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 (TB) and semi-defined (M9/YE) fermentation media used to culture a model E. coli strain engineered to produce a recombinant -galactosidase. Reductions of up to 70 did not adversely affect biomass yields attained; however, further P minimization lead 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 greater than 70 P negatively affected product expression levels. Protein functionality, assessed by km and Vmax, 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.