Detoxification of castor bean residues and the simultaneous production of tannase and phytase by solid-state fermentation using Paecilomyces variotii

In this work, we introduce a biological detoxification method that converts toxic waste from castor beans into animal feed material. This method simultaneously induces the production of tannase and phytase by Paecilomyces variotii; both enzymes have high levels of activity and have the potential to be used in feedstuffs because they decrease overall anti-nutritional factors. The maximum tannase and phytase activities obtained were 2600 and 260 U/g after 48 and 72 h, respectively. SDS–PAGE electrophoresis of the fermented castor cake extracts revealed a reduction in ricin bands during fermentation, and the bands were no longer visible after 48 h. The cytotoxicity of the extracts was evaluated by MTT testing on RAW cells, and a progressive increase in cellular viability was obtained, reaching almost 100% after 72 h of fermentation.