Degradation Of Gallic Acid Research Articles

From degrader to producer: reversing the gallic acid metabolism of Pseudomonas putida KT2440

Gallic acid is a powerful antioxidant with multiple therapeutic applications, usually obtained from the acidic hydrolysis of tannins produced by many plants. As this process generates a considerable amount of toxic waste, the use of tannases or tannase-producing microorganisms has become a greener alternative over the last years. However, their high costs still impose some barriers for industrial scalability, requiring solutions that could be both greener and cost-effective. Since Pseudomonas putida KT2440 is a powerful degrader of gallic acid, its metabolism offers pathways that can be engineered to produce it from cheap and renewable carbon sources, such as the crude glycerol generated in biodiesel units. In this study, a synthetic operon with the heterologous genes aroG4, quiC and pobA* was developed and expressed in P. putida, based on an in silico analysis of possible metabolic routes, resulting in no production. Then, the sequences pcaHG and galTAPR were deleted from the genome of this strain to avoid the degradation of gallic acid and its main intermediate, the protocatechuic acid. This mutant was transformed with the vector containing the synthetic operon and was finally able to convert glycerol into gallic acid. Production assays in shaker showed a final concentration of 346.7 ± 0.004 mg L−1 gallic acid after 72 h.

Synthesis of reduced graphene oxide incorporated bimetallic (Cu/Bi) nanorods based photocatalyst materials for the degradation of gallic acid and bacteria

Gallic acid (GA) is a polyphenols compound commonly present inwastewater that immensely affects aquatic and human life. GA is also responsible for the inhibitory effects on the microbial activity in the soil, thereby decreasing the fertility of the soil. Therefore, the removal of GA from the wastewater is necessary to combat such issues. The present study focused on the synthesis of reduced graphene oxide (r-GO) incorporated bimetallic (Cu/Bi) based nanorods (r-GO-Cu/Bi-NRs) and their photocatalytic applications. Incorporating GO within the CuBi2O4-NRs might decrease the bandgap value, thereby increasing the interfacial charge transfer. Moreover, GO increased the reactive sites and oxygen defects onto the r-GO-Cu/Bi-NRs that led to the separation rate of the photo-induced charge carriers and migration, thereby enhancing the photodegradation ability of the synthesized r-GO-Cu/Bi-NRs. Thesynthesis process of the r-GO-Cu/Bi-NRs is facile, novel, and economically viable for the photocatalytic degradation of organic pollutants.

Schinopsis brasiliensis Engl. to combat the biofilm-dependents diseases in vitro.

Dental caries and periodontal disease are the most prevalent of the biofilm-dependent diseases. With numerous side effects on the use of chlorhexidine, the search for new safe therapeutic alternatives for microorganisms involved with these diseases increases every day. This study aimed to evaluate the antimicrobial activity and cytotoxicity of extracts made from the bark of Schinopsis brasiliensis Engl. against five oral microorganisms and analyze their phytochemical and thermal degradation profile. The liquid-liquid partition was performed with hexane, chloroform and ethyl acetate. The identification and quantification of the chemical marker was done. Antimicrobial activity was evaluated based on the minimum inhibitory concentration. The cytotoxicity was analyzed based on the hemolysing potential of the samples. The thermal degradation profile was performed by two different methods. Gallic acid was identified as the main compound of the samples and showed the highest amount in the chloroform fraction. All samples were able to inhibit the growth of the microorganisms tested and showed no cytotoxicity. The ethanol extract absorbs less heat than the fractions. All samples exhibited exothermic peak consistent with degradation of gallic acid. Based on the results, the samples used are potential candidates for use in dental formulations for biofilm control.

Restoration of pretreated palm oil mill effluent using TiO2 based photocatalytic system: An optimization study

Phenolic compounds found in pretreated palm oil mill effluent (pre-POME) pose severe threat to aquatic ecosystem and human health due to their build-up in the environment and high toxicity. Thus, the removal of phenolic compounds from pre-POME is necessary to preserve environmental quality and protect human health. In this paper, the optimized degradation of phenolic compound, gallic acid (GA) from pre-POME under visible light assisted TiO2 based photocatalysis is reported. TiO2 nanoparticles (NPs) were synthesized by chemical precipitation technique followed by characterization with X-ray diffraction (XRD), diffuse reflectance UV-Vis spectroscopy (DR-UV-Vis) and field emission scanning electron microscopy (FESEM). The effect of process variables such as loading of TiO2 and H2O2 dose on the degradation of GA from pre-POME was investigated and optimized using response surface methodology (RSM) based on central composite design (CCD). Spherical shaped anatase phase TiO2 NPs with size 45.47 nm and band gap (Eg) of 3.16 eV were obtained. The results demonstrated that both variables, TiO2 loading and H2O2 dosage showed positive effect on GA degradation. The highest removal of GA from pre-POME (71.20%), from 44.85 ppm of initial concentration was observed for the optimal TiO2 loading of 0.88 g/L, H2O2 dosage of 8.5 wt% and 2 h reaction under visible light irradiation. The use of H2O2 combined with TiO2 NPs indicated a great potential for the removal of GA, which has been pointed out as the major phenolic compounds in pre-POME.

Changes in the Biotransformation of Green Tea Catechins Induced by Different Carbon and Nitrogen Sources in Aspergillus niger RAF106.

Biotransformation of green tea catechins mediated by microbes and/or enzymes could increase their bioavailability and improve their health benefits, but the regulatory mechanism remains unclear. Here, Aspergillus niger RAF106 isolated from Pu-erh tea was proved to be capable of degrading gradually ester-catechins into non-ester-catechins with higher bioavailability and gallic acid (GA) in aqueous solution only containing green tea catechins, and the products displayed similar radical-scavenging activity in vitro with the control. Meanwhile, the degradation was mediated by inducible enzymes as the extracellular form, and tannase might be an important enzyme among the extracellular enzymes. Moreover, it was found for the first time that the biotransformation was accelerated significantly by the addition of different nitrogen sources (i.e., yeast extract, peptone, NaNO3, and NH4Cl) and lactose through stimulating the hyphal growth and the tannase activities but was inhibited by glucose effect. Furthermore, nitrogen sources continued to promote the degradation of GA and/or non-ester-catechins by up-regulating the transcriptional expression of two dioxygenases and 10 monooxygenases. Besides, the addition of different nutrient sources except yeast extract did not alter the radical-scavenging activity of green tea catechins during the whole fermentation. These results provide a global insight into the roles of A. niger RAF106 and different nutrient sources in mediating the biotransformation of green tea catechins and modifying the radical-scavenging activity of biotransformed catechins.

Pulsed Light treatment below a Critical Fluence (3.82 J/cm2) minimizes photo-degradation and browning of a model Phenolic (Gallic Acid) Solution.

Pulsed light (PL) is one of the most promising non-thermal technologies used in food preservation and processing. Its application results in reduction of microbial load as well as influences the quality of food. The data about the impact of PL on bioactive compounds is ambiguous, therefore the aim of this study was to analyze the effect of PL treatment of a gallic acid aqueous solution—as a model system of phenolic abundant liquid food matrices. The effect of PL treatment was evaluated based on colour, phenolic content concentration and antioxidant activity measured by DPPH assay using a design of experiments approach. The PL fluence (which is the cumulative energy input) was varied by varying the pulse frequency and time. Using Response Surface Methodology, prediction models were developed for the effect of fluence on gallic acid properties. It was demonstrated that PL can modify the optical properties of gallic acid and cause reactions and degradation of gallic acid. However, application of PL did not significantly alter the overall quality of the model gallic acid solution at low fluence levels. Cluster analysis revealed that below 3.82 J/cm2, changes in gallic acid were minimal, and this fluence level could be used as the critical level for food process design aiming to minimize nutrient loss.

Gallic acid degradation by electron beam irradiation under various conditions.

In this study, aqueous solutions of gallic acid (GA) were irradiated in an electron beam (EB) accelerator under different experimental conditions (various initial GA concentrations, presence or absence of oxidant and oxygen). For an initial GA concentration of 50μM, complete GA degradation was achieved with an absorbed dose of 850Gy in the presence of dissolved oxygen. Both GA removal and mineralization are favored when oxygen is present. The addition of persulfate anions (S2O82-) or hydrogen peroxide (H2O2) also increased the efficiency of GA degradation and mineralization. For an absorbed dose of 14kGy, GA mineralization reached approximately 45%, 55%, and 72% for the EB, EB/H2O2, and EB/S2O82-systems, respectively. Three transformation products were tentatively identified in the presence of oxygen, these are the result of hydroxylation and ring opening reactions. No specific transformation product was found for the sulfate radical anion (SO4-●) reaction. Four additional compounds, including a dimer, were identified in oxygen-free solutions. These findings demonstrate that water radiolysis based on EB irradiation is an efficient process to activate H2O2 and S2O82- anions and is an advanced oxidation process (AOP).

Solvothermal Synthesis and Photocatalytic Activity of BiOBr Microspheres with Hierarchical Morphologies.

BiOBr microspheres with hierarchical morphologies (BiOBr-MicSphe) has potential application in heterogeneous photocatalysis for decontamination of water and air. For this reason, the synthesis, characterization an evaluation of photocatalytic activity of these materials become important. In this article, BiOBr-MicSphe were synthesized using different ranges of reaction temperature (120-200 °C) and reaction time (12 h - 24 h). Samples grown at 145 °C and 18 h showed the higher photocatalytic activity on gallic acid degradation. Morphological properties, chemical composition and structural analysis revealed that sample with higher photocatalytic activity exhibited a microspherical morphology with pure BiOBr tetragonal phase. Besides, adsorption-desorption analysis showed a smaller pore diameter for sample grown at 145 °C and 18 hrs. The results showed that the reaction temperature has a strong influence on the different properties of the material, affecting the photocatalytic activity.

Criegee mechanism as a safe pathway of color reduction in sugarcane juice by ozonation.

The production of crystal sugar is based on sugarcane juice clarification through sulphitation, that is, heat treatment with sulfur dioxide. The use of ozonation as an alternative to sulphitation aims to eliminate the disadvantageous presence of residual sulfite in crystal sugar. Both treatments are used to reduce color of sugarcane juice. The objective of this work was to evaluate two process parameters (temperature and pH) to reduce gallic acid, a low molecular weight pigment (MW 170gmol-1) widely found in sugarcane. Gallic acid was used as a model compound in sucrose solutions. The results showed that degradation of gallic acid was favored from pH 7.0 to 7.82 and temperature values between 50 and 70°C. The reaction mechanism was proposed for gallic acid degradation by ozone based on Criegee mechanism. Ozonation was an efficient method to reduce the potential low molecular weight pigment present in the sugarcane.

Synthesis and characterization of BiOI microspheres under standardized conditions

Bismuth oxyiodide (BiOI) has received much attention in the design of materials, because this material has proved its potential application in heterogeneous photocatalysis for environmental decontamination processes using visible light or simulated solar radiation. In this study, standard conditions and a reproducible method of solvothermal synthesis are established in order to obtain BiOI microspheres with higher photocatalytic activity in the degradation of gallic acid. Standard conditions of reaction temperature and reaction time turn out to be 126 °C and 18 h, respectively. In addition, results show that reaction temperature has a stronger influence on different properties of the BiOI, affecting the photocatalytic efficiency. BiOI materials were synthesized by solvothermal process using different ranges of reaction temperature (120–200 °C) and reaction time (12–24 h). Eleven experiments were designed, applying response surface methodology. The morphological, optical, and chemical properties of the best and worst material were determined using several techniques.

Mixed iron oxides as Fenton catalysts for gallic acid removal from aqueous solutions

A study was conducted on the behavior as Fenton catalysts of three commercial mixed iron oxides: copper ferrite, magnetite, and ilmenite, using H2O2 for the degradation and mineralization of gallic acid (GA) at temperatures between 15 and 35°C and pH of 4.3. Investigation of the activity of the catalysts was complemented by study of the metal ion leaching under reaction conditions. GA was completely mineralized with the three mixed iron oxides in the following order of catalytic activity: CuFe2O4>Fe3O4>FeTiO3, and the ferrites could be quickly and completely separated after the reaction by a magnetic field. According to these results, there appears to be a synergic effect between Cu and Fe ions placed in octahedral sites, and Cu ions may be the main active sites for HO radical generation. The efficiency of H2O2 utilization followed the inverse order of the catalytic activity of the mixed iron oxides, likely because the excess hydroxyl radicals generated during the reaction were quenched by hydrogen peroxide, yielding the less reactive hydroperoxide radicals. A very large amount of Cu and Fe ions leached from copper ferrite and decreased at higher reaction temperatures. These leached ions also acted as homogeneous Fenton catalysts in GA degradation and mineralization. A much lower amount of Fe ions was leached from magnetite and ilmenite in comparison to copper ferrite. From the perspective of long-term applications, magnetite with intermediate catalytic activity but with higher efficiency and much lower Fe ion leaching in comparison to copper ferrite may be more appropriate for GA removal.

BiOI microspheres for photocatalytic degradation of gallic acid

Abstract The photocatalytic degradation of gallic acid using BiOI microspheres under simulated solar radiation was studied. Response surface methodology (RSM) was applied to optimize the amount of photocatalyst and initial pH. To evaluate the interaction between these two parameters, and to optimize these parameters during the process, a factorial design central composite (CCC) and response surface methodology were developed. The results show that initial pH has a significant effect on the degradation of gallic acid, while the amount of photocatalyst presents a less significant effect. The optimized conditions were: amount of BiOI 560 mg L−1 at initial pH around 3.2. In addition, a BiOI synthesized with ionic liquid 1-butyl-3-methylimidazolium iodide ([bmim]I) was used to compare photocatalytic efficiency. Under these conditions, the maximum degradation percentage at 5 min of photocatalytic reaction was of 73% and 82% for BiOI synthesized with inorganic salt KI and ionic liquid [bmim]I respectively. Furthermore, the theoretical and experimental isoelectric points (IEP) of BiOI were obtained to analyze the influence of pH on the degradation of gallic acid, which was used as a winery effluent model pollutant.

Photocatalytic degradation of gallic acid over CuO–TiO2 composites under UV/Vis LEDs irradiation

Coupling TiO2 with narrow band gap semiconductors has been a strategy to obtain visible light active photocatalysts. In this work we present, the characterization and photocatalytic results of high-loaded CuO–TiO2 composites prepared by impregnation of TiO2 powder (Evonik, P25) with copper acetate followed by calcination. The resulting composite materials were characterized by X-ray diffraction, nitrogen adsorption/desorption, UV–vis diffuse reflectance, scanning electron microscopy, X-ray photoelectron spectroscopy and time-resolved microwave conductivity. The photocatalysts were used to degrade gallic acid by using low power ultraviolet and visible light emitting diodes (UV-LED and Vis-LED) as light sources. According to the results, the photocatalytic degradation of the pollutant was efficiently converted to several intermediate products and partially mineralized to CO2 by using visible light. These results were explained in terms of an enhancement of the optical and electronic properties of TiO2 by the presence of Cu2O and CuO phases.

Photocatalytic Treatment of Cork Wastewater Pollutants. Degradation of Gallic Acid and Trichloroanisole using Triphenyl(thia)pyrylium salts

The photocatalytic degradation of two typical pollutants present at the wastewaters of cork industry, namely gallic acid (GA) and 2,4,6-trichloroanisole (TCA) has been investigated using triphenylpyrylium (TPP+) and triphenylthiapyrylium (TPTP+) salts as organic photocatalysts. Fast removal of GA and slow but efficient degradation of the reluctant TCA were observed. The role of the transient species involved in the photodegradation has been investigated by means of photophysical experiments. Participation of singlet excited states was safely disregarded since lifetimes of both photocatalysts remained invariable upon addition of GA or TCA. Formation of photoactive ground state complexes was observed, and the complexation constants were estimated as KTPP-GA=468.4M−1, KTPP-TCA=528.0M−1 and KTPTP-TCA=657.1M−1. Moreover participation of the triplet excited states in the electron transfer oxidation of GA was very efficient, while no reaction occurred from the triplet excited states in the case of TCA. In addition, thermodynamic calculations support the participation of the triplet excited state in the case of GA, while the lack of triplet quenching in the case of TCA is associated with a thermodynamically disfavored process. Overall, photophysical experiments indicate that for GA, oxidative electron transfer occurs mainly from the triplet excited state with marginal contribution of the ground state complexes, while for TCA formation of ground state complexes constitutes the only mechanistic pathway.

Fenton oxidation of gallic and p-coumaric acids in water assisted by an activated carbon cloth.

The objective of this study was to investigate the effect of the presence of an activated carbon cloth (ACC) during the degradation and removal of gallic acid (GA) and p-coumaric acid (pCA) by Fenton oxidation using H2O2 and FeSO4 as catalyst. Removal of GA or pCA by Fenton oxidation was much higher than that of total organic carbon (TOC), indicating that a large proportion of GA or pCA degradation products was not mineralized. The presence of ACC increased the concentration of hydroxyl radicals generated in the FeSO4 + H2O2 system. The presence of ACC during Fenton oxidation largely increased TOC and GA removal, attributable to the adsorption of GA and its degradation products and the increased generation of OH(•) radicals that mineralize them. In the Fenton oxidation of pCA, the presence of ACC produced the same effects as for GA, but now the increased removal of pCA was due to adsorption on the activated carbon and not to the increased generation of hydroxyl radicals, due to the greater affinity of pCA for the carbon surface and its more difficult mineralization in comparison to GA.

Changes of gallic acid mediated by ultrasound in a model extraction solution

Ultrasound has been widely used as a new kind of auxiliary extraction technique in food industry, but its effect cannot be ignored on the potential degradation of the extracted target compound. In this paper, a model extraction solution was constructed with the standard gallic acid as target compound to be extracted, and its change was monitored by using high performance liquid chromatography (HPLC) under different ultrasonic extraction conditions, namely, solvent types, extractant concentrations, extraction time, extraction temperature, ultrasound power and frequency, in order to understand the effect of ultrasound on the extract during ultrasonic extraction and provide an objective evaluation of ultrasonic extraction of polyphenols. The results indicate that ultrasonic parameters had definite effect on the degradation of gallic acid during ultrasonic extraction, which implies that the extraction yield should not be over-focused in actual extraction applications of ultrasound, more attention should be paid to the potential degradation of the extracted target compound induced by ultrasound.

Photodegradation of gallic acid under UV irradiation: Insights regarding the pH effect on direct photolysis and the ROS oxidation-sensitized process of DOM

In this study, the degradation of gallic acid (GA), a model compound for dissolved organic matter (DOM) in controlled UV/N2, UV/air, UV/Fe3+/N2, and UV/Fe3+/air systems was investigated to elucidate the contribution of direct photolysis and reactive oxygen species (ROS) oxidation to GA degradation at various pH values. In general, the order of the degradation rate of GA in these four systems was as follows: UV/Fe3+/air>UV/air>UV/Fe3+/N2≈UV/N2. In the UV/N2 system, GA underwent slow direct photolysis, the rate of which decreased with decreasing pH. In the UV/Fe3+/air system, the most rapid GA degradation was achieved at pH 5. ROS are mainly derived from two sources. The first source is attributed to the role of DO and the other is attributed to the interaction of Fe3+ and DO. The contribution of ROS to GA oxidation is much greater (>71%) than that of direct photolysis (<29%) at each pH value and is most obvious at pH 5. H2O2 formation was detected during GA degradation in the UV/air and UV/Fe3+/air systems. Using ROS scavengers, it was found that oxidation by OH was the main mechanism of GA degradation in the UV/Fe3+/air system. Based on the experimental results, a mechanism for GA degradation and ROS formation involving the effect of pH was proposed. This study furthers our understanding of changes in DOM degradation mechanisms due to global acidification.

Degradation and Mineralization of Gallic Acid Using Fenton's Reagents

Performance of Fenton oxidation in the degradation of gallic acid (GA), one of the most representative phenolic compounds in wastewater, was studied. Factorial experimental design was used to study the main variables affecting the Fenton process as well as their interactions. Eight 22 factorial designs were performed to estimate the effects of the H2O2/GA and Fe2+/GA molar ratios on the degradation of GA and on its mineralization as percentage of initial carbon converted in carbon dioxide. H2O2/GA and Fe2+/GA ratios ranged from 0.3 to 32.3 and from 0.15 to 1.15, respectively. Experiments were conducted in batch mode and in an apparatus designed to directly measure carbon dioxide production. Results from the statistical processing of experimental data enlightened the oxidation mechanism and indicated that GA degradation is strongly influenced from both Fenton's reagents doses at low concentrations, whereas for mineralization efficiency only H2O2/GA molar ratio was statistically significant. The optimal H2O2/GA ratio resulting in the maximum phenolic compound degradation (95.5% ± 1.3%) and mineralization efficiency (41.6% ± 2.8%) was found to be 24.3 independently of the Fe2+/GA ratio.

Radiolytic degradation mechanism of gallic acid and its end‐products

Gallic acid is one of the most representative biorecalcitrant phenolic compounds present in cork processing wastewater. In this communication, chemical oxidation of gallic acid was studied by gamma irradiation as an advanced oxidation process. This technology turns out to be an advantageous tool for the degradation of gallic acid. The results obtained by UV-Vis and electrospray ionization mass spectrometry (ESI-MS) techniques are in agreement concerning the suitability of this technique to degrade gallic acid. ESI-MS and ESI-MS(2) monitoring of the non-irradiated and irradiated gallic acid solutions leads to the identification of the main intermediate products. Based on the overall results obtained a consistent mechanism of radiolytic degradation of gallic acid is proposed. The application of radiation as a tool to increase the biodegradability of wastewaters is an important issue from the perspective of Green Chemistry.

Electrochemical degradation of gallic acid on a BDD anode

The electrochemical oxidation of gallic acid (3,4,5-trihydroxybenzoic acid) has been studied on a boron-doped diamond anode (BDD). Cyclic voltammetries, chronoamperometries and bulk electrolyses were performed to characterise the electrochemical behaviour of gallic acid on diamond-type anode and to study the kinetics of gallic acid degradation. UV spectroscopy, HPLC analysis, COD and TOC measurements were conducted to study the reaction pathway for gallic acid mineralisation. The results showed that both direct and mediated electrochemical processes were involved in the oxidation of gallic acid. The degradation of gallic acid evidenced a pseudo first-order kinetics and the rate constant increased with applied current. Aliphatic acids were the main intermediates formed during the electrolyses and they were finally mineralised to CO 2 and water. The degradation rate on boron-doped diamond was under mass-transport control and was favoured by the increase of the flow rate of the solution into the electrochemical reactor.