The production of extracellular polysaccharide by $\underline{Methylomonas}$ $\underline{mucosa}$ (NRRL B-5696) was investigated. This microorganism utilizes only methanol as carbon source for growth and producing exopolysaccharide.
Batch, Fed-batch and continuous cultures were performed and the yield and productivity of polysaccharide in each system were compared. The continuous culture gave the best productivity but the yield was less than that of batch culture.
In batch culture the growth of the microorganism and production of polysaccharide was inhibited when methanol concentration was above 1%(v/v). And as the C/N ratio (g methanol/ g ammonium sulfate) was increased, more polysaccharide was produced and the cell mass decreased. $Mg^{2+}$ ion was found to be essential for polymer production.
In fed-batch culture the polysaccharide concentration was enhanced about 4 times than that of batch culture, but the yield was lower than batch culture. The productivity of continuous feeding fed-batch was higher than that of batch and intermittent feeding fed-batch culture due to no methanol limitation and inhibition condition that appeared in intermittent feeding fed-batch culture.
In continuous culture, pure oxygen was added to avoid the oxygen limitation. As the dilution rate was increased up to $0.21h^{-1}$, the yield and the productivity were increased.
The solution viscosity of the obtained polymer increased exponentially with the increase of the polymer concentration.