Removing phorbol esters from the biomass to add extra value to the byproduct from deoiling seeds of Jatropha curcas in the biodiesel industry

Abstract

Either pressing or solvent extraction of Jatropha curcas seed oil results in great amounts of cake as a byproduct. The direct use of these fresh biomasses threats the health of mammals as they contain phorbol esters (PEs), a highly toxic class of substance. Five different treatments were bench-assayed to degrade PEs: (i) ammonium hydroxide, (ii) urea, (iii) heat, (iv) ultraviolet radiation, and (v) gamma radiation. All used methods were evaluated for their efficiency on removing PEs from the biomass resulting from deoiling seeds of J. curcas. The treatments were variably effective in reducing PEs contents to nontoxic levels. Aqueous ammonium hydroxide solution (3% w/w) at 70 °C was found to reduce the contents of PEs down to 0.084 mg g−1 (cake) and 0.083 mg g−1 (bran). The treatment with an aqueous solution NH4OH 7% w/w with heating at 90 °C led to the most effective reduction, rendering PEs contents as low as 0.063 mg g−1 (cake) and 0.066 mg g−1 (bran). These are below the critical toxicity threshold, namely 0.1 mg g−1, which is found in seeds of nontoxic J. curcas varieties. The corresponding results from cytotoxicity tests and assessments of nutritional characteristics confirmed that these treated samples have become safe enough, making this affordable technology potentially scalable to be used in the feeding of livestock at the industrial level.