Optimization of rHtrA1 protein production in L. lactis. Growth conditions were optimized in order to improve protein yield. Strain MG1363(pVE8126) was grown in M17 medium supplemented with 2% glucose and buffered with β-glycerophosphate at two different concentrations (88 mM in lanes 1 and 3, and 176 mM in lane 2). Growth was performed either in fermenters at controlled pH (in 800 mL of medium, lanes 1 and 2) or in flasks (in 280 mL of medium, lane 3). Exponential phase cultures were induced by addition of EDTA at 500 μM, culture supernatants were concentrated and, after quantification, proteins were subjected to SDS-PAGE and stained by Coomassie Brilliant Blue. MWM molecular weight marker.