Process Biotechnology |
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Biofilms |
Electronic Journal of Biotechnology ISSN: 0717-3458 |
Vol.
10 No. 1, Issue of January 15, 2007 |
© 2007 by Pontificia Universidad Católica
de Valparaíso -- Chile |
Received April 26, 2006 / Accepted July 24, 2006 |
DOI: 10.2225/vol10-issue1-fulltext-2 |
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Production of lignocellulolytic
enzymes by Aspergillus niger
biofilms at variable water activities
Gretty
K. Villena
Laboratorio
de Micología y Biotecnología
Universidad Nacional Agraria La
Molina
Apartado 456 Lima
1, Perú
Tel: 51 1 3495647 Ext. 863
Fax: 51 1 3495670
E-mail: gkvch@lamolina.edu.pe
Marcel
Gutiérrez-Correa*
Laboratorio
de Micología y Biotecnología
Universidad Nacional Agraria La
Molina
Apartado 456 Lima
1, Perú
Tel: 51 1 3495647 Ext. 863
Fax: 51 1 3495670
E-mail: mgclmb@lamolina.edu.pe
*Corresponding author
Financial
support: This
work was partially supported by INCAGRO (Ministry of Agriculture,
Perú) and CONCYTEC (Ministry of Education, Perú) and by PhD grants
to G.K.V. (INCAGRO and CONCYTEC).
Keywords:
biofilm, cellulase, ethylene glycol, water activity, xylanase.
Abbreviations: |
aw:
water activity
BF: biofilm fermentation
ENG: endoglucanase
FPA: filter paper activity
IU: international unit
SAF: surface adhesion fermentation
SF: submerged fermentation
SSF: solid state fermentation
XYL: xylanase
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Lignocellulolytic enzyme production by Aspergillus niger was compared both in submerged fermentation (SF) and biofilm fermentation (BF) at varying water activities. Maximal filter paper activity, endoglucanase and xylanase activities were much higher in BF (2.96, 4.7 and 4.61 IU ml-1, respectively) than in SF cultures (1.71, 1.31 and 2.3 IU ml-1, respectively) but biomass yields were lower in BF than in SF (0.338 g g-1 and 0.431 g g-1, respectively). In the presence of 20% ethylene glycol (aw = 0.942) the enzyme activities decreased in both systems but BF still had higher levels (1.0, 1.0 and 2.6 IU ml-1, respectively) than SF cultures (0.6, 0.7 and 1.5 IU ml-1, respectively). An increase in xylanase specific activity of more than 2 fold (from 4.2 to 10.2 IU mg-1 biomass) was observed in the presence of 20% ethylene glycol, suggesting differential regulatory mechanisms in biofilm fermentation related to cell adhesion.
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