Nonsterile L-Lysine Fermentation Using Engineered Phosphite-Grown

Fermentation using is an important method for the industrial production of amino acids. However, conventional fermentation processes using are susceptible to microbial contamination and therefore require equipment sterilization or antibiotic dosing. To establish a more robust fermentation process, l-lysine-producing was engineered to efficiently utilize xenobiotic phosphite (Pt) by optimizing the expression of Pt dehydrogenase in the genome locus. This ability provided with a competitive advantage over common contaminating microbes when grown on media containing Pt as a phosphorus source instead of phosphate. As a result, the engineered strain could produce 41.00 g/L l-lysine under nonsterile conditions during batch fermentation for 60 h, whereas the original strain required 72 h to produce 40.78 g/L l-lysine under sterile conditions. Therefore, the recombinant strain can efficiently produce l-lysine under nonsterilized conditions with unaffected production efficiency. Although this anticontamination strategy has been previously reported for other species, this is the first time it has been demonstrated in ; these findings should aid in the further development of cost-efficient amino acid fermentation processes.