Kombucha Tea By-product as Source of Novel Materials: Formulation and Characterization of Films

The development of biodegradable materials from microbial exopolysaccharides has extraordinary potential to be applied in food packaging. Kombucha tea is a fermented drink produced by a symbiotic community of bacteria and yeasts, where a by-product based on bacterial cellulose is generated at the surface of the beverage. In this work, novel materials based on the integral kombucha tea by-product were developed from the floating and the intentionally submerged discs of biomass. Each disc was dispersed in water and subjected to ultrasonic homogenization. Films obtained by casting exhibited high homogeneity without cracks with a microstructure composed by a homogeneous and continuous cellulosic matrix of ribbon-shaped nanofibers. Infrared spectroscopy and thermogravimetric analyses indicated the further presence of low and high molecular weight compounds. The increase in glycerol content in the film decreased glass transition temperature and increased flexibility, hydration, and water vapor permeability. Films obtained from submerged discs had an additional plasticization given by substances incorporated during the immersion in the culture medium. Both types of films made from the floating and the submerged disc had a natural and remarkable antioxidant activity of 69 +/- 2% and 72 +/- 2% of radical inhibition, respectively, probably due to polyphenols or other compounds from the culture medium. Results revealed that using the integral cellulosic by-product of kombucha tea to prepare films could be advantageous due to the cost-effective process (no separation, no purification), interesting physical-chemical properties, and the retention of natural bioactive substances.