Cultivation Strategies to Improve <i>Chlamydomonas reinhardtii</i> Growth and Recombinant Mcherry Expression

Chlamydomonas reinhardtii is a promising model microalga for recombinant molecules production. Nonetheless, low yield is a challenge for its industrial use. This work investigated the influence of ammonium chloride (NH₄Cl) concentration and temperature on the growth of transgenic C. reinhardtii expressing the fluorescent protein mCherry on a laboratory scale. A Central Composite Rotatable Design was used to establish the cultivation conditions. NH₄Cl concentrations ranging from 400 to 647.49 mg/L and temperatures between 25°C and 32.1°C resulted in maximum values of cell concentration and mCherry fluorescence. Lower temperatures (15°C-17°C) were found to be more suitable for the accumulation of total soluble proteins. These results demonstrate that cultivation conditions can positively affect C. reinhardtii growth, with a range of conditions that can be used. Unlike genetic approaches, this study provides a solution to enhance both growth and recombinant protein expression in C. reinhardtii. These findings pave the way for scaling up the use of C. reinhardtii as a biofactory in industry and can be applied to other microalgal systems.