Filamentous fungi like Aspergillus niger are used as versatile and efficient cell-factories for the production of lipases and proteases, exopolysaccharides, nutrition additives, and therapeutic agents in many industrial bioprocesses. Although A. niger shows a high production capacity and secretion efficiency, and is capable of carrying out post-translational modifications, obtainable yields of recombinant proteins are considerably lower than those of homologous proteins. Besides improvement of productivity due to genetically modified strains, current research is focussed on the optimisation of cultivation processes resulting in an increased, controlled and tailored formation of desired products while avoiding by-products. The contribution displays the influence of pH-value, volumetric power input and inoculum concentration on the observed morphology and the formation of homologous recombinant β -fructofuranosidase under a constitutive promoter as model product. Batch cultivations are monitored starting with the germination of A. niger spores and ending with the stationary phase of growth. Every step of the protein formation path transcription, translation and secretion is shown: The expression of the β -fructofuranosidase gene as well as of genes, which show significant expression levels within the bioprocess, are quantified via real-time PCR. Intra- and extracellular enzyme activities are measured and related to gene expression levels and observed morphology, pellet size and concentration. Undesired by-products are analysed by HPLC. In conclusion, the protein formation in batch processes is linked to defined cultivation conditions to reveal bottlenecks within the complex production path from gene to product. Therefore the shown results indicate targets for improving, optimising and controlling industrial bioprocesses.
Full conference title:
10th EUROPEAN CONFERENCE ON FUNGAL GENETICS
- ECFG 10th (2010)