A new approach to obtain pure and active proteins from Lactococcus lactis protein aggregates

Abstract

The production of pure and soluble proteins is a complex, protein-dependent and time-consuming process, in particular for those prone-to-aggregate and/or difcult-to-purify. Although Escherichia coli is widely used for protein production, recombinant products must be co-purifed through costly processes to remove lipopolysaccharide (LPS) and minimize adverse efects in the target organism. Interestingly, Lactococcus lactis, which does not contain LPS, could be a promising alternative for the production of relevant proteins. However, to date, there is no universal strategy to produce and purify any recombinant protein, being still a protein-specifc process. In this context and considering that L. lactis is also able to form functional protein aggregates under overproduction conditions, we explored the use of these aggregates as an alternative source of soluble proteins. In this study, we developed a widely applicable and economically afordable protocol to extract functional proteins from these nanoclusters. For that, two model proteins were used: mammary serum amyloid A3 (M-SAA3) and metalloproteinase 9 (MMP-9), a difcult-to-purify and a prone-to-aggregate protein, respectively. The results show that it is possible to obtain highly pure, soluble, LPS-free and active recombinant proteins from L. lactis aggregates through a cost-efective and simple protocol with special relevance for difcult-to-purify or highly aggregated proteins.