Team:BroadRun-Baltimore/Solution

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Possible Solutions

To mitigate butyric acid production, Armstrong World Industries, USG, and other manufacturers use biocides and employ aeration and mechanical agitation to promote aerobic conditions. Despite these efforts, the butyric acid problem persists during normal manufacturing operations.

Our Solution

Our solution could either address the source of the problem, starch, or its effect, the butyric acid. We decided to focus on the source of the problem, starch. A seemingly straightforward solution is to add amylase enzyme to degrade the starch. However, completely eliminating the starch source is not a viable solution as it is also a necessary binding ingredient. Knowing how much amylase is needed at a given moment, at a given physical location, and at the prevailing plant conditions to degrade the starch to an extent that only anaerobic bacterial degradation is averted poses a challenge. This would require maintaining a fine balance point such that not too much starch is degraded, a challenge when other variables central to the butyric acid production pathway also change. Degradation of starch is significantly affected by the complex interactions between the manufacturing plant’s microorganisms, dissolved oxygen levels, and nutrient levels, all of which affect the degradation of starch into butyric acid. In researching other industries with high strength organic wastewater problems, we found that they typically address it with anaerobic microbial digestion [1, 2]. Employing a biological system with capabilities to degrade starch during problematic anaerobic periods is a potential solution. Amylases are a group of enzymes that catalyze the hydrolysis (breakdown) of starch into smaller sugars. Amylases act upon the beta and alpha bonds that link monosaccharides together to form polysaccharides like starch [3]. Amylases are versatile; they can react with many forms of substrate, making them well suited for the ever changing conditions of a large scale industrial setting [4]. In this work, an in situ biological solution is proposed; engineering yeast to produce alpha-amylase enzymes and degrade starch. Yeast is known to thrive in both aerobic and anaerobic conditions, in contrast to many bacterial obligate aerobes and anaerobes. Additionally, any floc––a loosely formed clump of cells joined by intertwining yeast mycelia––allows for better oxygen diffusion. This reduces the need for aeration because more dissolved oxygen is available to the cells [5]. This physiological aspect of yeast gives it a competitive advantage at a time when butyric acid would otherwise be produced anaerobically by bacteria during starch degradation. In a simplified system of two micro-organisms, bacteria and yeast, where generation times differ (~20 min for bacteria vs ~90 min for yeast), and organism growths are modulated differently by oxygen levels and fluctuations in nutrients (including starch), we anticipate that this natural selection process will allow for the genetically engineered yeast to compete the bacteria and degrade the starch, preventing the bacteria from partaking in the butyric acid pathway. As starch is a needed material in the production process, and complete elimination of starch is not desirable, we believe it is possible that the competition between the two organisms will cause a natural regulation of the level of starch.

References

1.Hu TL. The utilization of yeast in heavy wastewater treatment. Zhonghua Min Guo Wei Sheng Wu Ji Mian Yi Xue Za Zhi. 1989 Aug;22(3):217-25. 2.Monchai Wongkarnka. (2005). The application of aerobic yeast for treatment of high strength food processing wastewater containing furfural. Ph.D. Thesis, Iowa State University. http://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=2820&context=rtd 3.De Souza, P. M., & de Oliveira Magalhães, P. (2010). Application of microbial α-amylase in industry – A review. Brazilian Journal of Microbiology, 41(4), 850–861. http://doi.org/10.1590/S1517-83822010000400004 4. Raul, D., Biswas, T., Mukhopadhyay, S., Kumar Das, S., & Gupta, S. (2014). Production and Partial Purification of Alpha Amylase from Bacillus subtilis (MTCC 121) Using Solid State Fermentation. Biochemistry Research International, 2014, 568141. http://doi.org/10.1155/2014/568141 5.Yeast Cycle. Industrial Wastewater Treatment Equipment. Nishihara Environmental Sanitation Research Corporation. http://nett21.gec.jp/jsim_data/water/water_1/html/doc_199.html