Influence of the thickness of Symbiotic Culture of Bacteria and Yeast on purification and final properties of bacterial cellulose

The valorization of Symbiotic Culture of Bacteria and Yeast (SCOBY), an underutilized by-product of Kombucha fermentation, through a purification procedure has opened up possibilities for using bacterial cellulose in various applications. However, the impact of SCOBY thickness on properties and purity of bacterial cellulose post-purification remains unexplored. This study demonstrates the correlation between SCOBY thickness and the properties of resulting bacterial cellulose, thereby contributing to the expansion of its application range. The study examines four SCOBY samples of varying thicknesses, all subjected to the same purification process. This process utilized an optimized concentration of SCOBY in purification and washing solutions to ensure complete immersion of the samples while minimizing the environmental impact. As the SCOBY thickness increased, changes in morphology were observed, which influenced rehydration and mechanical properties, transitioning the material from rigid (Young modulus = 2572 ± 661 MPa) to soft (Young modulus = 282±140 MPa). Both the Bicinchoninic acid and Bradford assays confirmed the successful purification of all bacterial cellulose samples, as no proteins were detected. Thermogravimetric analysis supported these findings, also suggesting a higher concentration of fermentation residues in the thickest samples. This observation highlights the need to adapt the purification method based on SCOBY thickness.