| In this thesis,wheat bran has been used as the main raw material which was fermented through Neurospora sitophila.In order to increase the release rate of ferulic acid in wheat bran,the auxiliary carbon and nitrogen sources were added to the culture medium.Finally,the bacteriostasis of different kinds of ferulic acid derivative was explored.The results provided a theoretical basis for wheat bran as a functional feed,and also provided a reference for the new green large-scale production of ferulic acid from wheat bran.First,in order to increase the release rate of ferulic acid,wheat bran has been fermented through Neurospora sitophila.Different auxiliary carbon and nitrogen sources were added to the basic culture medium.The optimum fermentation time was determined to be three days with the content of ferulic acid,ferulic acid esterase activity,xylanase activity and cellulase activity as index.The relationship between ferulic acid content and the activity of three kinds o enzyme was investigated.The results showed that with the 0.2 g/L urea and 0.1 g/L glucose added to the basal medium,the highest ferulic acid content was 2.82 mg/g.Different auxiliary carbon and auxiliary nitrogen sources were added to the basic medium,and it has been found that the auxiliary carbon source that had the greatest influence on ferulic acid esterase activity was glucose,and the auxiliary nitrogen source that had the greatest influence on ferulic acid esterase activity was urea.Urea is the most important auxiliary nitrogen source for the activity of xylanase.Xylan is the most important auxiliary carbon source that affects the activity of xylanase.The auxiliary nitrogen source with the greatest influence on cellulase activity was ammonium sulfate.Xylan was the most important auxiliary carbon source for cellulase activity.Finally,it has been found that xylanase activity and ferulic acid esterase activity had obvious influence on ferulic acid release amount,while cellulase activity had little effect on ferulic acid release amount.After determining the optimum auxiliary carbon and nitrogen source,three kinds of enzymes were added to assist the fermentation of wheat bran by Neurospora sitophila and to increase the release of ferulic acid.The proportion of different kinds of ferulic acid derivative was determined.The best cooperation way with the auxiliary enzyme catalysis and Neurospora sitophila fermentation was obtained.The fermentation conditions were optimized by single factor and orthogonal experiment design.Used ferulic acid content as index,the temperature,pH value,the ratio of material to water,enzyme concentration and inoculum amount were optimized by single factor experiments.With the inoculum amount determined by blood cell counting method,the orthogonal test was carried out by selecting temperature,the ratio of material to water,enzyme concentration and inoculum amounts as factor.The results showed that the highest ferulic acid content was 3.58 mg/g after three days fermentation by Neurospora sitophila and further 8 h enzymatic hydrolysis reaction catalyzed by xylanase.In the single factor experiment and the orthogonal experiment,the ratio of material to liquid was the most import factor with the influence greater than that of enzyme concentration and the inoculum amount,and the influence of the temperature were the smallest.The optimal conditions were obtained as below.The temperature was 40 OC,pH was 5,the ratio of material to water was 1,enzyme amounts added was 80 U/mL,inoculum amount was 10%.Under the optimum condition,the highest ferulic acid release content is 4.05 mg/g.Finally,the inhibition effects of different types of ferulic acid derivatives on three kinds of bacteria(Staphyloccocus aureus,Escherichia coli and Bacillus subtilis)were studied respectively.The results showed that ester-binding ferulic acid derivative generally has the strongest inhibition effect on these three bacteria,followed by glycoside-binding ferulic acid derivative and free-type ferulic acid. |
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