Thesis (MSc (Microbiology))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Long chain omega-3 fatty acids such as eicosapentaenoic acid (EPA) are essential for the regulation of critical biological functions in humans and other mammals. Fish oil as the main dietary source of EPA holds several disadvantages and alternative sources and production processes such as microbial fermentation are increasingly being investigated. Therefore the aim of the first part of this study was to evaluate brewers’ spent grain (BSG) as substrate for the production of EPA by solid state fermentation with 29 fungal strains representing different Mortierella species. The effect of a 10% (w/w) linseed oil (LSO) supplement on EPA production was also studied. Consequently, fungal inoculated BSG was incubated at 22oC for three days to obtain optimal fungal growth, before the incubation temperature was lowered to 16oC for the following eight days. Cultures were then harvested and dried, followed by lipid extraction and analyses using gas chromatography. All the strains were found to produce EPA on BSG, while addition of the LSO improved the EPA yield of most strains. The strains which produced the highest levels of EPA on BSG supplemented with LSO were Mortierella antarctica Mo 67 and Mortierella epicladia Mo 101, which respectively produced 2.8 mg and 2.5 mg EPA per g of BSG. During the second part of the study eight Mortierella strains were used to study EPA production via solid state fermentation of sunflower press cake (SPC). Similar culture conditions and analytical methods were used as in the first part of the study. The effect of supplementing the SPC substrate with 10% (w/w) LSO was studied with regard to the supplement’s impact on EPA production and on the highly unsaturated fatty acid (HUFA) profile of the fermented substrate. Addition of LSO improved EPA yield of most strains on SPC, leading to a reduction in the average arachidonic acid (ARA):EPA ratio from 50.68 to 3.66. The ratio of HUFA to saturated and monoenoic fatty acids, was increased significantly (t=5.75, p=0.05) by the addition of LSO, with higher desaturation levels among the 20-carbon fatty acids. Addition of LSO also had a positive effect (r = 0.9291, p = 0.001) on the relative amount of long chain fatty acids (C≥20) produced. The strains which produced the highest levels of EPA on SPC supplemented with LSO were Mortierella alpina Mo 46 and Mortierella basiparvispora Mo 88, which produced 6.4 mg and 5.8 mg EPA per g of sunflower press cake, respectively. Fungi belonging to the genus Mortierella successfully converted LSO supplemented agro-processing wastes, such as BSG and SPC, to materials containing EPA, thereby adding value to these substrates. These EPA-enriched waste substrates could eventually find applications as animal or fish feed or as a source of EPA and other HUFA for the growing omega-3 market in the neutraceutical and therapeutics industry. / AFRIKAANSE OPSOMMING: Langketting omega-3 vetsure soos eikosapentaenoë suur (EPS) is noodsaaklik vir die regulasie van kritiese biologiese funksies in mense en ander soogdiere. Visolie, die mees belangrike EPS-bron in die dieet, hou verskeie nadele in en alternatiewe bronne sowel as produksie-prosesse, soos mikrobiologiese fermentasie, word dus toenemend ondersoek. Die doel van die eerste gedeelte van hierdie studie was dus om gebruikte brouersgraan (GBG) te ëvalueer as ‘n substraat vir die produksie van EPS deur soliede staat fermentasie met 29 fungus isolate wat verskillende Mortierella spesies verteenwoordig. Die uitwerking van byvoeging van 10% (m/m) lynsaadolie (LSO) op EPS-produksie is ook bepaal. Gevolglik is fungus-geïnokuleerde GBG vir drie dae by 22oC geïnkubeer om optimale fungusgroei te verkry, waarna die inkubasie temperatuur verlaag is na 16oC vir die volgende agt dae. Kulture is hierna ge-oes en gedroog, gevolg deur lipied ekstraksie en analise met behulp van gaschromatografie. Al die isolate het EPS geproduseer op die GBG substraat, terwyl byvoeging van LSO die EPS-opbrengs van die meeste isolate verbeter het. Die isolate wat die hoogste vlakke van EPS op GBG wat met LSO verryk is, geproduseer het, was Mortierella antarctica Mo 67 en Mortierella epicladia Mo 101, wat onderskeidelik 2.8 mg en 2.5 mg EPS per g GBG geproduseer het. Tydens die tweede gedeelte van die studie is agt Mortierella isolate gebruik om die produksie van EPS deur soliede staat fermentasie van sonneblom perskoek (SPK) te ondersoek. Kultuurtoestande en analitiese metodes soortgelyk aan die eerste gedeelte van die studie is gebruik. Die uitwerking van byvoeging van 10% LSO tot die SPK substraat is ondersoek met betrekking tot die impak van die byvoeging op EPS produksie asook op die profiel van hoogs onversadigde vetsure (HOVS) van die gefermenteerde substraat. Die byvoeging van LSO tot SPK het die EPS opbrengs van meeste isolate verbeter en het tot ‘n verlaging in die gemiddelde arachidoonsuur (ARS):EPS verhouding vanaf 50.69 tot 3.66 gelei. Die verhouding van HOVS tot versadigde en mono-onversadigde vetsure, is betekenisvol (t=5.75, p=0.05) verhoog deur die byvoeging van LSO, met hoër vlakke van onversadigheid onder die 20-koolstof vetsure. Byvoeging van LSO het ook ‘n positiewe uitwerking (r = 0.9291, p = 0.001) op die relatiewe aantal langketting vetsure (C≥20) gehad. Die isolate wat die hoogste vlakke van EPS geproduseer het op LSO-verrykte SPK, was Mortierella alpina Mo 46 en Mortierella basiparvispora Mo 88, wat onderskeidelik 6.4 mg en 5.8 mg EPS per g SPK geproduseer het. Fungi wat aan die genus Mortierella behoort, het LSO-verrykte agroprosesserings afvalprodukte, soos GBG en SPK, suksesvol omgeskakel na materiale wat EPS bevat, en sodoende waarde toegevoeg aan hierdie substrate. Die EPS-verrykte afvalsubstrate kan uiteindelik toepassings vind as diere- of visvoer of as bron van EPS of ander HOVS vir die groeiende omega-3 mark in die neutraseutiese en terapeutiese industrie.