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ndltd-OhioLink-oai-etd.ohiolink.edu-akron12366898242021-08-03T05:25:56Z Rhamnolipid Production with Denitrifying Pseudomonas Aeruginosa Chen, Chun Chiang Rhamnolipids causes severe foaming during its production by conventional aerobic fermentation of Pseudomonas aeruginosa. This problem necessitates the reduction of aeration, which in turn limits the cell concentration employable and productivity achievable in the process. As a continual work to the previous study conducted by Chayabutra and Ju [162], a mixed-mode operation of aerobic and anaerobic fermentation was examined for its potential to minimize foaming and for its related problems when implemented rhamnolipid production. The key factors investigated in this study included: [1] the method for nitrate delivery that would minimize the inhibitory or toxic effects of high nitrate concentration on cell metabolism; [2] the phosphorous supplementation to maintain specific rhamnolipid productivity while cells were still growing; and [3] the effects of quorum sensing systems, a nature population control mechanism, on cell growth and rhamnolipid production. It was found that in the micro-aerobic process, amixed solution of sodium nitrate and nitric acid could be used to meet cell respiration needs and support cell growth to a relatively high concentration (> 10 g/L). A 5-fold increase in cell concentration was achieved in this study when compared to the typical aerobic fermentation. According to the results from the phosphorous-limiting continuous cultureconducted in the study, high specific rhamnolipid productivity could be maintained when the specific cell growth rate was lower than 0.08 (h-1). It was also observed that, an early onset of stationary phase took place in the P. aeruginosa culture when there was no apparent nutrient limitation. The phenomenon was attributed to the effect of quorum-sensing systems of the bacterium. The rhl quorum-sensing system (involving rhlR and rhlI genes) was known to regulate cell growth and rhamnolipid production. The degradation and synthesis kinetics of the rhlI gene-derived product, an autoinducer, were therefore evaluated in this study. The autoinducer was found to be unstable in the fermentation broth and its degradation could be empirically described with a first-order decay kinetics. To maintain the maximal rhamnolipid productivity, at least 13% of the peak autoinducer concentration (v/v) needs to be added in the fermentation broth in the beginning. The micro-aerobic rhamnolipid fermentation overcomes foaming problem, that retards the productivity achievable and market applicables. The autoinducer degradation and synthesis kinetics could have a medicinal application through the development of a stable autoinducer analogue to control the population of P. aeruginosa that could cause death rate in the hospitals. 2006 English text University of Akron / OhioLINK http://rave.ohiolink.edu/etdc/view?acc_num=akron1236689824 http://rave.ohiolink.edu/etdc/view?acc_num=akron1236689824 unrestricted This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.
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NDLTD
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| language |
English
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NDLTD
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| author |
Chen, Chun Chiang
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| spellingShingle |
Chen, Chun Chiang
Rhamnolipid Production with Denitrifying Pseudomonas Aeruginosa
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| author_facet |
Chen, Chun Chiang
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| author_sort |
Chen, Chun Chiang
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| title |
Rhamnolipid Production with Denitrifying Pseudomonas Aeruginosa
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| title_short |
Rhamnolipid Production with Denitrifying Pseudomonas Aeruginosa
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| title_full |
Rhamnolipid Production with Denitrifying Pseudomonas Aeruginosa
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| title_fullStr |
Rhamnolipid Production with Denitrifying Pseudomonas Aeruginosa
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| title_full_unstemmed |
Rhamnolipid Production with Denitrifying Pseudomonas Aeruginosa
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| title_sort |
rhamnolipid production with denitrifying pseudomonas aeruginosa
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| publisher |
University of Akron / OhioLINK
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| publishDate |
2006
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| url |
http://rave.ohiolink.edu/etdc/view?acc_num=akron1236689824
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| work_keys_str_mv |
AT chenchunchiang rhamnolipidproductionwithdenitrifyingpseudomonasaeruginosa
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| _version_ |
1719419989026406400
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