Optimization Of Fermentation Conditions For Production Of Xylanase By Aspergillus Niger SD-03Using Corncob

Hemicellulose,which is the second rich recyclable natural resource after cellulose.Its effective transformation and utilization mainly depend on xylanase,which can be produced by the process of microbial fermentation.This paper made a primary study on characteristics of xylan degradation bacteria Aspergillus niger SD-03reserved in our lab. It focused on optimization of the solid fermentation parameters for xylanase by utilizing corncob as primary fermentation substrates.On that basis, the properties of the crude xylanase and the purification of xylanase were preliminarily studied.The main results are as follows:1.The degradability of xylan about Aspergillus niger in selective medium was studied by three point method,it began to emerge transparent ring after4days.The enzyme activity could achieve90.57IU/ml after72h by liquid fermentation and through the genetic stability test,the result showed that SD-03strain had good genetic stability.2.The optimum solid fermentation medium under optimal carbon sources for SD-03that produce xylanase were determined by single factor experiment and orthogonal experiment with five factors and four levels as follows:the mass ratio of wheat bran and corn-cob was7:3,the ratio of the materials and water was1:1.5,0.2%NaNO3for nitrogen source,0.1%NaCl,0.15%Tween80,particle radius for1-1.5mm.the optimal fermentation process as follows:the initial pH was4..the inoculum size was0.2ml(106/ml),cultivation temperature was30℃,cultivation time was84h.Under these conditions,the xylanase activity was up to3987.52IU/g,which was about3.29times higher than before.3.The research of enzyme production by utilizing corncob as main raw materials in solid state fermentation.The optimum solid fermentation medium for SD-03that produced xylanase were determined by single factor experiment and orthogonal experiment with five factors and four levels as follows:the mass ratio of wheat bran and corn-cob was1:9,the ratio of the materials and the salt solution was1:3,3.5%NaNO3,0.1%cellobiose,Tween800.1%,particle radius for1-1.mm.The optimal fermentation process as follows:the initial pH was4-5,the inoculum size was0.2ml(6x106/ml),cultivation temperature was37℃cultivation time was72h.Under these conditions,the xylanase activity was up to2464.41IU/g.The result of leaching experiment showed that the optimum extracting agent was acetic acid-sodium acetate buffer, temperature was30℃, time is180min,leaching speed is130r/min.The rough enzyme powder was obtained by suction filtration.ultrafiltration.ammonium sulfate fractionation, dialysis and freeze-dying.The results showed that:the main component crude enzyme was xylanase,the optimum reaction temperature was50℃, between temperature20-50℃enzyme activity was stable by heat-moisture treatment,heating treatment possess higher stability.the optimum pH was5,between pH2-6had high stability and belonged to acid resistance enzyme.In addition to Cu2+,the others metal ions restrained xylanase activity.EDTA had little impact on the xylanase activity.Tween-80and Triton X-100(10%) could promote xylanase activity to a certain degree.