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Retrofit process development for phytate extraction from cornethanol co-products using industrial anion exchange resins Cristiano E. Rodrigues Reis, Qiyang He, Aravindan Rajendran, and Bo Hu Ind. Eng. Chem. Res., Just Accepted Manuscript • Publication Date (Web): 14 May 2017 Downloaded from http://pubs.acs.org on May 19, 2017
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Industrial & Engineering Chemistry Research
Retrofit process development for phytate extraction from corn-ethanol co-products using industrial anion exchange resins Cristiano E. Rodrigues Reisa, Qiyang Hea, Aravindan Rajendrana, Bo Hua* a. Department of Bioproducts and Biosystems Engineering, University of Minnesota Keywords: Retrofit process, thin stillage, phytate extraction, kinetics, isotherm . Corresponding Author Department of Bioproducts and Biosystems Engineering University of Minnesota, 316 BAE 1390 Eckles Ave, Saint Paul, MN, 55108-6005 Tel.: 612-625-4215; Fax: 612-624-3005
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ABSTRACT
Phytate, the principal storage form of phosphorus in corn, is found to remain as a significant portion of phosphorus in the corn-ethanol co-products streams. This poses concerns over poor digestion of these co-products by monogastric animals and subsequent environmental issues on phosphorus. An ion-exchange based process was developed to extract the phytate from thin stillage, which was selected as the influent based on the inositol phosphate distribution conducted on different corn-ethanol co-products. Commercial industrial resins (IRA-93, IRA-68, IRA-900, IRA-400 and IRA-402) were characterized and screened for the phytate adsorption, specificity and capacity. Different types of eluents (NaOH, NaCl, NaHCO3, HCl, and NH4OH) were tested to evaluate the desorption capacity in all the six resins. Phytate-P isotherms and kinetics of the adsorption process, breakthrough profile on IRA-900 column and phytate elution curves were presented. This process yields a phytate-rich solution (11 g L-1), which is 25 fold concentrated compared to the concentration in thin stillage. The results show that the proposed retrofit process allows to leverage the existing corn-ethanol plants for high-value phytate production.
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Industrial & Engineering Chemistry Research
1. Introduction Commercial production of fuel ethanol involves breaking down the starch present in corn to simple sugars, followed by the bioconversion of sugar molecules to ethanol via yeast fermentation. The downstream processing involves the recovery of ethanol by distillation and the residual co-products are further processed to serve as animal feed. Accounting for over 80% of the total ethanol production in the United States, dry-grind ethanol processing differs from the wet-milling process by the absence of an initial steeping operation to the corn grain.1 Most of the co-products of interest are separated before the fermentation process in wet-milling industries. In the dry-grind process, the residual components are separated after the fermentation and distillation. In a typical dry-grind plant, coproduct recovery starts with whole stillage (WS), which accounts for the bottom fraction of ethanol distillation from fermented mash. WS, containing 6-16% of total solids, is a hot, acidic, and viscous fluid mixture, with limited shelf life. WS is usually dried for easier handling, storage, and end use. The most common practice to handle WS and transform it into a stable product consists on a series of separations. The first step is a solidliquid separation, where the solid fraction from this separation is known as wet distiller’s grains (WDG), and the liquid fraction, which contains about 90% to 95% of moisture, is thin stillage (TS). TS is processed into multiple-effect evaporators to produce Condensed Distillers Solubles (CDS), reducing its moisture content to about 60 to 75%. CDS is then combined with WDG to produce a nutrient-rich material, wet distiller’s grains with solubles (WDGS), which is dried in order to produce dried distiller’s grains with solubles (DDGS), the common commercial coproducts on the global feed market.1 3 ACS Paragon Plus Environment
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DDGS has high concentration of phosphorus (P), and often times P may be overdosed in situation in which DDGS is used above the recommendation limits for each animal.2 This may indirectly yield an increase in P excretion by animals.3 Alkan-Ozkaynak et al.4 developed the first study reporting in utilizing chemical coagulation and flocculation as a treatment for TS, in order to reduce P concentration. According to Alkan-Ozkaynak et al.4, the majority of P and solids in TS are in the dissolved form (
