The Optimization And Scale-up Of Enzymatic Conversion Of Isoeugenol To Vanillin

The increasing concern for health and nutrition stimulates a worldwide demand fornatural vanillin. Therefore, alternative processes for the production of natural vanillin shouldbe studied. Enzymatic conversion reaction is the reaction that is catalyzed by the enzymeextracted from plants or animals. Its merits are as follows, the mild reaction conditions, amityto environment, the high production efficiency and the better stereoselectivity. In this paper,conversion of isoeugenol to vanillin by crude enzyme extracted from soybean was studied.Different breeds of soybean were studied. It was found that the best for practicalproduction was 99-6 whose activity of lipoxygenase was highest and capability of convertingisoeugenol was the strongest.Main operation parameters of conversion were studied and optimised. The optimumtemperature, rotation speed and pH were 28℃,180r/min and 8.0 respectively. And theoptimum substrate concentration and liquid amount in flask were 15g/L and 20mLrespectively. The vanillin concentration reached its maximum for 72h with the amount oflipoxygenase of 1.20×106U/mL.Coupling of reaction and separation in bioconversion to vanillin by enzyme was alsostudied. Screening sorbent was investigated. The product inhibition can be preventedeffectively with the addition of resin HD-8. The technology of coupling was optimized byorthogonal test. All the operation parameters for coupling were obtained in 250mL flaskcontaining 20mL solution. It was found that the optimum concentration of substrate andamount of resin HD-8 added were 15g/L and 150g/L at the beginning of reaction. The vanillinconcentration reached its maximum of 3.41g/L for 72h, corresponding to a molar conversionof 24.53%, 1.84 times higher than the unoptimised.The enzymatic conversion at the pilot scale of 2L was also studied. The substrate amountof 15g/L, the stirring rotation and aeration were adjusted to 1.0vvm and 200r/min repectively.The best production of vanillin from isoeugenol in 2L bioreactor was 2.17g/L for 60 h,corresponding to a molar conversion of 15.61%.The methods for separating substrate and product were investigated. It was found thatn-hexane and ethyl acetate two-step eluting method was suitable for coupling of reaction andseparation in bioconversion. Simultaneously, optimum eluting conditions were obtained. Theyield of product and the recovery of substrate are 83.08% and 85.50% respectively.The cost of vanillin was estimated to be 105$/kg. The vanillin obtained was alsoidentified as bio-vanillin. It was testified that this technology would be prosperous.