Influence of carbon source on cell size and production of anti LDL (-) single-chain variable fragment by a recombinant Pichia pastoris strain

The aim of this work was to study the effect of the carbon source (glycerol, sucrose, glucose or a sucrose/glucose mixture) on the production of the anti LDL (-) single-chain variable fragment (scFv) by the recombinant Pichia pastoris SMD 1168 strain as well as on the cell size. The use of glucose as a carbon source in the growth phase led to a remarkable increase in cell size compared with glycerol, while the smallest cells were obtained with sucrose likely due to the occurrence of an energetic stress. The scFv concentration seemed to be related to cell number rather than to cell concentration, which in its turn showed no significant dependence on the carbon source. Yeast cells grown on sucrose had a mean diameter (0.736 ± 0.097 μm) about 35% shorter than those grown on glucose and allowed for the highest final concentration of the scFv antibody fragment (93.7 ± 0.2 mg/L). These results demonstrate that sucrose is the best carbon source for the expression of such an antibody fragment by the recombinant P. pastoris strain, which may be very useful for the diagnostic analysis of the so-called “bad cholesterol”.