Fig. 1

Carbon metabolism and energy conversion in glycolysis, CBB and TCA. In carbon fixation of microalgae, the metabolic engineering is traditionally focused on efficiency of CBB cycle and light reactions in chloroplast (i and ii). Advances have noticed that engineering TCA cycle increases the carbon fixation (iii and iv). Coupling carbon and energy fluxes have proposed as the trends of metabolic engineering in microalgae (v). The traditional technology based on cellular physiology focuses on conditions of CO₂, light and nutrient in microalgae cultivation. The carbon metabolites: G3P glyceraldehyde-3-phosphate, PYR pyruvate, PEP phosphoenolpyruvate, OAA oxaloacetate, MAL malate, FUM fumarate, SSA succinyl semialdehyde, SUC succinate, 2OG 2-oxoglutarate, CIT citrate, G3P glyceraldehyde 3-phosphate