Bacteria play a role in myriad industrial processes from fermentation to cleaning up environmental pollution. But floating freely in solution, the microbial cells constantly multiply, generating biomass that must be removed periodically, causing downtime. Additionally, the microorganisms cannot be localized to a specific region of interest.
Now, scientists at the U.S. Department of Energy's (DOE) Brookhaven National Laboratory and Stony Brook University have devised a way to encapsulate bacteria in a synthetic polymer hydrogel. These new, stable, bio-hybrid materials maintain the microbes' ability to exchange nutrients and metabolic products with their environment, and could find widespread applications, for example, as biosensors, catalysts, drug-delivery systems, or in wastewater treatment. The method and results are described in a paper published online by the Proceedings of the National Academy of Sciences the week of August 3, 2009.
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| This scanning electron micrograph shows rod-shaped Pseudomonas fluorescens bacterium completely encased within the polymer fibers of an open-weave, porous hydrogel formed by electrospinning. In these bio-hybrid materials, the bacteria remain immobilized but viable for applications in biotechnology. The white scale bar in the lower right corner measures 1 micrometer." |
"In many ways, our research is trying to mimic the biofilms many microorganisms form in nature," said Brookhaven Lab materials scientist Dev Chidambaram, corresponding author on the study. "These complex and dynamic communities form when microbes encapsulate themselves in an extracellular polymer matrix, which offers them considerable protection from environmental challenges such as changes in acidity or salinity, and even antimicrobial agents.
"Our goal is to develop synthetic biofilms, in the form of bioactive materials that could be produced reliably on an industrial scale, and used or reused continuously for a range of applications. This study, which reports the generation of a very thin polymeric fibrous material in which microbes maintain their ability to function, represents a significant step toward achieving that goal."
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| This scanning electron micrograph shows rod shaped Zymomonas mobilis in the cross-linked polymer fibers. These bio-hybrid materials are insoluble in water, and the bacteria remain immobilized but viable for applications in biotechnology. This particular microbe is used in the production of bioethanol. |
Previous attempts to encapsulate viable bacteria in insoluble materials suffered from several shortcomings, according to the researchers. Foremost, the encapsulating materials were usually orders of magnitude larger than thin films. Because nutrients or reactants had to diffuse far into these materials to reach the microbes, activity - and microbe viability - suffered as a consequence.