Water kefir grains as an innovative source of materials: Study of plasticiser content on film properties

Microorganisms' biomass is a sustainable and innovative source of biopolymers, such as proteins and polysaccharides, which are suitable for development of biodegradable films. In this work, an alternative material based on the entire biomass of water kefir grains was developed. The whole biomass was submitted to physical treatments of ultrasonic homogenization separated by a thermal treatment at 90 degrees C. The effect of glycerol on film properties was evaluated. The films obtained exhibited high transparency and homogeneity without cracks. Infrared spectroscopy revealed that the material is constituted basically by the polysaccharide dextran. The increasing plasticiser content decreased glass transition temperature. Indeed, the presence of plasticiser increased the amount of hydration water and the water vapour permeability. Moreover, the addition of 30 wt% of glycerol improved significantly the elasticity of films to 275 +/- 15%. Results revealed that water kefir grains biomass is a viable and innovative source of biodegradable materials.