The production of hemicellulases by Thermomyces lanuginosus strain SSBP: influence of agitation and dissolved oxygen tension |
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Authors: | S Singh J C du Preez B Pillay B A Prior |
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Institution: | (1) Department of Biological Sciences, ML Sultan Technikon, P.O. Box 1334, Durban 4000, South Africa e-mail: singhs@wpo.mlsultan.ac.za Tel.: +27-31-3085325 Fax: +27-31-3085351, ZA;(2) Department of Microbiology, University of Durban-Westville, Private Bag X54001, Durban 4000, South Africa, ZA;(3) Department of Microbiology and Biochemistry, University of the Orange Free State, P.O. Box 339, Bloemfontein 9300, South Africa, ZA;(4) Department of Microbiology, University of Stellenbosch, Private Bag X1, Matieland 7602, South Africa, ZA |
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Abstract: | Shake-flask cultivation of T. lanuginosus strain SSBP on coarse corn cobs yielded β-xylanase levels of 56,500 nkat/ml at 50 °C, whereas other hemicellulases (β-xylosidase,
β-glucosidase, and α-l-arabinofuranosidase) were produced at levels less than 7 nkat/ml. Cultivation on d-xylose yielded much lower levels of xylanase (350 nkat/ml), although other hemicellulase levels were similar to those produced
on corn cobs. The influence of agitation rate and dissolved oxygen tension (DOT) on hemicellulase production was studied further
in a bioreactor. On xylose, xylanase activities of 4,330 nkat/ml and 4,900 nkat/ml were obtained at stirrer speeds up to 1,400 rpm
to control DOT. At a constant stirrer speed of 400 rpm, xylanase activities of 10,930 nkat/ml and 15,630 nkat/ml were obtained
when cultivated on xylose and beechwood xylan respectively, despite DOT levels below 5% for the duration of fermentation.
The results indicate that there is an interaction between agitation rate and DOT, impacting on xylanase and accessory enzyme
production. Higher agitation rates favoured the production of xylosidase, arabinofuranosidase and glucosidase by T. lanuginosus strain SSBP, whereas the lower agitation rates favoured xylanase production. Rheological difficulties precluded cultivation
on corn cobs in the bioreactor. Volumetric xylanase productivities of 1,060,000 nkat/l · h and 589,000 nkat/l · h obtained
on beechwood xylan and xylose indicate that T. lanuginosus strain SSBP is a hyper-xylanase producer with considerable industrial potential.
Received: 5 May 1999 / Received revision: 31 May 2000 / Accepted: 3 June 2000 |
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