A Solar-Powered Solution for Bioremediation

June 22, 2016
A new paper from the Wackett and Aksan labs introduces innovative biotech for harnessing solar energy to clean up toxic waste.

Sometimes, humans create environmental messes that are so nasty, we just don’t know what to do. Emergent biotech developed at the University of Minnesota, however, is combining a few tricks from mother nature with sophisticated engineering approaches to help us clean up our act.

Collaborators from the labs of Larry Wackett, a CBS faculty and BTI member in the department of Biochemistry, Molecular Biology and Biophysics, and Al Aksan, a CSE faculty member in the department of Mechanical Engineering, have co-published a paper in the Nature online journal Scientific Reports that tackles the problem of eliminating toxic waste. “We're interested in using sunlight to drive processes,” says Wackett — and in this case, the process of interest is the elimination of noxious chemicals.

If you’ve ever sniffed that unmistakable musk of mothballs, you’re already familiar with naphthalene, a non-carcinogenic petroleum product similar to its far more toxic kin. Wackett and his collaborators have fine-tuned a system that uses two microbe species to clean naphthalene-contaminated water.

One group of photosynthetic bacteria uses sunlight to generate oxygen and sugar. Another group of non-photosynthetic bacteria literally eats and degrades toxic waste — in this case, naphthalene. Researchers calculated optimal conditions and population sizes for both species, so that the first group generates just the right amount of fuel for the second group. Microbial experts from Wackett’s lab handled the biological cultures and naphthalene assays, yet the challenge of building a functional (and practical!) system required help from mechanical engineers.

Baris Mutlu, first author on the paper and graduate of Aksan’s lab (co-advised by Wackett), developed a heavy-duty mathematical model for this microbial system. Mutlu also took the helm at developing a physical system for containing the microscopic milieu — a silica mesh laced with holes just large enough to trap bacteria. Under an electron microscope, the structure looks like a sponge. Contaminated water can flow through, and unwanted chemicals are degraded as they come into contact with the bacteria.

In commercial applications, this bioreactor could be used to safely and cleanly eliminate hazardous materials that would have otherwise been precariously sealed and dumped in toxic waste landfills. “If you degrade it, then it can't come back and hurt you later on,” says Wackett, who, together with Aksan, is already working to bring silica bioremediation technology to market via the startup Minnepura Technologies.

In nature, bacteria can rapidly evolve to consume these types of hazardous waste, but it doesn't always happen in the right place at the right time. “Our goal is to make engineered systems that do the job better, cheaper, faster,” says Wackett. “These bacteria are doing us a big favor. We make messes, and they help us out.”  — Colleen Smith