Effects of Nitrogen Source on Proliferation of Transformed Hairy Root and Secondary Metabolite Production for Promoting the Performance of Mist Trickling Bioreactor
Date Issued
2004
Date
2004
Author(s)
Chou, Shih-Nung
DOI
zh-TW
Abstract
The transformed hairy roots induced by Agrobacterium rhizogenes can have several advantages, including highly genetic stability, high growth rate, cultivation without hormones and production of high value of secondary metabolites. In this work the transformed Stizolobium hassioo hairy roots was cultivated in 250 ml of shake flasks as well as in a 9 L of mist trickling bioreactor (MTB) for producing L-DOPA. To overcome the shortage of nitrogen source in the later stage of culture, the optimal dosage and feeding time of inorganic nitrogen source as well as other nutrients were investigated. This is aimed at the enhancement of hairy root proliferation and L-DOPA production. In addition, the effects of addition of organic nitrogen source have also been studied.
In the shake flask study, the optimum concentration of the inorganic source fed at a mid-term stage was a 2-fold dosage of (NH4)2SO4 and KNO3 to that of B5 basal medium. The highest L-DOPA concentration in the culture medium was obtained in this dosage. It was found that the sucrose during the culture medium was exhausted. The overall productivity of L-DOPA can be increased further if the above-mentioned concentration of ammonium sulfate together with 0.75% sucrose was dosed at the mid-term stage of culture. The dosage of 0.33M glycine in a mid-term stage of culture enhanced the total L-DOPA productivity, nevertheless, the dosage of 1.38mM of tyrosine did not.
In the MTB study, less inoculum density promoted the hairy root proliferation owing to the larger growing space. For nitrogen source supplementation by feeding a 2-fold B5 ammonium sulfate greatly influenced the pH, conductivity, redox potential and sucrose consumption rate of the medium. Throughout an observation by rH, it was elucidated that ammonium sulfate feeding would inhibit the metabolism of nitrate as well as the other oxidation reaction (e.g. carbon source metabolisms) which resulted in the predominance of oxidation reaction over reduction reaction and increased the rH. As concentration of ammonium ions decreased to a critical value, the metabolism of nitrate triggered. Consequently, other metabolisms of carbon source were retarded resulted in the decrease of rH.
Subjects
轉殖毛狀根
L-DOPA
氮源
噴霧滴流式生物反應器
Nitrogen source
Mist trickling bioreactor
Transformed hairy root
Type
thesis
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