Supercritical fluid extraction of algae enhances levels of biologically active compounds promoting plant growth

Abstract

The aim of this research was to screen plant growth biostimulant properties of supercritical CO 2 macroalgal extracts. To this end secondary metabolites were isolated from the biomass of marine macroalgae from the Baltic Sea (species of Polysiphonia, Ulva and Cladophora). Chemical characteristics of the algal extracts were determined by inductively coupled plasma atomic emission spectroscopy for inorganic constituents and high-performance liquid chromatography and spectrophotometry for organic constituents. Inorganic (macro-and microelements) and organic (plant hormones: auxins and cytokinins; polyphenols) compounds were detected in the extract. Algal extracts were tested primarily on garden cress (Lepidium sativum L.; Brassicaceae) and wheat (Triticum aestivum L.; Poaceae). The extracts enhanced chlorophyll and carotenoid content in plant shoots, as well as root thickness and above-ground biomass. The most effective method of application of the extract was by foliar feed on cress and seed maceration for wheat. Algal extracts obtained by supercritical fluid extraction (SFE) were found to be a novel natural source of compounds, stimulating growth of cultivated plants. However, field trials will be required to show that the extracts can act as plant biopesticides and growth biostimulants.

Evaluation of Supercritical Extracts of Algae as Biostimulants of Plant Growth in Field Trials

“…Marine macroalgae were collected from the Baltic Sea directly from the water near Sopot beach (Poland). The detailed description of the harvesting of the biomass and pre-treatment before extraction process was described in the work of Michalak et al (2016). Brown macroalga – A. nodosum was supplied by Laboratoires Goëmar SAS 1 .…”

“…SFE of microalga Spirulina sp. was described in the work of Chojnacka et al (2014) and of Baltic green macroalgae in the work of Michalak et al (2016). In the case of brown macroalga A. nodosum , SFE was performed in the laboratory extractor with the volume – 1L.…”

“…The basis to conduct field trials were germination tests carried out on different species of plants using supercritical extracts: from the mixture of marine macroalgae from the Baltic Sea (species of Polysiphonia, Ulva , and Cladophora ) and Spirulina sp. on cress ( Lepidium sativum ) (Dmytryk et al, 2014a,b) and from the mixture of Baltic macroalgae on garden cress and wheat (Michalak et al, 2016). …”

The Application of Homogenate and Filtrate from Baltic Seaweeds in Seedling Growth Tests

“…In the case of soil application, the cotton wool was evenly moistened with the appropriate filtrates. In the foliar application, the seeds/seedlings were sprayed with the same volume of the appropriate filtrate [27,30].…”

“…Then macroalgae were transported to the laboratory and stored at −20 • C prior to extraction. Just before the homogenization process, algae were defrosted and rinsed with fresh water three times to remove salt, small insects, and epiphytes [27].…”