Antibacterial effects against pathogens of Vibrio genus using 5-aminolevulinic acid produced from recombinant Escherichia coli

Background: Vibrio genus comprises a group of notorious pathogens that cause diseases in aquatic animals, leading to a reduction in seafood production. With climate change, Vibrio spp. pose an increasingly severe threat to the growing aquaculture industry, thereby affecting global food production. This study explored the use of 5-aminolevulinic acid (5-ALA) as a biocompatible antibacterial agent due to the inducibility of antibacterial properties by light and in vivo conversion to photosensitizing protoporphyrin IX (PPIX). Methods: 5-ALA were produced by recombinant E. coli was introduced as a photodynamic therapy against three Vibrio strains; namely, Vibrio parahaemolyticus (Vp), Vibrio alginolyticus (Va), and Vibrio damsela (Vd). The effect of 5-ALA on the three Vibrio species was investigated at a neutral pH, considering various factors such as reaction time and concentration under both light and dark conditions. Significant findings: The antimicrobial photodynamic therapy (aPDT) utilizing 0.5 % (w/v) 5-ALA was effective against Vibrio sp. only at pH < 5.5. In a neutral pH environment and without light exposure, antimicrobial activity was still observed against V. alginolyticus and Vibrio parahaemolyticus when the concentration of 5-ALA was increased to 1 % and 2 %, respectively. The bactericidal effect was only 39 % for Vibrio damsela, indicating a slower biosynthesis of PPIX. Nonetheless, this also suggests the potential of 5-ALA as an in vitro antibacterial agent under acidic conditions. The bactericidal effect of crude and pure 5-ALA was found to be similar, indicating the potential of using cost-effective crude extracts as aPDT agent.