Production and accumulation of toxic by-products such as acetic acid can inhibit the growth of recombinant cells and the expression of exogenous gene in E.coli. An anionic exchange resin, A-D 3-1, which is high in adsorption selectivity and capability for acetic acid, was screened from a variety of resins based on its physical and chemical properties.On the scale of shake flask culture, the addition of 1.0 g resin per 30 ml medium was insignificant for the cell growth, however,it could improve the hEGF expression significantly. The batch culture in 2.5 L fermentor showed that in-situ adsorption of acetic acid by anionic exchange resin could enhance the expression level of interested protein and reduce the fermentation period by 2 hours. And up to 10% improvement of hEGF (human epidermal growth factor)volumetric productivity (225.0 mg·L -1 ) could be achieved by supplementing 3.3 g resin per 100 ml medium.
Recombinant B subtilis MU108 was immobilized in PUF matrix for enhanced production of PGA The results showed that PUF matrix was suitable for partial immobilization of recombinant cells in a three phase bioreactor With immobilized bacteria, the expression of PGA and the growth of cells were compared between batch cultivation in three phase fluidized bed and continuous bioprocess in three stage cultivation system The productivity of PGA in batch cultivation was improved significantly with the increase of aeration A new three stage continuous cultivation system was designed and tested.It separated the whole process into three stages: cell growth, high temperature induction and PGA expression After the beginning of nutrient continuous feed at mid or late log phase,cell density, pH and residual glucose in the first and third stage bioreactor would be maintained steady up to 65 h Compared with those in the batch fermentation, the average productivity of PGA was improved by 190% in the three stage continuous fermentation, and the time for PGA expression was also extended from ca.10 h to ca 60h These results suggested that this new three stage cultivation technique with immobilized cells might be very efficient for large scale production of heterogeneous
