eng Oriental Scientific Publishing Company Biosciences Biotechnology Research Asia 0973-1245 2023-03-30 20 1 85 95 10.13005/bbra/3071 44475 article Rutwika S. Thete 1 Shahriar Roushani 2 Faiyaz K. Shaikh 1 Jyoti Kulkarni 1 Raghavendra HL 1 Centre for Biotechnology, Pravara Institute of Medical Sciences (Deemed to be University), Rahata Taluk, Ahmednagar District, Loni-413736, Maharashtra, India. Department of Microbiology, Dr. Balasaheb Vikhe Patil Rural Medical College, Pravara Institute of Medical Sciences (Deemed to be University), Rahata Taluk, Ahmednagar District, Loni-413736, Maharashtra, India. The present study aimed to identify protease inhibitors (PIs) with antimicrobial activity from  sirisa (Albizia lebbeck) seed protein extracts that may be a natural alternative to overcome multi-drug resistance, toxicity, and side effects of existing antimicrobial drugs. The crude PIs were extracted from seeds of A. lebbeck in 1% PVP and further partially purified by ammonium sulphate (NH₄)₂SO₄ fractionation. The total protein content was found to be high in 0-30 % (NH₄)₂SO₄  saturated protein fraction F₁ (7.3 ± 0.17 mg/ml). Reasonably high PI activity towards trypsin was observed in 60–90 % (NH₄)₂SO₄ saturated fraction F₃ assessed by the agar well diffusion method and in vitro solution assay. Electrophoretic profiling of proteins from the F₃ fraction showed nine bands on the gel with differential mobility. The presence of a zone of inhibition (ZOI) for different concentrations of F₃- 60–90 % (NH₄)₂SO₄ saturated PIs on agar plate demonstrated antimicrobial activity against E.coli, S. aureus, and P. aeruginosa with MIC values of 100 ± 5 µg/ml, 100 ± 4 µg/ml, and  90 ± 3 µg/ml respectively. Our results indicate that PIs from seeds of sirisa display potent antimicrobial activity against the tested microorganisms and could be investigated further in the future use in designing or formulating natural antimicrobial drugs to treat microbial infection-related diseases. https://www.biotech-asia.org/vol20no1/isolation-and-characterization-of-protease-inhibitors-with-antimicrobial-activity-from-sirisa-albizia-lebbeck-seed-protein-extract/ Albizia lebbeck; Ammonium sulphate fractionation; Antimicrobial agent; PIs; Sirisa