Screening Of Pectinase Producing Strain And Optimization Of Conditions For Using Potato Pulp As Substrate To Produce Pectinase

The potato pulp is a kind of by-product of potato starch production.It is mainly made up with the wastewater and residue,which contain water,starch,cellulose,pectin,polypeptide and amino acid.Nowadays,the pollution caused by the potato pulp is a serious problem,which the potato starch industry faces and is needed to be solved urgently.Currently,it is an important aspect that using pectinase producing strains to ferment potato pulp.On the one hand,it can solve the pollution caused by the potato pulp.On the other hand,fermentation of the potato pulp is a pre-process for making it to be animal feed that decreasing the cost of drying and increasing the amount of dietary fiber.Therefore,it is a good biotechnology that using microorganisms to ferment and produce pectinase.This research screened a strain,which has higher ability to produce pectinase and to degrade pectin.First of all,ten fungi strains were screened from soil by repeated plate streaking on the plate which only uses pectin as carbon resource.Second,with the comparison of strain Aspergillus niger CGMCC 3.316 existed in laboratory,five strains were screened from this process according to their ratio of the transparent circle's diameter to the colony's diameter.Finally,strain H screened by determining the pectinase of the six strains above by DNS method and used for subsequent experiment.After sequencing the ITS sequence of strain H,and comparing with the sequences of 25 strains of Aspergillus sp.,the polygenetic tree of H was constructed by Neighbor-Joining method.The response surface method used to optimize the fermentation conditions.After carrying out the Single Factor Experiment,Plackett-Burman Design and BoxBehnken Design,the optimized conditions got(fermentation time 1 d,temperature 28.7 ?,p H 6.5,inoculum size 1.5%,the percentage of solid potato waste 2.5%,rotation speed 180 rpm and fermentation volume 100 m L).The result showed pectinase 431.52 U/m L,which is very close to the theoretical result 436.88 U/m L and is 3.03 times of the value of pectinase in initial conditions.For better understanding the effect the H strain's fermentation on potato pulp,the degradation rates of pectin and COD were test in initial and optimized conditions respectively,and they show the two latter are 1.54 and 2.19 times of the two former which present excellent optimization affection.