Microbial oxidation of dodecane and tridecane into a,w-dicarboxylic acids using recombinant Yarrowia lipolytica

• Main Author: Diedericks, Danie
• Other Authors: Harrison, STL
• Format: Dissertation
• Language: English
• Published: University of Cape Town 2014
• Subjects: Bioprocess Engineering
• Online Access: http://hdl.handle.net/11427/5377

Includes bibliographical references (leaves 137-150). === a,w-Dicarboxylic acids are reactive intermediates, widely used as raw materials to synthesise products such as perfumes, hot-melting adhesives, engineering plastics and high quality lubricants. These acids can be obtained via chemical or biological routes by using various feedstocks such as linear alkanes. Linear alkanes are chemically inert; hence, the production of reactive products requires complex and sophisticated reactions catalysed by either catalysts or enzymes. However, simultaneous by-product formation on chemical synthesis increases production cost and limits commercial availability, preventing their widespread application. Biological routes alternatively, selectively transform linear alkanes into fatty and a,w-dicarboxylic acids. Linear alkanes, due to their relative abundance and increased availability, following the expansion of gas-to-liquid fuels technology, are viewed as prospective feedstocks for the microbial production of a,w-dicarboxylic acids. The commercialisation of the biological conversion of linear alkanes is constrained by the low turnover frequency of the cytochrome P450 hydroxylase complex responsible for catalysing the first and rate limiting step of the monoterminal and diterminal pathways. Low product yields may be caused by the further catabolism of a,w-dicarboxylic acids, through the ~-oxidation pathway into energy, carbon dioxide and water. To prevent this, metabolic engineering techniques can be applied to prevent ~-oxidation by disrupting the genes encoding the enzyme catalysing the first step in the~-oxidation pathway. The specific productivity of bioconversion can then be increased further by over-expressing the genes encoding the cytochrome P450 hydroxylase complex. Recombinant Yarrowia lipolytica strains TVN 497, TVN 499, TVN 501 and TVN 502 were developed in such a manner by the collaborating research group at the University of the Free State and made available for this research.