Comparison of Addition Mold and Yeast Inoculants on the Production of Citric Acid in Liquid and Solid Media from Sorghum

The aim of the study was to determine the production of citric acid in liquid and solid media made from the juice and bagasse of sorghum plant. Sorghum has a great potential to be utilized as fermentation substrate for production of citric acid. The production of citric acid by fermentation is influenced by several factors including the type of media and used microorganisms. Fermentation to produce citric acid can be done by using mold as well as yeast. In this study, the mold isolates were Beauveria bassiana and Paelomyces lilacinus, while the yeast isolates were Candida utilis and Candida lessepsii. The fungal fermentations were conducted in two phases of medium, liquid and solid. Three formulas were prepared for liquid fermentation, namely sorghum juice only, sorghum juice supplemented with NH₄NO₃ and micronutrients, and sorghum juice supplemented with asparagine and micronutrients. Two formulas were prepared for solid fermentation, sulfuric acid hydrolyzed sorghum bagasse and non-hydrolyzed sorghum bagasse. The results showed that citric acid yield in solid fermentation is lower than liquid fermentation. For all formulas, the citric acid formation through liquid fermentation was higher in yeast than in molds. On the other hand, for solid fermentation, citric acid production was higher in hydrolyzed media than non-hydrolyzed media, except for yeast Candida lessepsii.