Process development for fed-batch production of medium-chain-length poly(3-hydroxyalkanoate) from decanoic acid
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Authors
Gao, Jie
Date
2015-12-16
Type
thesis
Language
eng
Keyword
β-oxidation inhibition , Decanoic Acid , MCL-PHA , Poly-hydroxydecanoate , Fed-batch , Fermentation , Medium-chain-length Poly-3-hydroxyalkanoate , Pseudomonas putida
Alternative Title
Abstract
The main goal of the thesis is to develop strategies for the fed-batch production of medium-chain-length poly(3-hydroxyalkanoate) (MCL-PHA) by Pseudomonas putida KT2440 from decanoic acid (DA) co-feeding with glucose (G). Since decanoic acid is poorly water soluble and a solid at room temperature, two methods were tested to maintain it as a liquid by either mixing it with acetic acid (AA) or heating it to feed into the bioreactor. Exponentially feeding the carbon substrates at a ratio of 3:3:4 of DA:AA:G at a specific growth rate (µ) of 0.15 h-1 resulted in 26 g L-1 biomass containing 57% PHA. The final PHA composition was 74 mol% 3-hydroxydecanoate (3HD), 14 mol% 3-hydroxyoctanoate (3HO) and 12 mol% 3-hydroxyhexanoate (3HHx). As the ratio of DA:AA:G increased from 3:3:4 to 5:1:4, 50% higher biomass and 73% higher PHA were obtained. An even higher biomass concentration of 75 g L-1 containing 74% PHA was achieved by applying the same specific growth rate followed by constant substrate feeding strategy. Heating decanoic acid without acetic acid was performed as a control experiment at feeding ratio of DA:G (1:1) resulting in a final higher biomass of 41 g L-1 but containing only 58% PHA.
A fadB and fadA knockout mutant of P. putida KT2440 named P. putida DBA-F1was constructed to increase the fraction of the dominant monomer (3HD) in PHA by limiting the fatty acid β-oxidation activity. Using a feeding ratio of decanoic acid and acetic acid (DAA) to glucose (G) (6:4) at specific growth rate of 0.15 h-1, significantly different monomeric composition (97% 3HD:3% 3HO) but a lower biomass (8.5 g L-1) and PHA concentrations (3.5 g L-1) were obtained compared to the wild type. The performance could be improved at a feeding ratio of DAA:G of 2:8, leading to 18 g L-1 biomass containing 100% poly(3-hydroxydecanoate) (PHD). MCL-PHA with enriched 3HD monomers could also be obtained using acrylic acid (Aa) as a chemical inhibitor of the β-oxidation pathway by P. putida KT2440. At a ratio of DAA:G:Aa (6:4:0.2), 21 g L-1 MCL-PHA with 84 mol% 3HD was produced.
Description
Thesis (Master, Chemical Engineering) -- Queen's University, 2015-12-15 10:11:43.51
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Queen's University's Thesis/Dissertation Non-Exclusive License for Deposit to QSpace and Library and Archives Canada
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Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.
ProQuest PhD and Master's Theses International Dissemination Agreement
Intellectual Property Guidelines at Queen's University
Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.