Utilization of Jatropha curcas seed cake as a plant growth stimulant

Jatropha curcas seed cake containing high protein has served as a source of protein hydrolysate applied for plant growth stimulation. Effects of enzymatic and acid protein hydrolysates on the growth of Hua Reau chili were investigated. Toxic compounds, phorbol esters in the seed cake, were removed first. The protein isolate prepared from the phorbol ester-free seed cake was digested by Neutrase, papain, trypsin, pepsin and HCl using various hydrolysis times. Degree of hydrolysis of the protein varied, ranging from 3.8% to 97.3% depending on hydrolysis methods and times. The growth of Hua Reau chili was considerably stimulated by the protein hydrolysate obtained from Neutrase digestion at 2 h and was significantly higher than that of all controls. In addition, the protein hydrolysate of 10 μg/ml obtained from Neutrase digestion at 2 h gave the maximum stem height and diameter of Chinese kale plants. Therefore, the protein hydrolysate of the phorbol ester-free seed cake of J. curcas would be an alternative and novel source of natural plant growth stimulant.