Biosynthesis and Characterization of PHA with Functional Groups by Pseudomonas oleovorans
Date Issued
2006
Date
2006
Author(s)
Ho, I-Ching
DOI
zh-TW
Abstract
Biosynthesis of biodegradable PHA (polyhydroxyalkanoate) using Pseudomonas oleovorans was investigated. Improve production of PHAs by regulating the culture conditions. PHAs with various side chain and physical properties were expected from carbon sources with functional group. Using sodium octanoate as carbon source, effect of concentration of carbon source, nitrogen source, and inorganic salts was examined. Cell growth and PHA accumulation were unfavorable with insufficient K2HPO2 and KH2PO4. High concentration of MgSO4 promoted cell growth but reduced PHA content. Considering DCW (dry cell weight) and PHA content, the optimal concentration of K2HPO4, MgSO4, and carbon source were 5.8 g/L, 0.4 g/L, and 48 mM, respectively. And the highest weight of PHA was obtained when C/N ratio (w/w) ranged between 3 and 5. To reduce the cost, non-related carbon sources were used and the results showed that non-related carbon sources were simply advantageous to cell growth. Among them, highest DCW and weight of PHA were attained with 2 g/L of glucose and 6 g/L of sodium octanoate. Fermentor cultivation was conducted by combining the above optimal culture condition. Feeding mixed carbon source of glucose and sodium octanoate once by the change of pH, weight of PHA was 1.996 g/L harvested from fermentor.
Four different carbon sources were dosed to introduce functional groups of PHAs in this work, and structure of every PHA was presented as follows. PHPV (poly-3-hydroxy-5-phenylvalerate) was produced when 5-phenylvaleric acid was dosed. PHA contained three species of saturated monomer and two species of monomer with double bond when linoleic acid was used as a sole carbon source. Copolymer with four species of saturated monomer and one unsaturated monomer was biosynthesized from oleic acid. Dosing 2-octenoic acid, the PHO-co-HC (poly-3- hydroxy-octanoate-co-3-hydroxycaproate) was obtained.
Structure, polymer form－blend or copolymer, and physical property of PHA varied with carbon sources and fermentation method. A random copolymer of PHA was supposed when sodium octanoate and undecylenic acid were used as mixed carbon source. Composition of PHA was not changed with accumulation or degradation of PHA. In addition, Tg and Tm were different according to composition of PHA. When main fermentation of sodium octanoate with nitrogen limitation and then feed of undecylenic acid was conducted, 1.257 g/L of PHO/ PHU blend was obtained. The PHA grown with mixture of undecylenic acid and 5-phenylvaleric acid was a blend of PHU and PHPV. Weight of PHA and ratio of unsaturated unit increased with dosage of undecylenic acid.
Subjects
官能基
聚羥基烷酯
食油假單胞桿菌
培養條件
混合碳源
functional group
polyhydroxyalkanoate
Pseudomonas oleovorans
culture condition
mixed carbon source
Type
thesis
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