Effect of storage on plant biostimulant and bioactive properties of freeze-dried Chlorella vulgaris biomass

• Published in: Journal of applied phycology Vol. 33; no. 6; pp. 3797 - 3806
• Main Authors: Stirk, Wendy A., Bálint, Péter, Vambe, McMaster, Kulkarni, Manoj G., van Staden, Johannes, Ördög, Vince
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01-12-2021; Springer Nature B.V
• Subjects: Algae; Antiinfectives and antibacterials; Antimicrobial activity; Antioxidants; Aquatic microorganisms; Bioactive compounds; Biodegradation; Biological activity; Biological control; Biomass; Biomedical and Life Sciences; Biostimulants; Cell walls; Chlorella; Chlorella vulgaris; Commercialization; Degradation; Disease resistance; E coli; Ecology; Freeze drying; Freshwater & Marine Ecology; Life Sciences; Marketing; Metabolites; Microalgae; Phytoplankton; Plant Physiology; Plant Sciences; Properties; Rooting; Secondary metabolites; Shelf life; Storage conditions; Storage temperature; Temperature; Antimicrobial activity; Rooting activity; Temperature; Storage time; Antioxidant activity; Light
• ISSN: 0921-8971; 1573-5176
• DOI: 10.1007/s10811-021-02596-9

Microalgae are potential plant biostimulants and biocontrol agents. A major hurdle towards their commercialization is the production of large volumes of biomass at the correct time of year. Secondary metabolites are unstable and the “shelf-life” of bioactive microalgal biomass needs to be investigated. The aim of the study was to investigate the effects of storage conditions on freeze-dried microalgae to determine how long the biomass retained its growth promoting and bioactive properties under various temperature and light conditions.
Chlorella vulgaris
biomass was stored in the dark at − 70 °C, 10 °C, and 25 °C and in the light at 25 °C. Samples were tested every 3–4 months for 15 months. Storage time significantly influenced the rate of change in the bioactivity in the
C. vulgaris
biomass with storage temperature also having some effect. Rooting activity decreased in the mungbean rooting assay over time up to 12 months and then increased slightly. Antimicrobial activity increased against
Staphylococcus aureus
and
Escherichia coli
for up to 12 months and then declined. Antioxidant activity measured in the DPPH assay remained relatively stable for up to 12 months and then significantly decreased with longer storage. The change in bioactivity over time was attributed to the gradual breakdown of the rigid cell wall of
C. vulgaris
, thereby improving extraction efficiency but exposing the secondary metabolites to oxygen, thus quickening their degradation. Biomass produced for commercial purposes requires preliminary validation as the results of the present study showed that bioactive compounds are susceptible to degradation over time.