Production of PHA from bacteria and the associated influence factors

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Production of PHA from bacteria and the associated influence factors


Author: Lo, Kin-wang
Title: Production of PHA from bacteria and the associated influence factors
Degree: M.Sc.
Year: 2004
Subject: Hong Kong Polytechnic University -- Dissertations
Polymers -- Biodegradation
Industrial microbiology
Department: Dept. of Applied Biology and Chemical Technology
Pages: xi, 91 leaves : ill. (some col.) ; 30 cm
Language: English
InnoPac Record:
Abstract: Three types of PHA accumulation bacterial strains were considered in this study. Two of them, Sphaerotilus natans (S. natans) and 0B17 (Pseudomonas sp.) are wild type strains isolated from activated sludge. The remaining one is the recombinant E. Coli DH5a/pUC19 /CAB. Based on the growth characteristics, S. natans and 0B17 are the bacterial strains that require the limitation of an essential element for the synthesis of PHA. However, E. Coli does not require any limitation of nutrient for PHB accumulation. The effect of fatty acids, Ca2+ & Mg2+ and heavy metals (Cu2+, Mn2+, Ni2+, Cr3+, Pb2+, Zn2+) were investigated in this study. For S. natans, Recombinant E. Coli and 0B17, Oleic acid will enhance the PHB production with glucose as the carbon sources. Under the effect of Lauric acid and Linoleic acid, the growth of S. natans and 0B17 will be totally inhibited. However, enhancement in the PHB accumulation is observed in Recombinant E. Coli. Under the effect of Ca2+ and Mg2+, the PHB accumulation rate inside the three bacterial strains will be reduced. It indicates that Ca2+ and Mg2+ are not essential elements for the PHB production. For heavy metals, Cu2+ will inhibit the growth of the three bacterial strains considered. Mn2+ is found to enhance the PHB accumulation in S. natans. In addition, Cr3+ and Ni2+ (low concentration) will enhance the PHB accumulation in 0B17. For E. Coli, Mn2+ (low concentration), Cr3+ (high concentration) and Ni2+ (high concentration) will also enhance the PHB accumulation. Activated Sludges and Leachate were used as the production media for the three bacterial strains. The activated sludges were collected from Tai Po Sewage Treatment Plants and Yuen Long Sewage Treatment Plants. Leachate was collected from Jordan Valley. It is found that filtered Tai Po activated sludge is favour to the PHB production of S. natans. In addition, with oleic acid as nutrient supplement, the filtered Yuen Long activated sludge is favour to the PHB production of 0B17. For Leachate, the three bacterial strains are unable to accumulate significant amount PHB within the cell. While utilizating the wastes to produce PHA, the PHA accumulation process can also be used to remove the BOD and COD content of the filtered activated sludge. The present experiment indicates that there is 60- 70% COD removal.

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