Acidic pH Range Research Articles

Efficacy of sodium chlorite in inactivating Vibrio parahaemolyticus attached to polyethylene terephthalate surfaces.

The inactivation of Vibrio parahaemolyticus cells attached to a polyethylene terephthalate (PET) disc in a sodium chlorite (NaClO2) solution was kinetically studied in a weakly acidic pH range of 4.0 - 6.5. The logarithmic reduction in the survival ratio depended on the concentration-time product. All inactivation curves showed a linear reduction phase, and the reduction in viable cells was greater than 4-log. No significant desorption of attached cells was observed during the inactivation treatment. The first-order inactivation rate constant (k) increased by approximately 4.5-fold for every 1.0 unit fall in pH. At all pH values, the k values calculated for the attached cells were approximately half of those for the unattached cells. These findings indicate that a weakly acidic NaClO2 solution is effective in inactivating bacteria attached to hard surfaces.

Determination of Survivability of Some Probiotic Lactic Acid Bacteria in Some Locally Produced Drinks

Foods are not only intended to placate hunger and supply essential nutrients but also to prevent the nutrition-related diseases and to improve physiological and mental wellbeing of consumers. This led to the development of probiotic foods. Probiotics are said to be live microorganisms which when adequately (106/107 CFU/mL) administered confer health benefits to the host. Probiotic drinks both dairy and non-dairy have been found to be carriers of these organisms to their site of action. This research aims at determining the survivability of probiotic lactic acid bacteria in some locally produced drinks. The isolation of the organisms from yoghurt and “nono” were conducted using cultural methods and further characterized using biochemical tests. Cell surface hydrophobicity (CSH), cellular auto-aggregation assays (CAA), hemolytic activities, bile salt and NaCl tolerance test were conducted to determine the probiotic properties of the organisms. The survivability of the organisms was evaluated after standardizing the inoculum using 0.5 McFarland standard and then serial dilution, plating and counting of visible colonies. Results were analyzed by ANOVA using SPSS software version 20.0. Out of the ten isolated and biochemically characterized lactic acid bacteria, three Lactobacillus species showed probiotic status, with CSH values of (79%, 75.2% and 91.3%) and CAA index of (79.3%, 74% and 83.5%), respectively, however there is no statistically significant difference between the CAA and CSH values of the isolates (p = 0.13 and p = 0.5, respectively), which indicates that all the isolates had approximately equal probiotic capabilities. “Kunun zaki” showed the highest survivability rate with the probiotic status being maintained for three days, and counts ranging from 1.4 to 1.05 x 106 CFU/mL; whereas “zobo” showed the least duration as a probiotic (one day, and a count of 1.16 x 106 CFU/mL. There is a significant difference (p=0.02) in the growth of the organisms over the incubation period (5 days), however, there is no significant difference (p=0.82) between the growth of the organisms growing on different drinks, indicating that time after incubation is the critical determinant of probiotic status, and that the isolates can grow equally well in all the drinks tested. This research reported the isolation of Lactobacillus species confirmed to be probiotics from yoghurt and “nono”. Enumeration of probiotic LAB in all the drinks revealed the drinks were probiotic containing 106 CFU/mL for two (2) days with the exception of “Kunun zaki” that reached up to three (3) days as a probiotic drink. The pH level of all the drinks decreased and the drinks became acidic (pH range 6.0-1.8).

Heterologous Expression and Characterization of a Novel Exo-Polygalacturonase from Aspergillus fumigatus Af293 and Its Application in Juice Extraction.

Exo-polygalacturonase (exo-PG) hydrolyzes pectin acids and liberates mono-galacturonate, which plays an important role in juice extraction, and has rarely been reported. Exo-PG (AfumExoPG28A) from Aspergillus fumigatus belongs to the glycoside hydrolase 28 family. In this study, its gene was cloned and the protein was expressed and secreted in Pichia pastoris with a maximal activity of 4.44 U/ml. The optimal temperature and pH of AfumExoPG28A were 55°C and 4.0, respectively. The enzyme exhibited activity over almost the entire acidic pH range (>20.0% activity at pH 2.5-6.5) and remained stable at pH 2.5-10.0 for 24 h. The Km and Vmax values of AfumExoPG28A were calculated by the substrate of polygalacturonic acid as 25.4 mg/ml and 23.6 U/mg, respectively. Addition of AfumExoPG28A (0.8 U/mg) increased the light transmittance and juice yield of plantain pulp by 11.7% and 9%, respectively. Combining AfumExoPG28A (0.8 U/mg) with an endo-PG (0.8 U/mg) from our laboratory, the enzymes increased the light transmittance and juice yield of plantain pulp by 45.7% and 10%, respectively. Thus, the enzyme's potential value in juice production was revealed by the remarkable acidic properties and catalytic activity in fruit pulp.

Simultaneous detection of copper and mercury in water samples using in-situ pH control with electrochemical stripping techniques

The performance of electrochemical sensors using an in situ pH control technique for detection of mercury and copper in neutral solutions is described herein. Sensors are comprised of two distinct parallel gold interdigitated microband electrodes each of which may be polarised separately. Biasing one interdigitated “protonator” electrode sufficiently positive to begin water electrolysis, resulted in the production of H+ ions, which, consequently droped the interfacial pH at the other second interdigitated “sensing” electrode. This decrease in pH permitted the electrodeposition (and consequent stripping) of metals at a sensing electrode without the need to acidify the whole test solution. In this work, the local pH could be adjusted in the acidic pH range in a stable and reproducible way just by tailoring the polarization of the protonator electrode. Using this approach, a linear range for copper 5 to 100 ppb and for mercury 1 to 75 ppb were obtained. The sensors also have an extremely high sensitivity for the metals. The in-situ pH control, coupled with electrochemical stripping, allowed metal detection in a complex water matrix, e.g., river water without the need for sample pre-treatment. The electrochemical results were confirmed by comparison to those obtained using inductively coupled plasma – optical emission spectroscopy. A very good agreement was observed between both sets of results. The electrode reproducibility was high (RSD < 10%) and the metals could be co-detected simultaneously. Thus, this work shows a fast and easy approach for in-situ pH control for multi metal detection using solid state sensors.

Construction of dual sulfur sites in metal–organic framework for enhanced mercury(II) removal

Highly efficient removal of mercury ion (Hg2+) from aqueous solution is a serious concern. Herein, a novel metal–organic framework (MOF) containing dual sulfur sites was successfully constructed via an in-situ method. Different with previous reports, thiophene and thiol sites were simultaneously introduced via organic linker and inorganic cluster, resulting in high-density sulfur sites. The composition and porosity of the newly synthesized DUT-67-SH (DUT, Dresden University of Technology) were systematically characterized. Based on abundant sulfur sites and strong host–guest interaction, DUT-67-SH exhibits a high adsorption capacity (370.2 mg g−1) and rapid adsorption kinetics (∼3 min for equilibrium). Excellent separation selectivity, regenerability, and applicability under wide acidic pH range were further confirmed. Mechanism analysis suggests that the chemical bonding between sulfurs and Hg2+ is the main driven force. Thus, our work demonstrates that DUT-67-SH is a potential adsorbent for Hg2+, and more importantly, provides a new insight for introducing high-density sulfur sites in MOFs.

Citrate effect on the swelling behaviour and stability of casein microparticles

Casein microparticles obtained from casein micelles by volume exclusion of added pectin and subsequent film drying remain stable in the acidic and neutral pH range, but swell strongly in the basic range. Calcium significantly impacts on the stability and water-binding behavior of phosphorylated caseins and the aggregates and gels formed from them. For a future effective and controlled use as a carrier for bioactive substances, e.g. via the gastrointestinal tract, we therefore investigated how the addition of the calcium chelating agent citrate affects the swelling and stability of the microparticles. Citrate concentrations of 2 mM and above cause a stronger swelling of the microparticles at pH 8, while above 4 mM the second characteristic swelling step starts earlier and thus can also be investigated within the observation time of 120 min. All swelling kinetics can be simulated using seven parameters of a dynamic model, which reproduces the individual swelling steps via volume inflows and outflows into a reservoir. While the rate coefficient for swelling step 1 increases linearly with citrate concentration, no such dependence could be found for swelling step 2. The more citrate is used, the faster the microparticles decompose in turbidity experiments after the addition of sodium dodecyl sulfate, which can be related to a weakening of the hydrophobic interactions.

Catalytic activity and mechanism of typical iron-based catalysts for Fenton-like oxidation

Heterogeneous Fenton-like systems were exploited for the degradation of Reactive Red X–3B (RR X–3B) using iron-carbon composite, sponge iron, chalcopyrite and pyrite as catalysts. The effect of operational variables on the catalytic activity and metal leaching behavior of catalysts was evaluated and the catalytic mechanism was discussed. The experimental results showed that under the optimum conditions, chemical oxygen demand (COD) removals by Fenton-like systems could reach 89.91%, 86.84%, 80.11% and 60.02% with iron-carbon composite, sponge iron, chalcopyrite and pyrite, respectively. Micro-electrolysis of iron-carbon composite and sponge iron resulted in higher COD removal at acid pH range. Electron Paramagnetic Resonance (EPR) analysis and quenching tests showed that •OH was the main reactive oxygen species responsible for the degradation of RR X–3B. A large amount of Fe2+ leached from iron-carbon composite and sponge iron, which served as a homogeneous Fenton catalyst during the degradation of RR X–3B. In contrast, much lower amount of Fe2+ was leached from chalcopyrite and pyrite, and surface catalysis of the minerals played more important role in the generation of •OH. Surface characterization and density functional theory (DFT) calculation results illustrated that ≡Fe(II) was the primary surface catalytic site during the reaction. The reduction of ≡Fe(III) and ≡Cu(II) can be facilitated by sulfides on the mineral surface. The Fenton-like systems catalyzed by iron-based materials exhibited higher H2O2 utilization and COD removal than classical Fenton system. With the lower metal leaching concentration and stable surface property, chalcopyrite and pyrite may be more practical applicable from a long-term catalytic activity point of view.

Protein Adhesives: Investigation of Factors Affecting Wet Strength of Alkaline Treated Proteins Crosslinked with Glyoxal.

Proteins obtained as side-products from starch production (potato and corn proteins) were investigated for wood adhesives application. To improve the wet strength of protein-based adhesives, glyoxal was added as a crosslinking agent. The effect of glyoxal on the wet strength of protein-based adhesives was investigated at different pH, protein: glyoxal ratios and solid content. The alkaline pretreatment of proteins was carried out by two different methods which reduced the molecular weight of proteins to different extents. The effect of molecular weight reduction on the wet strength of protein-glyoxal adhesives was also observed. It was found that pH level affects wet strength more significantly compared to solid content and protein-to-crosslinker ratio. Potato and corn proteins crosslinked with glyoxal showed maximal wet strength results in an acidic pH range

Cooperation of multiple active species generated in hydrogen peroxide activation by iron porphyrin for phenolic pollutants degradation

The narrow acid pH range and the nonselectivity of the dominant •OH limit the Fenton systems to remediate the organic wastewater. Inspired by the role of heme in physiological processes, we employed iron porphyrin as a novel homogeneous catalyst to address this issue. Multiple active species are identified during the activation of H2O2, including high-valent iron porphyrin ((por)Fe(IV)) species ((por)Fe(IV)–OH, (por)+•Fe(IV)=O) and oxygen-centered radicals (•OH, HO2•/•O2−), as well as atomic hydrogen (*H) and carbon-centered radicals. With the cooperation of these active species, the degradation of pollutants could be resistant to the interference of concomitant ions and proceed over a wide pH range. This cooperative behavior is further verified by intermediates identified from bisphenol A degradation. Specifically, the presence of *H could facilitate the cleavage of the C–C bond and the addition of unsaturated or aromatic molecules. (Por)+•Fe(IV)=O could hydroxylate substrates with an oxygen rebound mechanism. Hydrogen atom abstraction of contaminants could be performed by (por)Fe(IV)–OH to form desaturated products by attacking oxygen-centered radicals. The ecotoxicity of bisphenol A could be significantly decreased through degradation. This study would provide a new approach to wastewater treatment and shed light on the interaction between metalloporphyrin and peroxide in an aqueous solution.

Engineered biochar supported layered double hydroxide-cellulose nanocrystals composite-: Synthesis, characterization and azo dye removal performance

In this work, engineered biochar decorated layered double hydroxides and cellulose nanocrystals (B–CuFe–CNC) biocomposites were synthesized by the facile ultrasonicated-co-precipitation technique. The biocomposite was investigated for purification of Eriochrome Black T (EBT) dye from water. The characterization results showed that the presence of CNC in biochar-layered double hydroxides resulted in a two-dimensional rod-like structure with excellent crystallinity, improved surface functionalities, and provides an attractive platform for the enhanced adsorption of azo anionic dye molecules. The adsorption system was appropriately demonstrated by the BBD-RSM (R2 > 0.994). The biocomposite exhibited higher EBT adsorption in the acidic pH range (2–5) due to strong electrostatic and chemical interactions. The kinetic and isotherm results were well demonstrated by pseudo-second order, Freundlich, and Redlich Peterson models. The maximum adsorption capacity of biocomposite was 876.2 mg/g achieved within 45 min. The spectroscopic analyses imply that the high removal of EBT by biocomposite is mainly governed by electrostatic attraction, hydrogen bonding, and chemical/metal complexation mechanisms. The biocomposite maintained high EBT removal after six successive adsorption cycles and excellent dye adsorption in the different water matrices. The results suggest that tailoring biochar properties with layered double hydroxide and CNC is a promising way for the enhanced removal of dye contaminants from wastewater.

An iron chlorophyll derivative for enhanced degradation of bisphenol A: New insight into the generation mechanism of high-valent iron oxo species

The pressure to environmental concern from toxic precursors of metalloporphyrin synthesis and the inadequate understanding of metalloporphyrin with β-site substituents on activation of peroxides have impeded the full potential of metalloporphyrin for the oxidation of recalcitrant organic compounds. Here, we report a “green” iron(III) chlorophyll derived from naturally abundant chlorophyll. It shows remarkable degradation efficiency of bisphenol A in the presence of hydrogen peroxide, with a second-order rate constant of 87.3 ± 1.1 L·mmol−1·min−1, which is 7-fold faster than the degradation rate of the Fenton oxidation system. It also demonstrates a wide pH tolerance range of 4–12 and is barely affected by concomitant inorganic anions or natural organic matter. Different from the generation of oxygen-centered radicals, including •OH and •O2−, in the Fenton system, a high-valent iron (Ⅳ) -oxo chlorin π-cation radical is formed with an atypical pathway of homolytic O O bond cleavage via a proton-coupled electron transfer process and is responsible for the degradation of bisphenol A, which is confirmed with spectroscopic studies and theoretical analysis. This abundant “green” catalyst could be beneficial for wastewater treatment by addressing the limitation of a narrow acidic pH range and the susceptibility to scavenging of nonselective radicals in conventional Fenton reactions.

Degradation of phenolic inhibitors by laccase immobilized on tannic acid/polyethylenimine modified magnetic nanoparticles

Magnetic Fe3O4 nanoparticles were successfully functionalized with the low-cost mussel-inspired tannic acid (TA)/polyethylenimine (PEI) under mild conditions and then activated with glutaraldehyde (GA) to covalently immobilize laccase for degradation of four model phenolic inhibitors commonly found in lignocellulosic hydrolysate. The immobilized laccase showed the highest relative enzyme activity with the laccase loading of 39.9 mg/g and the enzyme activity recovery of 53.1%. Compared with free laccase, immobilized laccase possessed better relative enzyme activity at acidic pH and wide temperature range, as well as exhibited excellent storage stability and satisfactory reusability. Moreover, it was found that the phenolic degradation products by immobilized laccase did not exhibit obvious inhibition on subsequent enzymatic cellulose hydrolysis. Thus, the low-cost TA/PEI coating for modification of magnetic nanoparticles will provide a promising support for laccase immobilization and the immobilized laccase has great potential in removal of phenolic inhibitors present in lignocellulosic hydrolysate.

Iodine stability as a function of pH and its implications for simultaneous multi-element ICP-MS analysis of marine carbonates for paleoenvironmental reconstructions

Analyses of marine carbonates using solution-based ICP-MS typically occur in dilute acid, as alkaline solutions can cause CaCO3 and metal-oxide/oxyhydroxide precipitation. Measurement of iodine to calcium (I/Ca) ratios in marine carbonates—most often in the calcite shells, or tests, of foraminifera—are challenging to pair with those of pH-sensitive metals, as iodine is unstable in acidic solution and will volatilize in the presence of light and air. As a result, I/Ca ratios are routinely analyzed in basic solution, requiring additional sample material and analytical time. Leveraging the equilibrium relationships between thermodynamically stable, inorganic iodine species across a wide range of electrochemical potential (pE) and pH values, we determine which species are present in low-temperature, aqueous solutions characteristic of marine carbonate analysis on quadrupole ICP-MS, and suggest appropriate solution pH(s) for iodine measurement. Our results demonstrate that iodine is capable of volatilization at all pH values <10.5, though it is most volatile in the pH range of 0–1. Furthermore, at pH values above 10.5, solutions are susceptible to contamination from gas-phase molecular iodine, I2.Employing this knowledge of iodine speciation, we establish a high precision method for the solution-based analysis of iodine alongside twelve other elements (Li, Na, Mg, Al, Mn, Fe, Zn, Sr, Cd, Ba, U, and Ca) on a collision-reaction cell equipped quadrupole ICP-MS in the acidic pH range. Using a 9:1 volume/volume mixture of 0.5% tetramethylammonium hydroxide (TMAH) and 2% nitric acid (HNO3), we can reproducibly analyze iodine concentrations in a complex carbonate (calcite and aragonite) matrix alongside other elemental ratios used in paleo-environmental reconstructions. This mixture of dilute acid and base maintains acidic pH (1.5 ± 0.14), avoiding the precipitation of pH-sensitive metal oxides/oxyhydroxides and CaCO3 while minimizing iodine volatilization. We demonstrate that iodine concentrations measured using ICP-MS are only effectively stabilized in the pH range of 1.5–10.5 and recommend pH-matching sample and standard solutions. This method allows the extraction of considerably more directly comparable paleo-environmental information from the analysis of a single foraminiferal sample.

A Novel PNGase Rc for Improved Protein N-Deglycosylation in Bioanalytics and Hydrogen-Deuterium Exchange Coupled With Mass Spectrometry Epitope Mapping under Challenging Conditions.

N-linked glycosylation is a ubiquitous posttranslational modification of proteins. While it plays an important role in the biological function of proteins, it often poses a major challenge for their analytical characterization. Currently available peptide N-glycanases (PNGases) are often inefficient at deglycosylating proteins due to sterically inaccessible N-glycosylation sites. This usually leads to poor sequence coverage in bottom-up analysis using liquid chromatography with tandem mass spectrometry and makes it impossible to obtain an intact mass signal in top-down MS analysis. In addition, most PNGases operate optimally only in the neutral to slightly acidic pH range and are severely compromised in the presence of reducing and denaturing substances, which limits their use for advanced bioanalysis based on hydrogen-deuterium exchange in combination with mass spectrometry (HDX-MS). Here, we present a novel peptide N-glycanase from Rudaea cellulosilytica (PNGase Rc) for which we demonstrate broad substrate specificity for N-glycan hydrolysis from multiply occupied and natively folded proteins. Our results show that PNGase Rc is functional even under challenging, HDX quenching conditions (pH 2.5, 0 °C) and in the presence of 0.4 M tris(2-carboxyethyl)phosphine, 4 M urea, and 1 M guanidinium chloride. Most importantly, we successfully applied the PNGase Rc in an HDX-MS workflow to determine the epitope of a nanobody targeting the extracellular domain of human signal-regulating protein alpha (SIRPα).

Self-Adaptive Flask-like Nanomotors Based on Fe3O4 Nanoparticles to a Physiological pH.

In living bodies, pH values, which are precisely regulated and closely associated with diseased cells, can act as an efficient biologically intrinsic indicator for future intelligent biomedicine microsystems. In this work, we have developed flask-like carbonaceous nanomotors (FCNMs), via loading Fe3O4 nanoparticles (NPs) into a cavity, which exhibit a self-adaptive feature to a specific physiological pH by virtue of the pH-dependent dual enzyme-like activities of Fe3O4 NPs. Specifically, the peroxidase-like activity of Fe3O4 NPs in an acidic pH range, and the catalase-like activity in a near neutral and alkaline pH range, determine the products in the motion system (•OH, ions and O2), whose diffusions from the inner to the outside of the flask result in fluid movement providing the driving force for the movement of the FCNMs. Correspondingly, changes of the product concentrations and species in the physiological pH range (4.4–7.4) result, firstly, in velocity decrease and, then, with increase in pH, increase of the FCNMs occurs. Thanks to the non-linear velocity responsiveness, the FCNMs show intriguing pH taxis towards 6.8 (generally corresponding to the physiological pH in tumor microenvironments), where a maximum velocity appears. Furthermore, the superparamagnetic feature of the Fe3O4 NPs simultaneously endows the FCNMs with the abilities to be magnetic-oriented and easily separated. This work could significantly increase the possibility of nanomotors for targeted therapy of tumors and next-generation biotechnological applications.

Effect of pH, ionic strength, and temperature on the adsorption behavior of Acid Blue 113 onto mesoporous carbon

Mesoporous carbon (MC) derived from cassava starch was used to remove Acid Blue 113 azo dye from aqueous solutions. The influence of temperature, pH, ionic strength, and the adsorbent dose was investigated in a set of batch experiments. Experimental data showed that Acid Blue 113 adsorption was higher in the acid pH range than in the alkaline one, that dye adsorption increases when the ionic strength and temperature increase, and that adsorption results presented a good correlation with the Langmuir isotherm model. The adsorption capacity of MC was 295mgg-1, at pH = 7.0 and 298K, respectively. Zeta potential (ζ) showed the compression of the diffuse double layer of adsorbent with an increase in temperature and ionic strength, promoting the decrease of electrostatic repulsion between the negatively charged surface of the carbon particles and the anionic dye. Thermodynamic results demonstrate that the adsorption process was spontaneous and endothermic. Moreover, for the first time, this work has demonstrated that the pH, temperature, and ionic strength of the aqueous medium are also able to change the surface charge of carbon-based adsorbents and surely influence the adsorption capacity. Finally, the regeneration of the adsorbent by the photo-Fenton reaction regenerated the adsorption capacity of the adsorbent without generating secondary pollution to the environment.

A self-sufficient photo-Fenton system with coupling in-situ production H2O2 of ultrathin porous g-C3N4 nanosheets and amorphous FeOOH quantum dots

Photo-Fenton degradation of pollutants in wastewater involving hydrogen peroxide (H2O2) and Fe2+ ions to produce hydroxyl radicals (·OH) with high oxidative activity is an ideal and feasible choice in advanced oxidation processes (AOPs). However, the photo-Fenton degradation application is limited by the range of acidic pH and the external introduction of H2O2 and Fe2+ ions. Herein, a self-sufficient photo-Fenton system was developed by coupled ultrathin porous g-C3N4 (UPCN) nanosheets that spontaneously produce H2O2 with amorphous FeOOH quantum dots (QDs) via in-situ deposition method for efficient photo-Fenton degradation of oxytetracycline (OTC) under natural pH condition. The enhancement of photocatalytic degradation activity comes from the synergistic effect of amorphous FeOOH QDs and UPCN nanosheets as follows: on the one hand, the formation of photo-Fenton system combining in-situ generation H2O2 of UPCN with amorphous FeOOH QDs can better boost photocatalytic activity for degrading OTC solution in natural pH under light illumination; on the other hand, the ultrathin porous structure of UPCN can better promote the rapid transfer and dispersion of photo-generated electrons from UPCN to amorphous FeOOH QDs and then Fe3+ is reduced to Fe2+ to participate in the Fenton catalytic reaction.

Sperm Competition and Its Effects on the Evolution of Prostatic Acid Phosphatase in Hominids

Selective pressures and their effects on protein structure and function can be found by comparing genes or proteins from different organisms. These pressures can take varying forms. Sexual selection, a form of natural selection, occurs when an organism acquires traits that give it an advantage in mating and producing offspring. An example can be seen in hominid seminal proteins. Hominids exhibit different mating systems which has resulted in seminal proteins being affected by varying degrees of sperm competition. This can result in variation both in the sequences of these genes and the function of the gene products. One such gene, ACPP, is used to generate the protein prostatic acid phosphatase (PAP). This protein is known to dephosphorylate a number of targets in seminal plasma, and it functions as a phosphatase in the acidic pH range. It has been suggested computationally by comparing dN/dS ratios that ACPP may be under strong positive selection in chimpanzees (a species with high sperm competition) and purifying selection in humans and gorillas (both species with weaker sperm competition). We hypothesize that varying degrees of sperm competition have resulted in sequence and functional variation at ACPP/PAP among hominids. ACPPcoding sequences for human, chimp, and gorilla homologs were each inserted into a mammalian expression vector with a C‐terminal His6 tag and transfected into HEK‐293T cells. The phosphatase activities of the PAP homologs were compared using a DiFMUP fluorescent substrate assay. Each protein was tested for pH optima, phosphatase activity at a fixed substrate concentration, and kcat/km. The PAP orthologs exhibited similar pH profiles, with a pH optimum between pH 5.0‐6.0. However, it was found that chimp PAP exhibited elevated phosphatase activity when compared to the other hominids, and this was consistent across a varying pH range. These results suggest that positive selection of chimp ACPPhas resulted in a more efficient PAP protein with elevated activity when compared to human and gorilla PAP, perhaps due to strong sperm competition. Gorilla PAP showed the lowest activity, which is interesting considering that many genes that code for male reproductive proteins have become pseudogenes in gorillas, a species with very low sperm competition. Overall, the results suggest that the varying mating systems of the hominid primates have resulted in functional differences in the PAP homologs of humans, chimpanzees, and gorillas. By bridging together functional and computational techniques such as in this research, we are beginning to understand the effects of specific selective pressures on the function of male reproductive proteins.

Supplementation of tea polyphenols in sludge Fenton oxidation improves sludge dewaterability and reduces chemicals consumption

The Fenton oxidation improves sludge dewatering but faces notable technical and economic challenges, including a narrow acidic pH range, slow reduction of Fe(III), and the use of high doses of chemicals. Herein, we used a natural polyhydroxyphenol tea polyphenols (TP), as an iron redox conversion enhancer, to mitigate these issues. Compared with the classical Fenton process at pH 3.0, the process with TP (33.8 mg/g dry solids (DS)) improved sludge dewaterability at pH 7.5 in a Fenton-like system with faster Fe(II)/Fe(III) cycling and two times lower consumption of the Fenton reagent. Sludge capillary suction time and specific resistance to filtration decreased from 70 s to 22 s and from 2.7 × 1013 m/kg to 5.2 × 1011 m/kg, respectively, while the required doses of Fe(II) and H2O2 were cut to 25 mg/g DS and 31.2 mg/g DS. Mechanistically, TP could bond readily with Fe(II)/Fe(III) at neutral pH to form stable complexes with complexation constants of 34 ± 161 M−1 and 52 ± 70 M−1, respectively, and reduce part of the Fe(III) to Fe(II) simultaneously. This maintained sufficient soluble Fe in the sludge and boosted efficient conversion of Fe(II)/Fe(III) to yield more hydroxyl radicals (•OH). Subsequently, •OH oxidation resulted in the decomposition of biopolymers with a molecular weight of 108 Da (e.g., 58.2% of polysaccharides and 31.6% of proteins in tightly bound extracellular polymeric substances) into small molecules and disintegration of bioflocs into smaller particles with increased porosity, contact angle, and cell lysis; these changes helped reduce bound water content and improved sludge dewaterability. In addition, the TP-mediated Fenton process disinfected fecal coliforms in the sludge and preserved the sludge organic matters. This work proposes a new paradigm for developing cost-effective sludge dewatering technologies that relies on the synergistic effects of plant polyphenols and advanced oxidation processes.

Ultrahigh-Throughput Screening of High-β-Xylosidase-Producing Penicillium piceum and Investigation of the Novel β-Xylosidase Characteristics.

A droplet-based microfluidic ultrahigh-throughput screening technology has been developed for the selection of high-β-xylosidase-producing Penicillium piceum W6 from the atmospheric and room-temperature plasma-mutated library of P. piceum. β-xylosidase hyperproducers filamentous fungi, P. piceum W6, exhibited an increase in β-xylosidase activity by 7.1-fold. A novel β-D-xylosidase was purified from the extracellular proteins of P. piceum W6 and designated as PpBXL. The optimal pH and temperature of PpBXL were 4.0 and 70 °C, respectively. PpBXL had high stability an acidic pH range of 3.0–5.0 and exhibited good thermostability with a thermal denaturation half-life of 10 days at 70 °C. Moreover, PpBXL showed the bifunctional activities of α-L-arabinofuranosidase and β-xylosidase. Supplementation with low-dose PpBXL (100 μg/g substrate) improved the yields of glucose and xylose generated from delignified biomass by 36–45%. The synergism between PpBXL and lignocellulolytic enzymes enhanced delignified biomass saccharification, increased the Xyl/Ara ratio, and decreased the strength of hydrogen bonds.