A novel cold-tolerant Clostridium strain PXYL1 isolated from a psychrophilic cattle manure digester that secretes thermolabile xylanase and cellulase

摘要

A Clostridium strain PXYL1 was isolated from a cold-adapted cattle manure biogas digester at 15degreesC. It could grow at temperatures as low as 5degreesC up to 50degreesC with highest specific growth rate at 20degreesC and is a psychrotroph. It produced extracellular hydrolytic enzymes namely xylanase, endoglucanase, beta-xylosidase, beta-glucosidase and filter paper cellulase, all of which had maximal activity at 20degreesC. The induction of xylanase was highest on birch wood xylan (37 IU{mg protein}(-1)) compared with xylose (1.11 IU{mg protein}(-1)), cellobiose (1.43 IU{mg protein}(-1)) and glucose (no activity). The xylanase was thermolabile with a half-life of 30 min at 40degreesC and 8 min at 50degreesC but stable for over 2 h at 20degreesC. The crude enzyme released reducing sugars (1.25 g l(-1)) from finger millet flour at 20degreesC, while commercial food-grade xylanases showed no hydrolysis at this temperature. This is the first report of a Clostridium strain growing at 20degreesC and producing an array of xylanolytic and cellulolytic enzymes, possessing low temperature optima of 20degreesC, which may facilitate degradation of plant fibre under low-temperature conditions. (C) 2003 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved. [References: 26]