Factorial Optimization of Media Composition and Fermentation Conditions for Improved Novel Antimicrobial Compound Production by Geotrichum candidum OMON-1

Abstract

This study investigated the optimization of fermentation conditions to enhance the production of the antimicrobial compound GP-2B by Geotrichum candidum OMON-1 using a two-level factorial design. A resolution IV 1/8th factorial design was employed to evaluate the effects of sodium chloride, agitation, tryptone, pH, dextrose, dipotassium hydrogen phosphate, peptone, and fermenter volume on GP-2B production. Randomized experiments were conducted, and antimicrobial activity was determined using the agar well-diffusion method against Staphylococcus aureus. The highest antimicrobial activity (21 mm) was achieved under optimized conditions: low pH (5.5), dextrose (2 g/L), dipotassium hydrogen phosphate (2 g/L), fermenter volume (40%), and high peptone (8 g/L), tryptone (25 g/L), sodium chloride (25 g/L), and agitation (150 rpm). Analysis of variance (ANOVA) and a half-normal plot identified tryptone (48.04%), tryptone-agitation interaction (19.85%), dextrose (-1.75; 12.01%), and pH (8.82%) as significant factors influencing fermentation. Tryptone had the most positive effect (+3.5), while dextrose had the most detrimental effect (-1.75). A curved 3D response surface plot was generated to visualize the optimization process. GP-2B produced under optimized conditions exhibited higher antimicrobial activity (28 mm) compared to non-optimized conditions (19.5 mm). This study demonstrates the effectiveness of a two-factorial design in improving GP-2B production and identifying critical factors in the fermentation process. The findings highlight the potential of statistical optimization for enhancing antimicrobial compound production in industrial applications.