Natural Deep Eutectic Solvent Extraction of Bioactive Pigments from Spirulina platensis and Electrospinning Ability Assessment

Abstract

The first ever nanofibers produced by the electrospinning of polyvinyl alcohol (PVA) and Spirulina platensis extracts are presented in this article. Spirulina platensis extracts were obtained by ultrasound-assisted extraction (UAE) using two different solvents: a glucose/glycerol-based natural deep eutectic solvent (NADES) and water. Through spectrophotometry analysis, it was possible to determine the pigment yield of the extractions for both extracts: phycocyanin = 3.79 ± 0.05 mg/g of dry biomass (DB); chlorophylls = 0.24 ± 0.05 mg/g DB; carotenoids = 0.13 ± 0.03 mg/g DB for the NADES/Spirulina extracts, and phycocyanin = 0.001 ± 0.0005 mg/g DB; chlorophylls = 0.10 ± 0.05 mg/g DB; carotenoids = 0.20 ± 0.05 mg/g DB for water/Spirulina extracts. Emulsions were formed by mixing the microalgae extracts in PVA (9%, w/v) at different concentrations: 5, 20, 40, and 50% (v/v). Electrospinning was carried out at the following conditions: 13 cm of distance to collector; 80 kV of applied voltage; and 85 rpm of electrode rotation. After the nanofibers were collected, they were checked under a scanning electron microscope (SEM). ImageJ was also used to determine fiber diameter and frequency. SEM results showed the formation of nanofibers for 5 and 20% (v/v) of NADES/Spirulina extract content in the electrospinning emulsions, presenting diameters of 423.52 ± 142.61 nm and 680.54 ± 271.92 nm, respectively. FTIR confirmed the presence of the NADES extracts in the nanofibers produced. Overall, the nanofibers produced showed promising antioxidant activities, with the NADES/Spirulina- and PVA-based nanofibers displaying the highest antioxidant activity (47%). The highest antimicrobial activity (89.26%) was also obtained by the NADES/Spirulina and PVA nanofibers (20%, v/v). Principal Component Analysis (PCA) revealed positive correlations between both the antioxidant and antimicrobial activities of the electrospun nanofibers, and extract content in the emulsions. Moreover, PCA also indicated positive correlations between the viscosity and conductivity of the emulsions and the diameter of the nanofibers produced.

Upcycling Wool Waste into Keratin Gel-Based Nanofibers Using Deep Eutectic Solvents

“…Furthermore, it is important to emphasize that the percentages of bacterial reduction obtained are in accordance with the indications of the US FDA and their European counterparts, which consider that a bacterial reduction of at least 99.99% should be achieved for it to be considered as having antimicrobial properties [ 40 ]. Moreover, Wang et al extracted WK from wool waste following the reduction-C method, which uses organic solvents, and blended it with PCL to produce nanofibers through electrospinning.…”

“…The antioxidant activity of the produced gel-based electrospun PVA/L-Cys:LA DES-WK nanofibrous membranes was explored through ABTS assay. ABTS+ is a stable free radical commonly used for assessing the total antioxidant capacity of natural compounds, and displays a maximum absorption peak at 734 nm [ 39 , 40 ].…”

“…Moreover, the WK displays a high cysteine content, antioxidant functions of which have been demonstrated previously [ 26 ]. Therefore, the promising antioxidant capability of the produced gel-based electrospun PVA/L-Cys:LA DES-WK nanofibrous membranes arises from the ability of the DES mixture and the WK to donate a hydrogen atom to free radicals, reducing the ABTS+ radical to a colorless compound [ 40 ].…”

Emerging Applications of Chlorella sp. and Spirulina (Arthrospira) sp.

“…Depending on the type of wound, it is crucial to use appropriate dressing materials and structures that can maintain a moist environment at the wound site while simultaneously protecting it from contaminants. In recent years, both academic and industrial sectors have been making concerted efforts to develop a variety of wound dressings suitable for wound healing, specifically exploring the use of different microorganisms, such as microalgae, due to their beneficial bioactive compounds [ 59 , 60 , 103 , 105 , 106 ]. As mentioned in Section 3.3 , microalgae contain an extensive variety of bioactive compounds that can promote skin regeneration.…”

Green Extraction Techniques of Bioactive Compounds: A State-of-the-Art Review

“…The number of reviews focused on extraction techniques from food waste, microalgae, and lignocellulosic biomass is not surprising given the great potential of these sources. For instance, microalgae are autotrophic microorganisms that produce high-value compounds such as polysaccharides, polyunsaturated fatty acids (PUFAs), and bioactive pigments like carotenoids (mainly lutein, zeaxanthin, and astaxanthin) [15,16]. On the other hand, food waste has also gained interest in society due to the higher global population and the consequent rise in food waste generation [17].…”