A novel thermostable xylanase from Thermomonospora sp.: influence of additives on thermostability

An alkalothermophilic Thermomonospora sp. producing high levels of xylanase was isolated from self-heating compost. The culture produced 125 IU/ml of xylanase when grown in shake flasks at pH 9 and 50 degreesC for 96 h. The c ulture filtrate also contained cellulase (23 IU/ml), mannanase(1 IU/ml) and beta -xylosidase (0.1 IU/ml) activities. The xylanase was active at a broa d range of pH (5-9) and temperature (40-90 degreesC). The optimum pH and te mperature were 7 and 70 degreesC, respectively. The enzyme was stable in th e pH range 5-8 and was thermostable with half-lives of 8 and 4 h at 60 degr eesC and 70 degreesC, respectively, but only 9 min at 80 degreesC. The effe cts of a variety of compounds to enhance the stability of xylanase at 80 de greesC was studied. Addition of sorbitol, mannitol and glycerol increased t he thermostability of xylanase in proportion to the number of hydroxyl grou ps per polyol molecule. Glycine also offered protection against thermoinact ivation, Xylan, trehalose, gelatin and trehalose-gelatin mixture had margin al effect on the thermostability of xylanase at 80 degreesC. (C) 2001 Elsev ier Science Ltd. All rights reserved.