Production and Recovery of Lactic Acid for Polylactide—An Overview

In the recent past the ultimate disposability of synthetic plastics has been a greater environmental concern, and it has triggered the R&D efforts in the designing of material with an environmentally friendly life cycle by integrating material design concepts with ultimate disposability, resource utilization, and conservation. Traditionally, all plastics have been manufactured from nonrenewable petroleum resources, and these plastics are nonbiodegradable. Conventional disposal methods include incineration and secured landfill, which are associated with many environmental problems, such as production of dioxins. The continued depletion of landfill space and problems associated with incineration have led to the development of biodegradable plastics such as polylactides (PLA), which are manufactured from lactic acid that in turn is produced from starch. Although production processes for lactic acid and PLA are well known, very few processes have been commercialized and still the cost of PLA is not competitive with synthetic plastics. The crux of the PLA production technology is the fermentative production of optically active lactic acid and its recovery. Many processes are reported in the literature and through patents for the recovery of optically active lactic acid and still offer an extensive scope for research and development. This article critically reviews the production and recovery processes for lactic acid and PLA production.