Brewer's spent grain (BSG) is a main by-product of beer manufacturing and is rich in nutrients including 15-30% protein, making it a potentially valuable protein source for human food. Current challenges of extracting protein from BSG include low yields and high manufacturing costs, but the rising trend of plant-based diets for environmental and health reasons increases BSG's appeal. This research proposes an innovative extraction process utilizing wet fractionation and enzymatic purification that targets fiber to effectively separate proteins form BSG. Additionally, the feasibility of BSG protein as a food ingredient is explored, offering a unique approach that limits harsh processing commonly used for protein extraction. The choice of the enzyme (CTec 2 and Viscozyme L), enzyme dose, and incubation time (1, 3, 6, 9, and 24 hrs) were investigated to maximize protein content and recovery and further evaluate processing effects on protein functionality. Following wet fractionation, there was a notable reduction in fiber from 48.6% in the BSG to 22.5% in the filtrate (PRF) on a dry basis. Additionally, the protein content increased from 22.8 to 40.0% from the BSG to the PRF, respectively. The coarse fiber (CF) had an average protein content of 6.30%, highlighting the effectiveness of wet fractionation in enhancing protein recovery from BSG. The optimal enzymatic treatments condition identified was using CTec 2 to degrade fiber at a dose of 6.00% (g enzyme/g solid) for 24 hours. The enzymatic fiber hydrolysis proved to be able to remove lignocellulosic biomass from BSG resulting in a defatted protein concentrate (DPC) with a high protein content (52.8%) along with a high recovery rate (63%). All treatments resulted in protein functionality similar to the two control treatments. Varying fiber hydrolysis conditions did not have a significant effect on the functional properties. Several functional properties were improved using limited hydrolysis (LH) using proteases. LH had negative impacts on foaming stability and emulsifying properties; however, it improved the solubility, foaming capacity, WHC, and OHC of the BSG protein. Potential applications for the DPC include low moisture applications such as protein bars or granola. The DPCs could also have potential use in meat alternatives due to the high WHC and OHC and the need for varying protein solubility in meat alternatives. The LH protein has greater potential in applications such as protein beverages due to the high solubility. This process presents a promising protein extraction approach from BSG, offering producers the flexibility to tailor it to their specific application needs. After obtaining the protein concentrate, additional steps like defatting or limited hydrolysis can be applied to improve the purity and functionality of the result protein. Notably, this approach contributes to sustainable food production by addressing food waste and meeting the rising demand for sustainable protein sources to support the nutritional needs of a growing global population. / Master of Science in Life Sciences / Brewer's spent grain (BSG) is a by-product of beer manufacturing with rich nutrients, including 15-30% protein. It holds potential as a valuable protein source for human food. Current challenges of extracting protein from BSG include low yields and high costs, but the rising trend of plant-based diets for environmental and health reasons increases BSG's appeal. Its abundant availability year-round makes it an attractive option for human food. In this study, an innovative process to extract protein from BSG was explored using wet fractionation to separate the BSG by size. Enzymes were then used to remove remaining fiber. Various enzymes and times were tested to optimize extraction and achieve a high protein content and recovery rate. The protein's physicochemical and functional properties were then evaluated for potential uses in human food. After wet fractionation, nearly half the fiber was removed, and the protein content increased by 17.2%. Using an enzyme called CTec 2 for 24 hours worked best, resulting in a protein concentrate with a high protein content (52.8%) and good recovery (63.0%). Changes in enzyme treatments did not have a significant effect on the protein functional properties. Potential applications for the protein concentrates include low moisture applications such as protein bars or granola due to the poor solubility. The protein concentrates could also have potential use in meat alternatives due to the water and oil holding properties. The low solubility of the protein concentrates was improved using a process called limited hydrolysis making it possible to apply to products like protein beverages. This research highlights BSG's potential as a valuable protein source for protein bars, meat alternatives, and protein beverages. These findings provide a promising approach to utilize BSG as a valuable plant protein source for a healthier and more environmentally friendly food production.

Brewer's spent grain (BSG) is the major byproduct generated by the brewing industry, which contains 14–30% protein and 50–70% of fiber. Currently, BSG is predominantly used as low-value cattle feed or buried in landfills, which is a considerable loss of valuable resources, leading to economic loss and environmental problems. Although research has been done on BSG valorization, the studies are limited to producing a single product (e.g., polyphenols, ethanol, or active carbon) and without further utilization of the produced products. Besides, the economic information available about the production of value-added products from BSG is insufficient. The overall goal of this research is to develop an integrated process to convert BSG into value-added protein-rich feedstuff and cellulose absorbent. The objectives of the research detailed here were to 1) develop a process to simultaneously produce protein-rich (PP) and fiber-rich products (FP) from BSG, 2) assess the replacement of fishmeal with PP in shrimp feed, 3) evaluate the economics of the overall process of PP production at a commercial scale, and 4) explore the potential use of cellulose adsorbent obtained from the FP in removing heavy metals from contaminated water. To attain these objectives, BSG was first subjected to a wet fractionation process to produce PP and FP using different chemical/biological treatments, where the effects of sodium hydroxide, sodium bisulfite, and a protease (Alcalase) at different concentrations were investigated. Under the optimized conditions, the produced PP contained 46% protein and less than 1% fiber. The effectiveness of using PP to replace fishmeal at increasing levels (10–70%) was then evaluated by performing shrimp feeding trials. The results showed that up to 50% of fishmeal in shrimp feed can be replaced by PP without affecting shrimp growth and feed utilization. Moving forward, a techno-economic analysis was conducted to evaluate the economic feasibility of the production of PP. The experimental conditions and results were input into the process simulation model for determining the mass and energy flows. For a processing plant with a capacity of 590 t wet BSG per day, the minimum selling price of PP to achieve a 5% return was determined to be $1044/t, lower than the price of fishmeal, indicating that the use of PP to replace fishmeal in shrimp feed could potentially reduce shrimp farming cost. The utilization of FP will further improve the economic feasibility of the fractionation process. FP was sequentially treated by dilute acid, alkali, and bleach to produce purified cellulose fibers, which were then modified by 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) oxidation to produce a cellulose adsorbent. The feasibility of the adsorbent in removing heavy metals (especially lead and manganese) from contaminated water was then investigated. Based on the results, the produced cellulose adsorbent showed high adsorption capacities for lead (272.5 mg/g) and manganese (52.9 mg/g). Overall, this study demonstrated that BSG can be upcycled into multiple value-added products via an integrated process. The outcomes of this study not only provide a low-cost and sustainable protein source to the aquaculture industry, and provide a novel adsorbent for the water treatment industry, but also offer alternative ways for the brewing industry to manage BSG. / Doctor of Philosophy / Brewer's spent grain (BSG) is the major byproduct generated by the brewing industry. Currently, BSG is predominantly used as low-value cattle feed or buried in landfills due to its high fiber and low protein contents, which is a considerable loss of valuable resources. Besides, raw BSG contains other nutrients and high water content, the inappropriate management of BSG may introduce environmental concerns. Though technologies have been investigated to valorize BSG by extracting protein from it, the process scaled-up is limited by the high drying costs of wet BSG, heavy chemical consumptions, and a large amount of fiber residue. The overall goal of this research is to develop an integrated process to convert BSG into value-added protein-rich feedstuff and cellulose absorbent. In this study, we developed and optimized a process to produce protein and fiber products from wet BSG. The protein content of the produced protein product was doubled and the fiber content was reduced significantly compared with the raw BSG, which lighted the use of the protein product as an alternative to fishmeal. Fishmeal is an expensive aquafeed ingredient, the aquaculture industry is looking for alternatives to replace it. Herein, we investigated the effectiveness of the protein product as an alternative to fishmeal by conducting shrimp trials. A further economic analysis was conducted to evaluate the economic feasibility of the proposed process for protein and fiber production from BSG. In addition, the fiber product was used for producing a cellulose adsorbent to remove heavy metals from contaminated water. Overall, this study demonstrated that BSG can be upcycled into multiple value-added products via an integrated process. The outcomes of this study not only provide a low-cost and sustainable protein source to the aquaculture industry, and provide a novel adsorbent for the water treatment industry, but also provide alternative ways for the brewing industry to manage BSG.