Isolation of Cellulose Nanofibers from Kombucha Beverage By-Product by Chemo-Mechanical Routes

In a world where the negative consequences of natural resources' overexploitation for the environment are increasingly evident, repurposing waste to obtain high-value goods becomes essential. This study proposes the isolation of cellulose nanofibers from the bacterial cellulose (BC) membrane that results as a by-product during the fermentation of Kombucha tea by chemical treatment with sodium hydroxide (NaOH), sodium hypochlorite (NaClO), hydrogen peroxide (H₂O₂), sulfuric acid (H₂SO₄) or citric acid, followed by mechanical fibrillation via high-speed homogenization and microfluidization. Treatments with NaOH, NaClO, and H₂O₂ were effective in the purification of Kombucha-derived BC, while H₂SO₄ and citric acid exhibited a rather weak cleaning action, as revealed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Besides their cleaning effect, the applied chemical pretreatments had an important effect on the degree of fibrillation attained, as indicated by the scanning electron microscopy images. This study proposes simple and effective routes to obtain bacterial cellulose nanofibers from an inexpensive and abundant source, commonly regarded as a waste material, which can be further applied in medical and packaging applications as reinforcing agents, adsorbent materials, or scaffolds.