Specific uptake kinetics of glucose and nitrate in carbon-limited and nitrogen-limited C:N ratio under photoheterotrophic cultural conditions for Botryococcus brauniigrowth and lipid production

Abstract

Carbon and nitrogen are the most significant parameters for microalgal growth and an effective C:N ratio is critical to assess the biomass and lipid productivities of Botryococcus braunii. In this study, the effect of the C:N ratio on specific uptake kinetics of glucose and nitrate was evaluated using substrate kinetic equation, under glucose limited and nitrate limited photoheterotrophic conditions. In glucose limited conditions, the maximum specific growth rate, biomass and lipid productivity of 0.0873 h−1, 1.11 g L−1 d−1 and 0.390 g L−1 d−1 were observed respectively for C:N ratio of 29:1. Maximum specific nitrate uptake rate of 0.190 mM gb−1 h−1 was observed under glucose limited C:N ratio of 61:1 (i.e. carbon sufficient), while the maximum glucose uptake rate of 0.74 mM gb−1 h−1 was observed in nitrate limited C:N ratio of 13:1 (i.e. nitrogen sufficient). This suggests that carbon and nitrogen metabolism is linked together and significantly affects the specific uptake kinetics of the each other.