초록
Dissolved oxygen (DO) has been stated as a key parameter for Pichia pastoris (Mut<SUP>+</SUP>) cultures growing on methanol. DO set point (DO<SUB>SP</SUB>) - between 5 and 50% air saturation - with time-varying oxygen transfer rate (OTR) was investigated during the induction phase of fed batch cultures producing the heterologous Rhizopus oryzae lipase (ROL). DO around 25% was found to be the best operating condition in terms of ROL total productivity, with 4-fold increase in respect to DO<SUB>SP</SUB> of 5% (minimum value), and also corresponded with the highest specific rates of growth (μ), methanol consumption (q<SUB>S</SUB>), oxygen uptake (q<SUB>O2</SUB>), carbon dioxide production (q<SUB>CO2</SUB>) and ROL activity production (q<SUB>P</SUB>). However, the highest overall product yield (Y<SUP>*</SUP><SUB>P/X</SUB>) was obtained around DO<SUB>SP</SUB> of 10%, with an increase of 45% compared with maximal DO<SUB>SP</SUB> studied (50%). Specific rates and Y<SUP>*</SUP><SUB>P/X</SUB> were lower at the extremes of the DO range tested. The results validate that oxygen tension is essential to improve bioprocess efficiency in ROL production and enhances reliability of the system by keeping DO at optimal conditions. Productivity and yield can be optimized, thus reducing oxygen supply and energy requirements, even for different target proteins although presenting different DO optimal values.