Fermentative utilization of coffee mucilage using Bacillus coagulans and investigation of down-stream processing of fermentation broth for optically pure l(+)-lactic acid production.

In this study, mucilage, a residue from coffee production, was investigated as substrate in fermentative l (+)-lactic acid production. Mucilage was provided as liquid suspension consisting glucose, galactose, fructose, xylose and sucrose as free sugars (up to 60 g L −1 ), and used directly as medium in Bacillus coagulans batch fermentations carried out at 2 and 50 L scales. Using mucilage and 5 g L −1 yeast extract as additional nitrogen source, more than 40 g L −1 lactic acid was obtained. Productivity and yield were 4–5 g L −1 h −1 and 0.70–0.77 g lactic acid per g of free sugars, respectively, irrespective the scale. Similar yield was found when no yeast extract was supplied, the productivity, however, was 1.5 g L −1 h −1 . Down-stream processing of culture broth, including filtration, electrodialysis, ion exchange chromatography and distillation, resulted in a pure lactic acid formulation containing 930 g L −1 l (+)-lactic acid. Optical purity was 99.8%. [ABSTRACT FROM AUTHOR]