Simultaneous allergen inactivation and detoxification of castor bean cake by treatment with calcium compounds

M.G Godoy,M Dansa-Petretski,E.J.T De Melo,O.L.T Machado,V.V Nascimento,K.V Fernandes,D.M.G Freire,Z.A.S Guimarães,N Deus-De-Oliveira

doi:10.1590/s0100-879x2012007500132

Abstract

Ricinus communis L. is of great economic importance due to the oil extracted from its seeds. Castor oil has been used for pharmaceutical and industrial applications, as a lubricant or coating agent, as a component of plastic products, as a fungicide or in the synthesis of biodiesel fuels. After oil extraction, a castor cake with a large amount of protein is obtained. However, this by-product cannot be used as animal feed due to the presence of toxic (ricin) and allergenic (2S albumin) proteins. Here, we propose two processes for detoxification and allergen inactivation of the castor cake. In addition, we establish a biological test to detect ricin and validate these detoxification processes. In this test, Vero cells were treated with ricin, and cell death was assessed by cell counting and measurement of lactate dehydrogenase activity. The limit of detection of the Vero cell assay was 10 ng/mL using a concentration of 1.6 × 105 cells/well. Solid-state fermentation (SSF) and treatment with calcium compounds were used as cake detoxification processes. For SSF, Aspergillus niger was grown using a castor cake as a substrate, and this cake was analyzed after 24, 48, 72, and 96 h of SSF. Ricin was eliminated after 24 h of SSF treatment. The cake was treated with 4 or 8% Ca(OH)2 or CaO, and both the toxicity and the allergenic properties were entirely abolished. A by-product free of toxicity and allergens was obtained.

Highlights

The castor plant (Ricinus communis) is an oleaginous plant that has been cultivated since ancient times
These castor cakes are rich in protein and fiber, the presence of toxic compounds limits their use as an animal feed, and the presence of allergenic proteins could cause health problems for workers who manipulate these seeds or cakes
A gradual reduction in the number of living cells (Figure 1A) was observed during the first few hours of exposure to purified ricin, and after 48 h of incubation, the cell concentration had declined by approximately 90%, leaving just a few units still attached to the substrate (Figure 1A and B)

Summary

Introduction

The castor plant (Ricinus communis) is an oleaginous plant that has been cultivated since ancient times. Castor cake is currently used in fertilizers [1]. These castor cakes are rich in protein and fiber, the presence of toxic compounds limits their use as an animal feed, and the presence of allergenic proteins could cause health problems for workers who manipulate these seeds or cakes. The main toxic component of castor cake is ricin, a protein found exclusively in the endosperm of castor seeds. Leshin et al [3] demonstrated that the R. communis genome encodes seven full-length ricin family members, and all encoded ricin-like proteins can hydrolyze the adenine in 28S ribosomal RNA (rRNA) and may contribute to the toxicity of castor seeds. The ricin A chain is a 32-kDa polypeptide [4] with glycosidase activity, which removes an adenine

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