A microbial-flocculant-producing Gram-negative bacterium, strain KT201, was isolated from soil samples and identified as Alcaligenes cupidus. This strain secreted flocculant in a culture broth having a flocculant production medium which included sucrose. The flocculant (Al-201) was found to aggregate a suspended kaolin solution without cations, although its flocculating ability was significantly enhanced by the addition of bivalent/trivalent cations such as Ca²⁺ and Al³⁺. Al-201 was purified by precipitation with ethanol and cetylpyridinium chloride, and had a gel filtration chromatography molecular weight of over 2×10⁶. The constituent sugars of Al-201 were glucose, galactose, and glucuronic acid (molar ratio, 6.34:5.55:1.0), with this flocculant occurring in 10.3% acetic acid as an acetyl ester group.

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