Biosensor Development for Trace Gas Contamination

Kate Ziemer, Kostia Bergman, Bruce Applegate, and Al Sacco, Jr.

Volatile organic compound (VOC) concentrations found in closed environments are attributed to material out gassing, plants and produce. Chemicals, such as formaldehyde, dichloromethane, and acetaldehyde, are VOCs that impact human health. Plant-emitted VOCs, such as ethylene, benzylaldehyde, furan, and isoprene, also tend to accumulate in closed or poorly ventilated places. Ethylenewas selected as the test candidate for the biosensor development effort. Ethylene is naturally emitted from plants and produce at concentrations in air varying from 1 or 2 parts-per-billion to several parts-per-million. This ethylene emission signals the plant to begin to go to seed or maturate. An ethylene biosensor is needed in any plant or produce environment, where ethylene detection at the parts-per-billion level is the key to delaying plant maturation.

Whole-cell (i.e., bacteria as shown in Figure 1) biosensors utilize the natural processes of living cells to detect changes in their environment. The potential for taking advantage of the natural processes of whole-cell biosensors to maintain calibration (self-calibration) and respond to environmental perturbation (self-repair) is crucial in the successful development of long-term, robust biosensors. Self-calibration would allow biosensors to report specific analyte concentrations regardless of the growth phase or health of the culture. Bioluminescence of the Pseudomonas putida strain TVA8 bacterial-based biosensor is used to sense parts-per-billion levels of analytes or chemicals. However, the technical challenge in detecting changes in analyte concentration is to engineer a quantitative link between the bioluminescence signal and the analyte concentration. Factors such as cell number, growth phase, temperature and analyte concentration all influence the bioluminescence of Pseudomonas putida strain TVA8 (e.g. Figure 2). The quantitative effect of these parameters is currently under investigation.

Figure 1: P. putida strain TVA8 in stationary phase at 100x magnification.