Utilization of whey-based growth media for production of recombinant papain-like protease of SARS- CoV-2 under Escherichia coli host cells

Abstract

Abstract The Papain-like protease (Plpro) of the SARS-CoV-2 virus represents a potential therapeutic target for combating Coronavirus Disease 2019 (COVID-19). Due to its practicality and cost-effectiveness, recombinant production of Plpro is conventionally achieved through Escherichia coli. However, this process’s synthetic Luria-Bertani (LB) medium remains economically burdensome. This study explores the feasibility of substituting LB medium with whey, a by-product of cheese processing renowned for its rich nutritional profile. Employing whey as an alternative growth medium for E. coli, the study investigates various whey concentrations obtained from homemade cheese production. Pre-cultured E. coli BL21(DE3) cells hosting the Plpro expression system were initially cultivated in LB broth before being transferred to a medium containing different ratios of LB and whey. The expression of Plpro was induced with one mM isoprophyl-β-d-thiogalactosidase (IPTG) when the cells reached an OD of 0.5-0.6. Intriguingly, the cells grown in a 50% whey + 50% LB medium exhibited a faster OD increase than other media compositions. Subsequent SDS-Page analysis confirmed Plpro expression post-IPTG induction, with optimal expression observed in the 50% whey medium. These findings suggest that a 50% whey medium is optimal for the cost-effective production of recombinant Plpro.