Investigation of important biochemical compounds from selected freshwater macroalgae and their role in agriculture

Background Freshwater macroalgae possess a number of important secondary metabolites. They are an unexplored source of medicinal compounds. In this study, three freshwater macroalgae—Chara vulgaris, Cladophora glomerata and Spirogyra crassa—were collected from the river Swat and the river Kabul in the Charsadda district of Khyber Pakhtunkhwa, Pakistan. To assess the role of freshwater macroalgae in agriculture, various experiments were performed on their extracts. Methanolic extract of the three macroalgae were first analyzed through gas chromatography–mass spectrometry (GC–MS) for the presence of important medicinal secondary metabolites. The methanol based macroalgae extracts were tested for antibacterial, insecticidal, cytotoxic and phytotoxic activities. Results Initially, the algae were dried, crushed and treated with methanol for the extraction of secondary metabolites. The GC–MS results contained several important long chain fatty acids and other related long-chain hydrocarbons, such as alkanes and alkenes. Several benzene derivatives were also detected during the course of the investigation. Several of these compounds have established roles in the treatment of human ailments and can be supplied to farm animals. For example, phenylephrine is a decongestant, dilates pupils, increases blood pressure and helps in relieving hemorrhoids. Hexahydropseudoionone has uses in perfumes and other cosmetics. Several essential oils were also detected in the methanolic extract of the three macroalgae that can be utilized in various industrial products. Bioassays showed that these algal extracts—especially the Spirogyra sp. extract—contain moderate to maximum bioactivity. Conclusions Macroalgae possess important secondary metabolites with medicinal properties. These secondary metabolites can be used as biopesticides, plant growth enhancers, and remedies for various diseases in farm animals and for the control of weeds. They can be further explored for isolation and purification of useful biochemical compounds. Graphical Abstract

Valorization of Cladophora glomerata Biomass and Obtained Bioproducts into Biostimulants of Plant Growth and as Sorbents (Biosorbents) of Metal Ions

The aim of this study was to propose a complete approach for macroalgae biomass valorization into products useful for sustainable agriculture and environmental protection. In the first stage, the effects of macroalgal extracts and ZnO NPs (zinc oxide nanoparticles) on the germination and growth of radish were examined. Macroalgal extract was produced from freshwater macroalga, i.e., Cladophora glomerata by ultrasound assisted extraction (UAE). The extract was used to biosynthesize zinc oxide nanoparticles. In germination tests, extracts and solutions of ZnO NPs were applied on paper substrate before sowing. In the second stage, sorption properties of macroalga, post-extraction residue, and ZnO NPs to absorb Cr(III) ions were examined. In the germination tests, the highest values of hypocotyl length (the edible part of radish), i.e., 3.3 and 2.6 cm were obtained for 60 and 80% extract (among the tested concentrations 20, 40, 60, 80, and 100%) and 10 and 50 mg/L NPs, respectively. The highest sorption capacity of Cr(III) ions (344.8 mg/g) was obtained by both macroalga and post-extraction residue at a pH of 5 and initial Cr(III) ions concentration of 200 mg/L. This study proves that macroalgae and products based on them can be applied in both sustainable agriculture and wastewater treatment.

Soybean Germination Response to Algae Extract and a Static Magnetic Field Treatment

The present study examines the separate and synergistic effects of macroalgal extract and static magnetic field (SMF) on the germination of soybean seeds (Glycine max (L.) Merrill), cv. Abelina, seedling growth, chlorophyll, and carotenoids content in leaves. Algal extract was produced from freshwater green macroalga (Cladophora glomerata) using ultrasound-assisted extraction. The germination tests were conducted in two stages. Firstly, different concentrations of extracts, 20%, 40%, 60%, 80%, and 100%, were applied to a paper substrate. The best results (taking into account germination percentage, seedlings length and weight, and pigments content in leaves) were observed for 20% and 80% extracts. At the same stage, germination of seeds exposed to SMF (exposure times for 3 and 12 min and magnetic inductions of 250 and 500 mT) was studied. The best developed seedlings were determined for the group treated at 3 min with a magnetic induction of 250 mT. In the final step, the simultaneous effects of 20% and 80% algal extracts and treatment with 3 min at 250 mT SMF were tested. Taking into account all the parameters, the simultaneous use of 20% extract and 3 min of 250 mT magnetic induction is recommended.

The Effect of Algal Extract of Spirulina Platensis, Cladophora Glomerata on Some Positive and Negative Bacterial Isolates of Gram Stain

This study examines the efficacy of the algal alcoholic extract isolated from Cladophora Spirulina platensis and glomerata and testing their efficacy against positive bacteria of Gram stain Staphylococcus aureus and the negative bacteria for Escherichia coli and Klebislla sp. The organic solvent ethanol was used at 95%. The efficacy of the extract was tested against some strains of positive and negative bacteria of Gram stain. The results of the extract showed that the positive bacteria of Gram stain has sensitivity towards the extract higher than the negative bacteria. The highest inhibitory efficacy against Staphylococcus aureus by inhibitive diameter zone of 20 mm and less inhibitive against negative bacteria E.coli by inhibitive diameter of 16 mm.

Freshwater Cladophora glomerata Biomass as Promising Protein and Other Essential Nutrients Source for High Quality and More Sustainable Feed Production

A scientific justification, focused on the development of the sustainability of feed ingredients and farm animals’ ecosystems, is required. Thus, it is crucial to search for alternative feed materials from natural sources for potential applications. The aim of this study was to evaluate the prospective utilization of freshwater Cladophora glomerata (C. glomerata) as an alternative source of protein and other essential nutrients in animals’ feed. For this purpose, chemical analysis was performed on collected biomass samples from the Lithuanian rivers, Dubysa (B1), Šventoji (B2), Nevėžis (B3), and Jūra (B4). Microelements (Ca > K > N > P > Mg), trace elements (Zn > Cu), and heavy metals (Cr > Ni > Pb > Cd) have not exceeded permissible levels. The crude protein content of C. glomerata biomass ranged from 16% to 21.5% DM. The essential amino acid profile excelled, with the highest total amino acid amount of 140.99 g/kg in B4. The highest total presence of polyunsaturated fatty acids (11.71%) as well as the ratio of polyunsaturated to saturated fatty acids (0.22) was observed in B1. The lowest ratio of omega-6/omega-3 was in B1 (1.30). As a result of bioaccumulation, C. glomerata could serve as a source of proteins, as well as amino and fatty acids, implying that biomass could be an alternative and a beneficial component of animal feed.