Sorbitol as an Alternative Carbon Source for Enhanced Production of Acid α-Glucosidase under Sugar Starvation in Rice Cell Cultures

초록

Pompe disease is known to be caused by the deficiency of acid α-glucosidase (GAA) [1]. GAA could be produced by transgenic rice cell culture systems, which have several advantages such as safety as well as proper post translational modification. RAmy3D promoter, that is hexokinase-dependent and induced by surgar starvation, is used to overcome low protein productivity in rice cell cultures [2]. Since sugar starvation also induces cell death and proteolysis, alternative carbon sources which are not recognized by hexokinase can be used for the delay of cell death and enhancing target recombinant protein production [3]. In this study, alternative carbon sources such as fructose, mannitol, and sorbitol were supplemented into culture medium. In sugar-free media, most of the cells died at day 9. When sorbitol was added, cell viability could be maintained for longer period up to 24 days depending on added amount. In addition, GAA production was enhanced 1.7-fold compared to that of control condition. Addition of sucrose and fructose also increased GAA production, but this was due to the increase of cell mass. However, mannitol did not show any significant effects. In conclusion, sorbitol is thought to be a potential alternative carbon source under sugar starvation for enhancing both cell viability and GAA production.