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Enzyme-assisted aqueous extraction of rice germ oil (RGO) was performed in this study. The physicochemical properties, fatty acid composition, bioactive substances and antioxidant activity of RGO were analyzed. An enzyme composed of alcalase and cellulase (1:1, w/w) was found to be the most effective in the extraction yield of oil. The optimal oil yield of 22.27% was achieved under the conditions of an enzyme concentration of 2% (w/w), incubation time of 5 h, incubation temperature of 50°C, water to seed ratio of 5:1, and pH 6.0. The predominant fatty acids of RGO were oleic acid (39.60%), linoleic acid (34.20%) and palmitic acid (20.10%). The total saturated fatty acid (SFA), monounsaturated fatty acid (MUFA) and polyunsaturated fatty acid (PUFA) composition of RGO were 22.50%, 39.60% and 36.00%, respectively. RGO yielded a high content of γ-oryzanol (530 mg/100 g oil), tocotrienol (62.96 mg/100 g oil), tocopherol (23.24 mg/100 g oil) and a significant amount of phytosterol (372.14 mg/100 g oil). It exhibited notable antioxidant activities with IC50 values of 32.37 and 41.13 mg/mL, according to the DPPH radical scavenging assay and β-carotene/linoleic acid bleaching test, respectively.

In this paper, the esterification of phytosterol and free fatty acids (FFA) in rice bran oil (RBO) was studied using Novozym 435 in supercritical CO₂. It was found that with the increase in CO₂ filling pressure, the esterification reaction rate also increased. When the pressure exceeded the critical point, CO₂ fluid had a great effect on phytosterol conversion. Therefore, enzymatic esterification deacidification was studied when the CO₂ filling pressure was 8.0 MPa, the results showed that when the lipase dosage was 3.0%, the phytosterol concentration was 18.0%, the molecular sieve addition was 10.0%, and the esterification temperature was 78°C, after 41 hr the FFA content of RBO decreased to 1.1%, the phytosterol conversion rate reached 93.2%, and the vitamin E (VE) retention in the product was 80.0%. Therefore, the esterification by Novozymes 435 in supercritical CO₂ could have several applications in fats and oils industry. PRACTICAL APPLICATIONS: Much research has been done on the interesterification of vegetable oil in order to produce edible fats and oils. The current study provides a reliable and simple method for the esterification of phytosterol and free fatty acids (FFA) in rice bran oil (RBO). The optimal operating conditions lead to high quality oil. The FFA content of RBO decreased to 1.1%, the phytosterol conversion rate reached 93.2%, and the VE content in the product was 80.0%. The esterification by Novozymes 435 in supercritical CO₂ could be applied in fats and oils industry.

The mesoporous material MCM-41 was amino-modified with 3-aminopropyltriethoxysilane, and the amino content of modified MCM-41 was 0.16 mmol/g. Then G-MCM-41 was prepared by adding glutaraldehyde. Candida antarctica lipase B (CALB) was immobilized on G-MCM-41 at 45 °C for 5 h to obtain immobilized lipase G-MCM-41-CALB. The lipase protein loading of G-MCM-41-CALB was 87.4 mg/g and its expressed activity was 80.2%. The immobilization efficiency of G-MCM-41-CALB reached 93%. The characterization of G-MCM-41-CALB showed that the mesopores maintained the pore structure, the crystal surface was intact, and the pore size became smaller, indicating that the CALB was immobilized on the carrier. The optimum pH and temperature of G-MCM-41-CALB were 7.0 and 50 °C, respectively. The relative activity of G-MCM-41-CALB was still >50% after 40 days at 4 °C. The thermal stability of G-MCM-41-CALB was improved compared to free CALB. G-MCM-41-CALB was evaluated for its ability to catalyze the transesterification of soybean oil and phytosterol. Results showed a conversion rate of 87.4% and the relative activity of G-MCM-41-CALB was 83% after 7 reuses.

Three phase partitioning (TPP) technique was used to extract oil, protein and polysaccharides simultaneously from rice bran. The fatty acid composition of rice bran oil (RBO) and structure of rice bran protein (RBP) and rice bran polysaccharides (RBPS) were analyzed. Under the optimal conditions of (NH4)2SO4 concentration 28% (w/v), slurry to t-butanol ratio 1:1.1 (v/v), pH 5.10, extraction temperature 40 °C and extraction time 1 h, the highest extraction yields of RBO, RBP and RBPS were 17.28%, 6.81% and 2.09%, respectively. The fatty acid composition of RBO was analyzed by GC, the structure of RBP was analyzed by FTIR and SDS-PAGE, and the structure of RBPS was analyzed by FTIR. The results were similar to those obtained by other methods. Therefore, TPP can be used as an effective technology for simultaneous extraction of oil, protein and polysaccharide from rice bran.