Optimization of immobilized urease enzyme on porous polymer for enhancing the stability, reusability and enzymatic kinetics using response surface methodology.

The study examines the immobilization of the urease enzyme on a range of High Internal Phase Emulsion (polyHIPE) materials, assessing characteristics, efficiency, and performance. It also investigates the impact of polyHIPE type, quantity, incubation time, and various parameters on the process and enzyme activity. Surface morphology and functional groups of polyHIPE materials were determined through scanning electron microscopy (SEM) and fourier transform infrared spectroscopy (FT-IR) analyses, revealing significant alterations after modification with polyglutaraldehyde (PGA). The maximum immobilization efficiency of 95% was achieved by adding PGA to polyHIPE materials with an incubation period of 15 h. The optimized conditions for immobilized enzyme using a Box-Behnken design (BBD) of response surface methodology (RSM) were as follows: temperature (40.8 °C), pH (7.1) and NaCl concentration (0.007 g/L). Furthermore, the immobilized enzyme demonstrated remarkable reusability, retaining 75% of its initial activity after six cycles, and sustained shelf-life stability, retaining over 40% activity after 10 days at room temperature. Kinetic analyses revealed that immobilized urease exhibited higher affinity for the substrate, but lower rate of substrate conversion compared to the free enzyme. These findings offer valuable insights into optimizing urease immobilization processes and enhancing urease stability and activity, with potential applications in various fields, including biotechnology and biocatalysis.

Two-Dimensional Nanoporous Cross-linked Polymer Networks as Emerging Candidates for Gas Adsorption.

This paper illustrates the gas adsorption properties of newly synthesized nanoporous cross-linked polymer networks (CPNs). All synthesized CPNs possess N-rich functional groups and are used for the utilization of carbon dioxide and methane. Good gas adsorption and selectivities are obtained for all of the samples. Among the materials, HEREON2 outperforms better selectivity for methane separation from nitrogen rather than zeolites, activated carbons, molecular sieves, covalent organic frameworks, and metal-organic frameworks (MOFs). The accessibility of the N-rich functionalities makes these materials potential candidates for the separation of hydrocarbons via increased polarizabilities. High-pressure adsorption experiments showed that the synthesized two-dimensional nanoporous materials also have a high affinity toward carbon dioxide. HEREON2 powders showed an increased experimental CO2/N2 selectivity of ∼25,000 at 50 bar due to the presence of nitrogen groups in the structure. Fourier-transform infrared spectroscopy (FTIR), solid-state NMR, X-ray diffraction, thermogravimetric analysis, energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) were applied for the characterization of the synthesized nanoporous CPNs. The results show a potential new pathway for future CPN membrane development.

Treatment of tomato paste wastewater by electrochemical and membrane processes: process optimization and cost calculation.

This study investigated the treatment of wastewater from tomato paste (TP) production using electrocoagulation (EC) and electrooxidation (EO). The effectiveness of water recovery from the pretreated water was then investigated using the membrane process. For this purpose, the effects of independent control variables, including electrode type (aluminum, iron, graphite, and stainless steel), current density (25-75 A/m2), and electrolysis time (15-120 min) on chemical oxygen demand (COD) and color removal were investigated. The results showed that 81.0% of COD and 100% of the color removal were achieved by EC at a current density of 75 A/m2, a pH of 6.84 and a reaction time of 120 min aluminum electrodes. In comparison, EO with graphite electrodes achieved 55.6% of COD and 100% of the color removal under similar conditions. The operating cost was calculated to be in the range of $0.56-30.62/m3. Overall, the results indicate that EO with graphite electrodes is a promising pretreatment process for the removal of various organics. In the membrane process, NP030, NP010, and NF90 membranes were used at a volume of 250 mL and 5 bar. A significant COD removal rate of 94% was achieved with the membrane. The combination of EC and the membrane process demonstrated the feasibility of water recovery from TP wastewater.

Biofouling mitigation of Nb2AlC and Mo3AlC2 MXene-precursors doped polyether sulfone mixed matrix membranes for pathogen microorganisms.

This study explores the incorporation of Nb2AlC and Mo3AlC2 MAX phases, known for their nano-layered structure, into polyether sulfone (PES) membranes to enhance their antifouling and permeability properties for pathogen microorganism filtration against bovine serum albumin (BSA) and Escherichia coli (E. coli). The composite membranes were characterized for their structural and morphological properties, and their performance in mitigating biofouling was evaluated. The structural characterizations have been performed for all the prepared MAX phases and corresponding composite membranes. The antioxidant ability of Nb2AlC and Mo3AlC2 MAX phases was defined by the DPPH radical scavenging assay, and the highest antioxidant ability was found to be 59.35 %, while 53.69 % scavenging potential was recorded at 100 mg/L. The percentage scavenging ability was raised with an increase in concentrations. The antimicrobial properties of MAX phases, evaluated as the minimum inhibitory concentration, were stated against several pathogen microorganisms. The tested compounds of Nb2AlC and Mo3AlC2 composites containing MAX phases exhibited excellent chemical nuclease activity, and it was determined that Nb2AlC caused double strand DNA cleavage activity while Mo3AlC2 induced the complete fragmentation of the DNA molecule. Biofilm inhibition of Nb2AlC and Mo3AlC2 MAX phases was studied against Staphylococcus aureus, and Pseudomonas aeruginosa and the maximum biofilm inhibition of Nb2AlC and Mo3AlC2 MAX phases was found to be 77.15 % and 69.07 % against S. aureus and also 69.74 % and 65.01 % against P. aeruginosa. Furthermore, Nb2AlC and Mo3AlC2 MAX phases demonstrated excellent E. coli growth inhibition of 100 % at 125 and 250 mg/L.

The Syntheses of Chromium Aluminum Carbide (Cr2AlC) MAX Phase and Cr2CTx MXene and Investigation of Their Antimicrobial Properties.

Chromium aluminum carbide (Cr2AlC) MAX phase and Cr2CTx (MXene-Cr) were synthesized by the pressureless sintering method and hydrothermal method, respectively. In addition to this, the free radical scavenging activities (FRSA) of MAX-Cr phase and MXene-Cr compounds were tested and compared with ascorbic acid and trolox as standard compounds. The obtained FRSA results of MAX-Cr phase and MXene-Cr were 42.82 and 59.64%, respectively, at 100 mg/L concentration. MXene-Cr showed a 66.90% inhibitory effect on α-amylase at 200 mg/L. The DNA nuclease activity of compounds was determined to be extremely satisfactory at 50, 100, and 200 mg/L concentrations. Moreover, the prepared MAX-Cr phase and MXene-Cr were investigated for antimicrobial activity against six bacterial and two fungal strains by the broth microdilution method. Compounds provided more significant inhibition against Gram-positive bacteria than Gram-negative bacteria and fungi. MAX-Cr phase and MXene-Cr almost completely inhibited microbial cell viability at a 25 mg/L concentration. Additionally, MXene-Cr showed 89.86% and 87.01% antibiofilm activity against S. aureus and P. aeruginosa, respectively, while the antibiofilm activity of the MAX-Cr phase was over 90%.

Antibacterial and antioxidant activity of gold and silver nanoparticles in dextran-polyacrylamide copolymers.

Search for new antimicrobial agents is of great significance due to the issue of antimicrobial resistance, which nowadays has become more important than many diseases. The aim of this study was to evaluate the toxicity and biological effects of a dextran-graft-polyacrylamide (D-PAA) polymer-nanocarrier with/without silver or gold nanoparticles (AgNPs/D-PAA and AuNPs/D-PAA, respectively) to analyze their potential to replace or supplement conventional antibiotic therapy. The toxicity of nanocomplexes against eukaryotic cells was assessed on primary dermal fibroblasts using scratch, micronucleus and proliferation assays. DPPH (2,2-diphenyl-1-picrylhydrazylradical) assay was used to evaluate the antioxidant capacity of D-PAA, AgNPs/D-PAA and AuNPs/D-PAA. DNA cleavage, antimicrobial and biofilm inhibition effects of nanocomplexes were investigated. Nanocomplexes were found to be of moderate toxicity against fibroblasts with no genotoxicity observed. AgNPs/D-PAA reduced motility and proliferation at lower concentrations compared with the other studied nanomaterials. AgNPs/D-PAA and AuNPs/D-PAA showed radical scavenging capacities in a dose-dependent manner. The antimicrobial activity of AgNPs/D-PAA against various bacteria was found to be much higher compared to D-PAA and AuNPs/D-PAA, especially against E. hirae, E. faecalis and S. aureus, respectively. D-PAA, AgNPs/D-PAA and AuNPs/D-PAA showed DNA-cleaving and biofilm inhibitory activity, while AgNPs/D-PAA displayed the highest anti-biofilm activity. AgNPs/D-PAA and AuNPs/D-PAA were characterized by good antimicrobial activity. According to the findings of the study, AgNPs/D-PAA and AuNPs/D-PAA can be evaluated as alternatives for the preparation of new antimicrobial agents, the fight against biofilms, sterilization and disinfection processes. Our findings confirm the versatility of nanosystems based on dextran-polyacrylamide polymers and indicate that AgNPs/D-PAA and AuNPs/D-PAA can be evaluated as alternatives for the preparation of novel antimicrobial agents.

Novel extracellular synthesized silver nanoparticles using thermophilic Anoxybacillus flavithermus and Geobacillus stearothermophilus and their evaluation as nanodrugs.

In this investigation, two new thermophilic bacteria were isolated. The new isolates were characterized by 16S rRNA, biochemical, morphological, and physiological analyzes and the isolates were identified as Geobacillus stearothermophilus strain Gecek20 and thermophilic Anoxybacillus flavithermus strain Gecek19. Various biological activities of extracellular Ag-NPs synthesized from thermophilic G. stearothermophilus strain Gecek20 and thermophilic A. flavithermus strain Gecek19 were evaluated. The produced NPs were analyzed by SEM, SEM-EDX, and XRD analyses. The antioxidant abilities of new synthesized Ag-NPs from thermophilic G. stearothermophilus strain Gecek20 (T1-Ag-NPs) and new synthesized Ag-NPs from thermophilic A. flavithermus strain Gecek19 (T2-Ag-NPs) were studied by DPPH inhibition and metal chelating ability. The highest DPPH and metal chelating abilities of T1-Ag-NPs and T2-Ag-NPs at 200 mg/L concentration were 93.17 and 90.85%, and 75.80 and 83.64%, respectively. The extracellular green synthesized T1-Ag-NPs and T2-AgN-Ps showed DNA nuclease activity at all tested concentrations. Moreover, both new synthesized Ag-NPs had antimicrobial activity against the strains studied, especially on Gram positive bacteria. T1-Ag-NPs and T2-AgNPs also showed powerful Escherichia coli growth inhibition. The highest biofilm inhibition percentages of T1-Ag-NPs and T2-Ag-NPs against Pseudomonas aeruginosa and Staphylococcus aureus were 100.0%, respectively, at 500 mg/L.

Improving Biohydrogen Production by Dark Fermentation of Milk Processing Wastewater by Physicochemical and Enzymatic Pretreatments.

Biohydrogen is considered an alternative energy reserve. Dark fermentation is one of the important green hydrogen production techniques that utilizes organic waste as raw material. It is a promising bioconversion, easy, not expensive, and cost-effective process. Milk processing wastewater (MPWW) is an organic effluent generated in large volumes on a daily basis and disposed directly into the environment. In this research, the study of biochemical hydrogen potential (BHP) test of MPWW was evaluated and used as substrate (S). A waste sludge was used as an inoculum (I) and source of bacteria. Both substrate and inoculum were analyzed and the study was based mainly on the ratio of volatile solids (VS) of inoculum and substrate subsequently, which was noted as I/S. Different substrate pretreatments were performed: ultrasonic, thermal, chemical, and enzymatic hydrolysis. The I/S ratio impact was investigated and evaluated the hydrogen production improvement. Modified Gompertz and modified Logistic kinetic models were employed for the kinetic modeling of cumulative hydrogen production values. Results show that I/S ratio of 1/4 gVS/gVS resulted from the best hydrogen production of 59.96 mL during 30 days of MPWW fermentation without pretreatment. It was also shown that all the adopted pretreatments enhanced hydrogen production, whereas ultrasonic pretreatment for 5 min increased the production by only 14.84%. Heat pretreatment was more efficient, where the hydrogen production increased from 60 to 162 mL (170% of improvement) using heat shock at 90 °C for 30 min. The impact of chemical pretreatment was different from a reagent to another. Pretreatment using calcium hydroxide resulted in the biggest hydrogen production of 165.3 mL (175.5%) compared to the other chemical pretreatments. However, the best hydrogen production was given by the biological pretreatment using enzymatic hydrolysis (Lactase) resulting in 254 mL of hydrogen production, which is equivalent to 323.62% of production improvement. Modified Gompertz and Logistic kinetic models fitted well with experimental data. Thus, the enzymatic hydrolysis of MPWW proved to be a promising technique for biohydrogen production enhancement.

Simultaneous production of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) from recovered volatile fatty acid with treatment of leachate by Pilot-Scale Mechanical Vapor Recompression.

Serious global problems faced due to many petroleum-based materials in the last century, which is called the plastic age, constitute the main motivation of this research. Considering wastewater treatment from this perspective, both the recovery of organic acids from wastewater and their conversion into bioplastics are extremely important in terms of reducing petroleum dependency. In this study, while the treatment of landfill leachate was provided with biological process integrated into Mechanical Vapor Recompression (MVR), simultaneously PHBV production was carried out with 84.9% recovered VFA as carbon source. The effects of C/N/P ratio and feeding regime on PHBV storage were investigated by Cupriavidus necator. PHBV storage of 96% (g PHBV/g DCW) was maximized by 2-stage feeding and nitrogen restriction. The ratio of 3HV to 3HB of PHBV was 45%. In addition, extracted PHBV was compared with standard PHA in terms of thermal and chemical properties with FTIR, XRD, TGA and DSC analyses.

Synthesis of PES membranes modified with polyurethane-paraffin wax nanocapsules and performance of bovine serum albumin and humic acid rejection.

Membrane fouling is a serious handicap of membrane-based separation, as it reduces permeation flux and hence increases operational and maintenance expenses. Polyurethane-paraffin wax (PU/PW) nanocapsules were integrated into the polyethersulfone membrane to manufacture a composite membrane with higher antifouling and permeability performance against humic acid (HA) and bovine serum albumin (BSA) foulants. All manufactured membranes were characterized by scanning electron microscopy (SEM), scanning electron microscopy-energy dispersive spectrometry (SEM-EDS), and contact angle. The contact angle of the pristine polyethersulfone (PES) membrane was measured 73.40 ± 1.32. With the embedding of nanocapsules, the contact angle decreased to 64.55 ± 1.23 for PES/PU/PW 2.0 wt%, and the pure water flux of all composite membranes increased when compared to pristine PES. The pristine PES membrane also has shown the lowest steady-state fluxes at 45.84 and 46.59 L/m2h for BSA and HA, respectively. With the increase of PU/PW nanocapsule ratio from 0.5 to 1.0 wt%, steady-state fluxes increased from 51.96 to 71.61 and from 67.87 to 98.73 L/m2h, respectively, for BSA and HA. The results depicted that BSA and HA rejection efficiencies of PU/PW nanocapsules blended PES membranes increased when compared to pristine PES membranes.

Physico-chemical adsorption of cationic dyes using adsorbent synthesis via hydrochloric acid treatment and subcritical method from palm leaf biomass waste.

Today, where water resources are polluted rapidly, the need for eco-friendly green methods is gradually increasing. Conversion of waste biomass into functional adsorbents that can be utilized in water treatment is a win-win practice for both recycling and water pollution treatment. In this study, the adsorbent material was obtained from the palm leaf to contribute to sustainable green energy. This cellulose-containing adsorbent material was tested in the removal of Methylene Blue (MB) and Basic Red-18 (BR18). The properties of palm leaf adsorbent were determined. The best removal efficiencies and optimum conditions were determined in the adsorption process. In both dye types; the original pH value, 2 g/L adsorbent dose, 25 mg/L dye concentration, and 120 min were chosen as the optimum conditions since the best removal efficiency was obtained in the experiments performed at 25 °C. At these conditions, the removal efficiencies were found to be 100% and 90% for BR18 and MB, respectively. In addition, adsorption kinetics, isotherms, and thermodynamic data were analyzed. For BR18 and MB, it was found to fit the Langmuir isotherm and pseudo-2nd order. Palm leaf adsorbent was used with an efficiency of over 50% in four consecutive cycles.

Boron-based magnesium diboride nanosheets preparation and tested for antimicrobial properties for PES membrane.

Antimicrobial resistance to antibiotics for current bacterial infection treatments is a medical problem. 2D nanoparticles, which can be used as both antibiotic carriers and direct antibacterial agents due to their large surface areas and direct contact with the cell membrane, are important alternatives in solving this problem. This study focuses on the effects of a new generation borophene derivative obtained from MgB2 particles on the antimicrobial activity of polyethersulfone membranes. MgB2 nanosheets were created by mechanically separating magnesium diboride (MgB2) particles into layers. The samples were microstructurally characterized using SEM, HR-TEM, and XRD methods. MgB2 nanosheets were screened for various biological activities such as antioxidant, DNA nuclease, antimicrobial, microbial cell viability inhibition, and antibiofilm activities. The antioxidant activity of nanosheets was 75.24 ± 4.15% at 200 mg/L. Plasmid DNA was entirely degraded at 125 and 250 mg/L nanosheet concentrations. MgB2 nanosheets exhibited a potential antimicrobial effect against tested strains. The cell viability inhibitory effect of the MgB2 nanosheets was 99.7 ± 5.78%, 99.89 ± 6.02%, and 100 ± 5.84% at 12.5 mg/L, 25 mg/L, and 50 mg/L, respectively. The antibiofilm activity of MgB2 nanosheets against S. aureus and P. aeruginosa was observed to be satisfactory. Furthermore, a polyethersulfone (PES) membrane was prepared by blending MgB2 nanosheets from 0.5 wt to 2.0 wt %. Pristine PES membrane also has shown the lowest steady-state fluxes at 30.1 ± 2.1 and 56.6 L/m2h for BSA and E. coli, respectively. With the increase of MgB2 nanosheets amount from 0.5 to 2.0 wt%, steady-state fluxes increased from 32.3 ± 2.5 to 42.0 ± 1.0 and from 15.6 ± 0.7 to 24.1 ± 0.8 L/m2h, respectively for BSA and E. coli. E. coli elimination performance of PES membrane coated with MgB2 nanosheets at different rates and the membrane filtration procedure was obtained from 96% to 100%. The results depicted that BSA and E. coli rejection efficiencies of MgB2 nanosheets blended PES membranes increased when compared to pristine PES membranes.

A combined process of chemical precipitation and aerobic membrane bioreactor for treatment of citric acid wastewater.

The wastewater generated from citric acid production has a high organic loading content. The treatment and reuse of citric acid wastewater with high organic loading become extremely important. In this study, the performance of calcium hydroxide (Ca(OH)2) precipitation as a low-cost and environmentally friendly pre-treatment method and aerobic membrane bioreactor (MBR) combined treatment system was investigated for the treatment of citric acid (CA) wastewater. At the first step, optimization parameters such as agitation speed (100, 150, 200 rpm), temperature (30, 50, 70 °C), and reaction time (2, 4, 6 h) for Ca(OH)2 precipitation as a pre-treatment method were investigated using response surface methodology (RSM) to achieve maximum chemical oxygen demand (COD) removal. Experimental sets were designed using Box-Behnken Design. As a result of pre-treatment with Ca(OH)2 precipitation, a COD removal efficiency of 97.3% was obtained. Then, pre-treated CA wastewater was fed continuously to the MBR process for 10 days, which was the second stage of the combined process. As a result of the MBR process, 92.0% COD removal efficiency was obtained for 24 h HRT and 10 days SRT. In total, 99.8% COD removal efficiency was obtained when combined process was used and COD concentration decreased from 52,000-114 mg/L. For the treatment and reuse of wastewater from citric acid production, Ca(OH)2 precipitation and MBR combined treatment systems demonstrated an effective strategy.

Fabric dyeing wastewater treatment and salt recovery using a pilot scale system consisted of graphite electrodes based on electrooxidation and nanofiltration.

In this study, color removal, suspended solids removal, and salt recovery were investigated from different fabric dyeing wastewaters using a pilot scale treatment system. A pilot scale system was installed in the wastewater outlet area of five different textile companies. Experiments were planned for pollutant removal and salt recovery from wastewater. First, the wastewater was treated by electrooxidation (EO) using graphite electrodes. After a reaction time of 1 h, the wastewater was passed throughout the granular activated carbon (AC) coloumn. The pre-treated wastewater was passed through the membrane (NF) system to recover the salt in the wastewater. Finally, the recovered salt water was used for fabric dyeing. In the pilot scale treatment system (EO + AC + NF), 100% of suspended solids (SS) and an average of 99.37% of color were removed from fabric dyeing wastewaters. At the same time, a high amount of salt water was recovered and reused. Optimum conditions were determined as 4 V current, 1000 A power, wastewater's own pH values and 60 min of reaction time. The energy and operating cost for treatment of 1 m3 of wastewater were determined as 40.0 kWh/m3 and 2.2 US$/m3, respectively. In addition to the prevention of environmental pollution by the treatment of wastewater using the pilot-scale treatment system, the reuse of the recovered water will contribute to the protection of our valuable water resources. In addition, using the NF membrane process after the EO system, it will be possible to recover salt from wastewater with high salt content such as textile wastewater.

A comparative study of iron nanoflower and nanocube in terms of antibacterial properties.

It is known that heavy metal containing nanomaterials can easily prevent the formation of microbial cultures. The emergence of new generation epidemic diseases in the last 2 years has increased the importance of both personal and environmental hygiene. For this reason, in addition to preventing the spread of diseases, studies on alternative disinfectant substances are also carried out. In this study, the antibacterial activity of nanoflower and nanocube, which are easily synthesized and nanoparticle species containing iron, were compared. The antioxidant abilities of new synthesized NF@FeO(OH) and NC@α-Fe2O3 were tested by DPPH scavenging activity assay. The highest DPPH inhibition was achieved with NC@α-Fe2O3 as 71.30% at 200 mg/L. NF@FeO(OH) and NC@α-Fe2O3 demonstrated excellent DNA cleavage ability. The antimicrobial capabilities of NF@FeO(OH) and NC@α-Fe2O3 were analyzed with micro dilution procedure. In 500 mg/L, the antimicrobial activity was 100%. In addition to these, the biofilm inhibition of NF@FeO(OH) and NC@α-Fe2O3 were investigated against S. aureus and P. aeruginosa and it was found that they showed significant antibiofilm inhibition. It is suggested that additional studies can be continued to be developed and used as an antibacterial according to the results of the nanoparticles after various toxicological test systems. Supplementary Information: The online version contains supplementary material available at 10.1007/s13204-023-02822-5.

Antifouling and antibacterial performance evaluation of polyethersulfone membranes modified with AZ63 alloy.

Antibacterial membranes have attracted researchers' interest in recent years as a possible approach for dealing with biofouling on the membrane surface. This research aims to see if blending AZ63 Mg alloy into a polyethersulphone (PES) membrane can improve antifouling and separation properties. The composite membranes' pure water flux continued to increase from pristine PES to PES/AZ63 2.00 wt%. The results showed that PES/AZ63 2.00 wt% membrane supplied the highest permeate flux of E. coli. The steady-state fluxes of AZ63 composite membranes were 113.24, 104.38 and 44.79 L/m2h for PES/AZ63 2.00 wt%, 1.00 wt%, and 0.50 wt%, respectively. The enhanced biological activity of AZ63 was studied based on antioxidant activity, DNA cleavage, antimicrobial, anti-biofilm, bacterial viability inhibition and photodynamic antimicrobial therapy studies. The maximum DPPH scavenging activity was determined as 81.25% with AZ63. AZ63 indicated good chemical nuclease activity and also showed moderate antimicrobial activity against studied strains. The highest biofilm inhibition of AZ63 was 83.25% and 71.63% towards P. aeruginosa and S. aureus, respectively. The cell viability inhibition activity of AZ63 was found as 96.34% against E. coli. The photodynamic antimicrobial therapy results displayed that AZ63 demonstrated 100% bacterial inhibition when using E. coli.

Optimization of the anaerobic fermentation process for phosphate release using food waste.

Phosphorus (P) problem worries the whole world due to the increasing demand for finite and non-renewable natural phosphate resources and the inadequacy of sustainable phosphate production technologies. In this study, bio-acidification processes using waste sludge and food waste for simultaneous sustainable phosphate release and biogas production were investigated. Response surface methodology (RSM) was used for bio-acidification optimization. High performance was achieved with the addition of 10% FW and a temperature of 45 °C, which provided 5.30 pH and 371 mg/L P release for 10 days. A total of 196 mL of cumulative biogas was produced. Using food waste potentially reduces operating costs, eliminating the need for external chemical additions for pH control. Also, this approach offers benefits such as waste management, recovery of valuable resources, cost reduction, and environmental friendly.

Antimicrobial and antioxidant activity of phenolic extracts from walnut (Juglans regia L.) green husk by using pressure-driven membrane process.

In this study, antioxidant (DPPH and metal chelating), DNA cleavage, biofilm, and antimicrobial properties of extracted phenol from the walnut green husk (WGH) and its different concentrate and permeate samples were evaluated. For maximum phenolic compound extraction from the WGH first, the effects of solvent type (deionized water, methanol, n-hexane, acetone, and ethanol), solvent temperature (25-75 °C), and extraction time (0.5-24 h) were optimized. Then to concentrate phenolic compounds a pressure-driven membrane process was used with four different membrane types. The phenol contents of the concentrate samples were found to be microfiltration (MF) concentrate 4400 mg/L, ultrafiltration (UF) concentrate 4175 mg/L, nanofiltration (NF) concentrate 8155 mg/L, and reverse osmosis (RO) concentrate 8100 mg/L. LC-MSMS was used to determine the quantification of phenolic compounds in permeate and concentrate streams. In addition, all of the concentrate samples with high phenol content showed a high antioxidant activity as 100% with MF concentrate, UF concentrate, NF concentrated and RO concentrated. Likewise, concentrate samples were found to have very high antibiofilm activity as 82.86% for NF concentrate againts S. aureus, 85.80% for NF concentrate against P. aureginosa, 80.95% for RO concentrate against S. aureus, and 83.61% for RO-concentrate against P. aureginosa. When the antimicrobial activity of the extracted phenol from WGH and its different concentrate and permeate samples were evaluated by micro dilution and disk diffusion methods, it was found that the ability of the concentrate samples to inhibit bacterial growth was much higher than permeate ones. In addition, extracted phenol from WGH and its different concentrate and permeate samples showed significant DNA nuclease activity. Supplementary Information: The online version contains supplementary material available at 10.1007/s13197-022-05588-w.

Preconcentrations of Pb(II), Ni(II) and Zn(II) by solid phase bio-extractor using thermophilic Bacillus subtilis loaded multiwalled carbon nanotube biosorbent.

An alternative biotechnological solid phase bio-extraction (SPE) method was developed. Bacillus subtilis loaded multiwalled carbon nanotube was designed and used as biosorbent for the preconcentrations of Pb(II), Ni(II), and Zn(II). The experimental parameters such as sample flow rate, pH of sample solution, amounts of Bacillus subtilis and multiwalled carbon nanotube, volume of sample solution and reusability of column which affects the analytical characteristics of the SPE method were investigated in details. Surface structures were examined by using FTIR, SEM. The best pH was determined as 5.0 and the percentages recoveries of Zn(II), Ni(II), and Pb(II) were determined as 99.1%, 98.7%, and 96.2%, respectively, at a flow rate of 3 mL/min. In this study, in which the profitable sample volume was determined as 400 mL and the amount of multiwalled carbon nanotube (MWCNT) as 50 mg. It was also observed that the column had a significant potential to preconcentrate Zn(II), Ni(II), and Pb(II) even after 25 reuses. The biosorption capacities for Zn(II), Ni(II) and Pb(II) were calculated as 39.67 mg/g, 45.98 mg/g and 51.34 mg/g respectively. The LOD values were calculated as 0.024 ng/mL for Pb(II), 0.029 ng/mL for Ni(II), and 0.019 ng/mL for Zn(II). The linear range was detected as 0.25-25 ng/mL. The concentrations of Pb(II), Ni(II), and Zn(II) in a variety of real food samples were determined by using developed method after application of certified reference sample.

Investigation of diode laser effect on the inactivation of selected Gram-negative bacteria, Gram-positive bacteria and yeast and its disinfection on wastewater and natural milk.

Disinfection can be accomplished by adding external chemical agents to kill harmful microorganisms or by removing them using membranes. However, most chemicals are toxic for humans and animals if it is consumed above a certain concentration. Likewise, membranes have fouling problems. The aim of this study is to investigate the effect of diode laser, which is an environmentally friendly application, on pathogenic microorganisms such as Escherichia coli (ATCC 10536), Staphylococcus aureus (ATCC 6538) and Candida albicans. To reveal the effect of diode laser on aforementioned, various parameters have been studied on how diode laser type, laser irradiation time, laser power density, laser penetration efficiency and biofilm inhibition affect microorganisms. As a result of the study, it was observed that the blue laser was more effective than red and green lasers, and the inhibition rates for 15 min at 0.36 W/cm2 laser power density were 65.9% > 34.52% > 43.63% for S. aureus, E. coli and C. albicans, respectively. After 30 min of blue laser irradiation, the microbial growth inhibitions were found as 85.39%, 41.18% and 54.55% for S. aureus, E. coli and C. albicans, respectively. The highest biofilm inhibition was 94.61% when S. aureus cells were exposed to blue laser irradiation for 60 min. The microbial growth kinetics on three microorganisms were tested by using at 0.54 W/cm2 laser power density for 28 h, and there were not observed any microbial development in microbial cultures. Moreover, blue laser irradiation was successfully disinfected wastewater and natural milk at 0.54 W/cm2 laser power density.