Bioresource Technology 318 (2020) 124260 Available online 15 October 2020 0960-8524/© 2020 Elsevier Ltd. All rights reserved. Short Communication A simple downstream processing protocol for the recovery of lactic acid from the fermentation broth Sumit Kumar a , Neerja Yadav a , Lata Nain b , Sunil Kumar Khare a, * a Enzyme and Microbial Biochemistry Lab, Department of Chemistry, Indian Institute of Technology, Delhi, India b Division of Microbiology, ICAR-Indian Agricultural Research Institute, New Delhi, India HIGHLIGHTS • A simple and economical process for downstream of lactic acid has been developed. • The pH of the extraction medium was critical during lactic acid purification. • Optimized downstream process conditions resulted in a yield of 86% and 93% purity. • The purified lactic acid was further characterized by FTIR and NMR. A R T I C L E INFO Keywords: Lactic acid Downstream process Lactic acid bacteria (LAB) Solvent extraction Fermentation broth ABSTRACT Lactic acid is one of the essential platform chemicals, and despite the availability of a range of downstream processes, its effective recovery is still elusive. A phase partitioning process using n-butanol and a chaotropic salt ammonium sulphate was developed to recover lactic acid from the fermentation broth of Lactobacillus pentosus SKL-18. During the optimization of various process parameters, the extraction medium’s pH was found to be critical, with 2.5 being the best. The optimized process resulted in a lactic acid yield of 86% and found it to be 93% pure. The purity and characteristics of lactic acid were confirmed by FTIR and NMR spectra. This solvent- based extraction procedure is an economical and straightforward downstream process for purifying lactic acid produced from agro- and bakery-residues. The pure lactic acid can further be used for enzymatic synthesis of high value-added product PLA, a biodegradable and biocompatible plastics. 1. Introduction Lactic acid is an essential chemical with widespread applications in food, textile, leather, cosmetic, and pharmaceutical industries. Chemical synthesis and fermentation are two routes to produce commercial lactic acid. The fermentation process has an advantage over the chemical process as it produces optically pure L-lactic acid, while the latter makes a racemic mixture of DL-lactic acid. L-form of lactic acid is desirable in food and pharmaceutical applications as human beings metabolize it. Enantiopure L-lactic acid also serves as feedstock for the synthesis of polylactic acid (PLA), a biodegradable and biocompatible plastic (Alves de Oliveira et al., 2018; Nampoothiri et al., 2010). For all the end-use application, the purified form is requisite. Purification of lactic acid is a costly process, and its economic analysis has shown that the cost can vary in the range of 0.78–1.74 USD/kg lactic acid (Phanthumchinda et al., 2018; Posada et al., 2012). The downstream process of lactic acid accounts for 40–70% of the cost, and thus there is a need to develop a convenient and economic downstream strategy for lactic acid purifica- tion (Joglekar et al., 2006; Li et al., 2016). Generally, due to the presence of media components, salts, and re- sidual sugars in the fermentation broth, the purification of lactic acid becomes a multistep process involving filtration, dialysis, and tedious column exchange procedures. A range of methods has been employed for lactic acid recovery (Bishai et al., 2015; Komesu et al., 2017a; Phanthumchinda et al., 2018). Precipitation is one of the methods to recover lactic acid from fermentation broth by adding calcium hydrox- ide. A significant disadvantage of this downstream process is the gen- eration of a large amount of gypsum as waste, which poses * Corresponding authors at: Enzyme and Microbial Biochemistry Laboratory, Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India. E-mail address: skkhare@chemistry.iitd.ac.in (S.K. Khare). Contents lists available at ScienceDirect Bioresource Technology journal homepage: www.elsevier.com/locate/biortech https://doi.org/10.1016/j.biortech.2020.124260 Received 26 August 2020; Received in revised form 8 October 2020; Accepted 10 October 2020