Solar radiation influences virtually all biological process on earth. Yeasts, the microbial driver of ethanol fermentation, evolved on the surface of vegetation and had to adapt to survive photonic assault. Past research has demonstrated that white light affects yeast metabolism along with the ability to entrain circadian rhythms, although no known genetic mechanism accounts for this. High intensity narrow wavelength light-emitting diodes were employed to illuminate synthetic cultures under fermentation. Multiple colors along the visible spectrum were used, corresponding to the peak absorbance wavelengths of Saccharomyces sp. yeast. Impacts in primary metabolite evolution were found, dependent on wavelength. Longer wavelengths produced higher amounts of acetic acid and glycerol; shorter wavelengths produced more ethanol. Because past research showed light timing had pronounced effects, illumination schemes on the scale of milliseconds to hours were tested for ethanol production. Light schemes on the scale of enzymatic reactions, yeast generation times, and circadian rhythms produced the most ethanol. Discrete blocks and duration of illumination were used to elucidate where light had the most influence over yeast metabolism and fermentation. Late lag phase and mid log phase illumination impacted ethanol fermentation more than any other period of time. Light effects were tested on apple juice to see if they extended from synthetic media to natural products. Significant impacts on ethanol production were discovered and flavor/aroma impacts were noted. Light, color, intensity, and timing have all been shown to control and affect fermentation with both positive and negative effects established. / Doctor of Philosophy / Sun light influences virtually all biological process on earth. Yeasts, the microbial drivers of ethanol fermentation, evolved on the surface of vegetation and had to adapt to survive destructive effects of the sun. Past research has demonstrated that white light affects yeast metabolism along with the ability to develop growth cycles similar to day / night patterns, although it is currently not believed this possible due to the biology of yeast. High intensity single color light-emitting diodes were employed to illuminate laboratory formulated cultures under fermentation. Multiple colors along the visible spectrum were used, corresponding to the peak absorbance wavelengths of Saccharomyces sp. yeast. Green/yellow/red wavelengths produced higher amounts of acetic acid (vinegar) and glycerol; blue and ultraviolet wavelengths produced more ethanol. Because past research showed light timing could change how yeast grow and consumed carbohydrates, light timing on the scale of milliseconds to hours were tested for ethanol production. Light timing on the scale of milliseconds, hours, and daylight cycles produces the most ethanol. Discrete blocks and duration of illumination were used to find where during fermentation light had the most impact. It was found that from immediately after the beginning of fermentation to the middle of fermentation is where yeast responded the most strongly. Light effects were tested on apple juice to see if they extended laboratory cultures to natural products. Significant changes in the amount of ethanol produced were discovered and changes in the taste and smell of fermented apple juice were noted. Light, color, intensity, and timing have all been shown to control and affect fermentation with both positive and negative effects established.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/112678 |
| Date | 28 May 2021 |
| Creators | Hurley Jr, Eldon Kenneth |
| Contributors | Food Science and Technology, Williams, Robert C., Marcy, Joseph E., Senger, Ryan S., O'Keefe, Sean F. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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