| China is one of the most important origin country of potatoes,whose area and output are ranked first in the world.In addition to the direct consumption of potatoes,most of the potatoes are used for starch processing.Potato starch processing is not only the main channel for digesting defective potatoes,but also an important link in the potato industry chain.The treatment of by-products of potato starch processing is imminent and it has become one of the most important problems which restricts the development of potato industry.Microbial fermentation turns the by-products of potato starch processing into treasure.It can not only solve the pollution of direct discharge of potato starch juice,but also improve the added value of potato and reduce the waste of resources,which can achieve the dual purpose of treating sewage and producing bioactive substances.In this study,48 strains,including 15 fungi and 33 strains of Streptomyces,were isolated and purified by screening soil which is rich in humus.6 strains of high efficiency pectin degradation were further selected according to the results of pectinase activity in experiments of Congo red staining and liquid fermentation.According to the results of 16 S rRNA sequence determination,the system evolution tree was constructed to determine that four strains of QGS69,QCPA72,QDPA48 and QDPA53 all belonged to Streptomyces.The growing characteristics of the strain were observed,and 48 h was the best inoculation age.Using plate confrontation method in order to achieve the fusion of the strains of the compound bacteria,it was found that there was no significant inhibition of the growth of other strains among the strains,so the QGS69,QDPA48,Aspergillus H and Aspergillus S purchased in the laboratory are selected to live with single strain pectinase.There are four kinds of enzymes in degrading pectin,and the construction of compound flora can make up for the deficiency of enzyme production characteristics of different strains,and achieve the optimal effect of enzyme production.Screening the conditions for constructing complex flora,the conditions were as the following: the combination of QGS69,QDPA48 and Aspergillus H as the best strains,at the same time,12 h after picking up QGS69,QDPA48,which is the best inoculation time for adding to Aspergillus H,the best inoculation ratio is QGS69:QDPA48: Aspergillus H =1:1:2.Then,according to the results of single factor experiment and orthogonal test,the optimum production temperature of Pectinase was 25 ?,the initial pH of medium was 6.0,the total amount of bacteria was 1 %,and the co-culture time of fungi and Streptomyces was 48 h.It was proved that the pectin enzyme produced by the optimized condition fermentation liquid was 450.7493 U/mL.After optimization of pectin degradation efficiency is 65.84 %,1.59 times before optimization,COD degradation efficiency is optimized after 57.64 %,twice times before optimization. |
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