Bioresource Technology Reports 24 (2023) 101638 Available online 27 September 2023 2589-014X/© 2023 Elsevier Ltd. All rights reserved. Advances and challenges in bio-based 2,3-BD downstream purifcation: A comprehensive review Pramod M. Gawal a, * , Sanjukta Subudhi b a Department of Chemical Engineering, Indian Institute of Technology Guwahati, Assam 781039, India b Advanced Biofuels and Bio-commodities, The Energy and Resources Institute, New Delhi 110003, India A R T I C L E INFO Keywords: Fermentation broth 2,3-Butanediol Downstream processing Separation technologies Techno-economic evaluation ABSTRACT Bio-based 2,3-butanediol (2,3-BD) is gaining prominence as an alternative to costly petroleum production. It fnds diverse applications in chemicals, food, cosmetics, and more, notably as a polybutadiene rubber compo- nent. Recent advancements in 2,3-BD purifcation and increased concentration in fermentation solutions (exceeding 150 g/L) resulted from identifying 2,3-BD-producing bacteria and understanding productivity factors. Nevertheless, challenges arise from its high boiling point, hydrophilicity, complex fermentation broth compo- sition, and costly separation from the broth (accounting for 50–70 % of production costs). The development of a cost-effective and effective separation method for 2,3-BD is essential. Recent developments in separation tech- niques, such as solvent extraction, pervaporation, and others, have been comprehensively reviewed for their in- situ and ex-situ applications. A techno-economic evaluation of these innovative approaches demonstrates sig- nifcant reductions in energy consumption (up to 54.8 %) and downstream separation expenses (ranging from 25.8 % to 61.2 %), highlighting their potential to enhance the industrial production of 2,3-BD. 1. Introduction Global energy consumption has increased dramatically due to industrialization and improved living standards (Chaudhari et al., 2018; Negi and Das, 2023). Annually, over 80 million tons of industrial chemicals are manufactured worldwide, predominantly relying on non- renewable sources such as petroleum and natural gas for their raw materials (Maina et al., 2022). The extensive consumption of fnite fossil fuels has resulted in depleted crude oil reservoirs and unsustainable environmental effects. Therefore, the development of alternative and renewable energy resources fulflls the energy demand and addresses the depletion of crude resources (Priya et al., 2021a). On the other hand, the production of bio-based chemicals from renewable sources has attracted more attention due to the energy crisis and environmental pollution. The advancement of microbial strains in bio-based chemical production has opened up a renewable pathway for the chemical in- dustry (Mahesh et al., 2021; Narisetty et al., 2021a). In recent years, the swift advancement of genetic engineering technology has substantially elevated the concentrations of desired products, concurrently dimin- ishing the fermentation costs (Maina et al., 2022). Various chemicals previously produced through chemical synthesis can now undergo biotransformation using renewable resources. Among those chemicals, 2,3-BD is a valuable chemical with a high commercial application. It serves as a precursor for various synthetic chemicals through several chemical reactions to obtain some valuable chemicals. The worldwide market produces around 32 million tons of downstream 2,3-BD products annually, valued at approximately US$43 billion (Narisetty et al., 2021b). Methyl ethyl ketone, derived from the dehydration of 2,3-BD, plays a vital role as a low-boiling solvent in various applications such as coatings, lubricants, adhesives, fuels, and inks. The production of methyl ethyl ketone typically depends on n a complex, high-temperature, and high-pressure petrochemical process (Song et al., 2021). 2,3-BD's strong water affnity and UV resistance make it a common ingredient in skincare and sunscreen products (Clendenning and Wright, 1946). Due to its low freezing point (60 ◦ C), 2,3-BD is an antifreeze agent(Ra et al., 2021). Under the action of de- hydrogenase enzymes, 3-hydroxy-2-butanone (acetoin) can be produced from 2,3-BD and widely utilized as a natural food favoring agent(Xiao and Lu, 2014). The dehydrogenation of 2,3-BD generates diacetyl, which serves as a valuable spice and is incorporated into liquor in China to enhance its favor(Petrov and Petrova, 2021). The esterifcation of 2,3- BD with acetic acid results in the formation of butane-2,3-diyl * Corresponding author. E-mail address: g.pramod@iitg.ac.in (P.M. Gawal). Contents lists available at ScienceDirect Bioresource Technology Reports journal homepage: www.sciencedirect.com/journal/bioresource-technology-reports https://doi.org/10.1016/j.biteb.2023.101638 Received 12 August 2023; Received in revised form 20 September 2023; Accepted 23 September 2023