference between forest soils at low and high altitude in a 126-day incubation period under ambient temperature. Soil organic carbon content of high altitude soil was significantly higher than that from low altitude. The dynamics of SOC mineralization could fitted by the first-order kinetics. Both mineralization potential (CP) and mineralization rate constant (K) values of two soils had no significant difference, but CP/SOC value and mineralization ratio were significantly higher at low altitude, indicating that the carbon sequestration capacity of low altitude soil was relatively lower than that of high altitude under ambient temperature. Soil microbial biomass carbon and microbial quotients were significantly higher than that of low altitude with the increase of incubation time, indicating that the ability of microbial carbon assimilation was greater at high altitude. On the other hand, the activities of β-1,4-glucosidase and cellobiohydrolase in high altitude soil were higher, suggesting that more labile carbon would be decomposed by soil microbes. The carbon sequestration capacity and microbial carbon utilization efficiency in high altitude soil would be reduced and thus result in a decline of soil organic carbon storage under the scenarios of climate warming.

Anaerobic biodegradation of 8:2 fluorotelomer alcohol in anaerobic activated sludge: Metabolic products and pathways

The anaerobic biodegradability and metabolic pathways of 8:2 fluorotelomer alcohol (8:2 FTOH) were investigated in anaerobic activated sludge. The biodegradation was well described by a double exponential decay model. 8:2 FTOH was biodegraded to poly- and perfluorinated metabolites with the release of fluoride ion. All polyfluorinated metabolites were intermediate metabolic products and could be further transformed to other metabolites, while perfluorinated metabolites were terminal products. 2H-perfluoro-2-decenoic acid (8:2 FTUA) and perfluorooctanoic acid (PFOA) were verified as the most abundant poly- and perfluorinated metabolites, respectively. Two shorter-chain perfluorinated metabolites, perfluoropentanoic acid (PFPeA) and perfluorobutyric acid (PFBA), were first reported in the biodegradation of 8:2 FTOH. However, the total molar recovery of 8:2 FTOH decreased with increasing incubation time, indicating that there might be some unknown metabolites. Thus, the anaerobic biodegradation pathways were proposed as follows: 8:2 FTOH was oxidized to 8:2 FTUA and 2-perfluorooctyl ethanoic acid (8:2 FTCA) via 2-perfluorooctyl acetaldehyde (8:2 FTAL), and then 8:2 FTUA and 8:2 FTCA were further transformed to 1-perfluoroheptyl ethanol (7:2 sFTOH) via 3-perfluoroheptyl propionic acid (7:3 acid) or/and 3-perfluoroheptyl acrylic acid (7:3 Uacid), and eventually 7:2 sFTOH was further biodegraded to PFOA and other perfluorocarboxylates containing less than eight carbons.

Effect of zinc on the collagen degradation in acid-etched dentin

Background/purposeMatrix metalloproteinases (MMPs) play a crucial role in the pathogenesis of dental caries, collapse of adhesive interface, and chemical erosion of teeth. The objective of this study was to investigate the inhibitory effect of zinc on collagen degradation. Materials and methodsHuman dentin was ground and demineralized by citric acid (pH 2.0). The demineralized ground dentin was incubated in six different media: artificial saliva (AS); 5 mg/ml doxycycline in AS; 3.33, 6.82, 13.63, and 27.26 mg/ml of zinc chloride (Zn) in AS. Each group was divided into two subgroups, and active MMP-2 was incorporated into one subgroup. Specimens were incubated for 24 h, 1 week, and 2 weeks. Collagen degradation product was assessed using ELISA. The results were analyzed using repeated measured ANOVA and Duncan's post hoc analysis (α = 0.05). ResultsThe amount of collagen degradation was the lowest in Doxy group. Zn groups showed a significant inhibitory effect in collagen degradation for all concentrations (P < 0.05). In subgroups without exogenous MMP-2, zinc-mediated inhibition increased in a concentration-dependent manner with increasing zinc concentration. The amount of collagen degradation product slightly increased with increased incubation time from 24 h to 2 weeks. However, in subgroups with exogenous MMP, the inhibitory effect of zinc on collagen degradation did not depend on zinc concentration. ConclusionAll Zn groups for the four concentrations tested exhibited statistically significant inhibitory effect on collagen degradation.