Development of a microwave-assisted solvent extraction process for the extraction of high-value carotenoids from Chlorella biomass

The commercial production of carotenoids as bioactive commodities from microalgae has been severely limited due to the nature of the microalgal outer cell matrix. Microwave technology offers a rapid method for obtaining larger amounts of these biochemical compounds. The process facilitates cell-wall rupture, releasing the inner cell components. Chlorella biomass, raised in an outdoor raceway pond, is used for downstream extraction of carotenoids by following the microwave-assisted solvent extraction (MAE) approach. The response surface modeling (RSM) strategy was employed to optimize the two independent parameters, power and extraction time, with a two-level central composite design (CCD). Acetone, hexane, methanol, hexane : acetone (1:1), hexane : ethanol (7:3) were used as solvents of choice. Acetone gave a total carotenoid yield of 0.061 +/- 0.003 mg gm(-1) under optimum microwave power and time; 130 W and 1.69 min. The optimized yield from hexane was 0.00173 +/- 0.005 mg gm(-1) with an exposure time of 1 min to 100 W. The total carotenoid yield of the methanol-based extraction batch was 0.0371 +/- 0.004 mg gm(-1) with 157 W and 1 min of extraction time. The solvent mixtures of hexane : acetone gave 0.0398 +/- 0.002 mg gm(-1) (185 W for 1.7 min) and hexane : ethanol gave 0.0383 +/- 0.004 mg gm(-1) (195 W, 1.6 min), respectively. The results indicate a satisfactory outcome to the process. They also show microwave-based extraction to be a fast, economic, reproducible, and repeatable method in comparison with the conventional strategies used for recovering the sensitive natural pigments. (c) 2021 Society of Chemical Industry and John Wiley & Sons, Ltd

Automated summary

Microwave-assisted solvent extraction is an effective method for obtaining higher carotenoid yields from microalgae. Acetone is shown to be the optimal solvent under the optimized microwave power and time settings. This approach is fast, cost-effective, and reproducible compared to traditional extraction methods.