Recombinant expression of sweet plant protein MNEI in food-grade Lactococcus lactis

GARAY NOVILLO, J. N.; AMARANTO, M.; BARRA, J. L.

Córdoba

Congreso; LII Reunión anual SAIB; 2016

SAIB

The world prevalence of metabolic diseases due to the consumption of sugar is increasing dramatically. Sweet proteins are rising as potential replacements for the currently available sweeteners in industrial food and beverage preparations. These natural sweet compounds can be 100,000 times sweeter than sucrose on a molar basis. In this study we analyzed whether the expression of MNEI protein (a single chain derivative of the sweet plant protein Monellin) in food-grade Lactococcus lactis could be used for industrial purpose. We initially designed an expression vector containing a strong constitutive promoter followed by a lactococcal signal peptide downstream fused with L. lactis codon optimized MNEI coding sequence and a His-tag sequence for later affinity protein purification. In addition a derivative plasmid for cytosolic expression in L. lactis was generated by elimination of the signal sequence. The current results exhibited that recombinant MNEI has been successfully secreted and expressed intracellularly in food-grade L. lactis. Cytosolic production of MNEI showed to be both effective and reproducible, and large quantities of soluble MNEI were purified. On the other hand, although extracellular purification showed to be minority, further expression in an extracellular protease mutant strain is currently in process. This is the first time that MNEI is expressed in L. lactis.