Date of Award


Degree Type


Degree Name

Master of Engineering Science


Chemical and Biochemical Engineering


Dr. Amarjeet Bassi

Second Advisor

Dr. Jingxu Zhu


Although soybeans have been used in Eastern Asia for the past 2000 years, only recently have they become a key global commodity and agricultural crop. Soybeans are a versatile crop. They have been shown to have a high protein content, high nutritional value and functionality, and have many applications in medical and food industries. The current soy protein market has need of a high quality soy protein which can be used in many protein and food products. Cunent soy protein production methods such as alcohol dehydration and acid precipitation use harsh materials and conditions to extract and recover the protein. These conditions lead to high amounts of protein denaturation and lower protein recovery yields. These techniques also tend to produce proteins with lowered functionality and nutritional value because of their numerous production steps.

The liquid-solid circulating fluidized bed (LSCFB) system provides an improved method for soy protein extraction. This system can extract high concentrations of soy protein with little denaturation and loss of functionality. This system has the ability to run two different processes in a single reactor independent of one another. The LSCFB uses fluidization and packed bed technology to improve upon current ion exchange processes.

This study was designed to show the LSCFB as a viable alternative to current soy protein production methods. This system was designed to extract and recover soy proteins from a reconstituted soy protein solution. The first step was finding a buffer solution which would extract the highest concentration of soluble proteins for use when preparing the reconstituted soy solution. It was found that a 50 mM TRIS buffer solution at pH 8.5 extracted a high concentration of proteins and reduced material costs. The LSCFB system consists of two columns: a riser and a downcomer. The downcomer column was used for the adsorption process while the riser was used for protein desorption. The two columns are coupled by circulating ion exchange particles. The ion exchange particles adsorb protein in the downcomer and are regenerated/desorbed in the riser. A suitable ion exchange resin for the adsorption and desorption of soy proteins was selected. Amberlite IRA-67 was selected as the ion exchange resin to be used in the LSCFB system. Once selected, a thorough analysis of soy protein adsorption and desorption kinetics using the Amberlite IRA-67 was conducted. Lastly, the concentration


of elution buffer used in the riser must be determined. It was found that a 50 mM NaCl solution desorbed the majority of the bound proteins in a small packed column and was selected for use in the LSCFB system. The 50 mM NaCl elution buffer desorbed a protein concentration of 4.7 g/L which was 67% of the total bound proteins in the column.

A series of experiments were designed to investigate soy protein ion exchange in the LSCFB as well as to analyze the effect the downcomer feed flow rates have on the protein recovery yield and productivity. These studies showed that there is a trade off between protein recovery yields and productivity. Lower downcomer feed flow rates have higher protein recovery yields but lower productivities. High downcomer feed flow rates have larger liquid throughputs and therefore higher productivities, but leads to lower protein recovery yields. A downcomer soy protein feed flow rate of 5 L/hr rendered the most beneficial results of the four flow rates tested, resulting in the highest protein recovery yield of 94.6%.

Lastly, a trivalent aluminum pretreated soy solution was used to investigate its effect on protein recovery yield and productivity. It was found that at the lower downcomer feed flow rates of 5 and 15.5 L/hr, the pretreated soy solution reduced protein recovery and productivity slightly. At the higher flow rates, pretreated soy solution increased protein recovery and productivity. The trivalent aluminum acts to inactivate the phytic acid present in soybeans. Phytic acid forms complexes with the soy proteins which hinders protein adsorption and lowers protein functionality. By pretreating the soy solution, there is a higher concentration of active soluble soy proteins in the solution which can interact with the ion exchange particles binding sites resulting in a better chance of protein adsorption.

From these series of experiments, it can be seen that the pilot plant scale LSCFB system investigated, is a capable and viable alternative to the current soy production processes used. The LSCFB system can continuously and simultaneously extract and recover soy proteins in high concentration without protein denaturation and functionality loss. This technology should be developed further and scaled up for industrial use.



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