Metabolic engineering of Escherichia coli for the production of Lacto-N-neotetraose (LNnT)

Lacto-N-neotetraose (LNnT), one of the most important human milk oligosaccharides, can be used as infants’ food additives. Nowadays, extraction, chemical and biological synthesis were utilized to obtain LNnT, while these methods still face some problems such low yield high cost. The aim current work is construct a de novo biosynthesis pathway LNnT in E. coli K12 MG1655. lgtA lgtB first expressed by plasmid, resulting titer 0.04 g/L. To improve on substrate lactose, lacZ lacI knocked out, lacY was over-expressed. As result, lactose increased from 0.01 0.09 mol/mol, elevated 0.41 In addition, regulated using Lacto-N-triose II (LNTII) measure, obtained strain for 1.04 Finally, gene expressions fine-tuned, reached 1.2 g/L, which 93% higher than control strain, 0.28 mol/mol. engineering strategy construction modulation this study applicable facilitate microbial production other metabolites coli.