(362c) Enhancing Soybean Value through Systematic Economic Evaluation of Isoflavone Extraction Options for Material Syntheses

The concerns for sustainability keep increasing as resources are depleting from continued unplanned use. Research efforts have been made toward finding sustainable chemical feedstock for the production of high-performance bio-based polymers, made from biomass-derived monomers, with competitive economics and properties in comparison to existing petroleum-based polymers [1]–[6]. The United States produces over 125 million metric tons of soybeans annually for animal feed, export, and human consumption [7]. Soybeans are rich in nutrients such as amino acids, proteins, and carbohydrates. There are also small quantities of underutilized chemicals, such as isoflavones, that can prove beneficial in the health and nutraceutical sector due to their anti-inflammatory and cancer inhibition effects in humans [8], [9]. Conversely, these compounds contain no nutritional value for the livestock and can adversely affect their physiological and pathological processes when consumed in excess. Recent research progress has shown that isoflavones have been used to synthesize high-performance materials with strong thermal resistance [10], [11]. The extraction of soy isoflavone from soybean meal is a process that has been optimized at lab-scale with little considerations for costs or the environment as they generally involve the usage of large quantities of toxic organic solvents [12]–[14]. If isoflavone extraction is proven economically viable at a larger scale with safer operations involving non-hazardous chemicals, the commercialization of bio-based materials can be more attractive and would have a chance to compete against traditional petroleum-based products.

Three objectives were devised to accomplish this work. (1) Information on alternative soy isoflavone extraction methods was collected based on proven successes. (2) A generalized extraction framework was developed, which encompasses all the possible cases involving bio-based chemical extraction to minimize cost, environmental impact, waste discharge, and encourage safe design and process operation. (3) The robustness of the commercial-scale extraction framework was tested through a mathematical modeling and optimization approach in programming tools such as General Algebraic Modeling Systems (GAMS).

In Figure 1, we present a superstructure-based optimization framework [15], [16] for designing a commercial-scale soy isoflavones extraction process. This framework includes mathematical models for various separation technologies with details involving mass and energy balances, equipment design and costing. We considered four essential stages of acquiring purified isoflavone from soybean meal, which includes pre-processing, extraction, acid hydrolysis, and purification. Pre-processing is used for particle-size reduction for enhanced product dissolution in the extraction stage. The extraction stage generally includes conventional mixing (TE), holding tank (MC), ultrasonication (SONC), Soxhlet extraction (SXLT), and supercritical fluid extraction (SCF) for removing isoflavone-glucosides from soy. The recovered soy can be recycled back to the animal feed industry without disrupting the existing food chain. The isoflavone-glucosides is then subjected to acid hydrolysis, which effectively removes the natural glucose attached to the isoflavone molecule. A purification stage is used to meet the desired isoflavone purity requirements.

The multiple pathways shown in Figure 1 were compared and optimized simultaneously in GAMS using mathematical models to determine the most economical pathway to extract isoflavone at the commercial scale. The analysis of each model considered material and energy balances, utilities, design options, industrial constraints, and costings. By analyzing alternative options simultaneously, this study shows that commercial-scale soy isoflavones extraction can be viable. Thus, the superstructure optimization framework presented herein is a powerful tool for systematically assessing the viability of commercializing bio-based chemical extraction processes to fulfill the current demands and producing sustainable products.

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