Strains tentatively identified as Bacillus sp. were isolated from sewage sludge and soil and shown to elaborate extracellular enzymes that degrade the extracellular polysaccharide (xanthan gum, polysaccharide B-1459) of Xanthomonas campestris NRRL B-1459. Enzyme production by one strain was greatly enhanced when the strain was incubated in a mixed culture. Products of degradation were identified as D-glucuronic acid, D-mannose, pyruvylated mannose, 6-O-acetyl Dmannose, and a (1-4)-linked glucan. These products correlate with the known structure of the gum. The complexity of the product mixture indicated that the xanthanase was a mixture of carbohydrases. The xanthanase complexes were similar to one another in temperature stability, pH and temperature optima, degree of substrate degradation, and enzymolysis products. Differences in pH stability, salt tolerance, recoverability, and yields of enzyme were observed. MATERIALS AND METHODS Microorganisms. A pure culture of a salt-tolerant strain of Bacillus sp. strain Kll (NRRL B-4529) was isolated from soil inside a decaying tree trunk (Iowa City, Iowa). A more prolific enzyme-producing mixed culture consisting of strain Kit and one other isolate (strain K17) was designated 11 + 17 (NRRL B-4530). Strain K17, isolated from the same soil sample, was tentatively identified as a Flavobacterium sp. (NRRL B-14010). Another xanthanase-producing strain, Bacillus sp. strain 13-4 (NRRL B-4533), was isolated from sewage sludge (Peoria, Ill.). Xanthomonas campestris NRRL B-1459S-4L was used to produce xanthan gum (1). The following species of Bacillus (Agricultural Research Culture Collection) were tested for xanthanase activity: B. badius, B. cereus, B. circulans, B. firmus, B. lentus, B. licheniformis, B. megaterium, B. pasteuriana, B. polymyxa, and B. subtilus.
