iTRAQ based characterization of proteomic change in petroleum hydrocarbon-degrading Pseudomonas aeruginosa in different pH conditions.

In this study, a global proteomic change was characterized by iTRAQ analysis and bioinformatics analysis to study the influence by different pH conditions on proteins accumulation when Pseudomonas aeruginosa P6 degraded petroleum hydrocarbons. Compared with the condition of pH 7.2, 228 proteins in pH 5.0 and 93 proteins in pH 8.5 were identified as differentially accumulated proteins. The results further showed that in the condition of pH 5.0, fourteen chemotaxis-related proteins, two uptake-related proteins, two cytochromes, nineteen ABC transporters and five porins were downregulated, while two dioxygenases, five ß-oxidation-related proteins and one acyl-CoA metabolism-related protein were upregulated. In the condition of pH 8.5, one fimbrial protein, one aldehyde dehydrogenase, eight ABC transporters and six porins were downregulated, while five terminal oxidation-related proteins, one alcohol dehydrogenase, one ß-oxidation-related protein and one acyl-CoA metabolism-related protein were upregulated. The results indicated that in the condition of pH 5.0, chemotaxis and uptake of carbon, terminal oxidation of short-chain alkanes and transmembrane transport which are considered as key cellular processes in biodegradation of petroleum hydrocarbons in P.aeruginosa P6 may be disturbed. While in the condition of pH 8.5, the activity of transmembrane transport may decrease.

Effect of replacing corn grains with date palm kernels on ruminal fermentation, feed degradability, and methane production under different initial in vitro pH conditions.

Date kernels (DK) are cheap by-products rich in energy and phenolic compounds. It can be used as an alternative to the conventional sources of energy in ruminant diets while reducing methane (CH4) production. Using a semi-automated gas production (GP) system, the initial pH of buffered rumen liquor was adjusted to 5.5 and 6.8. Five experimental diets were evaluated, control (0% DK), and DK25, DK50, DK75, and DK100 presented 25, 50, 75, and 100% replacement of maize by DK, respectively. Of the 16 phenolic compounds detected in DK, protocatechuic, p-hydroxybenzoic and catechin were the most abundant. At pH 6.8, the control diet recorded higher (p < 0.05) GP values throughout the first 12 h incubation than all other DK diets, while at 5.5 pH, DK50 displayed the highest (p < 0.05) GP at 3 and 6 h compared to all other diets. At either pH conditions, all DK diets reduced (p < 0.05) CH4 compared to the control without affecting protozoal counts. At 5.5 pH, DK diets showed enhanced (p < 0.05) nutrients degradability compared to control. DK modified (P < 0.05) the fermentation patterns toward more propionate than the control under either pH conditions. Substitution of maize by 50% DK was highly recommended in ruminant diets.

Enzyme-Functionalized Piezoresistive Hydrogel Biosensors for the Detection of Urea.

Urea is used in a wide variety of industrial applications such as the production of fertilizers. Furthermore, urea as a metabolic product is an important indicator in biomedical diagnostics. For these applications, reliable urea sensors are essential. In this work, we present a novel hydrogel-based biosensor for the detection of urea. The hydrolysis of urea by the enzyme urease leads to an alkaline pH change, which is detected with a pH-sensitive poly(acrylic acid-co-dimethylaminoethyl methacrylate) hydrogel. For this purpose, the enzyme is physically entrapped during polymerization. This enzyme-hydrogel system shows a large sensitivity in the range from 1 mmol/L up to 20 mmol/L urea with a high long-term stability over at least eight weeks. Furthermore, this urea-sensitive hydrogel is highly selective to urea in comparison to similar species like thiourea or N-methylurea. For sensory applications, the swelling pressure of this hydrogel system is transformed via a piezoresistive pressure sensor into a measurable output voltage. In this way, the basic principle of hydrogel-based piezoresistive urea biosensors was demonstrated.

Piezoresistive Hydrogel-Based Sensors for the Detection of Ammonia.

Ammonia is an essential key compound in the chemical industry. However, excessively high ammonia concentrations can be harmful to the environment. Sensors for the detection of ammonia are therefore particularly important for environmental analysis. In this article, a novel hydrogel-based piezoresistive ammonia sensor is presented. In aqueous solution, ammonia reacts as a base. This alkaline pH change can be detected with stimuli-sensitive hydrogels. For such an application, highly sensitive hydrogels in the alkaline range with sufficient mechanical stability for the sensor application has to be developed. These conditions are fulfilled by the presented hydrogel system based on acrylic acid (AAc) and 2-(dimethylamino)ethyl methacrylate (DMAEMA). The hydrogel composition has a significant influence on the swelling behavior of the gel. Furthermore, the hydrogel swelling in ammonia solutions was tested and a detection limit in the range of 1 mmol/L ammonia depending on the buffer solution was determined. Ammonia-sensitive hydrogels can be used multiple times due to the repeatable swelling of the gel over several swelling cycles. To generate a measurable output voltage, the swelling pressure of ammonia-sensitive hydrogels were detected by using piezoresistive pressure sensors. All results of the free hydrogel swelling were verified in the sensor application. This low-cost ammonia sensor with a high sensitivity could be interesting for industrial chemical and biotechnological applications.

A comprehensive study on structures and characterizations of 7S protein treated by high intensity ultrasound at different pH and ionic strengths.

High intensity ultrasound (HIU) effects on soy 7S proteins in various pH (pH = 3.0 and 7.0) and ionic strengths (I = 0.1, 0.3 and 0.5) were investigated. When dissolved in pH = 7.0, the 7S proteins formed aggregates at the low ionic strength (I = 0.1), while large aggregates were dissociated as the ionic strengths increased (I = 0.3 or 0.5) after HIU treatments. Moreover, the 7S proteins were unfolded at I = 0.3 and I = 0.5 through HIU. When dissolved in pH = 3.0, the 7S proteins were extensively positively charged, which favored the HIU-induced denaturation of the proteins. When the ionic strengths were increased, the larger aggregates of the proteins were found after HIU. The electrostatic screening from the ions was essential for the unfolding/refolding and aggregating behavior of the HIU proteins, which was also proved from the structural measurements. The current study illustrated that environmental factors were of great importance for the HIU effects on food protein functionalities.

Nanoparticles Containing Tamarind Isolate Protein Potentiate the Satiety without Promoting the Anti-Inflammatory Effect in a Preclinical Model of Diet-Induced Obesity.

The study aimed to evaluate the nanoparticles (ECW) containing tamarind trypsin inhibitor (TTI) concerning the storage effect under different conditions on antitrypsin activity and the bioactive potential in a preclinical model. ECW was exposed to different pH and temperatures to evaluate the interaction between TTI and its encapsulating agents, monitored by antitrypsin activity. Wistar rats (n = 25) with obesity induced by diet were divided into groups: untreated; treatment with nutritionally adequate diet; treatment with nutritionally adequate diet and ECW/12.5 mg/kg; treatment with ECW/12.5 mg/kg; and treatment with TTI/25 mg/kg. The groups were evaluated over ten days with regards to satiety, zoometric, biochemical, and inflammatory parameters, using ten times less TTI (2.5 mg/kg) contained in ECW. TTI was protected and encapsulated in ECW without showing residual inhibitory activity. Only at gastric pH did ECW show antitrypsin activity. At different temperatures, it showed high antitrypsin activity, similar to TTI. The animals treated with ECW had significantly reduced body weight variation (p < 0.05), and only TTI treatment reduced the inflammatory parameters significantly (p < 0.05). The study showed that by using lower concentrations of TTI in ECW it was possible to perceive promising effects with perspectives of use in functional products for managing obesity and its complications.

Effects of humic acids on the recovery of different bacterial strains in an in vitro chicken digestive model.

Humic acids (HA) have been evaluated as growth promoters in poultry, but their effects on the gut microbiota remains controversial using in vitro and in vivo models. The objective of this study was to determine the effect of HA extracted from a wormcompost on the recovery of bacteria: Salmonella Enteritidis (S. Enteritidis), Escherichia coli (E. coli), Clostridium perfringens (C. perfringens), Bacillus subtilis (B. subtilis) and Lactobacillus salivarius (L. salivarius) using an in vitro chicken digestive system. Independent in vitro trials were run for each bacteria using six treatments: 1) Negative control with no bacteria added (Control-), 2) Positive control added with bacteria (Control+), 3) 0.1% HA + bacteria, 4) 0.2% HA + bacteria, 5) 0.5% HA + bacteria and 6) 1% HA + bacteria. Data was subjected to analysis of variance and linear regression. In the crop, S. Enteritidis was lower, C. perfringes and B. subtilis were not affected by HA, while E. coli and L. salivarius were higher at 0.5 and 1% HA inclusion (P ≤ 0.0001). In the proventriculus, S. Enteritidis, E. coli and B. subtilis were higher at 0.5 and 1% HA inclusion (P ≤ 0.0001); C. perfringens and L. salivarius were not affected by HA. In intestine, significant increases of all bacteria strains were observed (P ≤ 0.0001). In conclusion, the results suggests that HA can be used as prebiotic, but their mechanisms of action to stimulate the growth of gut bacteria remains to be elucidated.

The effect of biofilm growth on the sulfur oxidation pathway and the synergy of microorganisms in desulfurization reactors under different pH conditions.

Biofilm growth affects the oxygen transfer in biofilm and thus the oxidation pathway of sulfur and the synergy of microorganisms. In this study, the effect of biofilm growth on the oxidation pathway of H2S and the synergy of microorganisms in desulfurization reactors under different pH conditions was first discussed to enhance the understanding of desulfurization process. A biotrickling filter (BTF) was operated for 168 days under acidic condition (pH<4.7) and 32 days under alkaline condition (7.0 89.0%). In alkaline period, the AGM raised to 0.97 g/L-BTF/d, and 77.0% of S-H2S was transferred to elemental sulfur (S0) and polysulfanes (R-Sx-R) accumulated in biofilm. The increase of biofilm and sulfur-oxidizing bacteria activity limited the oxygen transfer in alkaline biofilm, leading to the accumulation of S0 and the emergence of an obligate anaerobe- Acetoanaerobium (8.1%). The formation of R-Sx-R may be due to the reaction of S0 with thiols produced by a thiol-producing bacterium- Pseudomonas (6.7%). The uneven distribution of oxygen in biofilm caused by biofilm growth complicated the transfer pathway of sulfur and the synergy of microorganisms in desulfurization system.

[Investigation of the Performance of Organic Contaminant Degradation by Fe2+/PDS Under Environmentally Relevant pH Conditions].

Peroxydisulfate (PDS) activation by Fe2+ has proven to be a promising method to abate emerging organic contaminants by generating reactive oxidation species. Nevertheless, this process may only achieve good decontamination performance under acidic conditions, which has markedly limited its application in real practice. To address this issue, we comprehensively investigated the performance of the Fe2+/PDS process toward some probe contaminants at different pH levels and explored the potential change in reactive oxidative species and the influence of oxygen. Both SO4-· and Fe(Ⅳ) were identified to be involved in the Fe2+/PDS process, and the types of these oxidative species did not change with varying pH values. Although dissolved oxygen could compete with PDS for Fe2+, especially at high pH values, this competition process was not the major reason for the declined performance of the Fe2+/PDS process, since 37.6%-100% of PDS could also be activated with the presence of oxygen. Instead, the overdosing of Fe2+could greatly inhibit carbamazepine removal, indicating that the nonproductive consumption of reactive oxidants by Fe2+should account for the declined performance of Fe2+/PDS under environmentally relevant pH conditions. Accordingly, the feasibility of applying zero-valent iron and sulfidated zero-valent iron was further evaluated, and the formation of corrosion products was characterized using X-ray absorption fine structure spectroscopy. All these findings will improve our understanding about the Fe2+/PDS process and thus facilitate its application.

The effect of pH on the chemical and structural interactions between apple polyphenol and starch derived from rice and maize.

To date, how pH affects starch-polyphenol mixtures has not been thoroughly investigated. This study explored the impact of combining apple polyphenol (AP) with both normal rice starch (NRS) and normal maize starch (NMS) across a range of pH conditions. NRS-AP mixture particle sizes across a pH range of 3-8 varied from 169.9 ± 5.4 to 187.5 ± 6.9 µm, while for NMS-AP particles, these sizes ranged from 161.8 ± 8.0 to 176.0 ± 4.9 µm, indicating that the aggregation of starch-AP was inhibited under low pH condition. The melting enthalpy (△H) values of the NRS-AP mixture across a pH range of 3-8 were 8.50 ± 0.06-9.56 ± 0.12 J/g, while the corresponding value for the NMS-AP mixture was 5.77 ± 0.05-6.21 ± 0.08 J/g. FTIR analyses revealed that the degree of order of these starch-AP mixtures significantly decreased under low pH conditions. XRD analysis further revealed that both NRS-AP and NMS-AP mixtures exhibited V-type structures, and relative crystallinity levels decreased significantly under low pH conditions. Together, these results indicate that low pH values inhibit the recrystallization of NRS-AP and NMS-AP mixtures. Overall, these findings provide additional evidence regarding the interactions between AP and specific starches under a range of pH conditions.

Arsenate-reducing bacteria-mediated arsenic speciation changes and redistribution during mineral transformations in arsenate-associated goethite.

The fate of Fe(III)-(oxyhydr)oxides-bound As was generally regulated by dissimilatory As(V)-reduction. However, the impact of pH and bacterial conditions on the coupled processes of microbially-mediated As speciation changes and Fe-mineral transformation remains unclear. Our study therefore incubated As(V)-associated goethite with different As(V)-reducing bacteria at a range of pH. Results show that As reduction was most prominent at pH 7 as the bacterial growth was optimal. However, aqueous As concentration was the lowest (0.8-3.7 mg/L), due to rapid microbial Fe(II) formation at pH 7 triggered secondary mineralization and significant As-readsorption. Our study provides the first spectroscopic evidence for mineral-phase temporal evolution, and indicates in the presence of phosphate, vivianite will precipitate first and adsorb large amount of As(III) (40-44% of solid As). Thereafter, continuously increased Fe(II) may catalyze lepidocrocite and eventually magnetite formation, which further sequestrate aqueous As(III). Conversely, at pH 5 and 9, bacterial growth was inhibited, the corresponding lower microbially-derived Fe(II) concentrations caused no secondary minerals formation. Released As(III) was therefore largely remained in solution (6-9.7 mg/L). Our study demonstrates that As-bound Fe(III)-(oxyhydr)oxides could pose greater risks under acidic or alkaline conditions in biotic reactions. Additionally, bacterial species could strongly impact Fe-mineral transformation pathways and As solid-solution redistribution.

Effects of extreme pH conditions on the stability of As(V)-bearing schwertmannite.

Schwertmannite (Sch) is known to be an effective scavenger of arsenic (As) due to its strong binding affinity for toxic As species. However, the evolution of As-bearing schwertmannite under extreme pH conditions is poorly understood. In this study, we investigated the effects of extremely acidic and alkaline conditions on the stability of schwertmannite with structurally incorporated As(V) (CO-Sch) and schwertmannite with adsorbed As(V) (AD-Sch). The results show that both extremely acidic and alkaline conditions have significant effects on the evolution of minerals and liberation of iron and sulfate. At extremely acidic pH, the maximal release of ferric iron (Fe(III)) and sulfate from CO-Sch were greater than that from AD-Sch, whereas 6.2% and 0.3% of total As released from AD-Sch and CO-Sch, respectively. At extremely alkaline pH, aqueous Fe(III) was not observed, and Fe(III) was retained in As-bearing schwertmannite due to the chemical equilibrium between the dissolution of schwertmannite and re-precipitation of goethite; structurally incorporated As(V) promoted the liberation of sulfate. In addition, the adsorbed As on schwertmannite is more stable, which led to a minor release of As (0.8%) over a 30-d period, however, the liberated As(V) from CO-Sch accounts for up to 3.2%. Under extremely acidic and alkaline conditions, portions of AD-Sch and CO-Sch transformed from schwertmannite to goethite after 30 d, while schwertmannite was still the dominant mineral. Adsorbed As(V) inhibited the transformation of As-bearing schwertmannite to goethite more significantly than structurally incorporated As(V).

Nanosheets of MoSe2@M (M = Pd and Rh) function as widespread pH tolerable hydrogen evolution catalyst.

In this present study we have developed method for the synthesis of MoSe2 nanosheets following a simple hydrothermal technique. Palladium (Pd) and rhodium (Rh) nanoparticles were decorated on the surface of MoSe2 following a simple wet-chemical route. Pd and Rh nanoparticles decorated MoSe2 were applied for hydrogen evolution reaction (HER) in different pH conditions like acidic (0.5 M H2SO4), neutral (pH-7 buffer) and in alkaline (1 M KOH) medium and 3.5 wt% of saline water. Pd and Rh decorated MoSe2 show efficient activity towards HER irrespective of the applied electrolyte. In 0.5 M H2SO4, MoSe2 can produce 10 mA/cm2 current density with applied potential of -0.256 V vs. RHE. Rh decorated MoSe2 shows more shift in the onset potential. Upon applied potential of -0.192 V vs. RHE, MoSe2/Rh can produce 10 mA/cm2 current density. MoSe2/Rh is electrocatalytically more active than MoSe2/Pd which is established from the calculated electrochemically active surface area (ECSA) value. Significantly lower (47 mV/decade) Tafel value is observed for MoSe2/Rh in 0.5 M H2SO4 which indicates the superior activity. MoSe2/Rh is more stable in neutral and alkaline medium compared to acidic medium and it can retain its own activity even after continuous 12 h reaction.

Encapsulation and release of egg white protein in alginate microgels: Impact of pH and thermal treatment.

Edible alginate microgels are widely used to encapsulate, retain, protect, and release bioactive molecules in foods. Encapsulation of food proteins within alginate microgels may be advantageous for certain applications, such as creating controlled release delivery systems or for protection of other co-encapsulated bioactive components. Egg white protein-loaded alginate microgels were fabricated in this study using a simple injection-gelation method. The impact of pH (pH 3, 5 and 7) and thermal treatment (25 to 85 °C) on the encapsulation efficiency, retention, and physicochemical properties of the microgels was measured. Protein encapsulation efficiency and retention was highest at the lowest pH, which was attributed to the strong electrostatic attraction between the cationic egg white proteins and anionic alginate. Thermal treatment of the egg white proteins before microgel formation enhanced their encapsulation and retention, which was attributed to an increase in their physical dimensions due to unfolding and aggregation. As a result, it was more difficult for them to diffuse through the pores in the alginate microgels. The information obtained in this study may facilitate the design of more effective protein-loaded alginate microgels for food and other applications.

Phenotype-driven strategies for screening Candida parapsilosis complex for molecular identification.

In this study, phenotypic methods presented >80% agreement with the molecular identification of 59 Candida parapsilosis complex. Growth at 15% NaCl or pH 7.0 significantly reduced cfu-counts of Candida orthopsilosis, suggesting these conditions may support the development of phenotypic methods for the differentiation of the cryptic species of C. parapsilosis complex.

Transporter engineering for cellobiose fermentation under lower pH conditions by engineered Saccharomyces cerevisiae.

The aim of this study was to engineer cellodextrin transporter 2 (CDT-2) from Neurospora crassa for improved cellobiose fermentation under lower pH conditions by Saccharomyces cerevisiae. Through directed evolution, a mutant CDT-2 capable of facilitating cellobiose fermentation under lower pH conditions was obtained. Specifically, a library of CDT-2 mutants with GFP fusion was screened by flow cytometry and then serial subcultured to isolate a CDT-2 mutant capable of transporting cellobiose under acidic conditions. The engineered S. cerevisiae expressing the isolated mutant CDT-2 (I96N/T487A) produced ethanol with a specific cellobiose consumption rate of 0.069g/gcell/h, which was 51% and 55% higher than those of the strains harboring wild-type CDT-1 and CDT-2 in a minimal medium with 2g/L of acetic acid.

Biophysical studies on the interaction of platinum(II) complex containing antiviral drug ribavirin with human serum albumin.

This study describes HSA binding properties of a platinum(II) complex with an antiviral drug ligand; ribavirin. Spectroscopic analysis of the emission quenching at different temperatures and UV-vis spectra revealed that the quenching mechanism of HSA by Pt(II) complex is static quenching mechanism. The binding constants and the number of binding sites were determined by fluorescence quenching method. Pt(II) complex binding is characterized by one high affinity binding site. Through the site marker competitive experiment, site I was assigned to possess high affinity binding site for Pt(II) complex. The calculated thermodynamic parameters (ΔG, ΔH and ΔS) confirmed that the binding reaction is spontaneous, and hydrophobic forces played a major role in the reaction. Fluorescence quenching studies showed that the binding affinity of Pt(II) complex with HSA in the buffer solution at different pH values is: Kb (pH3.0)>Kb (pH9.0)>Kb (pH7.4). The CD spectrum shows the binding of Pt(II) complex leads to a change in the α-helical structure of HSA. CD spectroscopy studies further indicated the influence of pH on the complexation process and the alteration in the protein conformation upon binding.

Effect of aluminum speciation on fouling mechanisms by pre-coagulation/ultrafiltration process with different NOM fractions.

Ultrafiltration is an emerging technology for drinking water production, but the membrane fouling is still a challenge. This study was carried out to investigate the effect of aluminum speciation on UF membrane fouling behavior by different NOM fractions-humic substances and proteins, as represented by humic acid (HA) and bovine serum albumin (BSA), respectively. The interesting results showed that the total fouling resistance of the mixture of HA-BSA-kaolinite solution without coagulant demonstrated a slight decrease in comparison with those of the individually filtered substances, indicating a mitigatory fouling effect. The hydrolysis of aluminum products was various as pH and membrane fouling was related to aluminum speciation. The average size of flocs dramatically increased and fractal dimension of flocs decreased with the increasing of pH value independent on water quality, which indicated that aluminum speciation had a significant impact on floc properties. For the mixture of HA-BSA-kaolinte, the slightly larger of flocs average size in comparison with the individual organic fraction after coagulation was probably attributing that BSA was encapsulated by HA to enlarge the molecular length and floc size further increased. The membrane performance also showed that coagulation effluent of HA-BSA-kaolinite mitigated membrane fouling. The strong linear relationship was observed between flocs fractal dimension and final membrane flux in this research. From the results, the control of flocs fractal dimension should be considered as a new technique for traditional hybrid coagulation/ultrafiltration system, which resulted in minimized total and irreversible fouling and has a meaningful engineering application value.

Physiological functions at single-cell level of Lactobacillus spp. isolated from traditionally fermented cabbage in response to different pH conditions.

Changes in pH are significant environmental stresses that may be encountered by lactobacilli during fermentation processes or passage through the gastrointestinal tract. Here, we report the cell response of Lactobacillus spp. isolated from traditionally fermented cabbage subjected to acid/alkaline treatments at pH 2.5, 7.4 and 8.1, which represented pH conditions of the gastrointestinal tract. Among six isolates, four species of Lactobacillus plantarum and two of Lactobacillus brevis were identified by fluorescence in situ hybridization (FISH). The fluorescence-based strategy of combining carboxyfluorescein diacetate (CFDA) and propidium iodine (PI) into a dual-staining assay was used together with epifluorescence microscopy (EFM) and flow cytometry (FCM) for viability assessment. The results showed that the cells maintained esterase activity and membrane integrity at pH 8.1 and 7.4. There was also no loss of culturability as shown by plate counts. In contrast, the majority of 2.5 pH-treated cells had a low extent of esterase activity, and experienced membrane perturbation. For these samples, an extensive loss of culturability was demonstrated. Comparison of the results of an in situ assessment with that of the conventional culturing method has revealed that although part of the stressed population was unable to grow on the growth media, it was deemed viable using a CFDA/PI assay. However, there was no significant change in the cell morphology among pH-treated lactobacilli populations. These analyses are expected to be useful in understanding the cell response of Lactobacillus strains to pH stress and may facilitate future investigation into functional and industrial aspects of this response.

Phenotype-driven strategies for screening Candida parapsilosis complex for molecular identification

Abstract In this study, phenotypic methods presented >80% agreement with the molecular identification of 59 Candida parapsilosis complex. Growth at 15% NaCl or pH 7.0 significantly reduced cfu-counts of Candida orthopsilosis, suggesting these conditions may support the development of phenotypic methods for the differentiation of the cryptic species of C. parapsilosis complex.