Study On Screening And Fermentation Conditions Of Low Temperature Resistant Strains For Potato Starch Juice Fermentation

Potato starch wastewater is rich in nutrients and contains a lot of organic matter,including soluble starch,protein,cellulose,sugar,etc.But its COD,nitrogen,phosphorus,suspended solids and so on are seriously over the standard.If it is discharged directly,not only is water environment polluted,but also a lot of resources are wasted.Because the potato starch production season is in autumn,winter and spring,the treatment temperature of starch is lower,commonly used microbial agents grow slowly or cannot grow,only screening out low-temperature-resistant microorganisms is the only way to solve the current problem of biological treatment of potato starch wastewater.By continuously lowering the temperature,screening out microorganisms that ferment potato starch wastewater at a low temperature of 12?,investigate its characteristics and growth conditions,optimize its process,and using them to treatstarch wastewater,not only can the cost be reduced,the water quality can be improved but also the resource utilization rate of the waste water can be improved.This paper analyzed the main components of potato starch wastewater,and separated 55 strains from the mixed bacterial liquid and activated sludge using the method of decreasing temperature,screen layer by layer and finally obtain a strain with low temperature tolerance and strong organic decomposition ability.The strain was applied to the treatment of starch wastewater,and the water quality of starch wastewater was significantly improved,which provided a reference for microbial treatment of potato starch wastewater under low temperature conditions.The specific research conclusions are as follows:1.Water Quality Analysis of Potato Starch WastewaterIt is indicated that the contents of various components in potato starch wastewater seriously exceeded the discharge standard of water pollutants for starch industry by analyzing the contents of COD,NH₃-N,TN,TP,pH,SS,sugar,protein,amino acids and the kinds of amino acids in potato starch wastewater.2.Screening and Identification of Low Temperature Resistant Strain55 strains isolated from LB and PDA medium were screened with COD removal rate as the main index,and 10 strains with COD removal rate more than 30.0%were obtained;5 strains able to stably degrade COD and NH₃-N in starch wastewater were obtained from 10 strains with COD and NH₃-N removal rate as the main index;one strain with good fermentation performance at 12? was screened at 15? and 12?.After morphological,biological and molecular identification,the strain was identified as cladosporium cladosporioides.3.Process Optimization of Potato Starch Wastewater Fermented by Cladosporium cladosporioidesIn order to reduce the cost of treatment,the starch wastewater was treated by anaerobic fermentation,and the fermentation temperature was determined at 12?.Therefore,the inoculum amount,fermentation cycle and initial pH of fermentation were optimized by single factor,and the optimal values of each factor were optimized by response surface optimization.The optimal fermentation conditions were as follows:inoculum amount is 23.0%,fermentation cycle is 5.5 days,and initial pH of fermentation is 6.8.The results showed that the removal rates of COD,NH₃-N,TN,TP,total sugar,SS and protein were 45.06%,20.66%,39.05%,71.01%,50.00%,40.39%,42.69%,respectively.The kinds of amino acids increased from 2 to 10 and the content of amino acids increased by doubled.The water quality of starch was obviously improved.4.Preliminary application test of Cladosporium cladosporioides in productionCladosporium cladosporioides was conducted with scale up cultivation and inoculated in It fermentor for 30 days,and the inoculation amount was 23.0%.The pH of starch juice was adjusted to 6.8,and the fermentation temperature was natural environment temperature.The results showed that the removal rates of COD,NH₃-N,TN,TP and SS were 40.00%,34.77%,31.37%,50.73%and 43.30%respectively,reducing sugar were reduced by 95.00%when fermenting to 5 days(fermentation temperature was-7?15?).Total sugar were reduced by 75.00%and the protein degradation rate was 38.26%when fermenting to 10 days(fermentation temperature was-8?15?).The kinds of amino acids increased from 2 to 10 and its content increased from 1.485g/L to 8.833g/L when fermenting to 20 days(fermentation temperature was-10?15?).The strain can be used for the treatment of potato starch wastewater under low temperature conditions in actual production.