Recombinant human growth hormone (r-hGH) is used to treat dwarf patients, and to enhance the physio- logical functions of middle-aged or elderly persons so that senility can be delayed. As with other proteins such as intcrferons, colony-stimulating factors insulin like growth factors and human serum albumin, r-hGH has been successfully produced using recombinant Escherichia coli [1]. Because most proteins are intra- cellularlyaccumulated in recombinant Escherichia coli ,productivity is proportional to the final cell-density and the specific productivity (i.e. the amount of product formed per unit cell mass per unit time). High cell-density fermentation (HCDF) techniques for culturing Escherichia coli have been developed to improve productivity,and to provide advantages such as reduced volume,lower production costs and reduced investment in equipment.
Fed-batch processes have most often been used to obtain high cell-density [2-7]. However, this technique has drawbacks, the formation of growth-inhibitory *Corresponding author. by-products, such as acetate. Acetate fl)rmation can be reduced or prevented by altering the formulation of the medium, for example, acetate is not produced when glycerol is used as a carbon source [1]. The objective of this study was to investigate the effects of fermentation conditions including the types of carbon source (glucose and glycerol), dissolved oxygen and culture system (normal and high cell density fermentation) on the production of recombinant human growth hormone in Escherichia coli.