Screening For Microorganisms That Produce Only Endo-inulinase And Research On Their Properties

Halianthus tuberosus is a kind of valuable raw materials due to its low cost,abundant in nature and easy to grow,while it also could be used for the production of FOS which had gradually attracted people’s extensive attention for its superior physiological function.Therefore,the development of FOS products possessed great significance.Main contents and research results in this thesis were demonstrated as follows:①Isolation of endoinulinase-producing strains:Two strains produced endoinulinase were isolated from soil samples with medium containing inulin as a sole carbon substrate.They were named 713 and 724 respectively,The results which compared two strains working on utilization of inulin and production of FOS showed that 724 was better than 713,so 724 was selected as objective strains.Then optimization of fermentation conditions and properties of the enzyme on 724 were experimented.②Optimization of endoinulinase-producing strain’s Fermentation conditions:The results showed that the optimum fermentation conditions of the strain was as follow.the extract juice of Helianthus tuberosus 15%,NH4NO3 0.5%,yeast extract 0.2%,ZnSO40.01%,NaCl0.5%,30 ℃,100 mL/250 mL,inoculum 3%,natural pH(6.3-6.5).The polymerizat-ion degree of FOS was about 6.2.③The research on strain’s enzymatic properties:The results showed that the optimum reaction temperature for this endoinulinase was 50℃,and the most suitable pH was 4.8.The enzyme activity was basically stable at 30℃ to 60℃ in 5 h,and the enzyme activity had decreased rapidly under 70℃ to 80℃ after 1 h.The optimum substrate concentration for this endoinulinase was 2%of inulin.The concentration of metal ions in 0.01%to 0.03%,the effect of Cu2+was the best for the enzyme activity.When the concentration of metal ions in 0.05%to 0.07%,the effect of Zn2+was the best for the enzyme activity.And the enzyme activity was inhibited by all other ions except Cu2+at the concentration of metal ions in 0.1％.Overall,0.01%concentration of Cu2+was the best for promoting of the enzyme activity.