Dilute sulfuric acid hydrolysis of Chlorella vulgaris biomass improves the multistage liquid-liquid extraction of lipids

Abstract

Chlorella spp. have been successfully cultured at commercial scale and show potential for the production of advanced biofuels. A current challenge in the downstream processing of Chlorella spp. is the sequential fractionation of whole biomass in different macromolecules such as lipids and carbohydrates. Herein, the biorefinery concept was used to evaluate the best sequence of extraction of carbohydrates and lipids of C. vulgaris. It is also important to develop biorefinery processes that produce green chemicals like ethanol because large volumes of solvents are required for lipid extraction. First, the extraction conditions were optimized to achieve maximum yields of carbohydrates and lipids separately. The extraction of carbohydrates was less complex than the multistage extraction of lipids from C. vulgaris. The use of ethanol and hexane mixture resulted in a lower extraction of lipids from C. vulgaris, even after 4 stages of extraction, and the final lipid content corresponded to only 65% of the lipids extracted with standard methods. Moreover, the multistage extraction of lipids did not improve the subsequent extraction of carbohydrates (lipids-carbohydrates route). However, the dilute sulfuric acid hydrolysis drastically improved the subsequent multistage extraction of lipids (carbohydrates-lipids route), and the lipid yield using this route was twice higher in comparison with the lipids-carbohydrates route. The hydrolysates obtained using the routes carbohydrates-lipids and lipids-carbohydrates showed levels of 2.6 ± 0.2 and 2.7 ± 0.1 g L−1 of total neutral carbohydrates, respectively. The different routes did not exert a great effect on the levels of inhibitors.