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Group of Environmental Biotechnology

Universidade de Santiago de Compostela

Universidade de Santiago de Compostela Campus Vida Cretus
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Group of Environmental Biotechnology

Universidade de Santiago de Compostela

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1.1.2 Advanced oxidation processes: Enzymatic, Fenton and photocatalysis



In 1990 it was initiated a research line based on the application of white rot fungi for the degradation of polycyclic aromatic hydrocarbons, using the in vivo system and producing extracellular peroxidases, responsible of the oxidative attack of these compounds. The first works in this area consisted on the selection and optimization of white rot fungi capable of degrading polycyclic aromatic hydrocarbons (PAHs), attaining high percentages (up to 90%) of degradation of different PAHs (anthracene, pyrene and benzo(a)pyrene). In parallel, diverse studies on the production of extracellular peroxidases were performed. These peroxidases were applied for the degradation of several organic compounds: PAHs, pesticides, industrial dyes, etc. These works have been carried out within the projects funded by CICYT: BIO95-377, BIO98-0610, PPQ2001-3063 y VEM2003-20089-CO2-01. Another application was the biobleaching of Kraft pulp by enzymes. This research enabled the group to take part of the European project OXEPI (FAIR CT95-0805).
Nowadays, we have focused on the design and modelling of two types of enzymatic reactors for the removal of recalcitrant compounds: PAHs and microcontaminants (essentially PPCPs and EDCs).

The enzyme membrane reactor has been successfully applied for the removal of industrial dyes. The presence of the membrane allowed increasing the residence time of the biocatalyst into the reactor, which increased notably the efficiency. The system was modelled, under steady state and transient state. This will be useful to implement the control of the system in further stages of the research. The system has been patented (P20010670) and extended to different countries in the EU.
Biocatalysis on two phase systems, including the selection of an appropriate reaction medium, the reactor design and the operational variables, can be considered as a challenge in biochemical engineering. Biphasic media allow to work at high concentrations, hence this system presents obvious advantages for those reactions where one or more components have limited solubility. The key of the biphasic reactor design is to equilibrate the rates of the two mechanisms: the substrate transfer from the organic to the aqueous phase and the catalytic reaction.

Projects

· Chemical and biochemical catalysis reactors ruled by nanosize Metal OxiDes, Enzyme Nanoparticles and Atomic Clusters applied for the removal of emerging contaminants (MODENA) feder_color_2_0.png
Spanish Government MINECO. RETOS 2016. Co-funded by FFEDER (UE) (CTQ2016-79461-R). (2016-2019)

Completed Projects

The main objective of this project is the development of an enzymatic reactor for the tertiary treatment of wastewaters aiming at the removal of micropollutants. The enzymatic system is based on laccase immobilized onto magnetic nanoparticles (mNPs), a support that permits an easy separation of the biocatalyst from the reaction medium by simply applying a magnetic field. In this way, it is intended to develop a procedure for the immobilization of laccase onto mNPs and its further application for the removal of pollutants in a sequencing batch reactor (SBR). The project integrates the complementary skills of researchers from three departments at the University of Santiago de Compostela. - The research group Nanomag (Department of Physical Chemistry and Department of Applied Physics) will be responsible of the production, functionalization of mNPs and the design of a magnetic separation system to be used in the SBR. -On the other side, the biotechnology tasks, related with the enzyme immobilization, characterization of the biocatalyst and development of new technologies for the removal of pollutants will be carried out by the BioGroup (Department of Chemical Engineering). The work plan of this project consist on the following phases:

  1. Production of single and multi-core mNPs with different functionalizations and sizes;
  2. Immobilization of laccase onto the mNP by covalent bonding with two different activation methodologies as well as enzyme immobilization by electrostatic interactions;
  3. Characterization of the biocatalysts in terms of kinetic parameters, pH and T stability, presence of inactivating agents, influence of the composition of real wastewater, etc;
  4. Evaluation of the capacity of the different biocatalysts to remove three different recalcitrant pollutants: the dye Methyl Green, selected as model compound as well as type of pollutants included in the priority list of target contaminants reported by UE: the endocrine disruptor bisphenol A and the pharmaceutical compound diclofenac;
  5. Economical and environmental analysis of the biocatalyst, in order to select the one that provides not only high removal efficiency but also low cost and minimal environmental impact;
  6. Development of a SBR based on laccase immobilized onto mNPs for the removal of the target pollutants present in real wastewaters.


The main focus of the proposal is the development of new enzymatic reactors, operated with free or immobilized enzymes for the removal of endocrine disrupting compounds (EDCs). Diverse research phases were proposed: (i) EDC degradation by laccase and versatile peroxidase, evaluating the effect of the parameters involved in the catalytic cycle such as the level of enzymatic activity, adequate concentration of hydrogen peroxide, cofactors and mediators on the EDC degradation; (ii) identification and characterization of reaction by‐products; (iii) study of a new immobilization procedure for both enzymes, based on the formation of aggregates; (iv) evaluation of new enzyme reactor configurations: ultrafiltration and microfiltration stirred tank reactors, operating with free and immobilized enzymes, as well as two‐stages membrane reactor and microreactor to produce the oxidative Mn3+ species, which will be applied in a second reactor for the EDC degradation and, (v) modelization and environmental evaluation of the enzymatic processes.


The project deals with the design and operation of biphasic enzymatic reactors for the oxidation and removal of xenobiotics compound with low water solubility such as the polycyclic aromatic hydrocarbons anthracene, dibenzothiophene and pyrene. A fungal peroxidase with high oxidation potential was proposed as biocatalyst. The different goals to be attained were: (i) selection of the appropriate solvent; (ii) study of the different parameters involved in the catalytic cycle, such as enzyme activity, concentration of hydrogen peroxide and concentration of other cofactors; (iii) study of the different operational parameters involved in the degradation and enzymatic activity, such as pH and temperature; (iv) improvement of mass transfer, evaluating the agitation mechanisms and agitation speed, in order to obtain an adequate interfacial area and minimum deactivation of enzyme due to mechanical stress; (v) study of two different reactor configuration: stirred tank reactor and airlift reactor, using free and immobilized enzyme; (vi) design, modelling and control of the process.


Publications
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