Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)


Biology and Microbiology

First Advisor

William R. Gibbons


bioconversion, bioprocessing, feed, fermentation, fungi


Plant feedstuff by-products such as soy processing wastewater, guar korma meal, and sorghum hominy are very different, however, all possess a rich nutrient profile. Lessening their value is the presence of lignocellulose, plant anti-nutritional factors, and unfavorable protein profiles. Fungal conversion processes are an attractive approach to improving the value of these by-products by degrading detrimental fractions of each while simultaneously creating nutrient-rich cell mass. The aim of this research was to improve the value of each by-product for potential application in monogastric diets such as fish. Fungal organisms, both yeast and filamentous fungi, were examined for their ability to enhance the nutritional value of each by-product. Soybean processing supernatant contains a high amount of organic matter (carbohydrates and proteins) resulting in a high chemical oxygen demand (~55,000 mg/L), meaning that this by-product cannot be disposed of without treatment. Typically evaporation is used to concentrate the material from 7-10% solids to 40-50% solids which can be used in animal feeds. To improve the nutritional value of this material, eight fungal strains were tested for their ability to metabolize the soluble nutrients in the wastewater and produce protein-rich cell mass for potential application in animal feeds. Flask incubations trials of 100 ml total volume were conducted at 30°C and 150 rpm. Trichoderma reesei, Paecilomyces variotii and Neurospora crassa produced 51.7, 47.1 and 43.2 g/L of biomass while reducing solids present by 46.5, 48.9, and 49.1% respectively. The two best performing strains were further examined in fermenters using 3 L total volume. Trichoderma reesei and Neurospora crassa produced 55.5 and 62.0 g/L of protein-rich biomass while simultaneously reducing chemical oxygen demand levels by 10.53 and 23.04% respectively. Microbial processing produced a protein-rich animal feed ingredient while concurrently reducing organic matter present in the wastewater. Sorghum hominy contains a high amount of starch (34.5%), fiber (7.6%), and low amount of protein (12.9%) which inhibits its inclusion into higher value feed industries such as aquafeeds. To improve the nutritional value of the sorghum hominy, eight fungal strains were assessed for their ability to degrade the carbohydrate fractions of the sorghum hominy while simultaneously improving the protein profile for potential use in aquadiets. Flask incubations were performed using 100 ml total volume at 30°C and 150 rpm. Trichoderma reesei, Rhizopus oligosporus, Neurospora crassa and Aurebasidium pullulans were the best performing fungi in flask trials, increasing the protein titer of sorghum hominy by 53.6, 48.0, 47.8, and 41.5% compared to the raw material. T. reesei and A. pullulans were further tested in 5 L benchtop reactors, where biomass yields of 65.1 and 73.6 g/L were obtained with similar increases in protein to the previous flask trials. Lastly, T. reesei was examined in 70 L and 150 L fermenters, increasing all amino acids in the range of 33.3-152.3%. Thus, T. reesei submerged fermentation effectively increased the nutritional value of sorghum hominy. Guar korma meal contains a high amount of protein (55.6%), but also contains fiber (6.6%) and residual guar gum (0.77%) which inhibits its effectiveness as a feed ingredient in monogastric diets. To improve the nutritional value of guar korma meal, the prospect of subjecting the guar korma meal to a centrifugal wash pre-fungal incubation was examined. For both the washed concentrate and washed solubles, five fungal strains were examined for their ability to create a protein-rich biomass for potential application as a feed ingredient, while degrading detrimental fractions of the washed concentrate. Flask incubations of 100 ml total volume were conducted at 30°C and 150 rpm. T. reesei was the most effective treatment on the washed guar korma meal as it reduced guar gum levels to 0.17% and increased the protein titer to 66.8% yielding 65.8 g/L of biomass. A. pullulans was the most effective treatment on the guar korma meal solubles, producing 12.8 g/L of protein-rich (40.6%) biomass. Together the two-step fungal incubation process yielded 78.6 g/L of biomass containing 61.5% protein.


Includes bibliographical references



Number of Pages



South Dakota State University


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