A study of the residual fermentation sugars influence on an alternative downstream process for first and second-generation lactic acid

Abstract

Lactic acid is an important biomolecule with a substantial market share. Currently, investments in the area are concentrated on new substrates and technologies, in order to boost production and separation performance. Molecular distillation has been recognized as a promising technology in the separation, purification, and concentration of natural products and hence with potential for application in the lactic acid production process. In this study, lactic acid was produced by fermentation using first (1G) and second-generation (2G) substrates, producing a complex mixture of lactic acid and residual sugars. The influence of the residual sugars, such as glucose, sucrose, and xylose, was investigated. For the 1G process, the results showed that the highest lactic acid concentration (99.51 g/L) can be obtained using the feed stream with the lowest sugars composition. For the 2G process, the highest lactic acid concentration reached (75.87 g/L) was lower than that observed for 1G experiments. The concentration of lactic acid using 1G or 2G lactic acid were, respectively, 2.73 times and 2.12 times higher than the initial raw material concentration, without the use of any extra solvent. The final process analysis showed that the use of molecular distillation for lactic acid downstream has different challenges to defeat for the separation of 1G and 2G lactic acid, which is relevant since many different feedstocks may be used in the lactic acid production.