Screening Of Aspergillus Aculeatus ZC-1005Based On Citrus Mesocarp Degradation And Basic Research For Application

In order to enhance the enzyme specifity, efficiency and industrial feasibility, this research was conducted to screen a strain for producing hemicellulase for degrading citrus mesocarp. And to be as the research object, the fermentation process and enzymatic properties of the strain was studied to provide some theoretical basis for application in citrus processing industry.The main parts of this research are as follows:(1) According to the plate and flask screen, a strain with the ability of producing hemicellulase and degrading citrus mesocarp was obtained. It was identified as Aspergillus aculeatus by observation of morphological characteristics and identification of molecular biology. And it was named Aspergillus aculeatus ZC-1005.(2) Based on single factor test and response surface method, the optimal fermentation conditions were4%wheat bran,0.7%NaNO3, spore concentration105cell/mL, initial pH7.16,10mL (50mL flask) culture medium at37.5℃for66.5h under shaking cultivation (170r/min), and the xylanase activity reached153.6U/mL.(3) The sole microwave radiation technology was used to pretreat the bran at radiation power of350W for8min with the material and water ratio of1:5, the xylanase activity was176.6U/mL which increased by12%compared with the untreated wheat bran sample.(4) The xylanase eluent was obtained by the way of dialysis and Sephadex G-100gel chromatography. The xylanase molecular weight was confirmed at28970Da by the analysis of protein electrophoresis. It was also shown that the xylanase activity was195.2U/mL under the optimal reaction conditions of pH5.0at55℃. And it had a good thermostability and pH stability below50℃and at pH5.0.(5) The degradation of citrus mesocarp by crude enzyme from Aspergillus aculeatus ZC-1005showed that the mesocarp could be degraded completely at50℃in50min with the material and liquid ratio of1:5.