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The utilisation of oils in Saccharopolyspora erythraea cultures producing polyketides

Zormpaidis, Vassilios; (2000) The utilisation of oils in Saccharopolyspora erythraea cultures producing polyketides. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Actinomycetes are a very important group of bacteria for the pharmaceutical industry. They are responsible for the production of a vast array of secondary metabolites which are of great use to mankind. S. erythraea is a producer of erythromycin, a very powerful antibiotic used world-wide to combat many Gram-positive bacterial infections. In addition, some novel polyketides with a very high potential can be constructed by recombinant strains of the organism using a modified erythromycin biosynthetic pathway. Many industrial antibiotic fermentations use complex media where oils comprise a partial carbon source. This is because oils can lead to higher antibiotic yields and are cheaper compared to carbohydrates. The main problem of the use of oils is the level of residual oil at the end of a batch fermentation. The great similarities between the erythromycin biosynthetic pathway and the catabolic β-oxidation of fatty acids has led to a suggestion that oil-fed cultures of S. erythraea could yield high antibiotic titres. Oil utilisation in S. erythraea cultures was investigated in this project. S. erythraea was shown to be able to grow on oil complex media. Various initial rape seed oil concentrations were implemented to examine their effect on residual oil level. 23 g RSO / L proved to be the optimal concentration to start with, yielding a 43.5% oil utilisation. When the agitation rate was increased throughout the culture from 750 to 1500 rpm, oil utilisation reached 60.4%. Oxygen limitation seems to be a key factor in oil utilisation, however several other factors also influence the final level of residual oil. No fatty acid accumulation was observed in fermentations, however, oleic acid was the one of five fatty acid constituents of rape seed oil that was largely catabolised. It is not clear whether there is a preference of the organism towards oleic acid or that was seen just because the fatty acid is found in large quantities. Lipase activity was high in all cultures, indicating that there is little relation between lipase activity and oil utilisation. Lipase activity was clearly divided in two elements: a constitutive which is produced even when no oil is present in the medium and an inducible element which is produced after the addition of oil in the culture, to increase further the measured activity. Erythromycin production was enhanced when oil utilisation was improved; a 690% rise in antibiotic titre was seen in an increasing agitation rate culture compared to a similar culture at constant low stirrer speed.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: The utilisation of oils in Saccharopolyspora erythraea cultures producing polyketides
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
URI: https://discovery.ucl.ac.uk/id/eprint/10111210
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