Influence of wavelength-specific light on growth, chlorophyll synthesis, fatty acid, and carbohydrate production in <i>Chlorella sorokiniana</i>

This study evaluates the effects of LED light wavelength on the growth, chlorophyll synthesis, and biochemical composition of Chlorella sorokiniana for carbohydrate-rich biomass production. Four light wavelengths, namely white (400–700 nm), red (620–750 nm), blue (450–495 nm), and green (495–570 nm) were tested under continuous illumination with 2% CO₂ aeration over 7 days. Green LED yielded the highest biomass, achieving an optical density (OD) of 2.311 and dry cell weight (DCW) of 1.625 g/L on day 7. Blue LED supported moderate biomass production (OD: 1.634; DCW: 1.505 g/L) but induced the highest chlorophyll- a (5.173 µg/mL on day 6) and chlorophyll- b (4.371 µg/mL on day 7), indicating enhanced photosynthetic activity. In contrast, red LED resulted in the lowest biomass (OD: 0.868; DCW: 0.410 g/L), suggesting limited physiological adaptation. Carbohydrate content peaked under blue LED (373.2 mg/L on day 3), followed by red (340.1 mg/L) and green (328.7 mg/L) on day 6. Fatty acid analysis showed that red LED promoted lipid accumulation, particularly palmitic acid (78.00 mg/L) and oleic acid (36.91 mg/L), but resulted in lower polyunsaturated fatty acid levels. In contrast, green LED supported a more balanced fatty acid profile, including linoleic acid (8.34 mg/L) and α-linolenic acid (7.24 mg/L). Overall, green LED was most effective for maximizing biomass and balanced biochemical output. Blue LED enhanced chlorophyll and carbohydrate synthesis, while red LED favored saturated and monounsaturated fatty acid production. These findings highlight the critical role of light wavelength in optimizing microalgal productivity, with potential implications for biofuel production, value-added bioproducts, and sustainable bioremediation.