Thermotolerant B. coagulans Strains with Enhanced Ability to Produce Optically Pure D (-) Lactic Acid

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Researchers
Keelnatham T. Shanmugam
Lonnie O. Ingram
Qingzhao Wang
Managed By
John Byatt
Assistant Director 352-392-8929
Patent Protection
US Patent 8,900,835

Genetically Modified Bacterium Isolates D (-) Lactic Acid for Efficient Production of PLA Plastics

This genetically modified strain of Bacillus coagulans is a biocatalyst that produces optically pure lactic acid at 50-55 oC. Current industrial bacterial biocatalysts must be used at 30-37 oC ; using a biocatalyst that can be grown at higher temperatures increases the rate of production and reduces the risk of contamination, as other organisms don’t survive the higher heat. The major use for D (-) lactic acid is in the production of polylactic acid (PLA) plastics. Although the bulk of the lactic acid in these plastics is the L (+) form, small amounts of D (-) lactic acid are added to reduce the plastic melting temperature and thus improve ease of processing. Most biocatalysts produce a mixture of D (-) and L (+), which are difficult to separate from each other because their physiochemical properties are virtually identical. University of Florida researchers have developed a strain of B. coagulans that tolerates higher heat, lowering the risk of contamination, and produces only optically pure lactic acid, increasing ease and rate of production of the end product. Fermentation to produce PLA plastics using B. coagulans can be conducted at higher temperatures than those using other biocatalysts.

Application

Genetically modified bacterium used to produce optically pure D (-) lactic acid for use in PLA plastics

Advantages

  • B. coagulans can be grown and fermented at higher temperatures, minimizing contamination in large-scale, industrial fermentations
  • Produces optically pure D(-)-lactic acid required for PLA production, making isolation of D (-) easier and cheaper

Technology

Using growth-based selection, scientists genetically engineer a bacterial strain or biocatalyst to be more tolerant of temperatures ranging from 30 oC to 65 oC. The aim is to develop a clone that exhibits faster/higher cell growth, rapid consumption of different carbon sources, the ability to use multiple sugars simultaneously, tolerance of toxic chemicals in the carbon source, high production yield and productivity of lactic acid coupled with the low production of other organic acids. The resulting bacterium produces optically pure lactic acid.