Production of curdlan-type polysaccharide by Alcaligenes faecalis in batch and continuous culture

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Abstract
The biosynthesis of a thermogelable, extracellular homo-.beta.-(1 .fwdarw. 3)-glucan called curdlan was studied in batch and continuous cultures of A. faecalis var. myxogenes. Curdlan production is associated with the poststationary phase of a N-depleted, aerobic batch culture. Exopolymer is not detected in single-stage, C-limited continuous cultures, but curdlan can be isolated from the effluent of a N-limited chemostat operating at a dilution rate (D) of < 0.1 h. A spontaneous variant of strain ATCC 21680 was isolated and is compatible with long-term, N-limited chemostat culture. The specific rate of curdlan production is .apprx. 4 times higher in poststationary batch cultures than in single-stage continuous fermentations. The product yield (Yp/s) associated with batch processing (nongrowing cultures) is .apprx. 0.5 g curdlan/g glucose, with CO2 being the only detectable by-product.