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%. (C) 2016 Elsevier Ltd. All rights reserved.