Abstract. Erviana R, Saengkun Y, Rungsa P, Jangpromma N, Mustofa, Daduang S. 2022. The recombinant expression and antimicrobial activity determination of Cecropin-like part of Heteroscorpine-1 from Heterometrus laoticus. Biodiversitas 23: 5646-5653. Antimicrobial peptides are promising novel antibiotics that hold great potential in combating bacteria, fungi, viruses, and parasites. Recent interest has increased in their potential as new pharmacological agents. Large quantities of antimicrobial peptides are required in order to fulfill the demand for the peptides for scientific research and clinical trials. Gene expression systems for antimicrobial peptides have been developed, which may be utilized efficiently for various antimicrobial peptide-related studies and applications. However, many expression systems that have been developed require many steps that impact the expression cost. This study established the fast and easy expression system of recombinant Cecropin-like part of Heteroscorpine-1 (CeHS-1) and determined their activity. The gene was chemically synthesized, ligated to the expression vector pET32a, transformed to Escherichia coli BL21 (DE3) pLysS competent cell, and induced by 0.2 mM isopropyl ?-D-1-thiogalactopyranoside. The induction time optimization determined that the 3 hrs induction resulted in the highest peptides yield. The prolonged induction would decrease the peptides yield due to the toxicity of the peptides toward the host cells. The peptide purification was facilitated by His tag sequence through purifying the affinity chromatographic column of Ni-NTA. The induction was able to express the expected peptides in the soluble fraction. The antimicrobial activity assay showed that the recombinant peptides could inhibit the growth of many bacterial strains. However, their activity was lower compared to the synthetic peptides. This finding demonstrated that the developed expression system in this study might facilitate the easy and feasible expression system for CeHS-1. Additionally, the study revealed that the antimicrobial activity of the expressed peptides could be preserved.