Kinetics of standard fed batch cultures of P. pastoris overexpressing the RIB1 gene (A and B) or all RIB genes (C and D), respectively. The yeasts were cultivated on mineral medium with glucose as carbon source. Open circles represent dry cell weight (DCW), closed triangles indicate the riboflavin concentration (A and C). Open diamonds signify the specific growth rate and closed triangles (tip down) represent the specific productivity (B and D). Grey lines divide the three phases of the cultivations, namely the batch phase in the beginning, the central fed-batch phase and the stationary phase in the end.