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    Lactic acid the most widely occurring hydroxy-carboxylic acid has traditionally been used as food preservative and acidulent. So long, it has been produced through either chemical synthesis route or fermentation route the latter being the dominating one. Despite its tremendous potential for large scale production and use in a wide variety of applications, cost-effective production of high purity lactic acid has remained a challenge for decades, mainly due to high downstream processing cost. In the recent years, possibility of integration of highly selective membranes with the conventional fermentors has opened a golden opportunity for full commercial exploitation of the tremendous application potential of this wonder chemical. This paper discusses recent developments of such membrane-based processes representing process intensification in production of monomer grade lactic acid while suggesting a very promising production scheme.22329
    © 2009 Elsevier B.V. All rights reserved.
    1. Introduction
    The chemical and the allied process industries all over theworld
    are now confronted with the big challenges of developing inno-
    vative products and processes for survival in an era of emaciated
    profitmargins amidst highly globalized trade competition and fast
    growing environmental constraints. Thus process intensification
    through revolutionary development of newproducts and processes
    that ensure reducedmaterial and energy consumption and reduced
    environmental impacts while offering greater flexibility in scale
    of operation are the need of the hour. Production of monomer
    grade lactic acid (2-hydroxypropanoic acid) a traditionally used
    food preservative and acidulent has over the last few decades,
    attracted attention of the world researchers.
    By virtue of unique presence of both hydroxyl and carboxylic
    acid groups, lactic acid can participate in awide variety of chemical
    reactions like esterification, condensation, polymerization, reduc-
    tion and substitution and this has contributed to its tremendous
    potential as a platformchemical for a whole range of products that
    have very large-volume uses for industrial production and con-
    sumer products. Biodegradable thermoplastics (polylactic acid),
    green solvents (ethyl, propyl, butyl lactates) and oxygenated chem-icals (propylene glycol) are a few examples of lactic acid-derived
    products, market demands of which are growing exponentially
    over the years [1]. Exploitation of its full potential, however,
    depends largely on how cost-effectively it can be produced with
    high levels of purity. Themajor technology barrier in cost-effective
    production of high purity lactic acid is its down-stream separation
    and purification. And this is where; membrane-based processes
    are stepping in. Being modular in design, membrane-based pro-
    cesses offer great flexibility in scale of production depending on
    market demand. By virtue of high selectivity, membranes can
    ensure high levels of separation and purification. As membranes
    of chosen selectivity and permeability can easily be integrated
    with conventional fermentors, membrane-based processes permit
    simultaneous production and purification in the same unit. This
    eliminates the need for separate purification units and results in
    compactdesignwithreducedcapital investment.Membrane-based
    separation and purification (barring pervaporation) involves no
    phase change ensuring reduced energy consumption. Thus such
    processes can meet all the goals of process intensification. In this
    paper, we first briefly discuss the traditional processes to high-
    light themajor problems associated with these processes and then
    review the developments in membrane-based processes which
    have attempted to overcome the problems of traditional processes.
    The objective is to identify an environmentally benign, simple, eco-
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