Supporting the diagnostics industry
A better quality of life through better healthcare for the bottom billions can be facilitated by development of affordable diagnostics. However, diagnostics developed in this country still rely heavily on imported components such as membranes and bio-reagents. To address this limitation, the key objective of this project is to improve the efficiency of bio-reagent production using the latest bioprocessing strategies available and concurrently develop local manufacturing capabilities. Efforts in this project will support the local diagnostic industry in terms of sustainability and reduce the impact of supply chain disruption that could occur especially in event of a pandemic. The first bio-reagent selected for development was streptavidin, a key component to many diagnostic platforms.
An intensified process was developed that enables high level production of recombinant core streptavidin (cSAV), a non-glycosylated tetrameric protein utilised in a wide range of applications. A pH-stat fed-batch feeding strategy was employed to achieve high-cell-density and improve volumetric yield of cSAV which was expressed as inclusion bodies (IBs). The effect of induction at different cell densities (OD 20, 60 and 100) on volumetric and specific yield were then studied. Highest volumetric yield of cSAV (1550 mg L−1) was obtained from induction at OD 100 without significant reductions in specific yield. To recover active cSAV from IBs, the possibility of refolding using a temperature-based refolding method was investigated. Refolded cSAV obtained from temperature-based refolding were then compared against cSAV refolded with conventional dialysis anddilution methods using quantitative and qualitative metrics. The temperature-based refolding method was found to improve the yield of cSAV by 6–18% in comparison to conventional methods without compromising quality. Intensification was achieved by reductions in process volumes and a more concentrated product stream. Using the newly developed process, the volumetric yield of cSAV IBs was improved by thirty-six fold in comparison to low-cell-density shake flask cultivation, and 33% of cSAV can be recovered from IBs at 90% purity.