| Naringinase is a kind of glycosidase complex, which composed ofα-L-rhamnosidase (EC 3.2.1.40) andβ-D-glucosidase (EC 3.2.1.21). Naringinase can specifically hydrolyze naringin into naringenin and it has many important application value, such as debittering of citrus fruit juice, increasing beverage aroma, industrial preparation of rhamnosidase and flavonoids. However, owing to the immaturity of the technology of naringinase fermentation and preparation craft lacking, causes the price of naringinase enzyme preparation is too expensive, which limited the development of the naringinase applied technology. Therefore, establishes the mature technology of naringinase formalization fermentation and the reasonable preparation craft has the important significance.This paper, Aspergillus niger DB056 was the naringinase-producing strain, after the study on scale-up technology of naringinase fermentation, the naringinase preparation craft and its optimization were investigated into, followed by the food safety testing and the storage stability discussion. The main results were as follows:7 L, 20 L and 200 L Naringinase's fermentation scale-up research indicated, two components of naringinase,α-L-rhamnosidase andβ-D-glucosidase, of which enzyme activites had a certain range of fluctuation along with the process of gradually scale-up fermentation, but the change tendency of enzyme activities was consistent; The maximum enzyme activities ofα-L-rhamnosidase andβ-D-glucosidase were 1069 U/mL and 727 U/mL respectively in the 200 L scale fermentation, exceeding that in 7 L and 20 L scale fermentation. In this study, the 200 L scale fermentation of naringinase produced by Aspergillus niger DB056 was achieved successfully, suggesting that the strain owned the favourable fermentation performance and application value on the industry.The naringinase solid enzyme preparation were obtained by the process of freezing centrifugation, aseptic filtration, ultrafiltration enrichment and spray drying, during which the drying aid was maltodextrin and the content of the solid shape was 27%. Took the recovery ofα-L-rhamnosidase as a stand and on the basis of the single factor experimental result, the spray drying parameters were optimized by means of response surface analysis. The best spray drying condition was as follow: inlet air temperature 111.3℃, feeding speed 161.5 mL/h, hot air flow rate 5.1 m3/min, outlet air temperature 60℃, atomizer pressure 0.4 MPa. Under this condition, the recovery ofα-L-rhamnosidase was 79.7%. Using the established craft steps and parameters, solid enzyme preparation of naringinase with 7.5% water content was made, in which, the activity and total recovery ofα-L-rhamnosidase reached 19000 U/g and 78.1%, respectively, and that ofβ-D-glucosidase were 4700 U/g and 28.3%, respectively.As to the results of food safety detection, the aspects of naringinase solid preparation which has been made, including the total number of bacterial colonies, coliform bacterium, Salmonella and heavy metal content, met completely the requirement for the safety standard of food industry.During the preserve process, the facts of temperature, air and humidity had great influence for the storage stability of naringinase solid enzyme preparations but the light is not obvious. The retention rates ofα-L-rhamnosidase andβ-D-glucosidase of the naringinase solid enzyme preparation preserved in the condition that is -20℃, cacuum and evades the light, were 97.6% and 86.0%, respectively.The study realized the 200 L scale fermentation of naringinase, the technical process of naringinase preparation was established as well as its parameters optimized, at the same time, the food safety of the naringinase solid enzyme preparation was detected and its storage stability condition was investigated into. In a word, these studies will set an important foundation for the industrial enlarged-scale production of naringinase preparation and promote the development of application technology for naringinase. |
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