Optimisation of a recombinant Hepatitis B vaccine through the cultivation and fermentation of Aspergillus Niger

[摘要] The development of non-replicating vaccines is an emerging option for safe, effectivevaccines, several of which contain virus-like particles (VLPs). Many recombinantexpression systems have been evaluated as hosts for VLP production for the preventionof infectious diseases. The filamentous fungi Aspergillus niger has emerged as apotential alternative expression system for cost effective VLP vaccine production.Hepatitis B surface antigen (HBsAg) was used as a model VLP product to benchmarkA. niger's production capacity with those of Saccharomyces cerevisiae, Pichia pastorisand Hansenula polymorpha. Bioprocessing strategies were used to optimise VLPproduction by recombinant A. niger in batch culture. In particular, the effect of theparameters culture temperature, inoculum concentration, agitation intensity, dissolvedoxygen (dO2) concentration and culture pH on biomass formation, morphology andVLP (HBsAg) production concentration was quantified. At an optimum agitation of100 rpm and optimum dO2 concentration of 50 %, HBsAg production levels wereincreased 9-fold compared to yields obtained in shakeflask cultivation. Highest HBsAgproduction levels of 3.6 mg.ℓculture-1 and 350 μg.gDW-1 were recorded, at a biomassconcentration of 10.5 gDW.ℓculture-1. These production levels compare favourable withthose obtained by other production systems under similar conditions. HBsAg VLPsmostly accumulated intracellularly, although under optimum bioreactor conditionssignificant HBsAg accumulation in the cytoplasm and culture supernatant was alsoobserved. The impact of these process parameters on VLP production and cellmorphology was attributed to environmental stress conditions. Volumetric biomass andHBsAg production levels were maximised under conditions of lowest environmentalstress, resulting in the most optimal small-pelleted morphology. These results indicate asubstantial potential for further engineering of the A. niger production system for thehigh level of intracellular and extracellular VLP production.

[发布机构] Stellenbosch University