Exploring the production of citric acid with Yarrowia lipolytica using corn wet milling products as alternative low-cost fermentation media

Abstract

The unconventional yeast Yarrowia lipolytica is known for its capability to synthesize different metabolites of industrial interest such as citric acid (CA). The numerous applications of CA trigger continuous research on improved production systems and substrates costs reduction. In this context, the present contribution explored the production of CA using chosen strains of Y. lipolytica in fermentation media formulated with low-cost and non-seasonal nutrient sources derived from the corn wet milling process, such as food grade corn syrups and corn steep liquor (CSL). Besides nutrient sources assay, the effect of carbon source concentration and C/N ratio was evaluated. In media formulated with high fructose syrup and CSL proper manipulation of the mentioned variables allowed attaining CA productions of up to 38 g/L in flasks culture. Moreover, the bioreactor scale-up allowed a 130%-increase in productivity and drastic fermentation time reduction. Overall, the combination of these low-cost nutrient sources of predictable composition derived from the corn processing industry that may be stored at room temperature seems attractive for CA production. The simplicity of the fermentation medium further makes it promising for higher-than-laboratory scale production of CA.