Sabine San\u00e9, a doctoral student in the Department of Microsystems Engineering (IMTEK) at the University of Freiburg, has developed a concept that shows how micropollutants can be degraded in wastewater and how the latter can serve as a valuable source of raw materials. She is one of four researchers who have been awarded the 2014 Huber Technology Prize \u201cFuture Water\u201d with a purse of 10,000 euros. Her concept is based on an enzyme that is secreted by the turkey tail fungus Trametes versicolor. This enzyme, known as laccase, has been shown to efficiently degrade pollutants and increase the performance of biofuel cells.<\/p>\n
Wastewater contains a wide range of pollutants, including heavy metals, synthetic organic compounds, viruses and bacteria. Micropollutants are pollutants that occur in concentrations of less than a few micogrammes per litre. Technological progress has improved the detection of such small concentrations of substances. \u201cThe degradation of micropollutants has not previously been an issue, particularly because technologies that can detect them have only recently become available,\u201d says San\u00e9, doctoral student in the IMTEK\u2019s Bioelectrochemical Systems research group.<\/p>\n
Drug residues or hormones from private households are among those compounds that wastewater plants are unable to degrade. \u201cMany women take hormone-based contraceptives, which are partially excreted with urine,\u201d says San\u00e9. Ibuprofen and diclofenac are synthetic chemicals that cannot be broken down, and instead accumulate in the ecosystem. The same thing happens with X-ray contrast agents used in hospitals and antibiotics used in industrial livestock farming.<\/p>\n
Compounds that cannot be broken down in wastewater plants accumulate in aquatic ecosystems, and threshold limits need to be put in place in order to reduce the negative effects on the environment. Antidepressant drugs are known to impact the metabolism and behaviour of fish: it makes them more aggressive rather than happier. Oestrogens have been shown to render fish infertile.<\/p>\n
However, a fungus known as Trametes versicolor or turkey tail fungus has been shown to change the situation. This particular fungus is a polypore fungus commonly found on European beech. The fungus degrades fallen trees and is also able to break down lignin. These processes are achieved by the fungal enzyme laccase, which catalyses the oxidation of aromatic compounds concomitantly with the reduction of oxygen to water. The enzyme is extremely stable and withstands high temperatures and solvents. The fungus has been used in research for a number of years, and can be cultivated in a similar way to bacteria.<\/p>\n
The fungal laccase enzyme can be used to break down pollutants into their constituents. \u201cLaccase oxidises micropollutants and is far from selective,\u201d says San\u00e9. \u201cIt is completely non-specific and can use all kinds of substrates.\u201d Compared to ozone or activated charcoal for the treatment of wastewater, the fungus appears to be the smarter alternative. Activated charcoal is produced from carbonaceous materials and needs to be disposed of after use; the method involving ozone consumes a lot of energy and requires trained personnel to deal with the large number of dangerous products generated. Nevertheless, the production of laccase tends to be rather expensive as it needs to be expressed in and isolated from microorganisms.<\/p>\n
San\u00e9\u2019s project therefore involved looking for a cheaper way to produce laccase. She decided to use the crude culture supernatant without further treatment. \u201cWhen the fungus is grown on a liquid nutrient culture, it floats on top of it just like mould on apple juice.\u201d In this case, Trametes appears to secrete more than just laccase. \u201cThe fungus secretes the entire enzyme complex into the liquid medium and we are using the crude supernatant for the degradation of pollutants without further purification.\u201d<\/p>\n
This is only part of the concept for which San\u00e9 and three other up-and-coming scientists were recently awarded the 2014 Huber Technology Prize: Future Water for projects involving \u201cEnergy and Resources from Wastewater\u201d. The objective of this new prize is to encourage up-and-coming scientists to develop concepts that contribute to protecting the environment and saving resources. The second part of San\u00e9\u2019s concept foresees the use of the fungus for improving the performance of a hybrid microbial-enzymatic fuel cell.<\/p>\n
In a hybrid microbial-enzymatic fuel cell, microorganisms that are found in wastewater can attach to the anode and transfer electrons resulting from the degradation of compounds. \u201cThese microorganisms are able to \u2018breathe\u2019 with the anode rather than with oxygen,\u201d explains San\u00e9, going on to add \u201cat the same time, they metabolise the organic carbon in the wastewater. We do not need to feed them additional organic carbon compounds.\u201d An electric circuit is established when the electrons migrate towards the cathode where the laccase enzyme catalyses the transfer of electrons to oxygen.<\/p>\n
However, laccase has a lifespan of no more than two weeks, and laccase-based fuel cells can currently only be used in the laboratory. The isolation and purification of the enzyme is a rather complex process, even in the laboratory. San\u00e9 had the idea of skipping the isolation and purification steps and using the crude supernatant without further treatment. This solution contains the enzyme as well as many other molecules.<\/p>\n
San\u00e9 found no significant difference in the fuel cell performance when using crude supernatant that contains laccase compared to purified laccase in culture medium. \u201cThis was totally unexpected,\u201d says San\u00e9. \u201cWe have been able to show that the lifespan of the cathode can be greatly prolonged if we repeatedly exchange the crude culture supernatant.\u201d San\u00e9 ended up with a cathode that had a lifespan of four months, and was convinced that this could be prolonged further. \u201cUnfortunately, my reactor dried out,\u201d she says.<\/p>\n
San\u00e9\u2019s vision is to combine two methods based on the laccase enzyme: a wastewater fungus farm combined with a wastewater treatment plant, which would then be an autonomous wastewater plant that produces the energy it consumes at the same time as degrading micropollutants. \u201cThe smartest possible solution would be to grow the fungus on the surface of the wastewater that contains the fuel cell and in which the drug residues are broken down,\u201d says San\u00e9. \u201cWe would be able to purify water at the same time as generate electricity.\u201d The next step will now be to turn the concept into reality.<\/p>\n","protected":false},"excerpt":{"rendered":"
Sabine San\u00e9, a doctoral student in the Department of Microsystems Engineering (IMTEK) at the University of Freiburg, has developed a concept that shows how micropollutants can be degraded in wastewater and how the latter can serve as a valuable source of raw materials. She is one of four researchers who have been awarded the 2014 […]<\/p>\n","protected":false},"author":59,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_seopress_robots_primary_cat":"","nova_meta_subtitle":"","footnotes":""},"categories":[5572],"tags":[],"supplier":[409],"class_list":["post-23007","post","type-post","status-publish","format-standard","hentry","category-bio-based","supplier-universitaet-freiburg"],"_links":{"self":[{"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/posts\/23007","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/users\/59"}],"replies":[{"embeddable":true,"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/comments?post=23007"}],"version-history":[{"count":0,"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/posts\/23007\/revisions"}],"wp:attachment":[{"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/media?parent=23007"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/categories?post=23007"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/tags?post=23007"},{"taxonomy":"supplier","embeddable":true,"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/supplier?post=23007"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}