Continuous flow vortex fluidic transformation of kombucha cellulose into more compact and crystalline fibers

Abstract

A chemical-free and scalable novel route for generating more compact and crystalline cellulose from cellulosic biofilms formed at the air-water interface as an otherwise waste byproduct from the kombucha tea beverage fermentation industry has been developed. This involves processing the byproduct by treatment with aqueous 1 M NaOH at 50 °C and then 1% glacial acetic acid followed by washing with distilled water until the pH of the washing water is 7, followed by continuous flow processing in the vortex fluidic device (VFD). This thin-film microfluidic platform houses a 20 mm outside diameter and 17.5 mm inside diameter quartz tube with a hemispherical base. The induced high shear mechanical energy arising from the topological fluid flows within the thin film when the tube is tilted at θ +45° and spun at ω 6k rpm converts the kombucha cellulose to smaller fiber diameters ∼70 nm cf. ∼127 nm preVFD processing. The material is characterized using dynamic light scattering, scanning electron microscopy, atomic force microscopy, X-ray diffraction, thermogravimetric analysis/differential scanning calorimetry, Fourier transform infrared, and Brunauer-Emmett-Teller. The modification of the cellulose is understood mechanistically by the high shear topological fluid flow from the Coriolis force from the base of the tube, forcing the individual cellulose polymer strands together in an ordered array. Such transient localized high shear flow associated with high temperatures and pressures over the fibers on the surface of the tube force the backbone long cellulose strands together resulting in increased crystallinity. The findings lay the foundation for transforming a byproduct from kombucha tea beverage fermentation into unique material for other applications.