Aqueous oil extraction (AOE) is a method in which Jatropha seeds are cracked and the shells are carefully removed. Shah et al. [ 78] used Jatropha kernels for oil extraction. The suspension was prepared with powdered (obtained by using a homogenizer) Jatropha kernels in distilled water, and then was incubated at desired temperature with constant shaking at 100 rpm for specified time period. The upper oil phase was collected after a centrifugation at 10,000 x g for 20 min. Enzyme- assisted AOE was performed similar to AOE. The difference is that the prepara­tions, i. e., Protizymee, Cellulase, Pectinex Ultra SP-L, Promozyme, as well as mixture of all these enzymes, were added after the pH of the suspension was adjusted. The amounts of oil obtained were calculated as the percentage of total oil present in Jatropha kernels.

It is found that the use of ultrasonication as a pretreatment before aqueous oil extraction and aqueous enzymatic oil extraction is useful in the case of extraction of oil from the seeds of J. curcas L. [78]. The use of ultrasonication for a period of 10 min at pH 9.0 followed by AOE resulted in a yield of 67% of available oil. The maximum yield of 74% was obtained by ultrasonication for 5 min followed by aqueous enzymatic oil extraction using an alkaline protease at pH 9.0 (44 g oil/100 g Jatropha kernels was taken as 100% recovery). Use of ultrasonication can also reduce the process time from 18 to 6 h [78].

To obtain an optimized condition for an extraction using microwave is by using petroleum ether as the solvent, with the ratio of seed powder to solvent is at 1:3. It is done under a microwave power of 810 W for a total radiation time of 5 min [97]. The extraction rate was 31.49% with the oil product containing 5.22 mg/g of acid number and 8.78 meq/g of peroxide value. For the ultrasonic method, hexane was used as the solvent and the ratio of seed powder to solvent was 1:7; the soaking time applied is 18 h and the sonication is 0.5 h. The extraction rate was 37.37% contain­ing 5.91 mg/g of acid number and 8.37 meq/g of peroxide value in the final oil product [97] .

Alkyl acetates, especially methyl acetate and ethyl acetate, are important chemi­cals and suitable solvents for seed oil extraction which are assisted by Novozym 435 [83]. The results were compared to those obtained by extraction with я-hexane. Ground seeds were mixed with methyl acetate or ethyl acetate in screw-caped glass vials. And, 30% (w/w) of Novozym 435 based on theoretical oil content was added. The reactions were carried out at 50°C and 180 rpm for 6 h in a shaker which was fitted with a thermostat. After filtration, the ground seed mixture was mixed with another solvent and then extracted at the same condition for another 2 h. The two filtrates were pooled and centrifuged at 17,400 x g for 10 min; the supernatant was collected into a round bottom flask and the solvent was evaporated using a rotary evaporator. The oil content in g/100 g was 54.90% (я-Hexane), 55.92% (Methyl acetate), and 56.65% (Ethyl acetate) [83].