Influence of light irradiance and exposure duration on microalgal biomass valorisation using a solar simulator: An experimental and statistical modelling approach

This study investigates the combined effect of light irradiation (300, 475, and 650 W m −2 ) and exposure time (1.33–8.67 h) across three energy fluxes (3120, 6240, and 9360 kJ m −2 ), provided by a solar radiation simulator with a xenon lamp on the Chlorella vulgaris biomass concentration and composition in a two-step cultivation. Results showed that both light irradiance and exposure time affected the biomass concentration. The multiple linear regression (MLR) results indicated that increasing light irradiance and exposure time have a positive impact on microalgal growth, up to 546 W m −2 for light irradiance and 5.17 h for exposure time, beyond which the effects become detrimental to the cells. Higher energy flux values were associated with reduced biomass concentrations. The highest carbohydrate accumulation (16–17% DCW) was obtained with medium and high energy fluxes applied at high light irradiances, while the highest lipid content (17% DCW) was achieved at lower irradiances, 300 W m −2 . The protein content increased 26% under 300 W m −2 ; the highest carotenoid content increase was under 300 W m −2 after 8.67 h. The MLR analysis indicated that light irradiance initially did not impact carbohydrate accumulation, but beyond a certain threshold, it enhanced carbohydrate production. Principal component analysis (PCA) results suggested optimal lipid accumulation occurred under lower irradiance, longer exposure, and lower energy flux, while protein variation was greatest under low energy flux delivered at low and medium irradiances. Both PCA and MLR analyses suggest that additional operational factors may be influential. These findings highlight the importance of optimising energy flux conditions by adjusting light irradiance and exposure time to enhance microalgal biomass production and its biochemical profile. • Higher light irradiance and exposure time boost microalgal growth up to a limit. • Carbohydrate accumulation peaked with high irradiances (medium/high energy fluxes). • The greatest protein content variation was observed with low energy flux. • Optimal lipid accumulation occurred under lower irradiance and longer exposure. • Statistical analysis points to other influential factors beyond those tested.