Antimicrobial Activity of Pseudomonas fluorescens and Bacillus subtilis on Different Dilution Concentrations Against Various Citrus Post-Harvest Pathogens

Abstract

Pseudomonas flourescens and Bacillus subtilis are common antagonistic bacteria to various pathogens. These bacteria can produce various antimicrobial substances such as chitinase, siderophore, and antibiotic. This research aims to obtain the optimum dilution concentrations of Pseudomonas flourescens and Bacillus subtilis that can effectively inhibit the growth of Penicillium digitatum, P. paradoxum, and Aspergillus sp. This research was carried out in a complete randomized design with five different dilution concentrations of Pseudomonas flourescens and Bacillus subtilis ranging from 10 to 10. The antimicrobial activity tests against fungal pathogens were carried out in triplicate using a dual culture method. P. flourescens and B. subtilis displayed strong antimicrobial activities against all target pathogens. The highest inhibition activity of P. flourescens and B. subtilis was recorded against Aspergillus sp. with 45.7 % and 35.92 % and cell density of 168 x 10 CFU/mL and 14 x 10 CFU/mL, respectively. The highest antimicrobial activity was recorded at the 10 and 10 for P. flourescens and B. subtilis, respectively. The antimicrobial activity of P.flourescens and B.subtilis against P. digitatum and P. paradoxum are ranging from 17.59 % to 27.73 %.