Progress 11/15/03 to 11/14/06
Outputs
The overall objective was to develop high-value corn-based coproducts to enhance the economic viability of the dry-grind ethanol industry. Two coproducts were identified: zein, an underutilized alcohol-soluble protein with a long history of study and a multitude of potential uses, and xanthophylls (lutein and zeaxanthin) which are oxygenated carotenoids that have numerous health benefits. Together, they have the potential to almost double the income of a typical dry-grind ethanol plant, provided methods can be developed to extract and purify these compounds. Size exclusion chromatography (SEC) was selected as the best method to separate and purify zein and xanthophylls due to the large differences in molecular size between zein, xanthophylls and the impurities. Since this technology would be incorporated in a dry-grind ethanol plant, aqueous ethanol was the preferred solvent for the entire processing chain, from the initial extraction of whole corn ground to the final
purification steps. Three commercial resins were chosen based on their ethanol stability and rated molecular cut-off of 5000 Daltons. These resins were characterized for selectivity, fractionation range, pore size distribution and surface morphology using scanning electron and atomic force microscopy with a view to identifying structure-function relationships that could also be useful in designing better stationary phases for specific applications. Under optimum conditions, two resins satisfactorily separated zein and xanthophylls (as a group) from the impurities. These resins displayed some nonideal behavior due to interactions between the resin and the solutes. The fractions eluting from the size exclusion column are dilute and need to be concentrated to reduce load on downstream operations and to recover the solvent. Adsorption chromatography (AC), though not suitable for separation or purification, could be used to concentrate the fractions. Membrane technology (nanofiltration or
reverse osmosis) was also found to be technically feasible. A preliminary process design and economic analysis of the process suggested good economic returns by combining SEC and AC. About 80% of the capital cost and 85% of the operating cost of the process, as it stands now, is due only to the stationary phase. Our studies on the characteristics of the resins could be used to develop alternate lower-cost materials. In addition, the composition of the "impurities" fraction is unknown. There may be high-value compounds within that fraction that could further enhance the economic viability of the process.
Impacts
This project could have a significant impact on the economic viability of dry-grind ethanol plants. Xanthophylls are worth an additional $1-3 per bushel and zein another $2-3 per bushel. This represents a 70-100% increase in net revenue with no additional materials coming into the plant and no change in the yield of existing products such as ethanol and carbon dioxide.
Publications
- Kale, A.V. and Cheryan, M. 2005. Membranes, chromatography and membrane chromatography. Applied Membrane Science and Technology. 1: 59-86.
- Kale, A.V. 2006. Purification of zein and xanthophylls from corn by process chromatography. Ph.D. thesis, University of Illinois.
- Cheryan, M., Kale, A.V. and Zhu, F. 2006. Zein and xanthophylls by chromatography. Disclosure to University of Illinois, January 17, 2006. U.S. Patent Application filed May 8,2006
|
Progress 01/01/05 to 12/31/05
Outputs
At present, the major commercial source of lutein is marigolds. Corn also contains lutein (15 mg/kg corn), zeaxanthin (6 mg/kg) and about 1 mg/kg of beta-cryptoxanthin. A process has been developed to extract xanthophylls from whole ground corn using aqueous ethanol. The optimum conditions for maximum extraction of the xanthophylls in a batch process were a temperature of 50C, extraction time of 30 minutes, a solvent concentration of 85% ethanol (v/v) in water and a solvent-to-solids ratio of 4 L/kg corn. A single extraction under these conditions extracted 88% of the xanthophylls. A three-stage process where the spent solids were re-extracted with fresh solvent yielded 99% of the xanthophylls. Zein was also co-extracted under these conditions. Membrane technology was selected as the low-energy, low-cost method of separation and concentration. Ultrafiltration (UF) was used to separate zein and other large solutes from the extract. The xanthophyll-containing UF
permeate was concentrated and separated from the solvent using nanofiltration (NF). Several commercially available and prototype polymeric NF membranes were screened for stability to the organic solvent, and for flux and rejection of xanthophylls in aqueous ethanol as a function of operating parameters such as temperature, pressure and solute concentration. Initial flux was 10-60 liters per square meter per hour at 2.76 MPa and 50C. Flux decreased at higher concentration factors. Xanthophyll rejection was 98-99% for all membranes and the nanofiltered permeate was clear and colorless allowing it to be recycled within the plant.
Impacts
This project could have a significant impact on the economic viability of dry-grind ethanol plants. Xanthophylls could be worth an additional $1-2 per bushel. This represents a 30-50% increase in net revenue with no additional materials coming into the plant and no change in the yield of existing coproducts.
Publications
- Moros, E.E. 2000. Analysis and extraction of xanthophylls in corn. MS thesis, University of Illinois, Urbana.
- Cheryan, M. 2001. Method for extracting xanthophylls from corn. U.S.Patent 6,169,217.
- Tsui, E.M. 2002. Nanofiltration of xanthophylls from ethanol extracts of corn. MS thesis, University of Illinois, Urbana.
- Tsui, E.M. and Cheryan, M. 2004. Characteristics of nanofiltration membranes in aqueous ethanol. J. Membrane Sci. 237: 61-69
|
Progress 01/01/04 to 12/31/04
Outputs
An improved HPLC method for analysis of xanthophylls in corn has been developed. The method uses the YMC-30 carotenoid column, a photodiode array detector and a mobile phase of methyl tertiary-butyl ether/methanol/water. All three xanthophylls eluted in less than 25 minutes. Yellow dent corn had a total xanthophyll content of 22 mg/kg corn (equivalent to 0.5 g per bushel of corn) with lutein = 15.7 mg/kg, zeaxanthin = 5.7 mg/kg and beta-cryptoxanthin = 0.6 mg/kg. One major advantage of corn-based xanthophylls over marigold-based xanthophylls is that the latter does not contain zeaxanthin. Commercial corn gluten meal had 145 mg/kg and deoiled corn still contained 18 mg/kg xanthophylls, indicating that the xanthophylls are probably bound to the proteins in corn. White corn contained negligible amounts of xanthophylls. This is an improvement over prior HPLC methods described by Kurilich and Juvik (1999) and Weber (1987). We have used the same HPLC system to develop a
method for analyzing carotenoids and tocopherols
Impacts
An improved analytical procedure is the first step in developing a process for producing xanthophylls from corn. The next step is to optimize a method for extracting the xanthophylls using ethanol, followed by concentration and purification of the xanthophylls.
Publications
- Moros, E.E., Darnoko,D., Cheryan,M., Perkins,E.G. and Jerrell, J. 2002. Analysis of xanthophylls in corn by HPLC. J. Agric. Food Chem. 50: 5787-5790.
|
|