Development of a Cost-Effective Process for the Heterologous Production of SARS-CoV-2 Spike Receptor Binding Domain Using Pichia pastoris in Stirred-Tank Bioreactor

SARS-CoV-2 was identified as the pathogenic agent causing the COVID-19 pandemic. Among the proteins codified by this virus, the Spike protein is one of the most-external and -exposed. A fragment of the Spike protein, named the receptor binding domain (RBD), interacts with the ACE2 receptors of human cells, allowing the entrance of the viruses. RBD has been proposed as an interesting protein for the development of diagnosis tools, treatment, and prevention of the disease. In this work, a method for recombinant RBD production using Pichia pastoris as a cell factory in a stirred-tank bioreactor (SRTB) up to 7 L was developed. Using a basal saline medium with glycerol, methanol, and compressed air in a four-stage procedure, around 500 mg/L of the raw RBD produced by yeasts (yRBD) and 206 mg/L of purified (>95%) RBD were obtained. Thereby, the proposed method represents a feasible, simple, scalable, and inexpensive procedure for the obtention of RBD for diagnosis kits and vaccines' formulation.

Automated summary

SARS-CoV-2 is the pathogenic agent causing the COVID-19 pandemic. The Spike protein, an external and exposed protein encoded by this virus, interacts with the ACE2 receptors of human cells through a receptor binding domain (RBD), allowing virus entry. This study developed a method for producing recombinant RBD using Pichia pastoris in a stirred-tank bioreactor (SRTB) up to 7 L. By utilizing a four-stage procedure with a basic saline medium containing glycerol, methanol, and compressed air, approximately 500 mg/L of raw RBD and 206 mg/L of purified (>95%) RBD were successfully obtained. Therefore, this proposed method offers a feasible, simple, scalable, and cost-effective approach for obtaining RBD for diagnosis kits and vaccine formulation.