Abstract
The aquatic weed Azolla is a potential protein crop due to its prolific growth and high protein content, supported entirely by nitrogen-fixing symbionts. Alkaline protein extraction at pH 8 followed by acid precipitation allowed recovery of 16–26% of the biomass nitrogen, while at pH 10.5 nitrogen recovery improved to 35–54%. This pH effect was typical of ferns of the family Salviniaceae, and may be explained by high concentrations of condensed tannins (CTs) in the biomass that precipitate protein at mild pH. Two approaches were tested to increase protein yield and reduce protein binding by CTs. Pre-extraction with aqueous acetone (70 v/v%) removed 76–85% of the CTs and subsequent alkaline extraction at pH 12.5 and 95 °C recovered 38% of the biomass nitrogen. Extraction with 1.5% of PEG as a CT-binding agent, also permitted to recover 38% of the nitrogen, under milder conditions of pH 8 and 45 °C.
Original language | English |
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Article number | e00368 |
Journal | Biotechnology Reports |
Volume | 24 |
DOIs | |
Publication status | Published - Dec 2019 |
Funding
We would like to thank Arnold van Dijk for performing the numerous nitrogen analyses that form the basis of this paper. We would further like to acknowledge Mark Smit, Wouter Hoogland and Dally Shaffar for their help with the experimental work, Adrie van der Werf for supplying biomass of Lemna minor and the LPP foundation for their financial support. Appendix A
Keywords
- Alkaline extraction
- Aquatic weeds
- Azolla
- Condensed tannins
- Protein