Utilisation of edible oils and GLA production by Mucor in the presence of acetate
| dc.contributor.advisor | Kock, J. L. F. | |
| dc.contributor.author | Badenhorst, Jacqueline | |
| dc.date.accessioned | 2017-10-18T08:59:41Z | |
| dc.date.available | 2017-10-18T08:59:41Z | |
| dc.date.issued | 1998-10 | |
| dc.description.abstract | English: Surveys launched across South Africa indicate that many frying establishments abuse their frying oils and fats during the frying process, resulting in degradation and concomitant production of potentially toxic oxidation products. Some of these compounds have been shown to be toxic to animals and in human in vitro studies. Consequently, strict regulations under the Foodstuffs, Cosmetics and Disinfectants Act, 1972 (Act 54 of 1972) were published on 16 August 1996. It is now an offense to use or sell used cooking oil or fat for human consumption containing high levels of these degradation products. Since frying establishments are not allowed to discard their used oils and fats by selling to the public for consumption or dumping into municipal drainage systems, it is important that these oils and fats are collected for re-use in another form. Consequently, the aim of this study was the biotransformation of used oil wastes (containing no toxic substances) to high value lipids containing gamma-linolenic acid (GLA). This polyunsaturated fatty acid is prescribed for the treatment of eczema. In order to achieve this, Mucor circinelloides f. circinelloides CBS 108.16 was first grown on 40 gil unused sunflower oil and, as expected, produced neutral lipids (NL) similar in fatty acyl composition to the original oil. The apparent repression of the Á6 fatty acid desaturation was partially reversed when cells were grown on oil (30 g/l) and sodium acetate (10 gil) as mixed substrates resulting in an increase in GLA content. Furthermore, a three-fold increase in oil substrate utilisation and doubling of biomass production to 19.1 gil occurred when sodium acetate was added to the oil substrate. When sodium acetate (10 gil) was added to a growth medium containing used cooking oil (UCO) similar results were obtained. This experimental procedure was repeated for seven additional Mucor strains and again the stimulatory effect of sodium acetate in combination with UCO was obvious. Next, the effect of different UCO concentrations in the presence of 10 g sodium acetatell on biomass and lipid production was investigated in Mucor circinelloides CBS 108.16. According to our results, a maximum biomass concentration of 48 gIl consisting of 82 % oil yielding about 35 g NUl and up to 900 mg GLNI was achieved. The addition of 30 g UCO/I in combination with 10 g sodium acetate/l proved to be the optimum UCO concentration in order to obtain maximum GLA yield. Similar results with this strain were obtained when UCO was replaced with fresh unused cooking oil. When these experiments were repeated with linseed oil and sodium acetate as sole carbon sources, much less GLA was produced (351 mg GLNI). According to bioreactor studies, the effects of sodium acetate addition can be attributed to the change in pH of the medium during cell growth in the presence and absence of acetate. In the absence of sodium acetate the pH decreased to 2.2, whereas in its presence it increased to about pH 8.0. During metabolism of sunflower oil in the presence of sodium acetate, the percentage of saturated fatty acids in the extracellular lipids increased, suggesting a higher specificity of the fungal lipase for unsaturated fatty acids. When the sodium acetate was omitted from the medium and the pH gradually increased according to a pH profile mimicking the natural increase in pH found in the medium containing sodium acetate, similar results as in the presence of sodium acetate were obtained. This observation indicated that the pH increase alone during cultivation was responsible for the increased sunflower oil utilisation, biomass and GLA production. | en_ZA |
| dc.description.abstract | Afrikaans: Opnames deur Suid-Afrika het getoon dat menige diepbraai-ondernemings hulle kookolies en vette misbruik, wat lei tot die afbraak daarvan asook gelyktydige produksie van potensiële toksiese oksidasie produkte. Daar is bewys dat van hierdie verbindings toksies is vir diere en in menslike in vitro studies. Gevolglik is streng regulasies gepubliseer op 16 Augustus 1996 onder die 1972 Akte van Voedings-, Skoonheids- en Ontsmettingsmiddele (Akte 54 van 1972). Dit is nou teen die wet om gebruikte olies en vette wat groot hoeveelhede van die afbraakprodukte bevat, te gebruik of te verkoop vir menslike gebruik. Aangesien diepbraai ondernemings nie ontslae mag raak van hul gebruikte olies en vette deur dit aan die publiek te verkoop vir gebruik of om dit in die munisipale dreinsisteme te gooi nie, is dit belangrik dat die olies en vette versamel word vir hergebruik in 'n ander vorm. Die doel van die studie was derhalwe om die gebruikte olie-afval (wat geen toksiese verbindings bevat nie) te biotransformeer na hoë waarde lipiede wat gammalinoleensuur (GLA) bevat. laasgenoemde polionversadigde vetsuur word voorgeskryf vir die behandeling van ekseem. Om die doel te bereik, is Mucor circinelloides f. circinelloides CBS 108.16 eerstens gegroei op 40 g ongebruikte sonneblomolieII, en soos verwag, het die neutrale lipiede (Nl) geproduseer 'n soortgelyke vetsuursamestelling gehad as die oorspronklike olie. Die oênskynlike onderdrukking van die fl,6 vetsuuronversadiging, is gedeeltelik opgehef toe die selle gegroei is op olie (30 g/l) en natrium-asetaat (10 g/l) as gemengde substraat en het gelei tot In toename in die GLA inhoud. Daar was verder 'n drie-voudige toename in die benutting van die oliesubstraat en 'n verdubbeling in biomassa produksie tot 19.1 g/l toe natrium-asetaat by die oliesubstraat gevoeg is. Soortgelyke resultate is verkry toe natrium-asetaat (10 gIl) by die groeimedium bevattende gebruikte kookolie (GKO) gevoeg is. Die eksperimentele prosedure is herhaal vir In verdere sewe stamme van Mucor en die stimulerende effek van natriumasetaat in kombinasie met GKO was weereens duidelik. Die effek van verskillende GKO konsentrasies, in die teenwoordigheid van 10 g natriumasetaat/ I, op biomassa en lipiedproduksie is vervolgens ondersoek in Mucor circinelloides CBS 108.16. Volgens ons resultate, is In maksimum biomassa konsentrasie van 48 gIl bestaande uit 82 % olie wat ongeveer 35 g NUl en tot 900 mg GLAII opgelewer het, bereik. Die byvoeging van 30 g GKO/I in kombinasie met 10 g natrium-asetaatll, was die optimum GKO konsentrasie om maksimum GLA te lewer. Soortgelyke resultate is verkry toe die GKO vervang is met ongebruikte kookolie. Toe die eksperimente herhaal is met lynsaadolie en natrium-asetaat as enigste koolstofbronne, is baie minder GLA geproduseer (351 mg GLAlI). Na aanleiding van bioreaktorstudies, kon die effek van natrium-asetaat byvoeging toegeskryf word aan die verandering in pH van die medium gedurende groei in die teenwoordigheid sowel as afwesigheid van asetaat. In die afwesigheid van natrium-asetaat, het die pH na 2.2 gedaal, terwyl dit tot ongeveer pH 8.0 in die teenwoordigheid van asetaat gestyg het. Gedurende die metabolisme van sonneblomolie in die teenwoordigheid van natrium-asetaat, het die persentasie versadigde vetsure in die ekstrasellulêre lipiede toegeneem, wat 'n aanduiding is dat die fungale lipases 'n hoër spesifisiteit vir onversadigde vetsure het. Toe geen natriumasetaat by die medium gevoeg is nie en die pH geleidelik verhoog is volgens 'n pH profiel wat die natuurlike styging in pH naboots soos in 'n natriumasetaat- bevattende medium, is soortgelyke resultate verkry as in die teenwoordigheid van natrium-asetaat. Hierdie waarneming het aangetoon dat die verhoging in pH gedurende kweking alleen verantwoordelik was vir die verhoogde sonneblomolie-benutting. biomassa- en GLA-produksie. | af |
| dc.identifier.uri | http://hdl.handle.net/11660/7298 | |
| dc.language.iso | en | en_ZA |
| dc.publisher | University of the Free State | en_ZA |
| dc.rights.holder | University of the Free State | en_ZA |
| dc.subject | Linolenic acid | en_ZA |
| dc.subject | Biotransformation (Metabolism) | en_ZA |
| dc.subject | Oils and fats, Edible -- Biotechnology | en_ZA |
| dc.subject | Thesis (Ph.D. (Microbiology and Biochemistry))--University of the Free State, 1998 | en_ZA |
| dc.title | Utilisation of edible oils and GLA production by Mucor in the presence of acetate | en_ZA |
| dc.type | Thesis | en_ZA |