The Enzyme-Assisted Extraction of compounds of interest in agriculture: Case study of the red seaweed Solieria chordalis (C. Agardh) J. Agardh

For centuries, seaweeds have been spread on fields to improve soil properties and crop yield. Over the last thirty years, the use of seaweed-based extracts has attracted increased attention in agriculture. In comparison with raw seaweed, extracts may be more concentrated in bioactive molecules such as macro/microelements, peptides, polysaccharides and metabolites. These molecules are usually obtained by conventional Water Extraction (WE), which is most often time consuming, with low selectivity and extraction yields. Over the last decade, tailored extraction processes using microwave, ultrasound and enzyme have demonstrated their advantages to obtain enriched seaweed extracts. In this context, the aim is to determine, for the first time in Solieria chordalis, whether Enzyme-Assisted Extraction (EAE) is an effective way of producing extracts enriched in macro/microelements and Plant Growth Regulators (PGRs), which are some of the main compounds of interest for plant nutrition and biostimulation. The red seaweed S. chordalis (C. Agardh) J. Agardh (Gigartinales, Rhodophyta) has been chosen as a case study model since it proliferates on the South Brittany coast (France) during the winter. The extraction yield and biochemical composition of the extracts are determined to assess the efficiency of EAE in comparison with WE. The results demonstrate that EAE increases the contents compared with WE in terms of neutral sugars (×2) and proteins (×1.3). In addition, PGRs in S. chordalis are quantified here for the first time. The most abundant PGRs present in S. chordalis and its extracts are Indole 3-Acetic Acid (IAA), 1-Amino-1-Cyclopropane-Carboxylic Acid (ACC) and Salicylic Acid (SA). Indeed, EAE allow us to enrich the content of the extracts in SA (×3), ACC (×3) and IAA (×6), compared with WE. Therefore, this study demonstrates that EAE is an efficient process for enriching S. chordalis extracts in various compounds, and should be investigated on other seaweeds for agricultural purposes.