Department of Chemical Engineering
University of Vigo
Title: Novel physico-biological strategy for the remediation of effluents polluted with industrial contaminants
After my degrees in Chemistry and Chemical Engineering, I started to investigate the production of enzymes from mesophilic microorganisms, tackling different cultivation modes (free cells and immobilized cells), bioreactor configurations, microbial modelling and operation modes. Usually, the bottleneck of any industrial process to obtain enzymes is the biological reaction and the downstream processing, and the design of efficient operation units is crucial to make biotechnology competitive against the traditional processes. For these reasons, my first scientific contributions dealt with the study of the operating conditions for maximizing lipase synthesis. These enzymes have shown an enormous industrial potential in a wide range of sectors, going from detergents to dairy and bread-making industries, and making up the third group of enzymes in terms of sales. After having detected some important limitations of biomolecules obtained from mesophiles, such as deactivation or denaturation at conventional operating conditions used in industrial processes, I started my PhD in the field of extremophiles. The use of enzymes produced by these microorganisms allows circumventing the typical drawbacks of mesophilic enzymes due to their naturally developed resistance to drastic reaction conditions. Since this, the screening for thermostable enzymes from microorganisms adapted to living in extreme environments is thus an important way to find the right biocatalysts for desired reactions. This aspect was extensively tackled during my PhD thesis, including also a fruitful study stay in the Institut fÃ¼r Technische Mikrobiologie der Technische UniversitÃ¤t Hamburg-Harburg, under the supervision of Prof. Dr. Dr.h.c. Antranikian, one of the most renowned groups in this field. Finally, my posdoc period (2 years at the Institute of Chemical and Biological Technology in Lisbon) was focused on the introduction of a group of neoteric solvents, called ionic liquids, for biotechnological purposes. The widely renowned experience of the host institute in the ionic liquids field is demonstrated by the important contributions carried out by group of Prof. Dr. LuÃs Paulo Rebelo, one of the most outstanding leaders within the world of ionic liquids, with publications in the very best journals such as Nature, Chemical Society Reviews, or Green Chemistry.
One of the challenges faced by environmentalists is focused on the search of efficient wastewater treatments for industrial effluents containing persistent organic pollutants. These compounds represent an environmental and health threat due to their well-known problems such as carcinogenicity, toxicity and mutagenicity. For example, polycyclic aromatic hydrocarbons are introduced in the environment through a plethora of natural and anthropogenic activities, while 30,000 to 150,000 tons of dyes are discharged annually into receiving watercourses . These compounds are characterized by their inherent properties such as low vapour pressure and thermodynamic stability of the aromatic ring which make them persistent and recalcitrant . The presence of this contaminant charge makes it necessary to explore different technologies such as physical, biological and chemical methods. Thus, coagulation-flocculation, electrochemical, adsorption on activated carbon or other sorptive materials are recent remediation strategies followed by different authors. Very often the use of a single method does not allow reaching the standard quality requirements, so the combination of different alternatives is sometimes proposed . In this work, we have bet in a new strategy combining biological degradation and a surfactant-based aqueous biphasic system. We have selected a suitable organic salt for promoting phase disengagement in aqueous solutions of commonly used non-ionic surfactants such as Triton and Tween families. Thus, these compounds act both as contaminants solubilizers, enhancing its bioavailability, and as extractants. Different microbial agents were also screened for pollutant biodegradation, and the processes were carried out at flask and bioreactor scale. The experimental data of biodegradation and extraction were suitably modelled by fitting to mathematical equations in order to ease the process scaling-up and simulation. The versatility of this strategy was checked for different kind of contaminants such as polycyclic aromatic hydrocarbons, dyes and heavy metals, and the total remediation values were very high (higher than 70% in all cases).