| The acid pectase produced by solid fermentation of Aspergillus niger,due to the complexity of its culture medium,not only produced acid pectase,but also produced complex associated enzyme system to assist Aspergillus niger in material and energy metabolism.The diversity of zymograms affects the stability preservation and use effect of acid pectinase products,and limits its application market scope.In view of the problem of poor stability of acid pectinase,the existing research method is to prepare crude enzyme solids and apply it to the feed industry;95% ethanol crystallizes or(NH4)2SO4 to prepare high-enzyme live crude enzymes and apply to the food industry;The problem of poor thermal stability of pectinase still exists.In this thesis,by studying the enzymatic properties of acid pectinase products of solid fermentation,the common and different points of each enzyme species in the zymogram are analyzed to determine that acid protease is the main factor affecting the stability of acid pectinase.Optimize the post-treatment process to remove most acidic protease content,reduce instability factors,and extend the stability period.The results of this study indicate:1.There are 8 single enzymes in acid pectase,mainly including NSP,amylase and protease.2.In the study of the enzymatic characteristics of acidic pectase and its associated enzymes,it was found that the activity expression of cellulase,xylanase,meso-temperature amylase and acidic protease all appeared an inflection point at p H4.0-6.0.The turning point of cellulase and xylanase appeared at p H4.5,medium temperature amylase appeared at p H 5.5,acidic protease appeared at p H 4.0-5.0,acidic pectinase appeared at p H 5.0,acid proteases are the most sensitive to changes in p H.3.Acid protease can restrict the activity expression of acid pectinase,NSP enzyme and amylase to varying degrees under the appropriate temperature conditions.According to the size of the influence of enzyme activity,the order of influence from large to small is: medium temperature amylase> xylanase> acid pectinase> cellulase.4.In the isoelectric point test,three main components of pectase:PE/PG/PL.the isoelectric points of PL and PE were at p H 3.6-3.9,PG was at p H 6.0-6.4,and acidic protease was at p H 4.3-4.8.5.According to the enzymatic characteristics of acidic pectase,an experiment scheme was designed to enhance the stability of acidic pectase.The p H of acidicpectase extraction stage was adjusted between p H 4.3 and p H4.8,solution of 1mol/L citric acid and 2mol/L sodium hydroxide were applied for repeated adjustment for three times,each time for 30 min.The activity of acidic protease decreased from880u/m L to 50u/m L,95% acidic protease was deactivated and the activity of acid pectinase has almost no change.6.A single factor and L9(33)orthogonal experiment were carried out : the liquid acidic pectinase product was prepared by adding propyl P-hydroxybenzoic acid,benzoate 0.1g/L,potassium sorbate 1.0g/L,Na Cl 0.2g/L and glycerol 20% in the concentrated solution of ultrafiltration.Soluble solid acid pectinase was prepared by adding 6% soluble slushy and 2% sodium chloride.The yield of liquid enzyme was increased from 68% to 88%,and the production efficiency of acid pectinase was improved.7.After optimization,stable acid pectinase was obtained,and the activity retention rate of acid pectinase was doubled within 12 months shelf-life.Soluble solid enzymes of acid pectinase could fill the gap of the company's market. |
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