Isolation Of Lactic Acid Bacteria From Quinoa Sour Liquid And Its Application In Quinoa Protein Seperation

Sour liquid producing method has long been the main traditional producing method for sweet potato starch,legume starch and bean vermicelli.Sour liquid method has the advantages of high production efficiency and low production cost without consumption of organic solvents,which can relief industrial wastewater problems caused by other production methods.In this paper,we purified and identified several strains of lactic acid bacteria from the initial acidic slurry.According to their acid-producing ability and flocculation rate of quinoa starch,SQL12(Enteroccus lactis)strain was identified for the preparation of quinoa sour liquid.The main conclusions described as follows:(1)23 bacterial strain isolated from quinoa sour liquid initially,16 strains of lactic acid bacteria were identified by morphological and physiological characteristics.4bacterial strains,SQL4,QSL8,QSL9 and QSL12,were selected for further study by comparing the acid-producing ability of each strain and combining with its flocculation rate of quinoa starch.(2)The above 4 strains were identified by molecular biology and 16S r DNA sequence was amplified by general primers.The results were as follows:QSL4 shares 100%similarity with Enteroccus faecium(accession numbers in Gene Bank:MZ452347.1);QSL8 is 98.41%similar to Enterococcus durans(accession numbers in Gene Bank:OM838419.1);QSL9 is 98.01%similar to standard strains of Enteroccus mundtii(accession numbers in Gene Bank:MT159629.1);QSL12 was 100%similar to the standard Enterococcus lactis strain(accession numbers in Gene Bank:CP084248.1).(3)The strain QSL12 was applied to the preparation of quinoa sour liquid.Firstly,single factor test was used to research the effects of the inoculated volume,ferment concentration and time of secondary precipitation and fermentation time on the quality of quinoa sour liquid.On this basis,the preparation process of sour liquid was further optimized by the orthogonal experiment.The final process conditions showed as follows:The concentration of the ferment liquid of first precipitation was 50 g/L,the inoculated volume 7%,30min for the first precipitation,26?for the fermentation temperature,the concentration of the ferment liquid of the second precipitation was 120 g/L,and 20 h for the second precipitation.Under this condition,the p H of quinoa sour liquid was 3.79,and the bacteria number is 1.54×10~9cfu/m L.(4)Sour liquid prepared by optimum process was used in the extraction of quinoa protein.The effects of ferment concentration,sour liquid addition,extraction time and temperature on quinoa protein extraction rate were studied.Based on the above conditions,the optimum extraction process of quinoa protein by sour liquid producing method was further optimized by response surface design experiment.The optimal process conditions were as follows:The ferment liquid concentration was 50 g/L,sour liquid addtion 9.5%,116 min for the extraction time,and 25?for extraction temperature,The actual value of quinoa protein extraction under these conditions was 62.19%.