pH Control Research Articles

Electro-fermentation with Clostridium autoethanogenum: Effect of pH and neutral red addition

Clostridium autoethanogenum is a gram-positive anaerobic bacterium that grows heterotrophically using fructose as a substrate, producing organic acids (formic, lactic, and acetic acid) and alcohols (ethanol and 2,3-butanediol). Literature reports show that electro-fermentation (EF) helps achieve higher production yields with Clostridium strains. EF involves manipulating microbial metabolism by applying an external potential using solid-state electrodes with/without redox mediators. However, the decrease in pH value can limit cellular viability and substrate conversion during the fermentation process. This work studies the effect of pH and neutral red as an electron transport on the kinetic of the growth and metabolites distribution during EF of C. autoethanogenum. Fermentation and EF experiments using C. autoethanogenum were performed in two-chamber H-type reactors. Biomass generation and product distribution were recorded in fermentations at pH 5.8 with and without pH control. As a result, when pH was controlled at 5.8, higher substrate consumption and biomass concentration were reached than when an external potential was applied (−600 mV vs. Ag/AgCl), allowing 76.6% more biomass with a 100% fructose conversion. Experiments revealed that redox mediator addition and the application of potential in pH-controlled fermentations mainly affected the production of biomass, lactate, acetate and formate, improving the production of lactate and acetate during the EF. In contrast, the results show no improvement in ethanol and 2,3-butanediol during the EF of fructose.

Behavior and bioactive properties of aqueous L-cysteine–AgNO3 solution at different pH

Polypeptide-like supramolecular aggregates are formed in aqueous cysteine–AgNO3 solution. At low pH, their positively charged shell consists of several layers of cysteine–Ag+ complexes held by hydrogen bonds; with an increase in pH, the particles aggregate at isoelectric point; while at higher pH, the shell acquires negative charge and starts being destroyed. The pH control has been demonstrated for cytotoxic effect of the solution against MCF-7 breast cancer cells

Ammonia tolerance of filamentous algae Oedogonium, Spirogyra, Tribonema and Cladophora, and its implications on wastewater treatment processes

Filamentous algae have high potential for wastewater treatment due to their direct uptake of nitrogen and ease of harvesting. Theoretically, filamentous algae are best applied upstream to directly remove total ammonia nitrogen (TAN = ammonia + ammonium) from wastewater, however their tolerance to toxic free NH3 remains unclear. This study investigated the ammonia tolerance of four filamentous algae species from the Oedogonium, Tribonema, Spirogyra and Cladophora genera. The algae were cultivated using buffers at pH values from 7.0 to 9.0 at 15 °C and 25 °C using either 60 mg-N/L nitrate or ammonium as the nitrogen source. Using nitrate, an increase in productivity as a function of pH was observed for all four species. Comparison of the results and the corresponding experimental conditions with previous studies suggested that the effect of algal productivity enhancement via CO2 addition lies heavily on carbon provision rather than direct pH control. In the presence of ammonium, Oedogonium, Tribonema and Spirogyra showed stable growth at low pH followed by a sharp decline in productivity above certain pH thresholds, while Cladophora showed a very low growth rate irrespective of pH. At 60 mg-N/L initial TAN, the critical pH range was found to be approximately 8.0–8.6, 7.5–8.3 and 7.5–8.0 for Tribonema, Oedogonium and Spirogyra respectively. The critical threshold calculated based on the initial amount of free NH3 was 1.5–3 mg-N/L for Tribonema and Oedogonium and approximately 1 mg-N/L for Spirogyra. Oedogonium was also cultivated under TAN at pH 7.5 and 15 °C over three weeks, showing stable growth and capability to utilise TAN under controlled conditions. Nevertheless, a 30 % nitrogen loss, presumably due to ammonia volatilisation, was also observed. Based on the results of this study, it was concluded that the use of filamentous algae for downstream wastewater treatment rather than direct TAN removal may be a more practical option.

Enrichment strategies of heavy metals in the O/H/O process composed of biological fluidized bed for wastewater treatment: A case study of Cu and Zn

Municipal sludge can be utilized as a resource despite its polluting nature. However, the presence of heavy metals lowers its resource value, and their uniform dispersion in conventional biological processes because of sludge reflux poses enormous difficulties for the subsequent separation/recovery. In this study, the enrichment strategies of Cu and Zn in simulated wastewater based on a new biological process named oxic-hydrolytic & denitrification-oxic (O1/H/O2 or O/H/O) combination were investigated and the influence mechanisms of pH, chelate, operating parameters, and denitrification reaction control were illustrated. Results showed that the amount Cu and Zn in the sludge of H reactor exceeded those of both O1 and O2 when pH of O1＜6.5. The maximum sludge-water partition coefficients (Kd) of Cu and Zn in H reactor were 3128 and 3421 times when the influent concentration of NH3–N was at a certain value (210 mg/L NH4Cl for Cu and 140 mg/L NH4Cl for Zn). This was ascribed to the control of nitrification rate, ammonification/nitrosation in the O1 reactor, anaerobic ammonia oxidation combined with autotrophic denitrification in the H reactor, optimal hydraulic retention time (HRT) and sludge retention time (SRT). Under the pre-set conditions of water quality and operation parameters, the precipitates in the sludge were found to be Cu(OH)2, Zn(OH)2, CuS, ZnS which were theoretically and instrumentally characterized. In sum, the joint regulation of biological combination and biochemical reaction will provide new enrichment/separation strategies for heavy metals in municipal sludge management.

Expiratory Aerosol pH is a Driver of the Persistence of Airborne Influenza A Virus.

To mitigate the spread of a viral disease, it is crucial to understand the factors that influence airborne virus transmission. However, the micro-environment to which the virus is exposed in expiratory aerosol particles is highly complex. The relative humidity, the aerosol particle size and composition, and the air composition affect virus infectivity by modulating the salt and organic concentrations within the particle, as well as the phase state. A parameter that has been overlooked is the aerosol pH. Several viruses are sensitive to acidic pH; for example, the inactivation of influenza A virus becomes very fast at pH 5.5 and below, a threshold that is quickly reached in an expiratory aerosol particle exhaled in a typical indoor environment. Therefore, aerosol acidity plays a significant role in controlling the persistence of airborne, acid-sensitive viruses such as influenza virus, and aerosol pH control could be applied to limit the risk of airborne virus transmission.

Experimental Study on the Suitability of Local Egg Shell and Snail Shell as Additives for Drilling Mud pH Control

Millions of dollars associated with importation cost has and is still been spent by oil companies carrying out drilling operations in Nigeria, and this if allow to continue unchecked, does not align with the country policy of promoting local content in the oil and gas industry. This study experimentally evaluates the suitability of local eggshell and snail shell ash for use as pH control additives in water base mud by comparing it to that of conventional chemical additives (sodium hydroxide, NaoH) that served as the control experiment. The major drilling mud properties considered in this study are mud density, pH value and rheological properties, with additives concentration of 0.2g to 1.0g each. The result from the study shows that mud prepared with eggshell has a slight increase in density (8.70 – 8.75ppg) while that of snail shell was higher (8.85 – 8.90ppg). These result for the eggshell and snail shell closely compares to that of the control and satisfies the API required minimum standard specification (8.65 – 9.60pp) for drilling mud. At the same concentration, the pH values of mud prepared with eggshell responded positively, compares to that of the control and was within the API required minimum standard specification (9.5 – 12.5) while that of snail shell was seen to give low pH values but was favourable at 1.0g concentration. The result for rheological properties (viscosity and gel strength) shows an improvement with an increase in the concentration of the samples for the eggshell and snail shell. Generally, from the obtained result in this study for all the evaluated mud properties, it is concluded that with respect to API required standard specification for drilling mud, that the eggshell is the most promising and has a good potential for drilling mud purposes when beneficiated in the right amount. This study recommends that government should support and encourage purposeful research on eggshell and snail shell for use as additives in drilling mud formulation with the sole aim of supporting the local content aspiration of the nation.

Investigation of the effect of phosphoric acid as an acidic medium in flotation separation of dolomite from magnesite

Flotation separation of carbonate minerals is difficult because of their similar surface properties. A variety of collectors and depressants have been previously used to improve their separation in acidic or alkaline media. In the present study, the flotation of dolomite and magnesite in acidic to neutral pH was investigated using oleate as collector and hydrochloric acid or phosphoric acid as pH regulator. It was found that the recovery of dolomite was high and independent of pH while that of magnesite decreased with acid addition, especially when phosphoric acid was used. Results of mineral dissolution showed a higher dissolution of dolomite than magnesite in acidic pH, which therefore provides more calcium (than magnesium) ions to interact with the oleate collector. These results are in agreement with the larger quantity of oleate adsorbed/precipitated on dolomite than on magnesite revealed by the infrared spectroscopic study. Furthermore, the new PO4 species observed in the Raman and infrared spectra of these minerals at acidic pH when phosphoric acid was used may prevent mineral dissolution and/or collector adsorption. The surface passivation of magnesite therefore explain the decrease in magnesite flotation when using phosphoric acid as pH control.

Entering into 2.0 cystinuric management with a medical digital tool to monitor urine pH: a prospective, randomized study

Background and objectivesIndividuals with cystinuria can experiment recurrent lithiasis events due to the relative insolubility of cystine at physiological urine pH, resulting in renal function decline. The Lit-Control® pH Meter is a medical device that accurately allows urine pH self-monitoring. The main objective of this study was to compare the usability of the Lit-Control® pH Meter with the reactive strips for self-monitoring of urinary pH at home by patients with cystinuria, and their overall satisfaction with each tool. Patients and methodsWe included 28 patients (9 females and 19 males, age 19–76 years), who were randomly assigned to monitor their urine pH with reactive strips (n = 17) or the Lit-Control® pH-meter (n = 11). ResultsAfter six months of use, the satisfaction with the two methods was similarly high, but the patients rated (0–10 scale) the pH meter better in terms of ease of learning (mean ± SD, 8.11 ± 0.60 vs. 7.06 ± 1.18; P = 0.038), ease to prepare (8.22 ± 0.67 vs. 7.25 ± 1.18; P = 0.034), and ease of use (8.22 ± 0.67 vs. 7.25 ± 1.39; P = 0.062). Overall, patients did not reach the alkalinization goals (pH between 7.0 and 8.0). ConclusionsThe Lit-Control® pH Meter demonstrated to be an easy-to-use device that can facilitate urinary pH control by cystinuric patients. A prospective study is warranted to assess the correlation between urine pH monitoring, a treat to target approach, and the recurrence of cystine stones.

Organic buffers act as reductants of abiotic and biogenic manganese oxides

Proton activity is the master variable in many biogeochemical reactions. To control pH, laboratory studies involving redox-sensitive minerals like manganese (Mn) oxides frequently use organic buffers (typically Good’s buffers); however, two Good’s buffers, HEPES and MES, have been shown to reduce Mn(IV) to Mn(III). Because Mn(III) strongly controls mineral reactivity, avoiding experimental artefacts that increase Mn(III) content is critical to avoid confounding results. Here, we quantified the extent of Mn reduction upon reaction between Mn oxides and several Good’s buffers (MES, pKa = 6.10; PIPES, pKa = 6.76; MOPS, pKa = 7.28; HEPES, pKa = 7.48) and TRIS (pKa = 8.1) buffer. For δ-MnO2, Mn reduction was rapid, with up to 35% solid-phase Mn(III) generated within 1 h of reaction with Good’s buffers; aqueous Mn was minimal in all Good’s buffers experiments except those where pH was one unit below the buffer pKa and the reaction proceeded for 24 h. Additionally, the extent of Mn reduction after 24 h increased in the order MES < MOPS < PIPES < HEPES << TRIS. Of the variables tested, the initial Mn(II,III) content had the greatest effect on susceptibility to reduction, such that Mn reduction scaled inversely with the initial average oxidation number (AMON) of the oxide. For biogenic Mn oxides, which consist of a mixture of Mn oxides, bacterial cells and extracelluar polymeric substances, the extent of Mn reduction was lower than predicted from experiments using abiotic analogs and may result from biotic re-oxidation of reduced Mn or a difference in the reducibility of abiotic versus biogenic oxides. The results from this study show that organic buffers, including morpholinic and piperazinic Good’s buffers and TRIS, should be avoided for pH control in Mn oxide systems due to their ability to transfer electrons to Mn, which modifies the composition and reactivity of these redox-active minerals.

A Light Scattering Investigation of Enzymatic Gelation in Self-Assembling Peptides.

Self-assembling peptides (SAPs) have been increasingly studied as hydrogel-former gelators because they can create biocompatible environments. A common strategy to trigger gelation, is to use a pH variation, but most methods result in a change in pH that is too rapid, leading to gels with hardly reproducible properties. Here, we use the urea-urease reaction to tune gel properties, by a slow and uniform pH increase. We were able to produce very homogeneous and transparent gels at several SAP concentrations, ranging from c=1g/L to c=10g/L. In addition, by exploiting such a pH control strategy, and combining photon correlation imaging with dynamic light scattering measurements, we managed to unravel the mechanism by which gelation occurs in solutions of (LDLK)3-based SAPs. We found that, in diluted and concentrated solutions, gelation follows different pathways. This leads to gels with different microscopic dynamics and capability of trapping nanoparticles. At high concentrations, a strong gel is formed, made of relatively thick and rigid branches that firmly entrap nanoparticles. By contrast, the gel formed in dilute conditions is weaker, characterized by entanglements and crosslinks of very thin and flexible filaments. The gel is still able to entrap nanoparticles, but their motion is not completely arrested. These different gel morphologies can potentially be exploited for controlled multiple drug release.

LED Illumination Modules Enable Automated Photoautotrophic Cultivation of Microalgae in Parallel Milliliter-Scale Stirred-Tank Bioreactors

Scalable lab-scale photobioreactors are needed for the exploration of new and improved photoautotrophic bioprocesses. Microbioreactor systems in which parallel bioreactors operate automatically are frequently employed to increase the speed of strain selection as well as the bioprocess-based exploration of heterotrophic fermentation processes. To enable the photoautotrophic operation of a commercially available parallel microbioreactor system with 48 stirred-tank bioreactors, LED illumination modules were designed to allow for individual light supply (400–700 nm) for each of the parallel bioreactors automated by a liquid handling station that performs both individual pH control and OD750 detection. The illumination modules enable dynamic variation of the incident light intensities of up to 1800 µmol m−2 s−1. Automated liquid level detection and volume control of each individual mL-scale gassed photobioreactor has to be established to compensate for evaporation because of the long process times of several days up to weeks. Photoautotrophic batch processes with Microchloropsis salina that employ either varying constant incident light intensities or day and night dynamics resulted in a standard deviation of OD750 of up to a maximum of 10%, with the exception of high-photoinhibiting incident light intensities. The established photoautotrophic microbioreactor system enables the automated investigation of microalgae processes in up to 48 parallel stirred photobioreactors and is thus a new tool that enables efficient characterization and development of photoautotrophic processes with microalgae.

Mathematical Model of the pH Control System in an In Vitro Model of the Gastrointestinal Tract of Poultry

Introduction. Essential nonlinearity of the chemical reactions of acids and bases determines the control algorithms in the mode of acidification or alkalization, that is, periodic dosing of a minimum volume of acid or alkali. Such regulation may be ineffective, specifically, it allows insufficient or excessive concentration of the controlled substance. The article discusses the problem of precise regulation of the hydrogen index in mini-bioreactors. It is proposed to use a digital model of the acidity control system to select the concentrations of topped-up solutions, determine the regulation methodology, and improve accuracy. The objective of the work is the assurance of required accuracy of pH regulation in an in vitro mini-model of the gastrointestinal tract of a static type.Materials and Methods. The initial block diagram of the model included accumulators and flows. It was the base for the main differential equations characterizing the change in volume and acidity. To correct the acidity readings of the resulting solution by temperature, a static model based on the polynomial approximation of experimental data using the least squares method was created. The structural elements of the mathematical model were investigated in the Matlab Simulink application package. To validate the adequacy of the mathematical model, transient characteristics were determined on a real system of in vitro modeling of the artificial gastrointestinal tract of poultry.Results. Within the framework of this work, the authors created and analyzed a nonlinear mathematical model of pH changes in a bioreactor taking into account external control actions. The flows of hydrochloric acid solution, alkali solution and drain from the reactor were presented as elements of a differential equation describing the accumulation of liquid in the reactor. To improve the accuracy, the solution was modified taking into account the temperature dependence of the hydrogen index. A dosing mathematical model based on a regulator with alkali and acid channels was proposed. The data obtained made it possible to generate a combined model of the pH regulation process in the bioreactor. The adequacy of the solution was confirmed empirically. The models of pH regulator, regulation of the volume of contents in the reactor and chemical reactions were shown in the form of structural diagrams. The transients of a mathematical model and a real control system were compared. It was established that the transient characteristics of the mathematical model and the real system were identical in terms of regulation time. The relative error of regulation of the real system was 0.35 %, and the mathematical model — 0.1 %, which corresponded to the required accuracy of regulation ± 0.1 pH. The influence of the studied flows on the neutralization reaction was shown in the form of graphs.Discussion and Conclusions. The proposed mathematical model will provide selecting optimal methods and algorithms for regulating acidity, which will accelerate the creation of a regulator for the nonlinear process of regulating the hydrogen index. In the future, these developments can be integrated into a comprehensive digital model of the entire artificial gastrointestinal tract of poultry to optimize control algorithms (dosing, mixing, periodicity, etc.), as well as approximation to objects in vivo.

Soil pH change induced by smelting activities affects secondary carbonate production and long-term Cd activity in subsoils

Cadmium (Cd) is a typical element with contamination risk caused by anthropogenic sources. Cd is known to associate with Fe (hydr)oxides in pH-neutral to slightly acidic soils. However, field evidence on the effects of high pH on the long-term migration and redistribution of Cd in the soil is lacking. In this study, a comprehensive investigation of Cd, Pb, and Zn distribution in soils was performed at a Pb–Zn smelter site to unravel the pH control of long-term Cd activity in soils contaminated by non-ferrous metal smelting. Atmospheric deposition caused widespread contamination of the surface soil. In contrast, the discharge of heavy metals and alkaline waste liquid from two separate pollutant sources inside the smelter resulted in severe pollution migrating from the deeper layers up to a depth of 10 m. Elemental analysis showed that the Cd/Zn ratio in soil increased as the pH value increased, indicating that Cd was progressively decoupled from Zn and accumulated in the solid phase. Chemical extraction, SEM-EDS mapping, and micro-FTIR mapping analysis of soil particles revealed that most of the Cd were correlated with calcite, which formed as a secondary mineral at a higher pH. The production of secondary carbonate as a geochemical barrier enhanced the natural attenuation of Cd, which provides a reference for remediating Cd pollution. Overall, the results provide information for studying the transport and accumulation of heavy metals in deep soil layers. On the other hand, as carbonate is an unstable sink compared to other carriers, this mechanism should be considered in future studies on health and ecological risk assessment criteria for heavy metal pollutants in alkaline environments.

Characterization and Amelioration of Filtration Difficulties Encountered in Metabolomic Studies of Clostridium thermocellum at Elevated Sugar Concentrations.

Clostridium thermocellum, a promising candidate for consolidated bioprocessing, has been subjected to numerous engineering strategies for enhanced bioethanol production. Measurements of intracellular metabolites at substrate concentrations high enough (>50 g/L) to allow the production of industrially relevant titers of ethanol would inform efforts toward this end but have been difficult due to the production of a viscous substance that interferes with the filtration and quenching steps during metabolite extraction. To determine whether this problem is unique to C. thermocellum, we performed filtration experiments with other organisms that have been engineered for high-titer ethanol production, including Escherichia coli and Thermoanaerobacterium saccharolyticum. We addressed the problem through a series of improvements, including active pH control (to reduce problems with viscosity), investigation of different filter materials and pore sizes (to increase the filtration capacity), and correction for extracellular metabolite concentrations, and we developed a technique for more accurate intracellular metabolite measurements at elevated substrate concentrations. IMPORTANCE The accurate measurement of intracellular metabolites (metabolomics) is an integral part of metabolic engineering for the enhanced production of industrially important compounds and a useful technique to understand microbial physiology. Previous work tended to focus on model organisms under laboratory conditions. As we try to perform metabolomic studies with a wider range of organisms under conditions that more closely represent those found in nature or industry, we have found limitations in existing techniques. For example, fast filtration is an important step in quenching metabolism in preparation for metabolite extraction; however, it does not work for cultures of C. thermocellum at high substrate concentrations. In this work, we characterize the extent of the problem and develop techniques to overcome it.

Improving the Electron Transport Performance of TiO2 Film by Regulating TiCl4 Post-Treatment for High-Efficiency Carbon-Based Perovskite Solar Cells.

Titanium oxide (TiO2 ) has been widely used as an electron transport layer (ETL) in perovskite solar cells (PSCs). Typically, TiCl4 post-treatment is indispensable for modifying the surfaces of TiO2 ETL to improve the electron transport performance. However, it is challenging to produce the preferred anatase phase-dominated TiO2 by the TiCl4 post-treatment due to the higher thermodynamic stability of the rutile phase. In this work, a mild continuous pH control strategy for effectively regulating the hydrolysis process of TiCl4 post-treatment is proposed. As the weak organic base, urea has been demonstrated can maintain a moderate pH decrease during the hydrolysis process of TiCl4 while keeping the hydrolysis process relatively mild due to the ultra-weak alkalinity. The improved pH environment is beneficial for the formation of anatase TiO2 . Consequently, a uniform anatase-dominated TiO2 surface layer is formed on the mesoporous TiO2 , resulting in reduced defect density and superior band energy level. The interfacial charge recombination is effectively suppressed, and the charge extraction efficiency is improved simultaneously in the fabricated solar cells. The efficiency of the fabricated carbon electrode-based PSCs (C-PSCs) is improved from 16.63% to 18.08%, which is the highest for C-PSCs based on wide-bandgap perovskites.

Photo-Fenton process applied for the treatment of industrial wastewaters containing diclofenac: optimization with low iron ions concentrations and without pH control

Diclofenac (DCF) can cause several adverse effects in the environment and it should be removed from industrial pharmaceutical wastewaters. Advanced oxidation processes (AOPs) are promising methods for the DCF degradation. But, in many cases, AOPs require acidic pH. However, at this condition, DCF precipitates, which may hinder its oxidation. Thus, in this work, some AOP were studied for the DCF degradation, especially the photo-Fenton process, applying the experimental design technique (Doehlert matrix), operating without and with pH control (between 6.5 and 7.0). As independent variables, the initial ferrous ion concentration ([Fe2+]) and the molar addition rate of H2O2 (FH2O2) were evaluated. Empirical models were proposed and optimized conditions were determined without ([Fe2+] = 0.27 mmol L−1 and FH2O2 = 1.64 mmol min−1) and with pH control ([Fe2+] = 1.0 mmol L−1 and FH2O2 = 1.64 mmol L−1), with the following predicted mineralization percentages: 93% and 68%, respectively. So, photo-Fenton process without pH control presented the best performances. Furthermore, at this condition, iron concentration respects the limit value established by the Brazilian environmental legislation. That is, in this condition, additional processes, in order to remove iron ions, would not be necessary, that is very interesting for applications on an industrial scale.

Development of an electrochemical membrane bioreactor for succinic acid production and in situ separation with engineered Yarrowia lipolytica cultivated on municipal biowaste hydrolysate

A novel electrochemical membrane bioreactor (EMB) integrating succinic acid (SA) production and in situ separation in the anode compartment through an anion exchange membrane was employed in fed-batch fermentations with Y. lipolytica PSA02004 using hydrolysates from the organic fraction of municipal solid waste (OFMSW) as feedstock. The initiation of electrolysis cell operation and the reduction of pH from 6 to 5.5 at 30 h in a 6.7 L bioreactor improved the SA production efficiency, resulting in 66.7 gSA/L, 0.51 g/g yield, 0.78 g/(L·h) productivity, high coulombic efficiency (66.2%) and relatively low electricity consumption for SA separation (2.6 kWh/kgSA). The recirculation of the fermentation broth in the cathode compartment and the OH– produced by water reduction reduced NaOH consumption (35.4%) for pH control during fermentation. The fermentation was efficiently replicated in a 30 L bioreactor with a low membrane surface area (100 cm2) electrolysis cell, but it failed with a higher membrane surface area (702 cm2) electrolysis cell indicating that yeast cell viability, cell design and EMB configuration are important aspects for process scale-up. SA crystals were purified, at 99.95% purity and 95% yield, from the anolyte solution via activated carbon treatment, evaporation, crystallization and drying. Cell removal via centrifugation and acidification stages were not required as in conventional SA purification processes. The produced SA crystals were suitable for the production of polyester polyols for polyurethane urea dispersions applications.

Self-Tuning Pid (STPID) Control of pH in Recovering Process of Magnesium Hydroxide (Mg(OH)2) by Coagulation From Salt

The salt obtained from the salt sources are not desirable purity level and contains some impurities. In the scope of this study, coagulation of magnesium hydroxide (Mg(OH)2) in pH control has been carried out by adding sodium hydroxide (NaOH) to magnesium chloride (MgCl2) and by this way recovery process has been achieved by Self Tuning PID Control. To provide the best coagulation pH 11 has been obtained as optimum pH value in consideration of the performed calculations.

Temperature and pH Control of Dark Fermentation Bioreactor to Produce Biohydrogen from Palm Oil Mill Effluent by Using Fuzzy Logic Controller

Hydrogen is the main choice of renewable fuel since it brings significant benefits compared with the other conventional fuels, such as the use of waste substrate, cleaner and highest energy density. Biological hydrogen production route is cost efficient since it can be processed in ambient conditions, easy operational techniques while keeping the environment safe. Dark fermentation to produce bio-hydrogen has received widespread attention from researchers in the present decades especially due to not requires light sources. This work is a study of the optimization of process conditions particularly pH and temperature of a dark fermentation bioreactor to produce Bio-H2 from palm oil mill effluent (POME) by using fuzzy logic controller. The simulation started by developing process and instrumentation diagram (P&amp;ID) of bioreactor. Then a conventional PID controller and fuzzy logic controller were simulated by using MATLAB SIMULINK and the results were compared with each other in terms of safety aspect. The temperature of 37oC and pH of 6 is the optimum conditions that needs to be maintained to yield the hydrogen at 2.79 mol H2 mol-1 glucose. The pH is able to reach optimum value at 600s and 30s by using the PID controller and fuzzy logic controller, respectively. Same goes to temperature control, where the parameter reaches optimum value at 200s and 0.3s respectively. Based on these promising results, fuzzy logic controller is a good replacement for the conventional control systems since it requires shorter time to optimize process conditions, consequently making sure the safety aspect is well guaranteed.

Rutin Concentration and Characterization of Rutinosidase in Perennial Buckwheat (Fagopyrum cymosum) and Its Application in Foods

To evaluate the potential of perennial buckwheat (Fagopyrum cymosum; FC) as a food source, rutin concentration was investigated. FC contains more than 1% (w/w) rutin and 0.03% quercetin in the leaves, flowers, and seeds. In particular, rutin and quercetin concentrations were high in plant seeds. Therefore, FC is useful as a rutin- and quercetin-rich material. In contrast, the FC seed contained a large amount of rutinosidase. Purified rutinosidase in a homogenous mixture consisted of only one isozyme with M.W. of 58.4 KD and low Km for rutin (0.367 mM). The rutin concentration in the FC dough decreased to almost zero, 10 min after the addition of water. Parallel to the decrease in rutin, quercetin was increased, and strong bitterness was generated, whereas steam-heated flour in which rutinosidase was inactivated did not have rutin hydrolysis and bitterness. These results indicate that rutinosidase is a major cause of rutin hydrolysis and bitterness. The in vitro rutinosidase is inactivated at pH 8.0 and 65 °C. Therefore, the control of dough pH and temperature should be useful in preventing rutinosidase activity.