Lactic acid is an important chemical as starting chiral material in various applications. It has increased value in the global market. Different studies have presented the possibility to obtain rich lactic acid solutions with high isomeric purity (S-form) from second-generation (2G) feedstocks. The used downstream process is crucial, not only in terms of the overall cost but also for the achievement of high product purity, suitable for high-value applications. This review provides an overview of the current state-of-the-art on the separation and purification methods of lactic acid derived from the fermentation of second-generation feedstocks. The traditional precipitation method, solvent extraction, affinity-related processes, membrane separation, reaction-separation systems, salting-out extraction and molecular distillation are the main processes investigated so far. The different approaches are discussed in terms of lactic acid recovery yield and purity as well as their environmental impact.

Lactic acid is a high-value molecule with a vast number of applications. Its production in the biorefineries model is a possibility for this sector to aggregate value to its production chain. Thus, this investigation presents a biorefinery model based on the traditional sugar beet industry proposing an approach to produce lactic acid from a waste stream. Sugar beet is used to produce sugar and ethanol, and the remaining pulp is sent to animal feed. Using Bacillus coagulans in a continuous fermentation, 2781.01 g of lactic acid was produced from 3916.91 g of sugars from hydrolyzed sugar beet pulp, with a maximum productivity of 18.06 g L⁻¹h⁻¹. Without interfering in the sugar production, ethanol, or lactic acid, it is also possible to produce pectin and phenolic compounds in the biorefinery. The lactic acid produced was purified by a bipolar membrane electrodialysis and the recovery reached 788.80 g/L with 98% w/w purity.