Development of a cell immobilization technique for the conversion of polysialogangliosides to monosialotetrahexosylganglioside.

Monosialotetrahexosylganglioside (GM₁) prepared from the brain of pig or bovine is an effective clinical drug in the treatment of different nervous system diseases. Generally, polysialogangliosides are transformed into GM₁ by enzymic or chemical hydrolysis due to the very poor level of natural GM₁. To continuously obtain GM₁ by cell immobilization in a packed-bed reactor. Brevibacterium casei, which is Gram-positive bacteria belonging to the order Actinomyces and family Brevibacteriaceae, can produce high-activity sialidase, are encapsulated in silk fibroin hydrogel, and subsequently packed into a reactor. The crude ganglioside is pumped into the reactor and continuously turned to GM₁. The optimal silk fibroin concentration for hydrogel preparation is 6.0% (w/v). The optimal initial biomass for immobilization is ~12% (wet weight). The optimal conversion conditions are 35 °C and 6  mL/min of flow rate. Under above conditions, the maximum GM₁ productive strength and conversion ratio can reach to 4.2 g/L·h and 313.5%, respectively. Silk fibroin is a promising material for cell immobilization because it has predominant characteristics of higher permeability and intensity. Cell immobilization for continuous GM₁ transformation could eliminate the asialo GM₁ and decrease the foreign matter from transfer medium and metabolism product. In the packed-bed reactor, continuous production of GM₁ had been under effective running at least for 15 days indicating a potential for industrial production. It is significant that this is a first report on cell immobilization for GM₁ production.