Combined extraction methodology for simultaneous recovery of phycobiliproteins and agar from the red alga Gracilaria chilensis C. J. Bird, McLachlan & E. C. Oliveira

Abstract

The red alga Gracilaria chilensis C. J. Bird, McLachlan & E. C. Oliveira ( Agarophyton chilense Gurgel, J.N. Norris & Fredericq) is one of the few algae commercially farmed in Chile, where this alga is commonly named “Pelillo”. G. chilensis main by-product is agar, a gelling agent used in the food and pharmaceutical industries. This alga is also a valuable feedstock for the biorefinery of phycobiliproteins (PBPs), colored and fluorescent water-soluble proteins with industrial applications. This work aimed to valorize G. chilensis by sequentially extracting PBPs and agar. After freeze-thaw treatment, we successfully extracted two PBPs from alga: R-phycoerythrin (R-PE) and R-phycocyanin (R-PC). After two purification steps, we recovered 45 % of both PBPs (R-PE = 0.20 mg g −1 DW and R-PC = 0.23 mg·g −1 DW). After PBPs extraction, we successfully recovered agar from the residual algal matter. There were no significant differences between the physical parameters of agars obtained after PBP extraction and those from agars directly extracted from G. chilensis (melting and gelling temperature, and agar deformation). The agar yield after PBPs extraction was 24.9 ± 1.0 % and showed a gel strength of 726 ± 182.9 g·cm −2 , whereas agar directly extracted from alga yielded 23.1 ± 2.0 % with a gel strength of 730.5 ± 96.9 g·cm −2 . The agar obtained after PBPs extraction showed no inhibitory effects on microbial growth and allowed the effective separation of nucleic acids without agarose purification. Thereby, the method proposed in this work allowed the simultaneous extraction of PBPs and agar from G. chilensis . • The red seaweed Gracilaria chilensis ( Agarophyton chilense ) is a good source of phycobiliproteins and agar. • Phycobiliproteins are purified by salting-out and anion-exchange chromatography. • Purified phycobiliproteins (R-PE and R-PC) may be used in the food industry. • High-quality agar was successfully recovered from the residual algal matter after phycobiliproteins' extraction. • Agar extracted after phycobiliproteins' purification was useful for microbial growth and nucleic acid separation.