Improvement of the production of biomass and lipid by Papiliotrema laurentii combining flux balance analysis and central composite rotational design

The growing demand for oleochemicals, currently derived from edible oils, raises sustainability concerns due to competition for agricultural resources. Oleaginous yeasts are an alternative oil source. Among them, Papiliotrema laurentii stands out due to rapid lipid accumulation and high lipid contents. Nonetheless, the biomass and lipid titers by this yeast are low in the culture media used for oleaginous yeasts. Herein, we combined Flux Balance Analysis (FBA) and Central Composite Rotational Design (CCRD) to identify carbon and nitrogen sources that favour both biomass and lipid production by P. laurentii. Based on biomass yield predicted by FBA, we identified lactose and urea as suitable carbon and nitrogen sources, respectively. We also used a CCRD to evaluate the effects of carbon-to-nitrogen (C:N) ratio, volumetric oxygen mass transfer coefficient (kLa), and inoculum on biomass and lipid production. Optimal conditions for biomass production were: initial OD600 of 0.8, a C:N ratio of 63:1, and a kLa of 28.41 h−1, yielding 10.82 g/L of biomass. For lipid titer, optimal conditions were: initial OD600 of 0.1, a C:N ratio of 100:1, and a kLa of 28.41 h−1, resulting in 3.48 g/L of lipids. Bioreactor cultivations showed that increasing kLa to 49.42 h−1 significantly enhanced both lipid content and titer. Under optimized conditions, increases of 691% in biomass and 815% lipid titer were recorded. Thus, this is the first study systematically optimizing cultivation conditions of P. laurentii combining FBA and CCRD.