The effect of the feeding procedure on the formation of the product was investigated in more detail at the mRNA level. A quantitative sandwich hybridization assay which was developed earlier in our laboratory was applied [21, 22] . Figure 6 shows the levels of mRNAs encoding the procollagen II chain, AOX1, EF3 (translational factor), and C-P4H. The level of procollagen II mRNA was already high during the first 12 h when the cultures were grown in a batch mode on methanol in both types of cultivations. In the reference culture with pulse feeding, the procollagen II mRNA level decreased to a very low level after the start of the feeding. In contrast, the mRNA level stayed high during the whole cultivation in the culture with quasi-continuous feeding of methanol, being approximately 10 times higher when compared to the pulse feed method.