Optimum Initial pH Research Articles

Adsorption of copper by flocculated Chlamydomonas microsphaera microalgae and polyaluminium chloride in heavy metal-contaminated water

This study investigated a low-cost and sustainable use for microalgae and polyaluminium chloride (PAC) mixed waste collected during water treatment processes. The microalga Chlamydomonas microsphaera in the form of a dry powder (CM) and C. microsphaera collected by PAC flocculation (PCM) were evaluated as biosorbents of the toxic heavy metal contaminant Cu2+. The adsorption capacities of PCM and CM were determined in batch experiments at varying biosorbent concentrations, pH, contact times, and the presence of other metallic cations (Na+, Ca2+, Fe3+) at room temperature. After incubation, SEM and EDAX imaging detected copper ions adsorbed to the surfaces of both biosorbents. Adsorption capacity decreased and the adsorption ratio increased with increasing biosorbent concentration. The optimal initial pH for adsorption was between 5.0 and 6.0 for both biosorbents. The rate of adsorption for Cu2+ onto both biosorbents rose quickly within the first 30 min and reached equilibrium in less than an hour. Adsorption kinetics followed the pseudo-second-order model. The pseudo-second-order model rate constant and adsorption capacity at equilibrium were higher for PCM than for CM. Of the three metallic cations evaluated, only Fe3+ produced a significant effect, reducing the adsorption of copper onto both biosorbents. The adsorption capacity of PCM is well-described by the Langmuir and Freundlich isotherm models. The maximum adsorption capacity of Cu2+ onto PCM (79.4 mg g−1) was higher than that for CM (57.3 mg g−1). Our results suggest that PCM waste from drinking water treatment processes could serve as a low-cost, efficient biosorbent for the removal of toxic heavy metals from water.

Removal and recovery of phosphate anion as struvite from wastewater

Phosphorus is one of the controlling factors for water eutrophication, but it is also an essential nutrient for all living organisms and non-renewable resource. A feasibility study on PO43− recovery and conversion to struvite (NH4MgPO4·6H2O), a slow-release fertilizer, has been reported. However, the fertilizer efficiency of struvite is determined by its purity, which depends on the forms and molar ratio of reactants under different initial pH of the solution. Laboratory-scale experiments were carried out to determine the optimum initial pH of the solution and molar ratio of reactants on struvite crystallization. Meanwhile, the purity of the synthesis product struvite was analyzed. The experiment results revealed the optimum initial pH being 10 with molar ratio of PO43−:Mg2+:NH4+= 1:1.3:1 and 1:2:5 for struvite formation, which the removal of the PO43−, Mg2+ and NH4+ being 98, 92, 95% and 99.5, 85, 90%, respectively. A chemical equilibrium model (Visual Minteq) corroborated the experimental results. Thus, the possibility of synthesizing struvite from simulated wastewater utilizing the phosphate ions (PO43−) was confirmed.

An efficient process for co-production of γ-aminobutyric acid and probiotic Bacillus subtilis cells.

This study was to establish an integrated process for the co-production of γ-aminobutyric acid (GABA) and live probiotics. Six probiotic bacteria were screened and Bacillus subtilis ATCC 6051 showed the highest GABA-producing capacity. The optimal temperature and initial pH value for GABA production in B. subtilis were found to be 30°C and 8.0, respectively. A variety of carbon and nitrogen sources were tested, and potato starch and peptone were the preferred carbon and nitrogen sources for GABA production, respectively. The concentrations of carbon source, nitrogen source and substrate (sodium l-glutamate) were then optimized using the response surface methodology. The GABA titer and concentration of viable cells of B. subtilis reached 19.74g/L and 6.0 × 108cfu/mL at 120h. The GABA titer represents the highest production of GABA in B. subtilis. This work thus demonstrates a highly efficient co-production process for GABA and probiotic B. subtilis cells.

Isolation and characterization of a novel nicotinophilic bacterium, Arthrobacter sp. aRF-1 and its metabolic pathway.

Nicotine is a potent parasympathomimetic stimulant and an important natural alkaloid mainly found in the Nicotiana genus of plants. It can directly threaten ecological security and human health in tobacco waste, wastewater, and other forms of tobacco production. Therefore, it is the basis of nicotine pollution prevention and of great application value to explore efficient and a wide range of nicotinophilic bacteria for tobacco industry and environmental protection. In this study, one nicotinophilic bacterium was isolated from the soil, which accumulated tobacco waste over 50 years at a Hefei cigarette factory. The strain was named aRF-1, which was identified as Arthrobacter sp. by analysis. The nicotine degradation tests showed that the optimum temperature for cell growth and metabolism of nicotine of Arthrobacter sp. aRF-1 was 30°C, and the optimum initial pH value was about 7.0. Under the optimum experimented conditions, it can tolerance nicotine concentration as high as 8 g·L-1 . The highest removal rate of nicotine was 93.8% in 72 H in nonsterilization contaminated soil by Arthrobacter sp. aRF-1. LC-MS/MS was used to analyze the nicotine metabolic intermediates of strain Arthrobacter sp. aRF-1. A total of nine major metabolites that were detected were able to metabolize nicotine along a variant pathway of pyridine and pyrrolidine, and there may be more than two nicotine metabolic pathways for Arthrobacter sp. aRF-1 through the analysis of the main intermediate products.

Removal of Chromium(VI) from Groundwater Using Oil Shale Ash Supported Nanoscaled Zero-valent Iron

Oil shale ash(OSA) supported nanoscaled zero-valent iron(OSA-nZVI) was used as a rapid and efficient reductant for Cr(VI) reduction. The optimal mass ratio of nZVI to OSA and the optimal dosage were explored. The effects of initial pH, reaction temperature, initial Cr(VI) concentration, and common cations and anions in ground-water on Cr(VI) reduction were determined in batch experiments. The results show that the optimum initial pH is 5.0. The reaction temperature has a positive effect on Cr(VI) reduction while the real groundwater has a negative effect. Additionally, 84.22% Cr(VI) was still reduced by 3 g/L OSA-nZVI(1:2)(mass ratio of OSA to Fe0 was 1:2) within 120 min for 50 mg/L Cr(VI) under conditions of 10 oC and unadjusted pH.

Degradation of EDTA in H2O2 -containing wastewater by photo-electrochemical peroxidation

Semiconductor wastewater currently contains H2O2 which is an important reagent in wafers cleaning. Recalcitrant organic pollutant such as EDTA are always present in this type of wastewater and may represent a threat for the environment. In this work, a new photoelectrochemical reactor is proposed to remove EDTA from H2O2 contaning wastewater. First, photolysis, electrochemical peroxidation and photo-electrochemical peroxidation were compared. The results showed that the removal efficiency decreases in the sequence: UV/H2O2 «EC/H2O2 <UV/EC/H2O2. The main parameters affecting the photo-electrochemical peroxidation process were studied. The study revealed that the optimal current was 50 mA, while the optimum initial pH was found in the acidic range from 2.25 to 3.0, with a peak at 2.25. Increasing H2O2 concentration results in increasing in EDTA removal up to 92.1%, while decreasing initial EDTA concentration up to 22.5 mg L−1 gives a complete removal in only 90 min. It was also found that the degradation of EDTA greatly depends on the nature of the present cation.

Effects of Some Operating Parameters on Sorption and Desorption Kinetics Related to Spotted Golden Thistle Stalks and Methylene Blue; Isotherm Study at Optimal pH and Sorbent Regeneration

In this work, the sorptive removal assessment of methylene blue by spotted golden thistle stalks was enhanced. Sorption was positively impacted by increasing temperature, initial pH or ionic strength. The sorbent isoelectrical point is 2.6 according to zeta potential measurements. The Elovich and Avrami models best fitted the sorption kinetic data; and an original prediction of equilibrium time is proposed. At 25 °C and for optimal initial pH = 7, the experimental maximal sorption capacity is 75 mg g−1. The Langmuir, Redlich–Peterson, Sips and Tóth models led to good correlations of isothermal data. Desorption percentages are important in both mineral and organic acidic media; the highest levels up to 91% were recorded for 1 × 10−2M HCl solutions. The pseudo second-order model fitted satisfactorily the desorption kinetics. An innovative concept of regeneration is proposed, which promises significant savings of eluent and operating time. The sorbent regeneration assessment showed constant uptake abilities after five cycles of use.

A novel isolate of Clostridium butyricum for efficient butyric acid production by xylose fermentation

Bacterial fermentation of lignocellulose has been regarded as a sustainable approach to butyric acid production. However, the yield of butyric acid is hindered by the conversion efficiency of hydrolysate xylose. A mesophilic alkaline-tolerant strain designated as Clostridium butyricum B10 was isolated by xylose fermentation with acetic and butyric acids as the principal liquid products. To enhance butyric acid production, performance of the strain in batch fermentation was evaluated with various temperatures (20–47 °C), initial pH (5.0–10.0), and xylose concentration (6–20 g/L). The results showed that the optimal temperature, initial pH, and xylose concentration for butyric acid production were 37 °C, 9.0, and 8.00 g/L, respectively. Under the optimal condition, the yield and specific yield of butyric acid reached about 2.58 g/L and 0.36 g/g xylose, respectively, with 75.00% butyric acid in the total volatile fatty acids. As renewable energy, hydrogen was also collected from the xylose fermentation with a yield of about 73.86 mmol/L. The kinetics of growth and product formation indicated that the maximal cell growth rate (μ m ) and the specific butyric acid yield were 0.1466 h−1 and 3.6274 g/g cell (dry weight), respectively. The better performance in xylose fermentation showed C. butyricum B10 a potential application in efficient butyric acid production from lignocellulose.

STUDI PENGARUH pH AWAL MEDIA DAN LAMA FERMENTASI PADA PROSES PRODUKSI ETANOL DARI HIDROLISAT TEPUNG BIJI NANGKA DENGAN MENGGUNAKAN Saccharomycess cerevisiae

Jackfruit seed (Artocarpus heterophyllus) flour is a substrate used in ethanol production research.The purpose of this study was to determine the effect of the media initial pH and the time length of fermentation on the ethanol fermentation process from the jackfruit seed starch hydrolyzate using Saccharomyces cerevisiae and to obtain optimum initial pH of the medium and the optimum fermentation length in order to obtain the highest ethanol concentration. This research was designed with 2 factors. The first factor is the initial pH of the media consisting of 3 levels, namely 4, 4,5, and 5. The second factor is the fermentation length consisting of three levels, ie 5, 6, and 7 days. Data obtained from the research are analyzed and presented descriptively. The results showed that the initial pH of the media had an effect on ethanol content and final pH, but had no effect on total soluble solids. Hydrolyzate of jackfruit flour, fermentation length has an effect on total ethanol, final pH, and total dissolved solids. The interaction of the two treatments had an effect on total ethanol of fermented jackfruit seed flour. The best treatment to produce ethanol hydrolyzate of jackfruit seed flour is the initial pH of medium 4.5 and the duration of fermentation of 6 days to produce total ethanol of 3.67 mL. &#x0D; Key words: Artocarpus heterophyllus, ethanol, fermentation, initial pH of medium

Characterization of a Thermophilic Lignocellulose-Degrading Microbial Consortium with High Extracellular Xylanase Activity.

A microbial consortium, TMC7, was enriched for the degradation of natural lignocellulosic materials under high temperature. TMC7 degraded 79.7% of rice straw during 15 days of incubation at 65°C. Extracellular xylanase was effectively secreted and hemicellulose was mainly degraded in the early stage (first 3 days), whereas primary decomposition of cellulose was observed as of day 3. The optimal temperature and initial pH for extracellular xylanase activity and lignocellulose degradation were 65°C and between 7.0 and 9.0, respectively. Extracellular xylanase activity was maintained above 80% and 85% over a wide range of temperature (50-75°C) and pH values (6.0-11.0), respectively. Clostridium likely had the largest contribution to lignocellulose conversion in TMC7 initially, and Geobacillus, Aeribacillus, and Thermoanaerobacterium might have also been involved in the later phase. These results demonstrate the potential practical application of TMC7 for lignocellulosic biomass utilization in the biotechnological industry under hot and alkaline conditions.

Application of calcium peroxide for efficient removal of triamcinolone acetonide from aqueous solutions: Mechanisms and products

There are numerous studies identifying the presence and toxicity of glucocorticoids (GCs) in water; however, limited studies reported effective GC removal technologies. This study researched the efficiency of calcium peroxide (CaO2) in removing GC in wastewater treatment plants (WWTPs) with triamcinolone acetonide (TA) as the representative. Effects of CaO2 dosage, initial pH, and water matrix were investigated. The functional reactive oxygen species (ROS) during TA removal was tested. Specifically, TA degradation intermediates by CaO2 oxidation were identified for the first time. GC toxicity change during TA removal was deduced. The results indicated that CaO2 treatment can be an effective method for TA removal and toxicity decrease. At the reaction time of 60 min, more than 78% of TA can be degraded with CaO2 at 0.05–4 g L−1. The TA removal efficiency increased with the increase of CaO2 dosage. The optimal initial pH value is 6.8. HCO3−, Cl−, and NO3− had inhibitive effects on TA removal while SO42− had no effect and PO43− had positive effect. Humic acid (HA) had positive effects on TA removal because of its obvious adsorption effects. The HO and O2− released by CaO2 are the functional ROS for TA removal, among which HO is the most important one. Besides the oxidation of HO and O2−, the adsorption effects of CaO2 and Ca(OH)2 and the hydrolysis at alkaline conditions may also contribute to TA removal. Six intermediates were revealed during TA degradation, indicating the decrease in GC activity.

Enhanced thermophilic bioenergy production from food waste by a two-stage fermentation process

PurposeThe objective of research was emphasized on the optimal conditions (initial pH and C/N ratio) for enhancing bioenergy from food waste by a two-stage fermentation process.MethodsBioenergy production from food waste was operated by mixed culture under thermophilic temperature in batch reactor. Thermophilic biohydrogen production was optimized in terms of initial pH (5.0–9.0) and then was optimized in terms of C/N ratio (10–50) in the first stage. After that, thermophilic biomethane production was optimized in terms of initial pH (6.0–10.0) in the second stage.ResultsThe results revealed that the thermophilic biohydrogen production from food waste at an initial pH 7.0 presented the maximum hydrogen yield of 176.10 mL H2/g COD. At this optimal initial pH, the maximum hydrogen yield of 214.88 mL H2/g COD was achieved at C/N ratio 30. Subsequently, the effluent from the first stage of thermophilic biohydrogen production from food waste under the optimal initial pH of 7.0 and the optimal C/N ratio of 30 was used as a substrate in the second stage of thermophilic biomethane production. Thermophilic biomethane production from hydrogen fermentation effluent provided the maximum methane yield of 310.77 mL CH4/g COD at initial pH 7.0. At these optimal conditions, COD removal was achieved at 70–90%.ConclusionTherefore, a two-stage thermophilic fermentation process could effectively enhance biohydrogen and biomethane production, including reduction of organic waste at the same time.

Removal of copper, cadmium, and chromium from wastewater by modified wheat bran using Box–Behnken design: Kinetics and isotherm

ABSTRACTIn this work, copper, cadmium, and chromium were removed using hydrochloric acid-treated wheat bran as an adsorbent. Experiments were carried out in batch adsorption mode. Box–Behnken design of response surface methodology was used to determine the effect of initial metal concentration, pH, temperature, and adsorbent dose on removal efficiency of copper, cadmium, and chromium. Analysis of variance results are shown for all the three heavy metal, and the effect of the parameters is discussed. The optimum initial metal concentration, pH, temperature, and adsorbent dose were found to be 90.58 mg/L, 6, 35.9°C, and 2.39 g, respectively. Pseudo-second-order kinetic model was found to be the best suitable model for adsorption rate. The isotherms of adsorption data were analysed using various adsorption isotherm models such as Langmuir, Freundlich, Dubinin–Radushkevich, and Temkin isotherms. It was found that Langmuir and Temkin isotherms represent the equilibrium data for these heavy metal removals.

Effects of Cultivating Conditions on the Water Soluble Polysaccharides Content of Ganoderma lucidum Mycelium in Submerged Flask Culture

The carcinostatic substance in Ganoderma lucidum (Fr.) Karst (Polyporaceae) is a water soluble polysaccharides (WSP) which might be useful in immunotherapy. Attempt to produce effective substances from cultured mycelia is important to carry out since solid cultivation is a time consuming and quality fluctuating. The effects of cultivating conditions on the water soluble polysaccharides content of G. Lucidum mycelium were investigated in submerged flask cultures. Culture from fruiting bodies was maintained on potato dextrose-agar slope. Slopes were inoculated and incubated at 30°C for 7 days, and stored at 4°C. The flask experiments were performed in 100 ml erlenmeyer flasks containing 20 ml of the sterilized media. Actively growing mycelia (1 piece, 5 mm X 5 mm) from a newly prepared slant culture (about 7 days incubation at 30°C) were inoculated into the flask. The pH was measured and adjusted to the desired value by addition of either 4 M HCl or 2.5 M NaOH. Incubation temperature were 20, 25, and 30°C. At the end of inoculation period (14 days) mycelium consisting of individual pellets was harvested and wash for the analysis. WSP content was analysed using phenol-sulfuric acid method. The optimal initial pH for metabolite production would depend on the culture medium. Generally, high values of pH, such as 9, negatively affect both cell growth and WSP production. The optimum temperature range for the high G. lucidum mycelium and WSP production were found to be 25 – 30 °C at pH values 5 – 7 in both of media.

Process performance and methane production optimizing of anaerobic co-digestion of swine manure and corn straw

During anaerobic digestion (AD) process, process parameters e.g., VFA, pH, COD removal … and kinetic parameters e.g., hydrolysis rate, lag phase and methane production potential… are the important indicator for illustrating AD process performance, however, the AD process performance based on these parameters remains poorly understood. To estimate process performance focusing on initial pH and substrate composition, the effects of initial pH and swine manure to corn straw ratio on biogas production and these parameters and linkages of these parameters were analyzed. Also, the methane production was optimized. The results revealed that the maximum methane yield and methane production rate were obtained with initial pH 7.5 and SM/CS ratio of 70:30. Kinetic parameters are coupled with process parameters, especially for COD removal rate, VS degradation rate, VFA and pH. Hydrolysis constant positively correlated with pH, COD removal rate and VS degradation rate, then impacted methane production and lag phase. Meanwhile, lag phase and the maximum methane production rate were directly determined by VFA and COD removal rate. The optimum initial pH and SM/CS ratio were 7.15 and 0.62, respectively, with a predicted maximum methane content of 55.12%. Thinking these findings together, they provide a scientific theory for estimating AD performance.

Effect of pH on Fe0 and Anaerobic Microorganism Combined Degradation 2,4-Dichlorophenol

Batch laboratory tests were conducted through inoculating the anaerobic mixed microorganism, to examine the effect of different initial pH on the process of anaerobic biodegradation of 2,4-dichlorophenol(2,4-DCP) in the presence of zerovalent iron (Fe0). Furthermore, the degradation mechanism of the combined system was investigated. The results showed that, The combined use of Fe0 and anaerobic microorganism could accelerate the degradation of 2,4-DCP. Different pH value had a significant impact on the 2,4-DCP degradation of the combined system. The degradation effect was better in neutral or slightly alkaline condition. The optimum initial pH for the degradation of target contaminant was 9 in the combined system. The OH- from Fe0 anaerobic corrosion balanced the organic acid produced by fermenting of glucose effectively, that made the concentration of volatile fatty acid (VFA) remain at a lower level. The corrosion of iron was strong in acidic condition. Ferrous ion was the main corrosive product and the content of ferric ion was lower. Furthermore, the removal rate of COD in combined system at different pH had a relation to the biodegradation of contaminant in some extent.

Screening and Molecular Identification of a Bacterial Strain with Higher Lipase Productivity

The objective of this study was to screen lipase-producing strain from rich oil soil, then complete molecular identification and some culture characteristics of the isolated strain. One out of 10 strains isolated from different samples was obtained with higher lipase production, which was identified as Proteusbacillus vulgaris according to its 16S rDNA sequence and analysis phenotypic characterization together with its morphological and physiological characterization, it was nominated as Proteusbacillus vulgaris Cz-6. Some conditions of Proteusbacillus vulgaris Cz-6 for lipase production were studied in detail. The results showed that the optimal carbon source and nitrogen source in culture medium were glucose and peptone. The optimal initial pH and culture temperature were pH 5.5 and 37°C respectively. Under these conditions, after cultivated for 72 h, the measured strain’s enzyme activity grew up to 15.36 U•m L-1, which increased by 12% than the initial one before optimization.

Flexible hydroxyapatite fiber precipitated by urea through a hydrothermal route

Flexible hydroxyapatite fiber (HAF) with high crystallinity is hydrothermally fabricated through the precipitation of urea. By the analysis of field emission scanning electron microscopy, fourier transform infrared spectrometry and X-ray diffraction, a comprehensive composition and morphological characterization of the products is established. The optimal initial pH lies in the range of 3·0–4·0 for synthesizing ribbon-like fibers with lengths larger than 200 μm. The variation in hydrothermal temperatures from 160 to 200°C shows little effect on the constitution of the products, which are all carbonated hydroxyapatite. The formation of HAF is through a fractal growth of two splittings. The HAF paper formed by suction filtration suggests that the obtained HAF is flexible. Also, the phase and morphology transformation of the precursor and the thermal stability of calcium (Ca)–phosphorus (P) fibers are investigated. HAF is formed by the precursor of octacalcium phosphate fibers and is more stable than it. Bone mesenchymal stem cell culture studies indicate that HAF has potential biocompatibility.

Equilibrium, kinetics and thermodynamics of cadmium ions (Cd2 +) removal from aqueous solution using earthworm manure-derived carbon materials

Carbon materials (CMs) derived from earthworm manure via slow pyrolysis at 400–600°C were employed as adsorbents for the removal of cadmium ions (Cd2+) from aqueous solution. The influences of adsorption conditions (including initial concentrations, contact time, ambient temperature, solution pH, ionic strength and adsorbent dosage) on the removal of Cd2+ using the developed CMs were investigated in addition to the potential mechanism studies in the adsorption process. The increase of initial concentration promoted the adsorption capacity and confined the removal rate of Cd2+. Adsorption was vigorously commenced within the initial contact time of 1h, accounting for 63.81–76.52% to the total adsorption amount. It is found that the adsorption performance was not significantly influenced by the solution pH between 3.5 and 5.5 and the ionic strength between 0 and 0.01molNaNO3/L. Overall, the optimum initial concentration, contact time, ambient temperature, solution pH, ionic strength and adsorbent dosage were 80mg/L, 24h, 25°C, 5.5, 0molNaNO3/L and 2g/L, respectively, in terms of single factor test. The maximum adsorption capacity of the CM prepared from 400, 500 and 600°C were 32.468, 19.646 and 14.599mg/g, respectively. The uptake of Cd2+ by the CMs was subjected to the spontaneous and endothermic processes. Alkali and alkaline earth metallic, especially for Ca2+ and Mg2+, can accelerate the adsorption through ion exchange interactions. Complexation and precipitation driven by surface functional groups involving oxygen-containing groups and aromatic CC, and salt minerals (phosphates, carbonates or silicates) may also make important contributions to the adsorption process.

Effective enhancement of polylactic acid-degrading enzyme production by Amycolatopsis sp. strain SCM_MK2-4 using statistical and one-factor-at-a-time approaches

ABSTRACTThis study aims to find the optimal medium and conditions for polylactic acid (PLA)-degrading enzyme production by Amycolatopsis sp. SCM_MK2-4. Screening of the most effective components in the enzyme production medium by Plackett–Burman design revealed that the silk cocoon and PLA film were the most significant variables enhancing the PLA-degrading enzyme production. After an response surface methodology, a maximum amount of PLA-degrading enzyme activity at 0.74 U mL−1 was predicted and successfully validated at 95% after 0.39% (w/v) silk cocoon and 1.62% (w/v) PLA film were applied to the basal medium. The optimal initial pH value, temperature, and inoculum size were evaluated by a method considering one-factor-at-a-time. The values were recorded at an initial pH in the range of 7.5–9.0, a temperature of 30–32°C, and an inoculum size of 4–10%. The highest activity of approximately 0.95 U mL−1 was achieved after 4 days of cultivation using the optimized medium and under optimized conditions in a shake flask. Upscaling to the use of a 3-L stirred tank fermenter was found to be successful with a PLA-degrading activity of 5.53 U mL−1; which represents a 51-fold increase in the activity compared with that obtained from the nonoptimized medium and conditions in the shake flask.