The growth and recovery of an exopolysaccharide-producing Lactobacillus rhamnosus culture on growth media containing apple juice or molasses.

In response to client demands producers of probiotic cultures are challenged to develop novel growth media. Furthermore, some strains are difficult to recover by centrifugation due to exopolysaccharide production. The aim of this study was thus to evaluate apple juice and molasses as ingredients of media destined for biomass production of Lactobacillus rhamnosus and how it’s composition affects the viscosity of the fermented broth. Screening of 48 media by automated spectrophotometry (AS) showed that unsupplemented apple juice and molasses gave biomass levels 25 times lower than MRS-lactose. Six yeast extracts (YE) and peptone supplements were screened and a mixture of bakers YE and wheat peptone proved best. A mineral-rich by-product of lactose cristallization (LCB) was an effective growth supplement. There were correlations between biomass yields from apple and molasses-based media. In subsequent fermentations, mixtures of apple juice, LCB, YE and peptone ingredients generated similar Lactobacillus rhamnosus biomass as the MRS medium. There were correlations between biomass level, viscosity of the fermented medium and difficulty to recover cells by centrifugation. However, diluting MRS-lactose with apple juice or LCB enabled similar biomass levels as MRS alone but lower viscosities