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The corona virus disease 2019 (COVID-19) pandemic has become a global health emergency. The spike protein (S-protein) of SARS-CoV-2, consisting of S1 and S2 subunits, is critical to receptor recognition and virus-cell fusion. SARS-CoV-2 binds to host cell receptors via the receptor-binding domain (RBD) of S1, which induces the formation of 6-helical bundle (6-HB) between the two heptad repeats (HRs) in S2, namely HR1 and HR2, and the consequential conformational change of S2, which facilitates the virus-membrane fusion. In December 2020, several effective SARS-CoV-2 vaccines were authorized. However, the emergence of new SARS-CoV-2 strains attenuates the effi cacy of vaccines and neutralization antibodies. (1,2) Reduning Injection (热毒宁注射液, RDN), a p p r o v e d b y t h e C h i n e s e F o o d a n d D r u g Administration in 2005, is a Chinese medicine (CM) prepared from Lonicerae Japonicae Flos, Artemisiae Annuae Herba, and Gardeniae Fructus. CM has

BackgroundHuman lysozyme (hLYZ), an emerging antibacterial agent, has extensive application in the food and pharmaceutical industries. However, the source of hLYZ is particularly limited.ResultsTo achieve highly efficient expression and secretion of hLYZ in Pichia pastoris, multiple strategies including G418 sulfate screening, signal sequence optimization, vacuolar sorting receptor VPS10 disruption, and chaperones/transcription factors co‐expression were applied. The maximal enzyme activity of extracellular hLYZ in a shaking flask was 81,600 ± 5230 U mL−1, which was about five times of original strain. To further reduce the cost, the optimal medium RDMY was developed and the highest hLYZ activity reached 352,000 ± 16,696.5 U mL−1 in a 5 L fermenter.ConclusionThis research provides a very useful and cost‐effective approach for the hLYZ production in P. pastoris and can also be applied to the production of other recombinant proteins.

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