FIGURE 1.

Scheme of enhancing mechanisms of chemicals on microalgae. The major stimulatory mechanisms were indicted inside the cell. (I) Chemicals targeting on biosynthetic pathways of high-value product, such as JA, SA, GA, and EBR controlling the overall carotenogenesis process in H. pluvialis; (II) Chemicals inducing oxidative stress responses, including direct or indirect addition of active oxygen species and chemical triggers inducing antioxidant production; (III) Phytohormones and analogs effecting on photosynthetic efficiency, namely the light phase, including photosynthetic phosphorylation, photosynthetic rate, and chlorophylls synthesis; (IV) Phytohormones and analogs impacting CO₂ fixation, namely the dark phase of photosynthesis, such as diamines and polyamines stimulating production of Calvin cycle; (V) Phytohormones and analogs encompassed acid growth theory, alternating the plasticity of cell wall thus contributing to cell elongation; (VI) Degradation of photosynthetic pigments due to large amount of ethylene caused by high concentration of auxins; (VII) Phytohormones and analogs regulating genome and protein expression, such as IM modulating DNA and protein content in C. vulgaris; (VIII) Chemicals as metabolic precursors, such as pyruvate serving as a precursor of carotenoid synthesis thus stimulating the formation of astaxanthin and NADPH (led by malic acid) acting as a precursor of fatty acid synthesis increasing DHA content.