Process Biotechnology

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  
RESEARCH ARTICLE

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

Abstract
Full Text

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.

Supported by UNESCO / MIRCEN network