A novel alkalothermophilic actinomycete having optimum growth at pH 9 and 50 degreesC was isolated from self-heating compost from the Barabanki district of Uttar Pradesh, India. Based on its morphology, susceptibility of spores to heat and novobiocin, guanine-cytosine content of chromosomal DNA and cell wall composition, the organism was classified under Thermomonospora. The alkalothermophilic actinomycete produced 23 IU/ml carboxymethyl cellulase (CMCase). The CMCase was purified by fractional ammonium sulphate precipitation followed by cellulose affinity chromatography and Sephacryl S-200 gel filtration. The CMCase had a molecular weight of 38 KD and pH of 4.1. The enzyme exhibited optimum activity at pH 5 and temperature 50 degreesC. The CMCase showed pH stability in the range 7-10. The enzyme retained 100% activity at 50 degreesC for 72 h and had half-lives of 7 and 3 h at 60 degreesC and 70 degreesC, respectively. The CMCase was stable in the presence of commercial detergents such as Ariel, Henko and Surf Excel, indicating its potential as an additive to laundry detergents. (C) 2001 Elsevier Science Ltd. All rights reserved.