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Microbial Lactic Acid, Its Polymer Poly(lactic acid), and Their Industrial Applications

2009; Springer Nature; Linguagem: Inglês

10.1007/978-3-642-03287-5_13

1862-5584

K. Jim Jem, J. F. van der Pol, Sicco de Vos,

Carbon dioxide utilization in catalysis

Lactic acid occurs widely in nature and is produced by many life forms from bacteria to human cells. Identified in 1780 as a component of sour milk, it has been used in food, drink, pharmaceutical, cosmetics, chemical and electronic industries in different forms, such as free acid (typically 80–92% in water), salts (e.g., calcium lactate), and esters (e.g., ethyl lactate). If one calculates the amount of its derivatives back to the equivalent amount of original lactic acid, the total global market volume in 2008 is estimated at around 260,000 tons of lactic acid (calculated at 100% concentration) for traditional applications [excluding poly(lactic acid) (PLA)]. PURAC has a market share of over 60%, and other producers share around 30–40% of the global commercial market for lactic acid and its derivates. Whereas lactic acid was historically produced through a chemical process, today more than 95% of the lactic acid produced is derived from biological resources (e.g., sucrose or glucose from starch) by microbial fermentation, which typically produces the l-(+) form of lactic acid. Only one producer still uses petroleum-based chemicals to synthesize racemic mixture of the d-(−) and l-(+) forms of lactic acid. With the shortage and/or unstable supply of crude oil, its astonishing price variation, and the concerns of its environmental impact and the greenhouse gases released by petroleum-based plastic and chemical industries, bio-based plastics have gained significant attention. Among them, PLA is not only biodegradable, but is also regarded as most cost-competitive. NatureWorks, the largest producer of PLA, has expanded its annual production capacity from 70,000 to 140,000 tons in 2008–2009. Several other producers are setting up pilot plants in China and Europe. By 2020, the global annual production capacities of the lactic acid and PLA industries are very likely to exceed one million tons. Compared with traditional petroleum-based plastics, PLA is still more expensive and usually has less desirable mechanical and physical properties, which limit its commercialization and applications. The recent commercialization of d-(−)-lactic acid and lactide has the potential to improve the mechanical and thermal characteristics of PLA resins and blends by the crystallization of stereocomplex PLA, which allows application in previously unattainable high-end markets. The status and industrial (nonmedical) applications of microbial lactic acid and PLA are discussed in this chapter. The current issues and future work needed to develop the lactic acid and PLA industries are also reviewed. This chapter is meant to serve as an easy-to-read practical review for those interested in the general status and future of the lactic acid and PLA industries.