Search

This work investigated non-polar solvent hexane and polar solvents methanol and ethanol as inducers besides a well-known inducer, copper, for laccase production with and without mesoporous silica-covered plastic packing under sterilised and unsterilised conditions. The potential of waste-hexane water, which is generated during the mesoporous silica production process, was also investigated as a laccase inducer. During the study, the free and immobilised laccase activity on the packing was measured. The results showed that the highest total laccase activity, approximately 10,000 Units, was obtained under sterilised conditions with 0.5 mM copper concentration. However, no immobilised laccase activity was detected except in the copper and ethanol sets under unsterilised conditions. The maximum immobilised laccase activity of the sets that used waste hexane as an inducer was 1.25 U/mg packing. According to its significant performance, waste hexane can be an alternative inducer under sterilised conditions. Concomitant immobilised packing showed satisfactory laccase activities and could be a promising method to reduce operation costs and improve the cost-efficiency of enzymatic processes in wastewater treatment plants. [ABSTRACT FROM AUTHOR]

Global warming needs immediate attention to reduce major greenhouse gas emissions such as methane (CH4). Bio-oxidation of dilute CH4 emissions in packed-bed bioreactors such as biofilters has been carried out over recent years at laboratory and large scales. However, a big challenge is to keep CH4 biofilters running for a long period. In this study, a packed-bed lab-scale bioreactor with a specialized inorganic-based filter bed was successfully operated over four years for CH4 elimination. The inoculation of the bioreactor was the active leachate of another CH4 biofilter which resulted in a fast acclimation and removal efficiency (RE) reached 80% after seven weeks of operation for CH4 inlet concentrations ranging from 700 to 800 ppmv and an empty bed residence time (EBRT) of 6 min. During four years of operation, the bioreactor often recorded REs higher than 65% for inlet concentrations in the range of 1900–2200 ppmv and an EBRT of 6 min. The rate and interval of the nutrient supply played an important role in maintaining the bioreactor's high performance over the long operation. Forced shutdowns were unavoidable during the 4-year operation and the bioreactor fully tolerated them with a partial recovery within one week and a progressive recovery over time. In the end, the bioreactor's filter bed started to deteriorate due to a long shutdown of twelve weeks and the extended operation of four years when the RE dropped to below 8% with no sign of returning to its earlier performance. [ABSTRACT FROM AUTHOR]

Hazardous airborne pollutants are frequently emitted to the atmosphere in the form of a gaseous mixture. Air biofilters as the primary biotechnological choice for waste gas treatment (low inlet concentration and high gas flow rate) should run properly when the feed contains multiple pollutants. Simultaneous removal of pollutants in biofilters has been extensively studied over the last 10 years. In this review, the results and findings of the mentioned studies including different groups of pollutants, such as methane (CH4) and volatile organic compounds (VOCs) are discussed. As the number of pollutants in a mixture increases, their elimination might become more complicated due to interactions between the pollutants. Parallel batch studies might be helpful to better understand these interaction effects in the absence of mass transfer limitations. Setting optimum operating conditions for removal of mixtures in biofilters is challenging because of opposing properties of pollutants. In biofilters, concerns, such as inlet gas composition variation and stability while dealing with abrupt inlet load and concentration changes, must be managed especially at industrial scales. Biofilters designed with multi-layer beds, allow tracking the fate of each pollutant as well as analyzing the diversity of microbial culture across the filter bed. Certain strategies are recommended to improve the performance of biofilters treating mixtures. For example, addition of (bio)surfactants as well as a second liquid phase in biotrickling filters might be considered for the elimination of multiple pollutants especially when hydrophobic pollutants are involved. [ABSTRACT FROM AUTHOR]

Air polluted with methanol vapours was treated in a biofilter and a biotrickling filter, both packed with inert materials. The effects of the nitrogen concentration present in the nutrient solution, the empty bed residence time, and the methanol inlet load, on the biofilter and biotrickling filter performance were all examined and compared. The elimination capacity, the biomass and the carbon dioxide production rates all increased with the increase of the parameters tested. The maximum elimination capacity for the biotrickling filter was 240 g x [m.sup.-3] x [h.sup.-1] with corresponding removal efficiency of 75% and carbon dioxide production rate of 10 g x [m.sup.-3] x [h.sup.-1], whereas the maximum elimination capacity for the biofilter was 80 g x [m.sup.-3] x [h.sup.-1] with corresponding removal efficiency of 35% and carbon dioxide production rate of 70 g x [m.sup.-3] x [h.sup.-1]. The biomass production rate was similar for both the biofilter and the biotrickling filter. The carbon dioxide production rate was higher by a factor of 2 to 9 for the biofilter compared to the biotrickling filter. Key words: biotrickling filter, biofilter, methanol, empty bed residence time, nitrogen concentration, biomass, carbon dioxide De l'air pollue par des vapeurs de methanol a ete traite dans un biofiltre et un biofiltre percolateur garnis avec deux materiaux inertes. Les effets de la concentration d'azote presente dans la solution nutritive, du temps de residence en fut vide et de la charge de methanol a l'entree sur la performance du biofiltre et du biofiltre percolateur ont ete analyses et compares. La capacite d'elimination et les taux de production de biomasse et dioxyde de carbone ont augmente avec l'augmentation des niveaux des parameters testes. La capacite d'elimination maximale du biofiltre percolateur etait de 240 g x [m.sup.-3] x [h.sup.-1] correspondant a une conversion a 75 % et un taux de production de dioxyde de carbone de 10 g x [m.sup.-3] x [h.sup.-1] . La capacite d'elimination maximale du biofiltre etait de 80 g x [m.sup.-3] x [h.sup.-1] correspondant a une conversion de 35 %, et un taux de production de dioxyde de carbone de 70 g x [m.sup.-3] x [h.sup.-1]. Le taux de production de biomasse etait similaire pour les deux biofiltres. Le taux de production de dioxyde de carbone etait de 2 a 9 fois plus eleve pour le biofiltre par rapport a celui du biofiltre percolateur. Mots-cles : filtre biologique a lit filtrant, biofiltre, methanol, temps de residence en fat vide, concentration en azote, biomasse, dioxyde de carbone [Traduit par la Redaction], Introduction Biofiltration with or without percolation is an efficient air treatment biotechnology when the inlet loads of volatile organic compounds (VOCs) to be treated are high, specifically at VOCs concentrations [...]

Sewage from residents and industries is collected and transported to wastewater treatment plants (WWTPs) with sewer networks. The operation of WWTPs results in emissions of greenhouse gases, such as methane (CH4), mostly due to sludge anaerobic digestion. Amounts of emissions depend on the source of influent, i.e. municipal and industrial wastewater as well as sewer systems (gravity and rising). Wastewater is the fifth-largest source of anthropogenic CH4 emissions in the world and represents 7–9% of total global CH4 emissions into the atmosphere. Global wastewater CH4 emission grew by approximately 20% from 2005 to 2020 and is expected to grow by 8% between 2020 and 2030, which makes wastewater an important CH4 emitter worldwide. This review initially considers the emission of CH4 from WWTPs and sewer networks. In the second part, biotechniques available for biodegradation of low CH4 concentrations (<5% v/v) encountered in WWTPs have been studied. The paper reviews major bioreactor configurations for the treatment of polluted air, i.e. biotrickling filters, bioscrubbers, two-liquid phase bioreactors, biofilters, and hybrid reactor configurations, after which it focuses on CH4 biofiltration systems. Biofiltration represents a simple and efficient approach to bio-oxidize CH4 in waste gases from WWTPs. Major factors influencing a biofilter's performance along with knowledge gaps in relation to its application for treating gaseous emissions from WWTPs are discussed. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The article features the chemical engineering department of the University of Sherbrooke in Quebec. The university's chemical engineering faculty is presented, including biochemist Nathalie Faucheux. The faculty of engineering at the university was an early adopter of the cooperative system of engineering in North America. The studies program in chemical engineering was entirely overhauled for students set to start in September 2001 and graduate in December 2005.

Bisphenol A (BPA) and triclosan (TCS) are known or suspected potential endocrine disrupting chemicals (EDCs) which may pose a risk to human health and have an environmental impact. Enzyme preparations containing mainly laccases, obtained from Ganoderma stipitatum and Lentinus swartzii, two autochthonous Colombian forest white rot fungi (WRF), previously identified as high enzyme producers, were used to remove BPA and TCS from aqueous solutions. A Box-Behnken factorial design showed that pH, temperature, and duration of treatment were significant model terms for the elimination of BPA and TCS. Our results demonstrated that these EDCs were extensively removed from 5 mg L(-1) solutions after a contact time of 6 hours. Ninety-four percent of TCS and 97.8% of BPA were removed with the enzyme solution from G. stipitatum; 83.2% of TCS and 88.2% of BPA were removed with the L. swartzii enzyme solution. After a 6-hour treatment with enzymes from G. stipitatum and L. swartzii, up to 90% of the estrogenic activity of BPA was lost, as shown by the yeast estrogen screen assay. 2,2-Azino-bis-(3-ethylthiazoline-6-sulfonate) (ABTS) was used as a mediator (laccase/mediator system) and significantly improved the laccase catalyzed elimination of BPA and TCS. The elimination of BPA in the absence of a mediator resulted in production of oligomers of molecular weights of 454, 680, and 906 amu as determined by mass spectra analysis. The elimination of TCS in the same conditions produced dimers, trimers, and tetramers of molecular weights of 574, 859, and 1146 amu. Ecotoxicological studies using Daphnia pulex to determine lethal concentration (LC50) showed an important reduction of the toxicity of BPA and TCS solutions after enzymatic treatments. Use of laccases emerges thus as a key alternative in the development of innovative wastewater treatment technologies. Moreover, the exploitation of local biodiversity appears as a potentially promising approach for identifying new efficient strains for biotechnological applications.