Interview with research talents

Søren Dollerup Nielsen
Ph.D. student 

Soren Dollerup Nielsen

Søren's background
I studied biology at Aarhus University with a specialization in microbiology. My areas of interest are applied microbiology and geomicrobiology. For my master’s thesis I worked with microcalorimetry and developed a new method to quickly estimate abundances of endospores (dormant resting stages) of thermophilic bacteria in permanently cold marine sediments. One theory links their presence in the seabed with natural seeps of gas and oil and I investigated their use as bio-prospecting agents for diffusive seepage and thus for future gas and oil reservoirs.

Present your project
In august 2016 I started my PhD-project “Microbial induced healing of cement”. It is well established that bacteria embedded in a cement matrix can repair cracks in above ground structures by inducing the precipitation of calcium carbonate. The aim of my project is to modify the technique already in use in surface environments to develop cements that are able to “self-heal” under subsurface conditions. We will embed the endospores of bacteria in tiny capsules together with the necessary nutrients and incorporate them into the cement. The endospores will germinate, metabolize and precipitate calcium carbonate when cracks occur, effectively healing them. The goal is to prolong the life time of cements in deep offshore production facilities.

What do you expect the major challenges in your area of study will be?
The subsurface cement installations, where we want to apply this technique are characterized by a lack of oxygen, high temperature, high pH and high pressure. Combined, these 4 stressors challenge bacterial growth. Yet we need to identify bacterial cultures able to metabolize under such extreme conditions. Another challenge is to produce capsules that will protect the bacteria in the cement matrix both under the casting process and the final hardened cement. Additionally, the capsules must contain both the endospores and nutrients necessary for producing calcium carbonate.

How do you plan to contribute in solving these problems?
Axenic strains able to metabolize and grow under these conditions are rare. We have obtained a number of strains that are interesting candidates for our application. We will test the growth characteristics and ability to precipitate calcium carbonate of these strains under the relevant field conditions to find the best candidate. We are collaborating with the Department of Engineering, AU for designing capsules that will protect the bacteria during the cement casting process and during long-term embedding in the cement.

What are your expectations for your future career?
I wish to expand the applications of microbiology to non-traditional realms. The enzymatic capacities which bacteria possess are underutilized and are potential solutions to multiple commercial and industrial applications. I intend on continuing on this road either in academia or industry. Specifically, if our project of healing cement is successful in the lab, I would like to be involved in the implementation on a larger scale.

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6 APRIL 2020