Sequential Downstream Process for Concurrent Extraction of Lutein, Phytol, and Biochemicals from Marine Microalgal Biomass as a Sustainable Biorefinery

Abstract

In view of achieving the multi-product biorefinery model, this study strategically valorized the microalgal biomass for simultaneous production of two high-value products, lutein and phytol, along with value-added biochemicals such as protein, lipid, and carbohydrate by employing a systematic sequential extraction process. This sequential downstream process was carried out in two steps; first, the extraction of total pigments (chlorophyll and carotenoid) from the Chlorella variabilis biomass using methanol, followed by saponification and phase separation, resulted in simultaneous separation of lutein and phytol with a purity of 95.3 ± 1.2 and 94.4 ± 2.2%, respectively. Second, the depigmented biomass was sequentially valorized for the extraction of major biochemical compounds. In this step, three strategies, namely, I, IV, and VI, which were employed to extract protein (67.5 ± 0.7% recovery), lipid (76.4 ± 4.2% recovery), and carbohydrate (54.6 ± 0.8% recovery), respectively, as the primary product were found to be optimal in terms of their maximum recovery. Further, the impact of different sequential extraction methods on the composition of amino acids, sugars, and lipids was discussed and the suitability of the extracted biochemicals was critically examined for their application as aquaculture feed, bioethanol, and biodiesel production, respectively. This study also emphasizes the energy consumption by different unit operations that can be major energy sinks. Thus, this study presents an approach to developing an efficient biorefinery model, in which the commercially important products from microbial biomass are sequentially valorized to improve the asset value for the biorefinery industry.