Thesis (MScEng (Process Engineering))--University of Stellenbosch, 2005. / The development of non-replicating vaccines is an emerging option for safe, effective
vaccines, several of which contain virus-like particles (VLPs). Many recombinant
expression systems have been evaluated as hosts for VLP production for the prevention
of infectious diseases. The filamentous fungi Aspergillus niger has emerged as a
potential alternative expression system for cost effective VLP vaccine production.
Hepatitis B surface antigen (HBsAg) was used as a model VLP product to benchmark
A. niger’s production capacity with those of Saccharomyces cerevisiae, Pichia pastoris
and Hansenula polymorpha. Bioprocessing strategies were used to optimise VLP
production by recombinant A. niger in batch culture. In particular, the effect of the
parameters culture temperature, inoculum concentration, agitation intensity, dissolved
oxygen (dO2) concentration and culture pH on biomass formation, morphology and
VLP (HBsAg) production concentration was quantified. At an optimum agitation of
100 rpm and optimum dO2 concentration of 50 %, HBsAg production levels were
increased 9-fold compared to yields obtained in shakeflask cultivation. Highest HBsAg
production levels of 3.6 mg.ℓculture
-1 and 350 μg.gDW
-1 were recorded, at a biomass
concentration of 10.5 gDW.ℓculture
-1. These production levels compare favourable with
those obtained by other production systems under similar conditions. HBsAg VLPs
mostly accumulated intracellularly, although under optimum bioreactor conditions
significant HBsAg accumulation in the cytoplasm and culture supernatant was also
observed. The impact of these process parameters on VLP production and cell
morphology was attributed to environmental stress conditions. Volumetric biomass and
HBsAg production levels were maximised under conditions of lowest environmental
stress, resulting in the most optimal small-pelleted morphology. These results indicate a
substantial potential for further engineering of the A. niger production system for the
high level of intracellular and extracellular VLP production.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/1698 |
| Date | 12 1900 |
| Creators | James, Emmanuel Robin |
| Contributors | Gorgens, J. F., Van Zyl, W. H., University of Stellenbosch. Faculty of Engineering. Dept. of Process Engineering. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Rights | University of Stellenbosch |
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