| Rice bran,a major by-product of rice milling,is regarded as a natural nutrient resource.It constitutes 10% of the total weight of rice,but it has a high nutritional value.In general,rice bran accounted for 64% of total nutrient in the grain and contained more than 90% of essential elements of human body.Currently,rice bran is mainly either used as fuel in boilers or as an ingredient in animal feed,which is a great waste of resources.Therefore,taking full advantage of this abundant resource is extremely imperative.In this study,rice bran oil was extracted by ultrasound-assisted ethanol method,and then the deacidification of crude rice bran oil was performed by liquid-liquid extraction using methanol solvent.Then,ultrasonic,homogenization and microwave were used to assist alkali extraction of rice bran protein,respectively.Ferulic acid was recovered from waste residue of rice bran by alkaline hydrolysis.Subsequently crude ferulic acid was converted into 4-vinylguaiacol via alginate-immobilized cells of Bacillus licheniformis DLF-17056.The results of this study indicated:1.The highest rice bran oil yield reached 14.2% when the ultrasound treatment for 20 min at 40 kHz,with a 2.1% increase than that of single ethanol extraction(P<0.05).Meanwhile,the ?-oryzanol and ?-carotene content in rice bran oil was also improved after ultrasound treatment,and these changes were conducive to the improvment of antioxidant activity.Furthermore,it was also observed that the waxes content,peroxide value,thiobarbituric acid and saponification value were changed in different degrees due to ultrasound treatment.The deacidification of crude rice bran oil was performed by liquid-liquid extraction using methanol solvent and the highest removal efficiency of FFAs reached 86.0%.And the nutraceutical levels in the deacidified oil were preserved within an acceptable range.2.The highest extraction yield of protein reached 57.89% by using ultrasonic assisted alkali method,while only 43.74% by microwave assisted alkali method.Both ultrasonic and homogenization assisted alkali methods could improve oil holding capacity,emulsion stability and foaming capacity,and the effects of ultrasonic were better than those of homogenization.However,protein solubility,water holding capacity,emulsifying activity and foaming stability were subject to different degrees of impairments due to physical processing.By comparison,ultrasonic assisted alkali method is a potential method for the extraction of rice bran protein.3.The waste liquid and residue from the process of protein extraction were used to extract ferulic acid via alkaline hydrolysis(1.0% NaOH),and yield was 232.1 mg/100 g.And then the strain DLF-17056,with high-ability of conversion of ferulic acid into 4-vinylguaiacol,was newly isolated from soil.Based on 16 S rDNA gene sequence analysis,physiological and biochemical test,the isolated strain was identified as Bacillus licheniformis.B.licheniformis DLF-17056 was immobilized with sodium alginate as the carrier,then used as biocatalyst in the transformation of ferulic acid to 4-vinylguaiacol at 40°C with a shaking speed of 120 rpm.The maximum of 4-vinylguaiacol reached 762.3 mg/L at 24 h when the concentration of ferulic acid was 1.0 g/L.Furthermore,the conversion rate was still above 60% when the alginate-immobilized cell was reused for 8 times. |
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