Of Electrospinning and Algae

With growing environmental consciousness, algae has been has been investigated for various applications due to its abundance and relative ease of culture. Electrospinning is a versatile method for producing fibers down to the nanometer diameter scale and there are numerous opportunity to use algae or its derivative with electrospinning. Electrospun fibrous membrane may also be used in the culturing or consolidation of algae and there is a possibility that the material and its functional properties may come from algae.

Various anti-bacterial compounds have been blended into polymer solution for electrospinning to form fibers with anti-bacterial properties. Lanasol is a naturally occurring brominated cyclic compound that can be extracted from red sea algae. Andersson et al (2014) used this compound to produce electrospun poly(methyl methacrylate) (PMMA) and polyethylene oxide (PEO) fibers with anti-bacterial properties. Various tests were performed to determine the efficacy of Lanasol loaded electrospun fibers in S. aureus. With more than 10 wt% Lanasol loading, dynamic contact measurement where the fibrous membrane was immerses in aqueous bacterial suspension under agitation, showed no viable count of bacteria colonies. Tests based on bacterial viability after adsorption onto fibrous membrane surface showed viability reduction of ca. 4 orders of magnitude (99.99% reduction) with just 4 wt % Lanasol loading.

Microalgae offers many advantages as a potential food source and it is able to produce a greater amount of biomass compared to terrestrial plants. However, the main challenge with algae is finding a method to concentrate the mass from a relatively dilute source. Azizo et al (2017) proposed using electrospun nylon 6, 6 nanofibre membrane for microalgae harvesting. Electrospun membrane has been shown to be very effective as a microfiltration membrane. For algae harvesting, the electrospun nylon 6, 6 nanofibre membrane was able to demonstrate 2-5 times higher in productivity compared to phase inversion membrane while maintaining similar rejection of 92%. Superior performance of the electrospun membrane may be attributed to its greater hydrophilicity, 45% higher surface pore size and 20% surface pore population which gives it significantly higher clean water permeability (of 1018 and 493 l/m²hbar for nanofiber and polyvinylidene fluoride membranes respectively)

A number of polymeric compounds may be derived from algae which can been shown to be used for electrospinning to form fibers. Morais et al (2015) use polyhydroxybutyrate (PHB) extracted from Spirulina platensis for electrospinning into nanofibers. Spirulina PHB is dissolved in chloroform to prepare the solution for electrospinning. The resultant electrospun fibers have a diameter of 750 nm. Sodium alginate (SA) is naturally derived copolymer which is found widely in brown seaweeds. Although sodium alginate (SA) is easily dissolved in water, pure alginate solution exhibits poor electrospinnability due to lack of chain entanglement. Fang et al (2011) was able to overcome this limitation by introducing Ca²⁺ cations to SA solutions. With optimization of the Ca²⁺ content in SA solution, they were able to increase intermolecular interactions and decrease surface tension such that the solution is able to produce fibers by electrospinning.

Optical image of PHB nanofibers containing Spirulina biomass incorporated, 2,000x magnification [Morais et al 2015].

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