Symbiosis culture of probiotic Escherichia coli Nissle 1917 and Lactobacillus rhamnosus GG using lactate utilization protein YkgG

Abstract

The abundance and biodiversity of intestinal bacteria play a critical role in immune system. Escherichia coli Nissle 1917 (EcN), a tractable probiotic cell has emerged as a ‘smart microbe’ that can provide therapeutic modalities at the sites of disease. Additionally, Lactobacillus rhamnosus GG (LGG) represents one of the key probiotics in clinical studies with the ability to enhance intestinal immunity in symbiosis with other cells. To fully exploit the advantages of EcN and LGG, we optimized the commensal culture medium for LGG and EcN, succeeded by the establishment of a novel fluorescence-based colony quantification. From the metabolite analysis, more lactate was consumed when LGG is co-cultured with EcN; thus, YkgG was further explored as it was foreseen to be the enzyme responsible for lactate conversion to pyruvate. The YkgG enzyme from EcN has Vmax of 64.5 mM min-1 and catalytic ability kcat/Km of 2055 mM-1 min-1, that is 6-fold compared to E. coli MG1655. Co-culture strategy of EcN with LGG in the mimic gastrointestinal tract increased the CFU by 50 % and 40 % within 5 mins and 10 mins, respectively. This practical, feasible, and promising symbiosis system aims to accelerate the application of probiotic in healthy food industries.