Study On A Biological Method For Production Of Ferulic Acid

Defatted rice bran is used inadequately and inefficiently though it is produced in enormous quantities in China, which results in resource waste. Defatted rice bran is rich in ferulic acid, which is used widely in the field of medicine, food and cosmetics. Alkali is the most frequently used solvent to extract ferulic acid and the process will produce a great deal of waste water and waste residue. Enzymatic hydrolysis is another alternative method for ferulic acid extraction, however, it has not been applied in actual production because it is low in yield and high in cost. To solve this problem, a steam explosion pretreatment process followed by an enzymatic hydrolysis has been applied to the extraction of ferulic acid from defatted rice bran. Mixed enzymes produced by solid-state fermentation with Aspergillus niger, instead of commercial ferulic acid esterase,are used to release ferulic acid in order to improve the yield and reduce the cost.Main conclusions can be summarized as follows:(1) The defatted rice bran is steamed for 180 s under certain pressure before rapid decompression. It's necessary to choose an appropriate pressure to ensure the high yield because it's hard to cause disintegration of the cell wall if the pressure is too low and the product is easy to hydrolyze if the pressure is too high. The maximum yield of ferulic acid(1.6 times as the untreated control) occurs at a pressure of 0.6 MPa when NaOH is used as the solvent for extraction. 1.2 MPa is the most appropriate pressure when commercial ferulic acid esterase(3.8 times as the control) or mixed enzymes(5.3 times as the control)are used for extraction.(2) When the commercial ferulic acid esterase is used for the extraction, the optimal condition is: steaming pressure on steam explosion pretreatment- 1.2 MPa;dilution multiple- 50 times; liquid-solid ratio- 20:1; extraction temperature- 40 ?;reaction time- 90 min. The average yield of ferulic acid is 0.124%, which is equal to33.7% of the yield by an alkali extraction.(3) Considering the yield of ferulic acid, the optimal fermentation time and temperature of Aspergillus niger are 3 days and 28?. The yield of ferulic acid is 0.166%when using the defatted rice bran with a steam explosion pretreatment(1.2 MPa for 180 s)and the mixed enzymes for extraction.When the mixed enzymes are used for the extraction, the optimal condition is:steaming pressure on steam explosion pretreatment- 1.2 MPa; liquid-solid ratio- 30:1;extraction temperature- 40?; reaction time- 90 min. The average yield of ferulic acid is0.266%, which is equal to 72.3% of the yield by an alkali extraction and it is higher than the yield by an alkali extraction without a steam explosion pretreatment. In addition, the liquid-solid ratio has a significant influence on the yield of ferulic acid.In conclusion, a steam explosion pretreatment process followed by an enzymatic hydrolysis with the mixed enzymes is helpful to release ferulic acid from the defatted rice bran. Considering the yield of ferulic acid, the extraction with mixed enzymes is closer to the extraction with alkali than that with a commercial ferulic acid esterase.