08.08.2015   Advances in Biochemical Engineering/Biotechnology

Summary

E. coli has the capability of utilizing many different sugar substrates and produce a wide spectrum of fermentation products (Fig. 4). However, redirec­tion of a microorganism’s metabolism for the efficient production of a single compound is often far more complex than anticipated. The expression level of multiple genes, which may not be predictable, must be optimized for performance. Our success in generating microbial biocatalysts capable of pro-

Fig.4 Due to the plasticity of E. colfs metabolism, a variety of sugars are converted to a wide spectrum of microbial products. Acetate, D(-)-lactate, succinate, and pyruvate are natural E. coli products; recombinant strains use genes from Z. mobilis, C. boidinii, B. stearothermophilus and P. acidilactici for production of ethanol, xylitol, L-alanine, and L(+)-lactate, respectively. The maximum percent of the theoretical yield are shown as reported in [77,121,138,146] (Yomano et al. 2007)

ducing high titers of chemicals has been dependent on an approach that utilizes the organism’s natural ability to evolve. Genetically engineered mi­croorganisms require a period of time to adapt to the growth environment. This was accomplished by growing the microbial biocatalysts in the desired mineral salts medium with high sugar concentrations and allowing them to evolve in the new environment. This method has resulted in microbial bio­catalysts proficient in production of ethanol and other commodity products, demonstrating that this approach can be applied to many different microbial biocatalysts to improve the overall efficiency and titer.