Development of PLA Nanofibers with Scenedesmus Biomass for Applications as Biofertilizers

Intensive agriculture relying on chemical fertilizers causes environmental impacts, which calls for sustainable alternatives. In this context, PLA nanofibers produced by electrospinning stand out because they enable controlled nutrient release, while microalgae encapsulation rich in nutritious biomass reduces accelerated mineralization and increases the efficiency of biofertilizers. Thus, the aim of this study was to develop poly(lactic acid) nanofibers via needleless electrospinning containing microalgal biomass, with potential application as biofertilizers. For the development of the nanostructures, polymer solutions with PLA concentrations of 0.5, 1, and 14% (m v⁻¹) were prepared, containing 2% (m v⁻¹) of Scenedesmus sp. dissolved in trichloromethane. Nanofiber morphology was analyzed by Scanning Electron Microscopy, hydrophobicity by contact angle measurements, and the main thermal events were determined by thermogravimetry and differential scanning calorimetry. Solutions with low PLA content (0.5 to 1%) produced particles or beaded fibers due to low viscosity and jet instability, whereas the 14% PLA solution enabled the formation of continuous and stable nanofibers with an average diameter of 800  200 nm. Under this condition, the following process parameters were defined: electrode distance of 180 mm, electric potential of 45 kV, spinneret diameter of 0.8 mm, and polymer solution speed of 150 mm/s. Contact angle analysis indicated that PLA nanofibers with encapsulated microalgae exhibit hydrophobic behavior (θ=133.6°), a relevant feature for controlling water interaction and nutrient release. Incorporation of Scenedesmus sp. significantly increased the degradation temperature of the PLA nanofibers from 390 to 450 °C and raised the degree of crystallinity to 48%, higher than the value reported for the pure polymer in the literature (38.9%). These characteristics contribute to greater structural integrity of the nanofibers and favor controlled nutrient release in soil. These results indicate that PLA nanofibers containing microalgae biomass may be promising controlled-release biofertilizers, contributing to the reduction of environmental impacts.