Hepatitis B core (HBcAg) and surface (HBsAg) antigen molecules have the ability to form non-infectious, highly homogeneous virus-like particles that are widely used as drug or vaccine delivery platforms. These particles are most often obtained by their production in various biological expression platforms, such as in the yeast Pichia pastoris . In order to maximize the product yield, it is important to ensure optimal production conditions. One of the frequently utilized strategies to improve the recombinant biosynthesis productivity of the yeast P. pastoris, is to maintain a constant level of methanol in the culture medium. In order to realize it, it is necessary to control the feed flow rate of methanol in the bioreactor. In this study, a bioreactor feeding rate control program based on an PI algorithm was developed in the MATLAB environment, with the help of which the methanol concentration in the liquid culture medium was controlled at the selected level (0.1-6.0 g/L). As a result, 186 mg of purified HBsAg was obtained from one liter of culture during the production of hepatitis B surface antigen in a medium with a methanol concentration of 6.0 g/L. By screening different levels of methanol for HBcAg extraction, it was concluded that the highest productivity is achieved at a low methanol concentration (0.1 g/L) - 1308 mg per liter of culture, which is the highest yield published so far.
Methanol concentration control in two P. pastoris fermentations:
The red line represents the signal of the in-situ methanol sensor, the black line represents the filtered signal of the off-gas sensor. Green squares show experimentally determined methanol concentrations. The vertical dashed line indicates the start of the methanol induction phase and the green horizontal dashed line represents the methanol concentration control setpoint.
More information - https://doi.org/10.1007/s00449-022-02754-4 ; 10.4028/www.scientific.net/KEM.903.40
Gallery
