Graduation Term

2017

Degree Name

Master of Science (MS)

Department

Department of Chemistry

Committee Chair

Marjorie Jones

Abstract

Waste, minimizing it, and maximizing profit from it are major foci of most agricultural production processes today. Waste from two major production processes, namely tequila production and cocoa production, share several characteristics. Both these processes are still carried out as they have been for hundreds of years. They are both relatively concentrated in location; all tequila is produced in a small region of Mexico while cocoa pods only grow in tropical environments within 18° of the equator. In addition, both processes used to produce these commodities remain fairly inefficient; they generate huge amounts of waste that goes mostly unused. With both these processes, a new source of income is explored while major waste products, agave leaves from the tequila industry and cocoa pod husks from the cocoa industry, are utilized.

Agave leaves, which constitute about half the mass of mature Blue Agave plants, are discarded when agave hearts are harvested to produce tequila. Agave leaves are known to contain reducing sugars and inulin, as well as modest amounts of proteins. The nutrients contained in these leaves can be utilized by single celled organisms and converted into commodities. If the juice is pressed from them prior to fermentation, only the nutrients that fermenting organisms use is consumed, while solid portions, presumably, remain unaffected and available for other applications. Fermentation by strains of Kluyveromyces marxianus and Yarrowia lipolytica F of the nutrient-rich juice pressed from the leaves of a mature Blue Agave plant is explored in this work in an effort to generate valuable commodities such as the yeast themselves, ethanol and ammonia.

Cocoa pod husks are piled and left to rot in equatorial rain forest climates when cocoa farmers harvest the ripe pods and collect the precious cocoa beans from them. Cocoa pod husks possess a polysaccharide known as pectin, which can be metabolized by some single celled organisms. The husks, similar to agave leaves, constitute about half the mass of the whole pods; thus, the 4.5 million metric ton cocoa bean harvest forecast for this (2017-2018) growing season will leave about the same mass of waste behind. Fermentation of this waste by K. marxianus 7-1 and K. marxianus 8-1, then Y. lipolytica F in an effort to add value to this waste is explored in this work.

Fermentations with K. marxianus yeast strains were carried out using either agave leaf juice or cocoa pod husk pieces in water. Fermentations were allowed to progress for 72 hours from inoculation. Samples were collected at pre-determined time points and analyzed for colony forming units, reducing sugar concentration, soluble protein concentration, ethanol concentration, and the presence or absence of amines and sugars, both simple and complex. Upon termination of some of the K. marxianus fermentations, subsequent, second stage fermentations with Yarrowia were carried out by Mr. Mitchell Lindquist of the USDA through continued collaborative work with the Jones’ Lab. Again, fermentations were sampled at pre-determined time points and, with Yarrowia fermentations, analyzed for colony forming units and ammonia concentrations.

Results from these fermentations and subsequent analyses indicate that fermenting these waste products is an effective means of bioremediation. The unused portions of these two enormous cash crops can be used to produce commodities such as ethanol and yeast proteins. These commodities are not nearly as valuable as the cash crop that generate these wastes; however, they do hold substantial value. If the value of the waste products and commodities produced from them can be shown to be substantial enough, this may motivate crop farmers to use these current wastes instead of discarding them.

Access Type

Thesis-Open Access

DOI

http://doi.org/10.30707/ETD2017.Hart.D

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