Metalloproteases are one of the most important hydrolytic enzymes used in the biopharmaceutical industry (Velez-Gomez et al., 2019). Serratiopeptidase (EC: 3.4.24.40), belonging to the metalloprotease family is an important member of therapeutic enzymes. Serratiopeptidase, reported to be derived from the non-pathogenic bacterium Serratia marcescens E-15, is a highly effective anti-inflammatory medication with diverse therapeutic applications (Bhagat et al., 2013, Sharma et al., 2021, Rouhani et al., 2023, Yi, 2023). It is widely used as medication in the Asian and European countries (Gopinath et al., 2020). Serratiopeptidase possesses remarkable characteristics that encompass its ability to reduce inflammation, combat the formation of biofilms, alleviate pain, reduce swelling, and facilitate the breakdown of fibrin. Moreover, due to its promising anti-inflammatory and mucolytic properties, serratiopeptidase has been proposed as a potential treatment for COVID-19 (Sharma et al., 2021).

Several research groups have reported purification and characterization of serratiopeptidase from different sources (Melchor-Moncada et al., 2024, Chander et al., 2021, Velez-Gomez et al., 2019). The purification involves ion exchange chromatography leading to purified enzyme having molecular weight in the range of 50–55 kDa through SDS-PAGE (Suma et al., 2020). Our group has previously reported potential isolates of Serratia marcescens from the tissues of Morus rubra and soil (Koul et al., 2021, Chander et al., 2021). A novel strain, Streptomyces hydrogenans var. MGS13, isolated from Koringa mangrove soil was employed to produce serratiopeptidase having highest activity at 37 °C and pH 9.0 (Nageswara et al., 2019).

To enhance the enzyme activity, researchers employed various methodologies for the enhancement of metabolites (Manhas et al., 2022, Yusuf et al., 2013). Badhe et al. (2009) studied and optimized different physicochemical parameters to achieve 27.36 IU/mL of serratiopeptidase activity as compared to 17.97 IU/mL from Serratia marcescens ATCC 13880. In another study, it was demonstrated that the optimization of fermentation conditions for Serratia marcescens VITSD2 with a significant increase in serratiopeptidase activity i.e. 2155 U/mL (Devi et al., 2014). Plackett-Burman design was used by Luthra et al. (2014) to achieve the highest serratiopeptidase production of 15,000 SPU/mL from Serratia marcescens. Bhargavi and Prakasham (2016) demonstrated that the optimization of media components using the Plackett-Burman design and a response surface methodological approach may lead to multifold serratiopeptidase activity enhancement.

Present work reports an attempt for purification and characterization of serratiopeptidase from the endophytic isolate Serratia marcescens MES-4 from Murus rubra. Further, in order to enhance the productivity, Taguchi orthogonal L16 (2^13) design was employed. To the best of our knowledge, this is the first report on the purification, characterization and enhanced productivity of serratiopeptidase from an endophyte of Morus rubra.