Team:BroadRun-NorthernVA/Design
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Applied Design
Armstrong, manufacturer of ceiling tiles and our iGEM sponsor, encountered a real world problem of the formation of a pungent substance called butyric acid in their ceiling tile manufacturing plants. Butyric acid, which can lead to unacceptable smells in their finished products of ceiling tiles, became a problem with their move away from trees as raw ingredients to recycled paper products. (More details on the problem are detailed in Project/Problem page.)Armstrong’s manufacturing facility for producing ceiling tiles is a closed water system. Recycled paper in the system led to a high number of short chain cellulose fibers in the million gallon water system, providing nutrients for microbes to feed off in the system. Some bacterial strains produce butyric acid as a byproduct of anaerobic fermentation. Armstrong uses an oxygen pump to keep the million gallons of water they have in an aerobic environment. Despite the use of aeration basins and pumps, the excess starch left in the water from the manufacturing process clogs the pump, preventing the oxygen from flowing through the water and resulting in an anaerobic environment. Their current solution to the problem is to incorporate biocides and chemicals into the water system, killing all forms of microbes in the system. This solution is harmful to the environment, expensive, and is only a short term solution, as inevitably the microbes grow back and begin producing butyric acid once more.
The primary treatment plant of Armstrong's ceiling tile factory. Our cells would most likely not be able to survive in these conditions, the water is heated to a temperature that would denature the amylase proteins, and the water at this point is slightly basic (pH 7.5-8), so yeast growth may be hindered.
The secondary treatment plant of Armstrong's ceiling tile factory. We plan to incorporate our yeast cells into the aeration basin located in the upper left corner. This will allow the cells and amylase enzyme to be evenly distributed throughout the water system. Removing the starch molecules will also prevent the pipes that drain into the aeration basin from becoming clogged, causing the system to go anaerobic and triggering butyric acid production.
When Armstrong presented us with this problem, we examined this issue from all sides to determine the best way to tackle it. We considered several solutions that could
We weighed all of our options in terms of viability, feasibility, cost effectiveness, sustainability and environmentally safe.
Our solution was to engineer yeast cells to produce and secrete a starch degrading enzyme, amylase. We chose S.cerevisiae that can thrive in both aerobic and anaerobic conditions, making it an ideal candidate for the fluctuating conditions of the water system. The alpha amylase secreted by the yeast will break down the starch, serving two purposes; removing the food source of the unwanted butyric acid-producing bacteria, and allowing the oxygen pump to stay unclogged, preventing the system from turning anaerobic. This solution will be cost effective and environmentally conscientious.
Our genetically engineered yeast cells were highly successful in breaking down starch. We demonstrated this success with starch samples and water samples taken from Armstrong’s Lancaster, PA facility. We are continuing our work to quantify the efficiency and rate of starch conversion. In addition, we would like to improve the efficiency of the amylase gene construct so that our solution can be implemented on an industrial scale. Armstrong responded with the words ‘terrific’ and fantastic’ when we shared with them the results for our genetically engineered yeast.