Investigation On Degradation Of Potato Starch Processing Juice By Microorganism

A large amount of juice containing substances such as proteins and amino acids was inevitably produced during potato starch processing,and its direct discharge was liable to result in loss of nutrients and producing a lot of odor substances which pollute the environment due to protein decomposition.Based on this,the study was designed to screen primary strains capable of degrading proteins and inhibiting odor generation from juice,and which were optimized through single factor test and response surface test.Subsequently,the mixed strains were constructed by combining the primary strains screened with Serratia marcescens(NXYS-S),and which were further optimized through single factor test and response surface test.Ultimately,potato starch juice was fermented by the mixed strains and applied to capsicum pepper planting with the purpose of providing theoretical support for returning juice to field irrigation.(1)Screening of degrading strains of potato starch processing juiceFour strains(No.1-4)were screened with potato juice,potato residue and fish pond water as bacterial sources and casein degradation as evaluation indexes,which was screened again with potato juice as substrate to analyze the protein content,volatile components,ammonia nitrogen,phosphate and essential amino acid content in fermentation broth,which showed that the protein degradability of No.3 and No.4 were increased by 28.3%,22.42%,the phosphate content were increased by 4.95%and 8.79%respectively,total biogenic amines in fermentation juice of No.1 and No.4 were decreased by 88.56%and 85.52%,and ammonia nitrogen content of No.4 were decreased by 25.3%in fermentation juice when compared with the unfermented ones.Meanwhile,indole content(0.84%)was significantly lower than that of other groups(P<0.05),the sensory evaluation score was 83 and no off-flavor was displayed.In conclusion,No.4 was identified as the optimal strain and identified as Pseudomonas moss,named TXPA-Z.(2)Low temperature domestication and fermentation process optimization of TXPA-ZSince the production of potato starch is mostly concentrated in autumn,TXPA-Z bacteria were domesticated and their growth curves were plotted at low temperature of 15?.Single factor test and response surface optimization were carried out with the vaccination volume and pH as variables and the protein degradation rate as indexes,which showed that pH 6.18 and vaccination volume 4.99%were the optimum fermentation conditions for TXPA-Z bacteria,under which the protein degradation rate was 47.29%,ammonia nitrogen and phosphate content were 2.45 g/L and 1.78 mg/dL respectively,the contents of putrescine and cadaverine were 3.63 mg/L and 2.52 mg/L respectively,and the contents of indole were not detected in fermented juice.Sensory score of 72 points,with trace abnormal taste.(3)Optimizing conditions of potato juice by mixed bacteria fermentationIn order to improve the protein degradability of potato juice,Pseudomonas Bryophyta TXPA-Z was mixed with Serratia marcescens NXYS-S(aerobic-anaerobic)and fermented at 15? for 48 h.The single factor test and response surface optimization were carried out with the vaccination volume and mixing ratio as variables and the protein degradation rate as indexes,which showed that the optimum fermentation condition for mixed bacteria was 1.98%with a ratio of 1.7:2.0,under which the protein degradation rate was 65.32%.Compared with the group without fermentation,ammonia nitrogen content was decreased by 51.05%and phosphate content was increased by 18.67%reapectively,the total biogenic amines content was 0.93 mg/L,which was significantly lower than that of other treatment groups(P<0.05).Meanwhile,amino acids were abundant,and the contents of indoleacetic acid-valine methyl ester,oxidized indoleacetic acid,indoleacetic acid-leucine and 3-indoleacetamide were increased,respectively.The sensory evaluation score was 80,indicating excellent odor acceptance.These results synthetically determined that the mixed fermentation potato juice after the optimized process had no effect on the field discharge.(4)Field test on drip irrigation volume of potato fermentation juiceIrrigation and planting experiment on special capsicum pepper in Ningnan was carried out with potato fermentation juice,which showed that the soluble sugar content of capsicum pepper was significantly increased by the usage of fermentation juice at 1000 kg/mu(P<0.05),the plant height,stem diameter,fresh weight above ground,fresh weight under ground,soluble solids and Vc content of Capsicum in different periods were significantly increased by the usage of fermentation juice at 1500 kg/mu(P<0.05),and nitrate content was markedly reduced by the usage of fermentation juice at 2000 kg/mu,compared with the control group.These results could provide reference for potato fermentation juice drip irrigation in field planting.