Isolation of bacterial exopolysaccharides from Streptococcus thermophilus via dynamic cross flow filtration in pilot scale

Abstract

A variety of exopolysaccharides (EPS) producing bacterial starter cultures are manufactured for their use in food industry, leaving the almost cell free and EPS containing fermentation broth as waste product. The concentration of EPS in the fermentation broth is approximately 1 gL−1, depending on fermentation conditions and bacteria strain. The use of bacterially produced EPS as a food additive is promising because it has a high water binding capacity, which is beneficial for the stability and viscosity of emulsion-based products and enables a sustainable production process. However, concentration and separation of EPS from the complex fermentation broth is cost-intensive and time-consuming. This work presents a simplified EPS-isolation scheme in comparison to the established laboratory process, that can be transferred to pilot scale. The method consists of a microfiltration or ultracentrifugation for removal of the remaining cell, an ultrafiltration to concentrate the EPS and a final diafiltration washing step to remove lower molecular components like salts and sugars. Subsequent to freeze drying, the final product is isolated as EPS-powder. This can easily be integrated in industrial processes to replace herbal food additives like xanthan gum or locust bean gum.