A novel cold-tolerant Clostridium strain PXYL1 isolated from a psychrophilic cattle manure digester that secretes thermolabile xylanase and cellulase.
A Clostridium strain PXYL1 was isolated from a cold-adapted cattle manure biogas digester at 15 degrees C. It could grow at temperatures as low as 5 degrees C up to 50 degrees C with highest specific growth rate at 20 degrees C 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 20 degrees C. 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 40 degrees C and 8 min at 50 degrees C but stable for over 2 h at 20 degrees C. The crude enzyme released reducing sugars (1.25 g l(-1)) from finger millet flour at 20 degrees C, while commercial food-grade xylanases showed no hydrolysis at this temperature. This is the first report of a Clostridium strain growing at 20 degrees C and producing an array of xylanolytic and cellulolytic enzymes, possessing low temperature optima of 20 degrees C, which may facilitate degradation of plant fibre under low-temperature conditions.
Akila
G
G
Department of Chemistry, Biochemistry Laboratory, Indian Institute of Technology, Madras, 600 036, Chennai, India.
Chandra
T S
TS
D000818:Animals; D002417:Cattle; D002480:Cellulase / Q000378:metabolism*; D003013:Clostridium / Q000201:enzymology / Q000254:growth & development / Q000302:isolation & purification*; D003080:Cold Temperature; D004795:Enzyme Stability; D008372:Manure / Q000382:microbiology*; D008897:Panicum / Q000378:metabolism; D043325:Xylan Endo-1,3-beta-Xylosidase; D014990:Xylans / Q000378:metabolism; D014995:Xylosidases / Q000378:metabolism*
D008372:Manure; D014990:Xylans; D014995:Xylosidases; D043325:Xylan Endo-1,3-beta-Xylosidase; D002480:Cellulase