These findings were supported also by the higher amount of C-P4H activity (see Figures 3C and 3D , cf. Table 1 ). C-P4H activity was measured from several time points and found to be 2 to 8 times higher in different cultures with quasi-continuous methanol feeding compared to the parallel reference cultures in each experiment (see Figure 5 ). Doubling the methanol concentration in the feeding solution (cf. experiment 4 A in Table 1 , and grey bar in Figure  5 ) led to higher activities compared to the reference, but the C-P4H activity was slightly lower than in the experiment with the lower feed rate. Surprisingly, also the cell density was not increased in this cultivation compared to the culture with quasi-continuous feed of more diluted feed.