To quantify settling rate, samples were taken from 72 hour fed batch PBR cultures and diluted in sterile 0.9% NaCl to an OD730 of 0.8. 100µL was aliquoted into each well of a round bottom 96 well plate, with 100µL 0.9% NaCl as blank sample. Absorbance was measured at 730nm every 90 seconds for 30 minutes without shaking in a Tecan M1000 plate reader.