Evaluation of the Thermal Processes on Changing the Phenotypic Characteristics of Escherichia Coli Strains From Ice Cream Compared to Non-Pasteurized Milk Publisher



Ranjbar M^{1, 2} ; Nedaeinia R³ ; Goli M^{2, 4} ; Shahi S⁴ Show Affiliations
Source: Fermentation Published:2022

Abstract

Escherichia coli (E. coli) is shocked by various temperature processes in milk, which forces the organism to make proteins as a result of changes in the synthesis of enzymes that might give the strain special characteristics. The purpose of this study was to investigate the effects of the heat shock factor on changing the results of biochemical and molecular tests among E. coli strains obtained from ice cream and non-pasteurized milk when compared to a reference strain from the American-type culture collection (ATCC) in order to determine the phenotypic variation caused by the temperature conditions of the manufacturing process. Furthermore, isolates with characteristics similar to E. coli were discovered, but they were not E. coli and caused some ambiguity. To test the E. coli contamination of traditional and industrial ice cream, 82 samples were chosen at random. SDS-PAGE and 16S rDNA sequencing were carried out, as well as phenotypic testing. Isolated strains did not exactly match the reference strain. The results of biochemical testing and protein analysis revealed that the isolates were diverse. Samples E. coli phenons were classified. In the electrophoresis, the ice cream strain had two protein bands in the 20.75 and 23.59 kDa ranges that were distinct from the reference strain. These isolates appear to experience alterations in enzyme characteristics and structural proteins as a result of being exposed to various temperature conditions, such as pasteurization and frigidity. When compared to the reference strain, the calculated similarity percentage of the elicited isolate varied from 60 to 70%. The electrophoretic patterns of E. coli isolated elicited from milk samples differed from E. coli isolated obtained from the ice cream. The distinctions were in the intensity or position of the bands. The results also revealed that when isolates are subjected to thermal stresses, they exhibit a pattern similar to that of ice cream isolates. These considerations are made because a change in protein composition might result in a change in biochemical features, resulting in uncertainty in its identification. Sequences revealed that the sequences were related to E. coli 16S rDNA, despite differences in phenotypic and electrophoretic features between the isolated bacteria and the reference strain E. coli ATCC 25922. Our findings revealed that 16S rDNA could potentially be used to instantly implement an appropriate preventive measure for the purpose of identifying this type of bacteria and avoid some ambiguity. © 2022 by the authors.