Dataset Information

Aquatic weeds as novel protein sources: Alkaline extraction of tannin-rich Azolla.

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.

SUBMITTER: Brouwer P

PROVIDER: S-EPMC6728274 | biostudies-literature | 2019 Dec

REPOSITORIES: biostudies-literature

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Aquatic weeds as novel protein sources: Alkaline extraction of tannin-rich Azolla.

Brouwer Paul P Nierop Klaas G J KGJ Huijgen Wouter J J WJJ Schluepmann Henriette H

Biotechnology reports (Amsterdam, Netherlands) 20190811

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 pre ...[more]

PMID: 31516849

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Project description:BACKGROUND:The quest for sustainable production of renewable and cheap biofuels has triggered an intensive search for domestication of the next generation of bioenergy crops. Aquatic plants which can rapidly colonize wetlands are attracting attention because of their ability to grow in wastewaters and produce large amounts of biomass. Representatives of Azolla species are some of the fastest growing plants, producing substantial biomass when growing in contaminated water and natural ecosystems. Together with their evolutional symbiont, the cyanobacterium Anabaena azollae, Azolla biomass has a unique chemical composition accumulating in each leaf including three major types of bioenergy molecules: cellulose/hemicellulose, starch and lipids, resembling combinations of terrestrial bioenergy crops and microalgae. RESULTS:The growth of Azolla filiculoides in synthetic wastewater led up to 25, 69, 24 and 40 % reduction of NH4-N, NO3-N, PO4-P and selenium, respectively, after 5 days of treatment. This led to a 2.6-fold reduction in toxicity of the treated wastewater to shrimps, common inhabitants of wetlands. Two Azolla species, Azolla filiculoides and Azolla pinnata, were used as feedstock for the production of a range of functional hydrocarbons through hydrothermal liquefaction, bio-hydrogen and bio-ethanol. Given the high annual productivity of Azolla, hydrothermal liquefaction can lead to the theoretical production of 20.2 t/ha-year of bio-oil and 48 t/ha-year of bio-char. The ethanol production from Azolla filiculoides, 11.7 × 103 L/ha-year, is close to that from corn stover (13.3 × 103 L/ha-year), but higher than from miscanthus (2.3 × 103 L/ha-year) and woody plants, such as willow (0.3 × 103 L/ha-year) and poplar (1.3 × 103 L/ha-year). With a high C/N ratio, fermentation of Azolla biomass generates 2.2 mol/mol glucose/xylose of hydrogen, making this species a competitive feedstock for hydrogen production compared with other bioenergy crops. CONCLUSIONS:The high productivity, the ability to grow on wastewaters and unique chemical composition make Azolla species the most attractive, sustainable and universal feedstock for low cost, low energy demanding, near zero maintenance system for the production of a wide spectrum of renewable biofuels.

Project description:Aquatic weeds such as muskgrass (Chara spp.), water hyacinth (Eichhornia crassipes), water lettuce (Pistia stratiotes), hydrilla (Hydrilla verticillate), filamentous algae (Lyngbya wollei), and duckweed (Lemna minor) thrive in farm canals within the Everglades Agricultural Area of South Florida. Their presence, particularly during the summer months is an environmental concern with regards to water quality, in addition to being a nuisance because of their ability to multiply and spread rapidly in open waters causing restricted drainage/irrigation flow and low dissolved oxygen levels. Chemical control is effective but can have undesirable off-target effects, so reduced herbicide use is desirable. Hence, need exists to discover ways in which these weeds could be best managed or utilized. The objective of this research was to evaluate the allelopathic effect of these weeds to determine their use as potential biopesticides. Six aqueous extracts were tested against 100 bacterial strains isolated from plants and soil to evaluate their antimicrobial activity. These extracts were also used to determine their insecticidal and antifeedant effects on fall armyworm (FAW, Spodoptera frugiperda). Both extracts and powder form of the aquatic weeds were tested for their herbicidal activity towards seed germination and growth of three common terrestrial weed species. At a dilution of 1:100 and 1:1,000, none of the aquatic weeds inhibited in-vitro growth of the bacterial strains, with one exception (filamentous algae extract at 1:100 reduced growth of one bacterial isolate by 54%). Water lettuce reduced the survival rate of FAW by 14% while hydrilla and duckweed caused 11% and 9% reduction of FAW growth, respectively. Powdered duckweed inhibited the growth of nutsedge by 41%, whereas filamentous algae powder and extract reduced germination of amaranth by 20% and 28%, respectively. Harvesting these weeds and converting them into useable compounds could not only eliminate the in situ farm canal and water quality problems but also result in development of new soil amendments or biopesticides.

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Aquatic weeds as novel protein sources: Alkaline extraction of tannin-rich Azolla.

Publications

Aquatic weeds as novel protein sources: Alkaline extraction of tannin-rich <i>Azolla</i>.

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