Alam, Sabrina Sharmeen (2016-10). Evaluating and Enhancing Smectite's Efficiency in Removing Aflatoxins from Corn Fermentation Solution. Doctoral Dissertation.
Aflatoxins are the secondary toxic metabolites produced by fungi Aspergillus flavus and Aspergillus parasiticus. They are the most studied mycotoxins because of their carcinogenicity. Corn is the major biofuel crop used to produce ethanol in the U.S. Due to stringent regulations on aflatoxins in food and feed, and increasing demand on biofuel, it appeared to be reasonable to use aflatoxin contaminated corn for biofuel production. An up to three-fold enrichment of mycotoxins in the co-product of ethanol, known as dried distiller's grain (used as animal feed), is a great concern. It would be desirable if the mycotoxins can be inactivated or removed during biofuel production. More than two decades of studies on smectite-aflatoxin interaction proved the effectiveness of smectites as aflatoxin detoxifying agents. The ultimate goal of this study was to suppress the aflatoxin's toxicity level in animal feeds by using the environmentally safe smectites in biofuel industry. To achieve this goal, smectites were evaluated for their aflatoxin adsorption efficiencies in corn fermentation solution produced during biofuel production. In this study, some bentonites were revealed to be effective aflatoxin binders in aqueous solution with up to ~16% adsorption capacity based on their dry mass weight. The Fourier transform infrared (FTIR), X-ray powder diffraction (XRD), and UV/Vis isotherms adsorption experiments suggested that smectites had high aflatoxin adsorption ability in ethanol and glucose solutions, two major soluble components in fermentation solution. On the contrary, the smectite's adsorption was comparatively low in real fermentation solution. The FTIR and XRD investigations revealed the strong interlayer adsorption of organic molecules from fermentation solution in the smectites. When smectite was interacted with zein (protein extracted from corn), similar IR and XRD responses were observed. The comparative analyses suggested that proteins in fermentation solution were possibly the most interfering compounds for remarkably reduced aflatoxin adsorption. To minimize those compound's interferences on aflatoxin adsorption, smectites were modified with small nutritive organic compounds to make the interlayer space small enough to block the access of protein but large enough for aflatoxin's access. Encouragingly, the organo-smectites reduced interfering compound's adsorption but increased aflatoxin sequestration in both real and simulated fermentation solution as well as in pure protein solution. In summary, despite strong interferences of the organic compounds, and also some minor influences from ethanol, aflatoxin adsorption by smectites in fermentation solution was still considerable, and could be even increased significantly by applying non-toxic and moreover health beneficial organo-smectites.