DETOXIFICATION OF RESIDUAL TOXINS IN JATROPHA PRESS CAKE FOR ITS APPLICATION IN ANIMAL FEED DEVELOPMENT

Abstract

Jatropha curcas is an oil-seed plant with good adaptability to grow in barren lands with scanty rainfall. Jatropha oil had been well exploited for the production of biodiesel by trans-esterification process. The compressed press cake, after the oil extraction, is a rich source of protein but presence of certain toxic and anti-nutritional factors in the seed cake restricts its use for edible purposes as its ingestion may lead to various health problems. Thus, it becomes imperative to detoxify Jatropha press cake for its use as feed supplement. Phorbol esters have been identified as the main toxin present in the Jatropha press cake. Various physicochemical have been described for the detoxification of Jatropha seed cake and oil which includes use of organic solvents, UV-irradiation etc which were able to reduce phorbol esters completely from Jatropha press cake. But these treatments are expensive; also, handling or the disposal of the toxins raises an environmental and health concern. However, for environmental awareness, the biological method would be more advantageous than the others. Pseudomonas aeroginosa DS1 was isolated in laboratory and research was done to determine the effects of submerged fermentation (SMF) using Pseudomonas on the phorbol esters (PEs) degradation rate. For the proper understanding of the process, different parameters affecting the detoxification of Jatropha seed cake by submerged fermentation process were studied. Out of several factors, eleven crucial factors were identified and analysed for their inter-relationship using interpretive structural modelling (ISM). Temperature (level IV) was found to be the most crucial factor affecting all other factors for successful implementation of the detoxification process. PE, pH, RPM, esterase, and inoculum (level III) were identified as next crucial set of factors followed by tannins (level II). MICMAC (Matriced' Impacts Croise's Multiplication Appliquée a UN Classement) analysis was done to recognize the factor dependency in detoxification. Out of eleven factors, nine factors were identified as linkage variables; one each as the driver and dependence variable. No autonomous variable was identified. vi Taguchi design of experiments L18 orthogonal array was adopted for optimizing the SMF process for detoxification of Jatropha seed cake. Process parameters selected for the study were: pH, percentage of seed cake, time, temperature and rpm. The response parameter for detoxification was measured in terms phorbol ester degradation. Analysis of variance (ANOVA) was performed for predicting the optimum process parameters. The percentage contribution of the process parameters with reference to phorbol ester degradation was predicted. The optimum conditions were found to be seed cake (1%), temperature (35 ˚C), pH (7.5) and time (12 h). Fourier Transform Infrared (FTIR) spectroscopy was done to analyze the structural changes occurred in Jatropha seed cake during detoxification procedure. Jatropha seed cake contains good amount of proteins which were extracted from Jatropha seed cake by iso-electric precipitation method. For pilot scale experiments, one parameter at- a- time approach was followed and effect of temperature, solubilization pH and precipitation pH on protein content and protein yield of Jatropha seed cake was studied. Recovery of protein concentrate was highest when the extraction was carried out at 55°C temperature, solubilization pH 11.5 and precipitation pH 5. The results of these experiments were used to select different factors and their levels to optimize the process using Response Surface Methodology. The factors selected were extraction temperature, time, solubilization pH, precipitation pH and their effect were studied on response variables; dry matter, protein yield and protein content. The optimum values of the variables i.e. temperature, solubilization pH, time and precipitation pH for the extraction of protein from detoxified seed cake were 60°C, 11.0, 4.41 and 0.78 h respectively which yielded maximum dry matter, protein content and protein yield. The effect of bio-remediated seed cake on seed germination (Vigna radiata) and in vitro digestibility (Oreochromis niloticus, Cyprinus carpio) was studied. Jatropha seed cake in all forms (Raw, defatted and detoxified) was found to have inhibitory effects on green gram seed germination and overall seedling health. Germination was not affected by the addition of 1 and 5% defatted seed cake while a decrease in germination rate was observed in soil containing 10% defatted seed cake. The detoxified seed cake was found to have positive and eliminatory effect on the toxicity vii leading to improvement in both vigor index and pigmentation. Higher percentage of detoxified Jatropha seed cake did not affect the root length and very less reduction in the number of secondary roots observed. The vigor index was affected at 10% levels of all the treatments with detoxified seed cake having least effect. The plant pigments were also affected and found to have reduced in raw and defatted seed cake treatments. Addition of detoxified seed cake concentrations at 1% and 5% level matched with the control in chlorophyll b content. In vitro digestibility study also showed improvement in digestibility and confirmed the inactivation of toxins in the Jatropha protein concentrates. Though, this is a prospective step towards the use of Jatropha seed cake as fertilizer and fish feed after detoxification, the avenues are open for various applications.