Screening And Processing Of Xylanases Produced By Liquid Fermentation Of Aspergillus Niger

In this paper,Aspergillus niger TG-Y was treated by aerospace mutagenesis,and two mutants TG-Y-1 and TG-Y-2 with 20.22%and 21.76%increase of xylanase productivity were obtained.50L fermentors were used to investigate the technology for liquid fermentation,increasing the amount of corn cob in the carbon source,and choosing the corn steep liquor as an organic nitrogen source.The optimized basic medium:corn cob 60g/L,corn steep liquor 20g/L,(NH4)2SO4 5g/L,KH2PO4 3g/L,MgSO4 lg/L,polyethylene glycol 2000 0.5g/L,pH 5.20.Acid hydrolysis of B-starch slurry were used to replace glucose and corn cob as carbon source and inducer of feed medium,the problem that corn cob is easy to plug the pipeline has been resolved.The optimized feed medium is:B starch slurry by acid hydrolysis(based on glucose content)50 g/L,corn syrup 30 g/L,(NH4)2S0415 g/L,KH2P04 10 g/L,MgS04 5 g/L,calcium carbonate 0.75 g/L.The effects of temperature,pH,rotational speed,ventilation,dissolved oxygen,feed rate,seedling age,inoculum size,and loading factor were studied.A phased regulation strategy was developed and successfully amplified to 130m3 fermentor and the enzyme activity was stabilized above 2500U/ml.The following extraction process of xylanase consists of two procedures,filter pressing and membrane concentration,with yield at 81.03%.The study of enzymatic characteristics showed that temperature and pH had significant effects on the stability of enzyme,while the optimum temperature and pH were 50? and 5.0,respectively.The best preservative formula is NaCl 60g/L,sodium benzoate 3g/L,potassium sorbate 2g/L,sorbitol 40g/L.Treated as described above,the enzyme can retain 91.78%of its original activity after 90 days,which meets the requirements of industrial production.