The Science of the total environment, Jan 15, 2014
Laccase (EC 1.10.3.2) and tyrosinases (EC 1.14.18.1) are ubiquitous enzymes present in nature as ... more Laccase (EC 1.10.3.2) and tyrosinases (EC 1.14.18.1) are ubiquitous enzymes present in nature as they are known to originate from bacteria, fungi, plants, etc. Both laccase and tyrosinase are copper-containing phenoloxidases requiring readily available O2 without auxiliary cofactor for their catalytic transformation of numerous phenolic substrates. In the present study, laccase and tyrosinase have been insolubilized as combined crosslinked enzyme aggregates (combi-CLEA) using chitosan, a renewable and biodegradable polymer, as crosslinker. The combi-CLEA, with specific activity of 12.3 U/g for laccase and 167.4 U/g for tyrosinase, exhibited high enzymatic activity at pH5-8 and temperature at 5-30°C, significant resistance to denaturation and no diffusional restriction to its active site based upon the Michaelis-Menten kinetic parameters. Subsequently, the combi-CLEA was applied to the transformation of acetaminophen as a model phenolic compound in samples of real wastewaters in orde...
Our current global environmental challenges include the reduction of harmful chemicals and their ... more Our current global environmental challenges include the reduction of harmful chemicals and their derivatives. Bioremediation has been a key strategy to control the massive presence of chemicals in the environment. Enzymes including the phenoloxidases, laccases and tyrosinases, are increasingly being investigated as “green products” in the removal of many chemical contaminants in waters and soils. Both phenoloxidases are widespread in nature and attractive biocatalysts due to their ability to use readily available molecular oxygen as sole cofactor for their catalytic elimination of a large number of chemicals. Taking advantage of their catalytic potentials, remarkable advances have been made in the engineering of laccases to produce suitable biocatalysts in environmental applications. Studies about novel strategies of laccase immobilization and insolubilization for the treatment of chemical contaminants were provided. Likewise, tyrosinases are gaining increasing interest in environmental applications due to their catalytic similarities with laccases although they remain far less investigated to date. This disparity was addressed in this review along with the molecular features and catalytic mechanism of tyrosinases relevant in environmental applications. A perspective on the future use of laccases and tyrosinases in bioremediation was discussed.
African Membrane Society (AMS) a organisé en collaboration avec la Faculté des Sciences de Sfax (... more African Membrane Society (AMS) a organisé en collaboration avec la Faculté des Sciences de Sfax (Tunisie) la rencontre internationale sur 'L'exploitation des procédés membranaires pour le traitement de l'eau dans les petites communautés et les centres urbains' du 3 au 5 Mai 2016. La communauté sfaxienne a accueilli avec chaleur et enthousiasme le premier congrès international de l'AMS, AMSIC-1. Rappelons qu'une des priorités de l'AMS est de stimuler l'appropriation technologique via la formation d'une masse critique d'experts et la dissémination du savoir scientifique. Les problématiques d'accès à l'eau et de sécheresse sont d'une grande ampleur dans les pays africains et une gestion rigoureuse des ressources en eau s'impose. Cette démarche permettra de mieux faire face aux menaces transnationales posées par les conflits armés, aux crises alimentaires, et aux risques épidémiques. D'autre part, une bonne gestion des ressources naturelles permettra de mieux contrôler les besoins en eau (toujours en hausse) des communautés, de même que l'impact du stress hydrique qui sévit fortement dans les pays du Maghreb sous l'influence du réchauffement climatique. De nos jours, les états africains semblent avoir intégré la nécessité de mobiliser et de partager prioritairement les ressources du continent. L'AMS se réjouit de telles initiatives et considère que sa réussite est étroitement liée à une mobilisation active des décideurs africains. Dans le domaine du traitement de l'eau, les systèmes de filtration membranaires présentent plusieurs atouts technologiques pour l'Afrique (modularité et robustesse des équipements, contrôle de la qualité de l'eau, simplicité d'utilisation, etc.), d'autant que les coûts d'investissement et d'exploitation se rapprochent des plateformes conventionnelles. La rencontre internationale de Sfax (Tunisie) a mis l'accent sur les principales avancées de la recherche académique et industrielle dans le domaine des technologies de filtration membranaire pour le traitement de l'eau. Les retombées de cette manifestation seront analysées plus largement dans notre prochain bulletin mais les observations suivantes peuvent être déjà dégagées : Les spécialistes de la filtration se sont réunis pour échanger les résultats des projets de recherche menés en Afrique et pour formuler des recommandations sur les orientations futures en matière de gestion efficace de l'eau. Les objectifs à long terme consisteront à renforcer les capacités scientifiques et technologiques, stimuler la croissance économique à travers la valorisation des ressources en eau et en énergie. Nous espérons que la convergence de tels efforts permettra de mettre un frein aux conséquences désastreuses de la pauvreté et dans tous les pays du continent africain. Notre congrès AMSIC-1 s'est déroulé sur deux jours dont le premier était consacré aux procédés de filtration pout la production d'eau potable et pour les techniques de dessalement. Les volets Matériaux Membranaire, Mise au Point et Encrassement des Membranes, Performance des Filtres et Modules Membranaires ont été développés par les experts. Parallèlement, la question de l'apport des énergies renouvelables dans la gestion énergétique des procédés de filtration a été largement abordée. La deuxième journée a été dédiée à l'innovation dans les systèmes de filtration ainsi qu'à l'application de la filtration membranaire dans le domaine de l'irrigation, celui de la biotechnologie et des industries pharmaceutiques, et pour favoriser l'exploitation des eaux recyclées. Au cours de ces journées nous avons largement évoqué la nécessité de renforcer les partenariats institutionnels en Afrique dans le domaine de l'éducation et via les partenariats industriels. En outre cette rencontre internationale dont l'affluence a été excellente devrait contribuer au développement du continent africain dans les domaines scientifiques et socio-économiques. Un rapport détaillé est en cours de préparation visant à dégager les retombées et définir les futurs axes de travail pour notre association.
In order to transform a wide range of pharmaceutically active compounds (PhACs), the three oxidat... more In order to transform a wide range of pharmaceutically active compounds (PhACs), the three oxidative enzymes laccase (Lac) from Trametes versicolor, versatile peroxidase (VP) from Bjerkandera adusta and glucose oxidase (GOD) from Aspergillus niger were concomitantly cross-linked after aggregation, thus, making a combined cross-linked enzyme aggregate (combi-CLEA) that was versatile and involved in an enzymatic cascade reaction. From the initial enzymes about 30% of initial laccase activity was recovered along with 40% for each of VP and GOD. The combi-CLEA showed good results in conditions close to those of real wastewater (neutral pH and medium temperature) as well as a good ability to resist to denaturing conditions such as high temperature (60°C) and low pH (3). Batch experiments were realized to test the free enzyme's ability to degrade, a PhACs cocktail, mainly in a synthetic wastewater containing acetaminophen, naproxen, mefenamic acid, indometacin, diclofenac, ketoprofen, caffeine, diazepam, ciprofloxacin, trimethoprim, fenofibrate and bezafibrate, carbamazepine and its by-product 10-11 epoxy-carbamazepine. High removal was achieved (more than 80%) for the five first compounds. Then, the elimination ability of the combi-CLEA with or without hydrogen peroxide, glucose or manganese sulfate was determined. Globally, our results demonstrated that VP has a wider removal spectrum than Lac. These removal features are enhanced under more specific conditions, whereas the combi-CLEA combined advantages of both VP and laccase. Finally, the elimination of PhACs in a municipal wastewater treatment plant effluent using the combi-CLEA was marginally investigated. Concentrations of most of the selected PhACs were below the limit of quantification (lower than 20 ng/L) except for acetaminophen. Its combi-CLEA-mediated removal reached up to 25%.
h i g h l i g h t s " The organic/inorganic network stabilized the enzyme versus harsh environmen... more h i g h l i g h t s " The organic/inorganic network stabilized the enzyme versus harsh environments. " These structures did not limit the mass transfer of the substrate. " Applications of these biocatalysts are promising for bioprocesses. Enzyme polymer engineered structure Organic/inorganic surrounding network Chitosan a b s t r a c t Laccase and laccase-based cross-linked enzyme aggregates (CLEAs) were stabilized through the formation of a surrounding polymeric network made of chitosan and 3-aminopropyltriethoxysilane. The thermoresistance of the resulting enzyme polymer engineered structures of laccase (EPES-lac) and CLEAs (EPES-CLEA) were more than 30 times higher than that of free laccase and CLEAs at pH 3 and 40°C. The EPES showed higher residual activity than the unmodified biocatalysts against chaotropic salts (up to 10 times), EDTA (up to 5 times), methanol (up to 15 times) and acetone (up to 20 times). The Michaelis-Menten kinetic parameters revealed that the affinity for 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid) has doubled for the EPES-lac and EPES CLEA compared to their unmodified forms. The EPES-lac structures acted optimally at pH 4 and their activity was nearly temperature-independent, while the laccase activity of EPES-CLEA was optimal at pH 4 and 60°C. Globally, the EPES have shown significantly improved properties which make them attractive candidate for the development of laccase-based applications.
The Science of the total environment, Jan 15, 2014
Laccase (EC 1.10.3.2) and tyrosinases (EC 1.14.18.1) are ubiquitous enzymes present in nature as ... more Laccase (EC 1.10.3.2) and tyrosinases (EC 1.14.18.1) are ubiquitous enzymes present in nature as they are known to originate from bacteria, fungi, plants, etc. Both laccase and tyrosinase are copper-containing phenoloxidases requiring readily available O2 without auxiliary cofactor for their catalytic transformation of numerous phenolic substrates. In the present study, laccase and tyrosinase have been insolubilized as combined crosslinked enzyme aggregates (combi-CLEA) using chitosan, a renewable and biodegradable polymer, as crosslinker. The combi-CLEA, with specific activity of 12.3 U/g for laccase and 167.4 U/g for tyrosinase, exhibited high enzymatic activity at pH5-8 and temperature at 5-30°C, significant resistance to denaturation and no diffusional restriction to its active site based upon the Michaelis-Menten kinetic parameters. Subsequently, the combi-CLEA was applied to the transformation of acetaminophen as a model phenolic compound in samples of real wastewaters in orde...
tWidespread detection of numerous micropollutants including aromatic pharmaceuticals in effluents... more tWidespread detection of numerous micropollutants including aromatic pharmaceuticals in effluents ofwastewater treatment plants has prompted much research aimed at efficiently eliminating these contam-inants of environmental concerns. In the present work, a novel hybrid bioreactor (HBR) of cross-linkedenzymes aggregates of laccase (CLEA-Lac) and polysulfone hollow fiber MF membrane was developedfor the elimination of acetaminophen (ACT), mefenamic acid (MFA) and carbamazepine (CBZ) as modelaromatic pharmaceuticals. The MF alone showed removals of the three drugs varying approximatelyfrom 50 to 90% over the course of 8 h in the filtrate of aqueous solution. Synergistic action of the MFand CLEA-Lac during operation achieved eliminations from aqueous solution of around 99%, nearly 100%and up to 85% for ACT, MFA and CBZ, respectively. Under continuous operation, the HBR demonstratedelimination rates of the drugs from filtered wastewater up to 93% after 72 h for CBZ and near completeelimination of ACT and MFA was achieved within 24 h of treatment. Concomitantly to the drugs elimina-tions in the wastewater, the CLEA-Lac exhibited 25% residual activity while being continuously recycledwith no activity in the filtrate. Meanwhile, the filtrate flowrate showed only minor decline indicatinglimited fouling of the membrane.
Over the last few decades many attempts have been made to use biocatalysts for the biotransformat... more Over the last few decades many attempts have been made to use biocatalysts for the biotransformation of emerging contaminants in environmental matrices. Laccase, a multicopper oxidoreductase enzyme, has shown great potential in oxidizing a large number of phenolic and non-phenolic emerging contaminants. However, laccases and more broadly enzymes in their free form are biocatalysts whose applications in solution have many drawbacks rendering them currently unsuitable for large scale use. To circumvent these limitations, the enzyme can be immobilized onto carriers or entrapped within capsules; these two immobilization techniques have the disadvantage of generating a large mass of non-catalytic product. Insolubilization of the free enzymes as cross-linked enzymes (CLEAs) is found to yield a greater volume ratio of biocatalyst while improving the characteristics of the biocatalyst. Ultimately, novel techniques of enzymes insolubilization and stabilization are feasible with the combination of cross-linked enzyme aggregates (combi-CLEAs) and enzyme polymer engineered structures (EPESs) for the elimination of emerging micropollutants in wastewater. In this review, fundamental features of laccases are provided in order to elucidate their catalytic mechanism, followed by different chemical aspects of the immobilization and insolubilization techniques applicable to laccases. Finally, kinetic and reactor design effects for enzymes in relation with the potential applications of laccases as combi-CLEAs and EPESs for the biotransformation of micropollutants in wastewater treatment are discussed.
Laccase (EC 1.10.3.2) and tyrosinases (EC 1.14.18.1) are ubiquitous enzymes present in nature as ... more Laccase (EC 1.10.3.2) and tyrosinases (EC 1.14.18.1) are ubiquitous enzymes present in nature as they are known to originate from bacteria, fungi, plants, etc. Both laccase and tyrosinase are copper-containing phenoloxidases requiring readily available O2 without auxiliary cofactor for their catalytic transformation of numerous phenolic substrates. In the present study, laccase and tyrosinase have been insolubilized as combined crosslinked enzyme aggregates (combi-CLEA) using chitosan, a renewable and biodegradable polymer, as crosslinker. The combi- CLEA,with specific activity of 12.3 U/g for laccase and 167.4 U/g for tyrosinase, exhibited high enzymatic activity at pH 5–8 and temperature at 5–30 °C, significant resistance to denaturation and no diffusional restriction to its active site based upon the Michaelis–Menten kinetic parameters. Subsequently, the combi-CLEA was applied to the transformation of acetaminophen as a model phenolic compound in samples of real wastewaters in order to evaluate the potential efficiency of the biocatalyst. In batch mode the combi-CLEA transformed more than 80% to nearly 100% of acetaminophen fromthemunicipalwastewater and more than 90% fromthe hospital wastewater. UPLC–MS analysis of acetaminophen metabolites showed the formation of its oligomers as dimers, trimers and tetramers due to the laccase and 3-hydroxyacetaminophen due to the tyrosinase.
This paper presents the findings of a study to assess patterns in local knowledge of and response... more This paper presents the findings of a study to assess patterns in local knowledge of and response to water quality and waterborne diseases in relation to seasonal changes in the Niger River Inland Delta. The study draws on field data collected in four villages along the Niger River in the Mopti region of Mali during September 2008. The major findings suggest: (1) water use behaviors and diarrheal disease management are influenced by the tremendous seasonal fluctuations in the riverine environment; (2) local awareness of the relationship between poor water quality, oral-fecal disease transmission, and waterborne disease is low; (3) interventions to mitigate the high incidence of childhood diarrhea and degraded water quality are limited by ongoing socio-economic, cultural, and environmental factors; and (4) women's level of health knowledge is socially and culturally dependent.
The Science of the total environment, Jan 15, 2014
Laccase (EC 1.10.3.2) and tyrosinases (EC 1.14.18.1) are ubiquitous enzymes present in nature as ... more Laccase (EC 1.10.3.2) and tyrosinases (EC 1.14.18.1) are ubiquitous enzymes present in nature as they are known to originate from bacteria, fungi, plants, etc. Both laccase and tyrosinase are copper-containing phenoloxidases requiring readily available O2 without auxiliary cofactor for their catalytic transformation of numerous phenolic substrates. In the present study, laccase and tyrosinase have been insolubilized as combined crosslinked enzyme aggregates (combi-CLEA) using chitosan, a renewable and biodegradable polymer, as crosslinker. The combi-CLEA, with specific activity of 12.3 U/g for laccase and 167.4 U/g for tyrosinase, exhibited high enzymatic activity at pH5-8 and temperature at 5-30°C, significant resistance to denaturation and no diffusional restriction to its active site based upon the Michaelis-Menten kinetic parameters. Subsequently, the combi-CLEA was applied to the transformation of acetaminophen as a model phenolic compound in samples of real wastewaters in orde...
Our current global environmental challenges include the reduction of harmful chemicals and their ... more Our current global environmental challenges include the reduction of harmful chemicals and their derivatives. Bioremediation has been a key strategy to control the massive presence of chemicals in the environment. Enzymes including the phenoloxidases, laccases and tyrosinases, are increasingly being investigated as “green products” in the removal of many chemical contaminants in waters and soils. Both phenoloxidases are widespread in nature and attractive biocatalysts due to their ability to use readily available molecular oxygen as sole cofactor for their catalytic elimination of a large number of chemicals. Taking advantage of their catalytic potentials, remarkable advances have been made in the engineering of laccases to produce suitable biocatalysts in environmental applications. Studies about novel strategies of laccase immobilization and insolubilization for the treatment of chemical contaminants were provided. Likewise, tyrosinases are gaining increasing interest in environmental applications due to their catalytic similarities with laccases although they remain far less investigated to date. This disparity was addressed in this review along with the molecular features and catalytic mechanism of tyrosinases relevant in environmental applications. A perspective on the future use of laccases and tyrosinases in bioremediation was discussed.
African Membrane Society (AMS) a organisé en collaboration avec la Faculté des Sciences de Sfax (... more African Membrane Society (AMS) a organisé en collaboration avec la Faculté des Sciences de Sfax (Tunisie) la rencontre internationale sur 'L'exploitation des procédés membranaires pour le traitement de l'eau dans les petites communautés et les centres urbains' du 3 au 5 Mai 2016. La communauté sfaxienne a accueilli avec chaleur et enthousiasme le premier congrès international de l'AMS, AMSIC-1. Rappelons qu'une des priorités de l'AMS est de stimuler l'appropriation technologique via la formation d'une masse critique d'experts et la dissémination du savoir scientifique. Les problématiques d'accès à l'eau et de sécheresse sont d'une grande ampleur dans les pays africains et une gestion rigoureuse des ressources en eau s'impose. Cette démarche permettra de mieux faire face aux menaces transnationales posées par les conflits armés, aux crises alimentaires, et aux risques épidémiques. D'autre part, une bonne gestion des ressources naturelles permettra de mieux contrôler les besoins en eau (toujours en hausse) des communautés, de même que l'impact du stress hydrique qui sévit fortement dans les pays du Maghreb sous l'influence du réchauffement climatique. De nos jours, les états africains semblent avoir intégré la nécessité de mobiliser et de partager prioritairement les ressources du continent. L'AMS se réjouit de telles initiatives et considère que sa réussite est étroitement liée à une mobilisation active des décideurs africains. Dans le domaine du traitement de l'eau, les systèmes de filtration membranaires présentent plusieurs atouts technologiques pour l'Afrique (modularité et robustesse des équipements, contrôle de la qualité de l'eau, simplicité d'utilisation, etc.), d'autant que les coûts d'investissement et d'exploitation se rapprochent des plateformes conventionnelles. La rencontre internationale de Sfax (Tunisie) a mis l'accent sur les principales avancées de la recherche académique et industrielle dans le domaine des technologies de filtration membranaire pour le traitement de l'eau. Les retombées de cette manifestation seront analysées plus largement dans notre prochain bulletin mais les observations suivantes peuvent être déjà dégagées : Les spécialistes de la filtration se sont réunis pour échanger les résultats des projets de recherche menés en Afrique et pour formuler des recommandations sur les orientations futures en matière de gestion efficace de l'eau. Les objectifs à long terme consisteront à renforcer les capacités scientifiques et technologiques, stimuler la croissance économique à travers la valorisation des ressources en eau et en énergie. Nous espérons que la convergence de tels efforts permettra de mettre un frein aux conséquences désastreuses de la pauvreté et dans tous les pays du continent africain. Notre congrès AMSIC-1 s'est déroulé sur deux jours dont le premier était consacré aux procédés de filtration pout la production d'eau potable et pour les techniques de dessalement. Les volets Matériaux Membranaire, Mise au Point et Encrassement des Membranes, Performance des Filtres et Modules Membranaires ont été développés par les experts. Parallèlement, la question de l'apport des énergies renouvelables dans la gestion énergétique des procédés de filtration a été largement abordée. La deuxième journée a été dédiée à l'innovation dans les systèmes de filtration ainsi qu'à l'application de la filtration membranaire dans le domaine de l'irrigation, celui de la biotechnologie et des industries pharmaceutiques, et pour favoriser l'exploitation des eaux recyclées. Au cours de ces journées nous avons largement évoqué la nécessité de renforcer les partenariats institutionnels en Afrique dans le domaine de l'éducation et via les partenariats industriels. En outre cette rencontre internationale dont l'affluence a été excellente devrait contribuer au développement du continent africain dans les domaines scientifiques et socio-économiques. Un rapport détaillé est en cours de préparation visant à dégager les retombées et définir les futurs axes de travail pour notre association.
In order to transform a wide range of pharmaceutically active compounds (PhACs), the three oxidat... more In order to transform a wide range of pharmaceutically active compounds (PhACs), the three oxidative enzymes laccase (Lac) from Trametes versicolor, versatile peroxidase (VP) from Bjerkandera adusta and glucose oxidase (GOD) from Aspergillus niger were concomitantly cross-linked after aggregation, thus, making a combined cross-linked enzyme aggregate (combi-CLEA) that was versatile and involved in an enzymatic cascade reaction. From the initial enzymes about 30% of initial laccase activity was recovered along with 40% for each of VP and GOD. The combi-CLEA showed good results in conditions close to those of real wastewater (neutral pH and medium temperature) as well as a good ability to resist to denaturing conditions such as high temperature (60°C) and low pH (3). Batch experiments were realized to test the free enzyme's ability to degrade, a PhACs cocktail, mainly in a synthetic wastewater containing acetaminophen, naproxen, mefenamic acid, indometacin, diclofenac, ketoprofen, caffeine, diazepam, ciprofloxacin, trimethoprim, fenofibrate and bezafibrate, carbamazepine and its by-product 10-11 epoxy-carbamazepine. High removal was achieved (more than 80%) for the five first compounds. Then, the elimination ability of the combi-CLEA with or without hydrogen peroxide, glucose or manganese sulfate was determined. Globally, our results demonstrated that VP has a wider removal spectrum than Lac. These removal features are enhanced under more specific conditions, whereas the combi-CLEA combined advantages of both VP and laccase. Finally, the elimination of PhACs in a municipal wastewater treatment plant effluent using the combi-CLEA was marginally investigated. Concentrations of most of the selected PhACs were below the limit of quantification (lower than 20 ng/L) except for acetaminophen. Its combi-CLEA-mediated removal reached up to 25%.
h i g h l i g h t s " The organic/inorganic network stabilized the enzyme versus harsh environmen... more h i g h l i g h t s " The organic/inorganic network stabilized the enzyme versus harsh environments. " These structures did not limit the mass transfer of the substrate. " Applications of these biocatalysts are promising for bioprocesses. Enzyme polymer engineered structure Organic/inorganic surrounding network Chitosan a b s t r a c t Laccase and laccase-based cross-linked enzyme aggregates (CLEAs) were stabilized through the formation of a surrounding polymeric network made of chitosan and 3-aminopropyltriethoxysilane. The thermoresistance of the resulting enzyme polymer engineered structures of laccase (EPES-lac) and CLEAs (EPES-CLEA) were more than 30 times higher than that of free laccase and CLEAs at pH 3 and 40°C. The EPES showed higher residual activity than the unmodified biocatalysts against chaotropic salts (up to 10 times), EDTA (up to 5 times), methanol (up to 15 times) and acetone (up to 20 times). The Michaelis-Menten kinetic parameters revealed that the affinity for 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid) has doubled for the EPES-lac and EPES CLEA compared to their unmodified forms. The EPES-lac structures acted optimally at pH 4 and their activity was nearly temperature-independent, while the laccase activity of EPES-CLEA was optimal at pH 4 and 60°C. Globally, the EPES have shown significantly improved properties which make them attractive candidate for the development of laccase-based applications.
The Science of the total environment, Jan 15, 2014
Laccase (EC 1.10.3.2) and tyrosinases (EC 1.14.18.1) are ubiquitous enzymes present in nature as ... more Laccase (EC 1.10.3.2) and tyrosinases (EC 1.14.18.1) are ubiquitous enzymes present in nature as they are known to originate from bacteria, fungi, plants, etc. Both laccase and tyrosinase are copper-containing phenoloxidases requiring readily available O2 without auxiliary cofactor for their catalytic transformation of numerous phenolic substrates. In the present study, laccase and tyrosinase have been insolubilized as combined crosslinked enzyme aggregates (combi-CLEA) using chitosan, a renewable and biodegradable polymer, as crosslinker. The combi-CLEA, with specific activity of 12.3 U/g for laccase and 167.4 U/g for tyrosinase, exhibited high enzymatic activity at pH5-8 and temperature at 5-30°C, significant resistance to denaturation and no diffusional restriction to its active site based upon the Michaelis-Menten kinetic parameters. Subsequently, the combi-CLEA was applied to the transformation of acetaminophen as a model phenolic compound in samples of real wastewaters in orde...
tWidespread detection of numerous micropollutants including aromatic pharmaceuticals in effluents... more tWidespread detection of numerous micropollutants including aromatic pharmaceuticals in effluents ofwastewater treatment plants has prompted much research aimed at efficiently eliminating these contam-inants of environmental concerns. In the present work, a novel hybrid bioreactor (HBR) of cross-linkedenzymes aggregates of laccase (CLEA-Lac) and polysulfone hollow fiber MF membrane was developedfor the elimination of acetaminophen (ACT), mefenamic acid (MFA) and carbamazepine (CBZ) as modelaromatic pharmaceuticals. The MF alone showed removals of the three drugs varying approximatelyfrom 50 to 90% over the course of 8 h in the filtrate of aqueous solution. Synergistic action of the MFand CLEA-Lac during operation achieved eliminations from aqueous solution of around 99%, nearly 100%and up to 85% for ACT, MFA and CBZ, respectively. Under continuous operation, the HBR demonstratedelimination rates of the drugs from filtered wastewater up to 93% after 72 h for CBZ and near completeelimination of ACT and MFA was achieved within 24 h of treatment. Concomitantly to the drugs elimina-tions in the wastewater, the CLEA-Lac exhibited 25% residual activity while being continuously recycledwith no activity in the filtrate. Meanwhile, the filtrate flowrate showed only minor decline indicatinglimited fouling of the membrane.
Over the last few decades many attempts have been made to use biocatalysts for the biotransformat... more Over the last few decades many attempts have been made to use biocatalysts for the biotransformation of emerging contaminants in environmental matrices. Laccase, a multicopper oxidoreductase enzyme, has shown great potential in oxidizing a large number of phenolic and non-phenolic emerging contaminants. However, laccases and more broadly enzymes in their free form are biocatalysts whose applications in solution have many drawbacks rendering them currently unsuitable for large scale use. To circumvent these limitations, the enzyme can be immobilized onto carriers or entrapped within capsules; these two immobilization techniques have the disadvantage of generating a large mass of non-catalytic product. Insolubilization of the free enzymes as cross-linked enzymes (CLEAs) is found to yield a greater volume ratio of biocatalyst while improving the characteristics of the biocatalyst. Ultimately, novel techniques of enzymes insolubilization and stabilization are feasible with the combination of cross-linked enzyme aggregates (combi-CLEAs) and enzyme polymer engineered structures (EPESs) for the elimination of emerging micropollutants in wastewater. In this review, fundamental features of laccases are provided in order to elucidate their catalytic mechanism, followed by different chemical aspects of the immobilization and insolubilization techniques applicable to laccases. Finally, kinetic and reactor design effects for enzymes in relation with the potential applications of laccases as combi-CLEAs and EPESs for the biotransformation of micropollutants in wastewater treatment are discussed.
Laccase (EC 1.10.3.2) and tyrosinases (EC 1.14.18.1) are ubiquitous enzymes present in nature as ... more Laccase (EC 1.10.3.2) and tyrosinases (EC 1.14.18.1) are ubiquitous enzymes present in nature as they are known to originate from bacteria, fungi, plants, etc. Both laccase and tyrosinase are copper-containing phenoloxidases requiring readily available O2 without auxiliary cofactor for their catalytic transformation of numerous phenolic substrates. In the present study, laccase and tyrosinase have been insolubilized as combined crosslinked enzyme aggregates (combi-CLEA) using chitosan, a renewable and biodegradable polymer, as crosslinker. The combi- CLEA,with specific activity of 12.3 U/g for laccase and 167.4 U/g for tyrosinase, exhibited high enzymatic activity at pH 5–8 and temperature at 5–30 °C, significant resistance to denaturation and no diffusional restriction to its active site based upon the Michaelis–Menten kinetic parameters. Subsequently, the combi-CLEA was applied to the transformation of acetaminophen as a model phenolic compound in samples of real wastewaters in order to evaluate the potential efficiency of the biocatalyst. In batch mode the combi-CLEA transformed more than 80% to nearly 100% of acetaminophen fromthemunicipalwastewater and more than 90% fromthe hospital wastewater. UPLC–MS analysis of acetaminophen metabolites showed the formation of its oligomers as dimers, trimers and tetramers due to the laccase and 3-hydroxyacetaminophen due to the tyrosinase.
This paper presents the findings of a study to assess patterns in local knowledge of and response... more This paper presents the findings of a study to assess patterns in local knowledge of and response to water quality and waterborne diseases in relation to seasonal changes in the Niger River Inland Delta. The study draws on field data collected in four villages along the Niger River in the Mopti region of Mali during September 2008. The major findings suggest: (1) water use behaviors and diarrheal disease management are influenced by the tremendous seasonal fluctuations in the riverine environment; (2) local awareness of the relationship between poor water quality, oral-fecal disease transmission, and waterborne disease is low; (3) interventions to mitigate the high incidence of childhood diarrhea and degraded water quality are limited by ongoing socio-economic, cultural, and environmental factors; and (4) women's level of health knowledge is socially and culturally dependent.
Uploads
Papers by Sidy Ba
contaminants in environmental matrices. Laccase, a multicopper oxidoreductase enzyme, has shown great potential in
oxidizing a large number of phenolic and non-phenolic emerging contaminants. However, laccases and more broadly
enzymes in their free form are biocatalysts whose applications in solution have many drawbacks rendering them
currently unsuitable for large scale use. To circumvent these limitations, the enzyme can be immobilized onto carriers
or entrapped within capsules; these two immobilization techniques have the disadvantage of generating a large
mass of non-catalytic product. Insolubilization of the free enzymes as cross-linked enzymes (CLEAs) is found to yield a
greater volume ratio of biocatalyst while improving the characteristics of the biocatalyst. Ultimately, novel techniques
of enzymes insolubilization and stabilization are feasible with the combination of cross-linked enzyme aggregates
(combi-CLEAs) and enzyme polymer engineered structures (EPESs) for the elimination of emerging micropollutants
in wastewater. In this review, fundamental features of laccases are provided in order to elucidate their catalytic
mechanism, followed by different chemical aspects of the immobilization and insolubilization techniques applicable
to laccases. Finally, kinetic and reactor design effects for enzymes in relation with the potential applications of laccases
as combi-CLEAs and EPESs for the biotransformation of micropollutants in wastewater treatment are discussed.
to originate from bacteria, fungi, plants, etc. Both laccase and tyrosinase are copper-containing phenoloxidases
requiring readily available O2 without auxiliary cofactor for their catalytic transformation of numerous phenolic
substrates. In the present study, laccase and tyrosinase have been insolubilized as combined crosslinked enzyme
aggregates (combi-CLEA) using chitosan, a renewable and biodegradable polymer, as crosslinker. The combi-
CLEA,with specific activity of 12.3 U/g for laccase and 167.4 U/g for tyrosinase, exhibited high enzymatic activity
at pH 5–8 and temperature at 5–30 °C, significant resistance to denaturation and no diffusional restriction to its
active site based upon the Michaelis–Menten kinetic parameters. Subsequently, the combi-CLEA was applied to
the transformation of acetaminophen as a model phenolic compound in samples of real wastewaters in order to
evaluate the potential efficiency of the biocatalyst. In batch mode the combi-CLEA transformed more than 80% to
nearly 100% of acetaminophen fromthemunicipalwastewater and more than 90% fromthe hospital wastewater.
UPLC–MS analysis of acetaminophen metabolites showed the formation of its oligomers as dimers, trimers and
tetramers due to the laccase and 3-hydroxyacetaminophen due to the tyrosinase.
contaminants in environmental matrices. Laccase, a multicopper oxidoreductase enzyme, has shown great potential in
oxidizing a large number of phenolic and non-phenolic emerging contaminants. However, laccases and more broadly
enzymes in their free form are biocatalysts whose applications in solution have many drawbacks rendering them
currently unsuitable for large scale use. To circumvent these limitations, the enzyme can be immobilized onto carriers
or entrapped within capsules; these two immobilization techniques have the disadvantage of generating a large
mass of non-catalytic product. Insolubilization of the free enzymes as cross-linked enzymes (CLEAs) is found to yield a
greater volume ratio of biocatalyst while improving the characteristics of the biocatalyst. Ultimately, novel techniques
of enzymes insolubilization and stabilization are feasible with the combination of cross-linked enzyme aggregates
(combi-CLEAs) and enzyme polymer engineered structures (EPESs) for the elimination of emerging micropollutants
in wastewater. In this review, fundamental features of laccases are provided in order to elucidate their catalytic
mechanism, followed by different chemical aspects of the immobilization and insolubilization techniques applicable
to laccases. Finally, kinetic and reactor design effects for enzymes in relation with the potential applications of laccases
as combi-CLEAs and EPESs for the biotransformation of micropollutants in wastewater treatment are discussed.
to originate from bacteria, fungi, plants, etc. Both laccase and tyrosinase are copper-containing phenoloxidases
requiring readily available O2 without auxiliary cofactor for their catalytic transformation of numerous phenolic
substrates. In the present study, laccase and tyrosinase have been insolubilized as combined crosslinked enzyme
aggregates (combi-CLEA) using chitosan, a renewable and biodegradable polymer, as crosslinker. The combi-
CLEA,with specific activity of 12.3 U/g for laccase and 167.4 U/g for tyrosinase, exhibited high enzymatic activity
at pH 5–8 and temperature at 5–30 °C, significant resistance to denaturation and no diffusional restriction to its
active site based upon the Michaelis–Menten kinetic parameters. Subsequently, the combi-CLEA was applied to
the transformation of acetaminophen as a model phenolic compound in samples of real wastewaters in order to
evaluate the potential efficiency of the biocatalyst. In batch mode the combi-CLEA transformed more than 80% to
nearly 100% of acetaminophen fromthemunicipalwastewater and more than 90% fromthe hospital wastewater.
UPLC–MS analysis of acetaminophen metabolites showed the formation of its oligomers as dimers, trimers and
tetramers due to the laccase and 3-hydroxyacetaminophen due to the tyrosinase.