Minimization of phosphorus in the fermentation media of Escherichia coli producing a model recombinant protein

In the biotechnology sector, a main processing goal is the production of high cell (and hence product) yields. Therefore, little consideration is traditionally given to the potential environmental impacts of excess culture media ingredients. This study investigated the scope for reducing the quantities of phosphorus (P) present in both a complex terrific broth (TB) and semi-defined minimal media 9/yeast extract (M9/YE) fermentation media used to culture a model Escherichia coli strain engineered to produce a recombinant β-galactosidase. Reductions of up to 70 % did not adversely affect biomass yields attained; however, further P minimization leads to a drop in dry cell weight obtained, particularly in the case of semi-defined media. P concentration in TB media had little effect upon total recombinant protein expression levels achieved. In the case of M9/YE media, reductions >70 % P negatively affected product expression levels. Protein functionality, assessed by k_m and V_max, was not influenced by the type of media nor the P concentration present. Overall, the results indicate that P can be reduced by a minimum of 70 % without adversely affecting the biomass yield, the recombinant protein yield or functionality. Such reductions should lead to significant P savings in the large-scale manufacturing of proteins produced by genetic engineering in E. coli.