Precipitation and characterization of Pacific dulse (Devaleraea mollis) proteins

Previous work on Pacific dulse (Devaleraea mollis), a fast-growing protein-rich red algae, revealed that protein recovery can be significantly improved with cellulase pretreatment and sequential extraction approach. Since solubilized protein fractions need to be precipitated out of solution for enrichment and pellet recovery for downstream applications, this study aimed to evaluate the effects of precipitation strategies on macroalgal protein yield. Extracted protein fractions were precipitated using trichloroacetic acid (TCA) or pH-shift method (HCl/NaOH), and protein concentrations were assessed using three quantification methods, namely modified Lowry, Dumas, and total amino acid analysis (TAA). Specific to each Osborne fraction (albumin, globulin, glutelin and prolamin), the pH-shift precipitation approach was optimized in consideration to the amount of protein pellet recovered, protein retained in supernatant, and volume of acid required for pH adjustment. This work shows that the optimized pH-shift method has competitive yield compared to that of TCA precipitation. Ethanol wash post-pellet collection improved purity of the freeze-dried powders in both precipitation approaches but had more pronounced effects to TCA pellets. This then suggests that a single step precipitation using the optimized pH-shift method can be employed as a food-grade method in the recovery of extracted Pacific dulse proteins. Overall, this work provides a pioneering insight on the recovery of Pacific dulse protein using a pH-shift approach, and how three protein quantification methods were streamlined for protein recovery assessment. As a promising complementary food protein and potential bioactive peptide (BAP) source, this work offers an upscalable and ecologically sustainable recovery approach for seaweed protein from an abundant natural resource on the Pacific coast.

Automated summary

This study evaluated the effects of precipitation strategies on macroalgal protein yield and found that the optimized pH-shift method had competitive yield compared to TCA precipitation. Ethanol wash improved purity of the freeze-dried powders in both precipitation approaches.