Date of Graduation

8-2023

Document Type

Thesis

Degree Name

Master of Science in Food Science (MS)

Degree Level

Graduate

Department

Food Science

Advisor/Mentor

Lee, Sun-Ok

Committee Member

Lewis, Jeffrey A.

Second Committee Member

Threlfall, Renee T.

Keywords

Zinc deficiency; Selenium deficiency; Solid-state fermentation; Grain sorghum; Phytic acid

Abstract

Zinc (Zn) and selenium (Se) are essential minerals for human health and naturally found in many food sources. However, the risk of Zn and Se deficiency has been recognized in several countries. As most people throughout the world consume rice, grains, and cereals as staple foods in their daily diet, which contain a certain amount of phytic acid (antinutrients), the phytic acid content inhibits mineral absorption (Zn and Se) by the human body. Moreover, the low levels of Zn and Se content found in the crop's soil also reduce the amount of minerals in the food sources. Therefore, it is crucial to develop an effective method of naturally supplementing Zn and Se that promotes their absorption. There is yeast, bacteria, fungi, or a combination of these fermented products, enriched with Zn and Se, available in the market. In addition, the fermentation process can reduce the phytic acid content. However, there is no research or data on the application of solid-state fermentation (SSF) for the enhancement of Zn and Se. Therefore, in our study, SSF was applied to determine the amount of Zn and Se uptake by Aspergillus oryzae, Bacillus subtilis, and co-culture. The objectives of the study were to [1] determine the amount of Zn and Se uptake by A. oryzae, B. subtilis, and co-culture in sterile coarsely ground and whole sorghum grain by using solid-state fermentation and [2] measure the amount of phytic acid reduction (antinutrients) in the fermented coarsely ground biomass and whole grain samples containing Zn and Se. The sorghum grain (substrate) was treated with these organisms and supplemented with different concentrations of Zn or Se. After SSF, the samples were analyzed with Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The dried substrate was used to analyze the amount of phytic acid present in the grain sorghum after the SSF. The quantification of phytic acid in the substrate was determined using UV/VIS spectroscopy. The results showed that the biological efficiency of the organisms was affected by the addition of different concentrations of Zn and Se. Considering all the concentrations, the highest level of Zn absorption was obtained by adding 50 μg/g of zinc acetate. In the Se absorption, 3.2 μg/g of selenium aspartate was efficient. The obtained data show that A. oryzae, B. subtilis and Co-culture can grow in the Zn or Se-containing substrate. SSF process with coarsely ground sorghum grain containing A. oryzae and co-culture significantly reduced the phytic acid content. The results showed that the SSF process with A.oryzae and/or Co-culture positively reduced the phytic acid content, which could help in the proper absorption of Zn and Se by the human body. The fermented biomass could be used as a Zn and Se-enriched ingredient for functional food products.

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