African Journal of Biotechnology Vol. 5 (11), pp. 1135-1141, 2 June 2006   

ISSN 1684–5315 © 2006 Academic Journals        

Full Length Research Paper

Optimization of xylanase biosynthesis by Aspergillus japonicus isolated from a “Caatinga” area in the Brazilian state of Bahia

MARIA LÚCIA GARCIA SIMÕES*  and  SAMIA MARIA TAUK-TORNISIELO

Centro de Estudos Ambientais, Universidade Estadual Paulista, Avenida 24-A, 1515, Bairro Bela Vista, Rio Claro, SP 13506-900, Brazil.

*Corresponding author. E-mail: marialuciags@ig.com.br; Tel: (55) 77-34218655

Present address: Universidade Estadual do Sudoeste da Bahia, Km 4, Vitória da Conquista, Bahia, CEP 45050-020, Brazil.

Accepted 27 March, 2006

The objective of this research was to investigate the potential of xylanase production by Aspergillus japonicus and to determine the effects of cultivation conditions in the process, aiming toward optimization of enzyme production. The best temperature, as well as the best carbon source, for biomass production was determined through an automated turbidimetric method (Bioscreen-C). The enzyme activity of this fungus was separately evaluated in two solid substrates (wheat and soybean bran) and in Vogel medium, adding other carbon sources. Temperature effects, cultivation time, and spore concentrations were also tested. The best temperature for enzyme and biomass production was 25°C; however, the best carbon source for growth (determined by the Bioscreen C) did not turn out to be a good inducer of xylanase production. Maximum xylanase activity was achieved when the fungus was cultivated in wheat bran (without the addition of any other carbon source) using a spore concentration of 1 x 10⁷ spores/mL (25°C, pH 5.0, 120 h). A. japonicus is a good xylanase producer under the conditions presented in these assays.

Key words: Aspergillus japonicus, xylanase activity, enzyme optimization.