Versatile method to obtain protein- and/or amino acid-enriched extracts from fresh biomass of recalcitrant microalgae without mechanical pretreatment

Abstract

The aim of the study was to develop a sequential alkaline-enzymatic method to obtain protein- and/or amino acid-enriched extracts from fresh biomass of recalcitrant microalgae without any supplementary pretreatment. The effects of the initial biomass concentration, the use of freeze-dried or fresh biomass, enzyme dosage, processing procedure (two-step and single-step, with and without pH control) and species were studied. The method was evaluated with a consortium of microalgae isolated from a landfill leachate and was tested on other recognized recalcitrant microalgae such as Chlorella vulgaris, Nannochloropsis gaditana and Scenedesmus obliquus. The approach includes alternative pathways, provides high extraction yields of proteinaceous material and produces protein- and/or hydrolyzed peptide-enriched extracts with different amino acid compositions (e.g., a pathway without pH control achieves a yield of 81% of total protein and a concentration of 29 mg mL−1 of proteinaceous material). The versatility in processing procedures and the range of products obtained, along with applicability to different microalgal species, make this method an interesting option for algae biomass treatment. Furthermore, the high yield and simplicity from a technological point of view, gives it a great potential for process development and encourages further research for a wide variety of applications, such as feed, biostimulants, culture media, bulk chemicals, and biogas.