Growth and variation of cellular fatty acid composition of Escherichia coli as affected by supplementation of ethanol during submerged cultivation
| Autor: | Jui-Long Choiu, 邱瑞隆 |
|---|---|
| Rok vydání: | 2005 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 93 Two strains of Escherichia coli (BCRC 10675) and E. coli O157:H7 (BCRC 15374) were submerged cultivated with Tryptic soy broth (TSB) and TSB supplemented with 5% ethanol, respectively. During cultivation, broth turbidities and pH values were determined periodically. The growth rate shown by increase of turbidity for both cultures was retarded significantly by ethanol supplementation. The times transited from log phase to stationary phase were delayed 7 and 14 h for both cultures as affected by ethanol supplementation. When cultivated in TSB, broth pH values decreased from 7.18 to 5.96 in 5 and 6 h and increased to 6.02 in 9 h of incubation for E. coli and E. coli O157:H7, respectively. When cultivated with ethanol, broth pH values decreased from 7.19 to 5.54 and 5.63 in 12 and 20 h of incubation and increased to 5.62 and 5.76 in 17 and 26 h of incubation for the cultures correspondingly. In the log phase, decreases of broth pH value were closely related to increases of turbidity (growth). When the bacterial cells were respectively harvested from log and stationary phases and subjected to fatty acid extraction, methylation and gas chromatography equipped with HP-1 and Rtx-2330 columns for analysis and GC-MS equipped with HP-5 and Rtx-2330 column for identification, trans-9-octadecenoate (18:1, trans-9), five saturated fatty acids (SFAs), two cyclopropane fatty acids (CFAs) and four cis-unsaturated fatty acids (cUFAs) were detected. Under the conducted condition by using Rtx-2330 column, trans-9-octadecenoate (18:1, trans-9), cis-9-octadecenoate (18:1, ciss-9) and cis-11-octadecenoate (18:1, cis-11) could be resolved for quantitative quantification. As affected by ethanol supplementation for both cultures, in stationary phase, the higher trans-9-octadecenoate contents were observed in the cells harvested from TSB supplemented with 5% ethanol than the counterpart cells harvested from TSB. UFAs/SFAs ratios for the log-phase cells of E. coli and E. coli O157:H7 harvested from TSB and TSB supplemented with ethanol changed from 0.91 to 0.54 and from 0.87 to 0.59, respectively. CFAs contents were also higher in the cells harvested from TSB supplemented with ethanol. Those fatty acid variations due to supplementation of ethanol in the growing broth might result in necessary adaptation of membrane fluidity, permeability and mass transferring efficiency to achieve successful surviving growth under stress of ethanol. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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