Isolation,Identification,and Biological Characteristics And Application Of Lactic Acid Bacteria Attached To Manihot Esculenta Crantz

To analyze the diversity of microorganisms on cassava(Manihot esculenta Crantz),the lactic acid bacteria with excellent biological characteristics were screened to enrich the lactic acid bacterial library of plant sources and to develop new cassava processing products with added value.Isolation,identification,and biological characteristics of lactic acid bacteria from cassava were studied in this paper.The main test results are as follows:1.The microorganisms on cassava stems,leaves,and rods were counted by different media,and 43 strains of lactic acid bacteria were screened from cassava leaves.Through colony observation,gram staining,microscopic examination,and catalase test,18 strains of typical lactic acid bacteria were selected.Six strains(HNC5,HNC6,HNC7,HNC13,HNC17,HNC18)with representative phenotypic characteristics were screened out after physiological and biochemical identification.These strains were identified as Lactobacillus plantarum by 16 S r DNA sequence analysis.2.To screen out the lactic acid bacteria with probiotic potential,the tolerance,surface hydrophobicity,self-agglutination ability,and antibacterial activity of the above six strains of lactic acid bacteria were measured.The results showed that strain HNC5 had the highest survival rate under simulated gastrointestinal conditions,with a viable count of 7.41 log CFU/m L,and strain HNC13 had the worst tolerance,but its viable bacteria count was still higher than 6.8 log CFU/m L.In the hydrophobicity test,strain HNC7,HNC17,and HNC18 had high hydrophobicity,while strain HNC5 had the worst hydrophobicity,which indicated that strain HNC5 might have the weakest adhesion ability to the intestinal tract.The six strains had good self-agglutination ability,and the strain HNC5 had the weakest self-agglutination ability among the six strains,and its self-agglutination rate was more than 50%.The six strains showed strong antibacterial activity against Escherichia coli,Salmonella,Staphylococcus aureus,and Listeria monocytogenes,and the fermentation products such as organic acid and hydrogen peroxide were the main factors for the antibacterial activity of lactic acid bacteria.Among the six strains,the strain HNC7 has stronger probiotic potential.3.Lactobacillus plantarum HNC7 and Lactobacillus paracasei YLC92 were used to produce cassava-acerola cherry fermented beverages.The optimum conditions for enzymatic hydrolysis of potato pulp were as follows: enzyme dosage of 100 U/g,enzymatic hydrolysis temperature of 85 ℃,and enzymatic hydrolysis time of 2 h.The optimal fermentation conditions were as follows: inoculation amount of 3%,fermentation time of 23 h,fermentation temperature of 37 ℃,and sensory score predicted value of90.578 points.4.Lactobacillus plantarum HNC7,Lactobacillus plantarum J1,and Lactobacillus paracasei YLC92 were used as fermentation strains to ferment cassava-acerola cherry juice,and the indexes in the fermentation process were detected.The results showed that the HNC7-YLC92 binary fermentation showed higher acidity,p H drop,and soluble solid consumption value.Lactic acid bacteria mainly consume fructose and glucose for fermentation to produce acid,in which the HNC7-YLC92 binary group has a strong capacity of lactate production and citric acid metabolism,and fermentation significantly improved the antioxidant capacity of the beverage and enriched the volatile substances in the beverage.