High level production of a cellulase-free xylanase in glucose-limited fed batch cultures of a thermophilic Bacillus strain.
Bacillus sp. strain XE and its mutant derivative strain D3 produce a thermostable xylanase which is suitable for enzymatic bleaching of kraft pulp. Xylanase synthesis was shown to be induced by the soluble products of xylan hydrolysis (xylooligosaccharide) and equally, catabolically-repressed when these oligosaccharides accumulate in the medium. An optimal balance between these two antagonistic effects was obtained in a carbon-limited, fed-batch culture with continuous xylooligosaccharide feeding. To reduce substrate cost, the xylooligosaccharide could be 90% substituted by glucose without reduction of the xylanase production rate. Xylanase production ceased when the activity reached approximately 380 U ml-1 due to an amino acid shortage. A continuous supply of exogenous amino acids allowed the production to continue to more than 1000 U ml-1.
Samain
E
E
Centre de Recherches sur les Macromolecules Végétales (CERMAV-CNRS), Grenoble, France.
Debeire
P
P
Touzel
J P
JP
D000596:Amino Acids / Q000378:metabolism; D001407:Bacillus / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D001709:Biotechnology; D002480:Cellulase / Q000378:metabolism; D004795:Enzyme Stability; D005947:Glucose / Q000378:metabolism; D007700:Kinetics; D009154:Mutation; D009844:Oligosaccharides / Q000378:metabolism; D013696:Temperature; D043325:Xylan Endo-1,3-beta-Xylosidase; D014995:Xylosidases / Q000096:biosynthesis*
D000596:Amino Acids; D009844:Oligosaccharides; D014995:Xylosidases; D043325:Xylan Endo-1,3-beta-Xylosidase; D002480:Cellulase; D005947:Glucose