Antifoam addition increases the total yield of GFP in 20 mL P. pastoris cultures. Bar charts showing the total yield of GFP (μg) at 48 h in 20 mL P. pastoris cultures following addition of Antifoam A (A), Antifoam C (B), J673A (C), P2000 (D) and SB2121 (E) at concentrations from 0-1%. The error bars show the respective standard deviations. In all cases n = 9. The numbers within each bar are the corresponding specific yield (μg OD595-1) with the respective standard deviations in parentheses (n = 9). The horizontal line is a visual aid to link the mean optical density (grey squares) for each concentration of antifoam across the full experimental range; error bars show the respective standard deviations (n = 9). In each case a one-way ANOVA showed that P < 0.001. Asterisks show the significance of the total yield and specific yield data for each antifoam concentration compared to the respective 0% antifoam control as determined by a Dunnett's multiple comparison test, where * = P ≤ 0.05 and ** = P ≤ 0.01.