Fig. 4

Statistical approach to determine the minimal number of replicates for a fed-batch screening campaign. a Mean relative protease activity of fed-batch cultivations with three individual fed-batch MTP’s (fed-batch MTP 1–3). The same B. licheniformis strain was used for all cultivations. The mean protease activity of fed-batch MTP 1 was normalized to 100%. Protease activities of fed-batch MTP 2 and 3 were set in relation to fed-batch MTP 1. Error bars symbolize the standard deviation (n = 6). An univariate ANOVA (F (2 15) = 1.21, p = 0.33) showed that there is no significant difference (α = 5%) between the investigated plates. Cultivation conditions: fed-batch MTP, n = 1000 rpm, d₀ = 3 mm, V_{L, Main culture (fed-batch)} = 0.77 mL, 30 °C. b Number of replicates as a function of the detectable difference and standard deviation. The required detectable difference and statistical power are stated within the figure. The number of replicates was calculated with the MATLAB function sampsizepwr with a two-tailed t-test (normally distributed) as test type