| Naturally fermented pea sour paste is a pale yellow pulp formed by the natural fermentation of microorganisms after the peas have been ground into a pulp and left for a period of time.Vermicelli is a popular food both at home and abroad.There are many varieties of vermicelli,and mung bean starch products are the best.The quality of pea vermicelli is second only to that of mung bean vermicelli.Due to the high price of mung bean starch,most manufacturers use starch from peas and other legumes to produce vermicelli.The acid pulp separation method,a method of extracting starch by adding naturally fermented acid pulp and using microorganisms in the pulp,has been widely used in China and is the most traditional and common method in the production of pea vermicelli.The vermicelli processed by its separated starch is more transparent and elastic compared with the vermicelli prepared from starch processed by other separation methods.However,since pea sour pulp is the result of microbial interactions,it is easily affected by changes in the type of raw materials,temperature and other conditions and errors in operation,and the quality of the resulting pea starch varies greatly.Therefore,in this study,we used naturally fermented pea sour pulp to understand the diversity of bacterial and fungal communities,and isolated two bacterial strains with high flocculating starch activity from it using high-throughput sequencing technology.The best flocculating strain was selected to determine the flocculation characteristics of the fermentation broth through single-factor experiments and to briefly analyze the nature of its flocculating active substances,which will provide a theoretical basis and technical reference for the subsequent production of pea starch by sour pulp,and a theoretical reference for the further development of starch-specific flocculants and bio-modified starches.1.High-throughput sequencing analysis was performed on naturally fermented pea yogurt to understand the diversity of bacterial and fungal communities in it.At the phylum level,the thick-walled phylum accounted for 44.07% and the ascomycetes accounted for 99.32%,which were the most abundant phylum of bacteria and fungi in the naturally fermented pea sour pulp,respectively;at the genus level,the genus Lactobacillus accounted for 44.07% of bacteria and 99.30% of fungi,which were the most abundant genus in the naturally fermented pea sour pulp.2.Two strains with high flocculation activity on starch were isolated and screened from naturally fermented pea sour pulp by traditional plate separation method using flocculation rate as the index.The strain3 was identified as Lactobacillus fermentum and named as Lactobacillus fermentum FLL5429,while the strain 4 was Lactobacillus paracasei and named as Lactobacillus paracasei FLL4.3.The flocculation properties of Lactobacillus fermentum FLL5429 were investigated.The flocculation site analysis determined that Lactobacillus fermentum FLL5429 flocculation active component is its own extracellular secretion after fermentation,and the bacterium itself does not have flocculation activity;after that,a series of experiments through thermal stability analysis,enzyme inhibition experiments and infrared spectroscopy scan showed that the flocculation active material is most likely a kind of polysaccharide produced by the bacterium after culture.The flocculant was probably a polysaccharide produced by the bacterium through culture.4.Study of flocculation characteristics of the supernatant of Lactobacillus fermentum FLL5429 ferment broth after centrifugation.Through single-factor experiments,the flocculation rate was used as the index to finally determine that the supernatant of Lactobacillus fermentum FLL5429 fermentation broth had the best flocculation starch effect when the inoculum was 15%,the incubation temperature was 30 ? and the incubation was 48 h;and the presence of Ca2+ accelerated the flocculation. |
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