Kinetic modeling of cell growth and value-added products accumulation of Thraustochytrium striatum

A kinetic mathematical model was developed, calibrated, and validated to describe the fermentation performance of a marine protist, Thraustochytrium striatum. This model consists of equations describing substrate consumption, cell growth, and the accumulation of two important intracellular products (lipids and astaxanthin). Moreover, the substrate inhibition and the consumption of product lipids were also considered in the model. After calibration, this model can describe the fermentation performance of T. striatum with high fidelity (R2 values greater than 0.92) over a broad concentration range of individual (glucose 2.5-50 g/L, cellobiose 2.5-10 g/L, and xylose 2.5-10 g/L) and mixed sugar substrates (glucose/cellobiose/xylose, 10.0/2.5/2.5 g/L and 18.0/ 4.0/4.0 g/L, respectively). Besides synthetic substrates, this model was also proven to be able to simulate the utilization of natural sugar substrates (i.e., glucose, xylose, and cellobiose) generated from the enzymatic hydrolysate of corn stover. However, the presence of toxic compounds in corn stover hydrolysate might have slightly deviated the model prediction, indicating further improvement of this model is needed when it comes to the simulation of natural sugar substrates containing toxic compounds. This model is anticipated to serve as a fundamental framework to simulate and predict the fermentation performance of marine protist for upscaled applications.