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.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/4500 |
| Date | 03 1900 |
| Creators | Jacobs, Annali |
| Contributors | Botha, A., Van Zyl, W. H., University of Stellenbosch. Faculty of Science. Dept. of Microbiology. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 105 p. : ill. |
| Rights | Stellenbosch University |
Page generated in 0.0021 seconds