Doctoral dissertation

Digestate valorization for bioremediation of petroleum hydrocarbons contaminated soils: In search of functional genes

Microbial diversity studies and scanning of digestate microbial communities in terms of the presence of alkB genes – responsible for degradation of saturated hydrocarbons.

Petroleum industry generates substances, which may affect human health as well as soil and water ecosystems, including toxicity towards microorganisms, plants and animals. Petroleum contaminated soils constitute an environmental issue which may be solved with the help of bioremediation. Soil bioaugmentation with petroleum degrading microorganisms is an efficient clean-up strategy. Currently scientific interest is focused on searching new sources of microorganisms able to degrade hydrocarbons which serve as species pools for enrichments during inoculum preparation.

Digestate is an organic by-product of biogas production via anaerobic digestion processes and has a great potential as soil fertilizer due to concentrated nutrients and low content of easily biodegradable compounds. Digestate contains dense and diverse microbial population structure. However, the potential of microbial community of digestate was never studied in terms of petroleum hydrocarbons (PHCs) degradation.

In this doctoral dissertation, for the first time, digestate was studied in terms of indigenous microbial community which can be involved in degradation of saturated hydrocarbons. During her thesis, MSc Anna Gielnik focused on digestate as nutrients and microorganisms source in bioremediation of petroleum hydrocarbons contaminated soils and on the effect of digestate application on the structure of soil microbial community.

Gielnik's results demonstrated that the content of alkB genes (encoding enzymes responsible for degradation of saturated hydrocarbons) in digestate was interestingly high. After digestate application, the level of alkB genes in contaminated soil as well as the diversity of hydrocarbons degrading taxa were significantly increased and maintained. Monitoring of the concentration of alkB genes during the treatment reflected actual hydrocarbons removal rates which confirmed that this genetic marker can be a tool for assessing the biodegradation efficiency. Soil application of digestate increased petroleum hydrocarbons bioremediation level in a significantly greater extent than mineral fertilizers. Obtained results highlight that organic amendments like digestate can improve hydrocarbons metabolic capacity of contaminated soils.

Public defense of a doctoral dissertation on Wednesday, 11th of December 2019

MSc Anna Gielnik's dissertation in the field of environmental engineering entitled Digestate valorization for bioremediation of petroleum hydrocarbons contaminated soils will be publicly examined at University Paris Est, (address: Building Rabelais (UPEM), Boulevard Descartes, 77420, Champs-sur-Marne) on Wednesday, 11th of December 2019 at 14h00. The opponents will be Prof. Maria Pilar Bernal from Universitario de Espinardo, (Murcia, Spain), Prof. Paolo Roccaro from University of Catania, (Italy) and Prof. Frédéric Coulon from Cranfield University (United Kingdom).

Anna Gielnik's doctoral research has been conducted in the framework of the Advanced Biological Waste to Energy Technologies (ABWET) Innovative Training Network (ITN) European Joint Degree Programme. ABWET has four partner organizations: University of Cassino and Southern Lazio (Italy, coordinator), Université Paris-Est (France), IHE Delft (the Netherlands) and Tampere University of Technology (Finland). The Examination Committee of Anna Gielnik's doctoral dissertation includes one representative from each partner organization.

Anna Gielnik comes from Grodzisk Wielkopolski (Greater Poland, Poland) and works as a researcher in the Laboratory of Geomaterials end Environment at the University Paris Est in France.