Michael Waring, PhD, Shivanthi Anandan, PhD, and Jacob Russell, PhD, in front of the Biowall. Photo taken by Sean Corbett.
To better understand the benefits provided by this green technology, Shivanthi Anandan, PhD, and Jacob Russell, PhD from the Department of Biology have teamed up with Michael Waring, PhD, from Drexel’s Civil, Architectural, and Environmental Engineering department. Together, these three researchers will study how well the biowall works, how different plant types (and their root microbes) vary in their abilities to purify VOCs, and which of the root-associated microbes are involved in VOC degradation. Their work involves Drexel STAR Scholars and Co-op students. Financial support has been provided by the Office of the Provost and the College of Arts and Sciences at Drexel, as well as a GRID grant (Commonwealth of Pennsylvania, Department of Health, CURE grant SAP 4100050893 to Drexel University; awarded to PI’s Anandan, Russell, and Waring).
Measuring Air Quality and Purification
To facilitate this research, sampling ports have been installed on each floor of PISB, allowing access to air that has recently passed through the biowall. The quality of this air will be compared to the quality of the air in the atrium of the building using gas chromatography and detection methods to determine the efficiency of VOC removal. Measurements from each floor will reveal whether removal efficiency and, thus, air quality vary from floor to floor due to differences in temperature, light, humidity, or plant content.
Experiments will also be performed on VOC removal efficiency under controlled conditions. Here, plants will be grown aeroponically, with their roots receiving VOCs at known concentrations. Gas chromatography and detection measurements of the effluent (outgoing) air will allow an estimation of the plants’ (and microbes’) contribution to air purification. Those performing especially well will be selected for further study of root communities. Consideration will also be given to the greater use of such plants in biowalls to promote further air quality improvement.
Studying Microbial Root Communities
In addition to their studies on air quality, researchers will investigate the root-associated microbial communities on biowall-grown plants. One of the goals here is to understand how these communities change and respond to growth in a biowall after transplantation from soil and greenhouse conditions. Toward this end, researchers sampled and preserved root tissue from plants being installed on the biowall on July 6-7, 2011. Microbes from plants at this stage will be compared to those of the same plants after several weeks and months of growth in the wall, helping to determine whether growth in this artificial environment with increased VOC exposure favors the proliferation or decline of particular bacteria and fungi.
The microbial research will take two general approaches to better understand the root communities. First, conserved bacterial and fungal genes will be sequenced for these microbes, thus generating “barcodes” to identify the types of microbes that are present. Separate studies of how these populations respond to particular VOCs under controlled conditions will identify particular bacteria and fungi that may be capable of using these chemicals for food. Second, fungi and bacteria that degrade VOCs will be cultured directly on media containing VOCs (or their close mimics), providing a source of beneficial microbes for use in future experiments involving root inoculation and genetic manipulation. Prior work using these approaches has been performed on plants from the Dodge Foundation biowall in Morristown, NJ (www.grdodge.org), revealing diverse communities of bacteria and fungi, including several that break down benzene.
The research performed by Anandan, Russell, and Waring and their team will transform the biowall into a living laboratory, helping to quantify the benefits of this beautiful structure while shedding light on the mechanisms by which the plants and their microbes improve air quality. In the long term, this work should help to identify plants and microbes that are efficient VOC degraders, paving the way for the design of more efficient living walls, and even healthier indoor environments.