Klebsiella sp. isolated from the Sumida River produced an extracellular polysaccharide (BS-1) whose physical properties are of interest to the food industry. However, the yield of BS-1 was not so high; only 3.2% of carbon source in the medium was converted into BS-1.
In order to increase the yield of BS-1, optimal conditions for cultivation i.e. composition of the medium, temperature, pH, aeration, and shaking were surveyed. As a result, it was found that lactose was the most effective carbon source for BS-1 production and that the yield increased when the organism was incubated at 30°C under aerobic conditions. The maximum yield was obtained when the initial pH of the medium was adjusted to 10.0. Under the optimum condition as mentioned above, the yield of BS-1 increased to 12.8g/l and the conversion ratio of the carbon source into BS-1 reached 43%.