High-Temperature Citric Acid Production from Sugar Cane Molasses using A Newly Isolated Thermotolerant Yeast Strain, Candida parapsilosis NH-3

Abstract

Citric acid is a commodity chemical mainly used as an acidulant in the food and beverage industry. In the present study, the potential use of sugar cane molasses as cheap agro-industrial waste carbon source for isolation and screening of citric acid producing microbes was investigated. Yeast isolates were obtained from soil samples, using serial dilution agar plating method and the most potent citric acid-producing isolate, coded NH-3, was identified based on macroscopic, microscopic and molecular characteristics. This strain was identified as Candida parapsilosis NH-3 and used for optimization of citric acid production using both classical and statistical methods. In classical method various parameters were investigated including: temperature, pH, molasses concentration, pre-treatment of molasses, nitrogen and phosphorus limitation and alcohol addition. Moreover, Plackett-Burman design was used for further optimization. In this assay, the maximum production of citric acid was obtained at temperature 40±1° C, pH 5.0, molasses concentration 30%, pre-treatment of molasses using EDTA, nitrogen and phosphorus limitation excluding dipotassium hydrogen phosphate, and alcohol addition of 1% methanol.