Improved method for extraction of castor seed for toxin determination

Authors: McKeon, Thomas; Brandon, David; He, Xiaohua

Submitted to: Biocatalysis and Agricultural Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/10/2015
Publication Date: 12/11/2015
Citation: McKeon, T.A., Brandon, D.L., He, X. 2015. Improved method for extraction of castor seed for toxin determination. Biocatalysis and Agricultural Biotechnology. 5:56-57. doi: 10.1016/j.bcab.2015.12.007.

Interpretive Summary: Castor oil is a key chemical feedstock with numerous applications including surfactants, engineering polymers, plasticizers, lubricants and greases, with lithium grease the most familiar of these products, all of which provide superior replacement products to similar ones from petroleum. The presence of the toxic protein ricin in the seed residue remaining after oil extraction is a deterrent in widespread cultivation of castor. USDA-ARS Albany scientists have previously established methods for detecting and quantifying ricin, but the methods employ a time-consuming step that generates an inhalation hazard. This manuscript describes a method for extracting soluble proteins including the toxin without generating a fine powder. This method will facilitate higher-throughput screening of castor seed in breeding programs aimed at ultra- low-ricin castor. Since castor can produce as much as 7 barrels of oil per acre, the availability of ultra-low-ricin castor would provide a profitable renewable resource to replace products derived from petroleum.

Technical Abstract: The effort to identify castor seeds with low ricin content is considered to be a key to increasing cultivation of the castor plant for industrial applications. The procedure used to obtain soluble protein from the seed is a limiting factor for screening large numbers of seeds. Usually, the seed is extracted with acetone by grinding with mortar and pestle to remove the oil, generating a fine powder from which the soluble protein is extracted. The steps required to obtain the soluble extract restrict the number of seeds that can be processed. Moreover, the powder generated is highly hazardous, especially via inhalation . This report describes an alternative procedure, homogenization of seed in toluene followed by extraction into buffer and centrifugal separation. Samples prepared using the two methods had similar ricin levels, but the use of toluene and buffer extraction results in higher throughput for ricin analysis and eliminates the inhalational hazard of castor acetone powders.