Resumo

IZARRA, Myriam L; SANTAYANA, Mónica L.; VILLENA, Gretty K.  e  GUTIERREZ-CORREA, Marcel. Influence of inoculum concentration on the cellulase and xylanase production by Aspergillus niger. Rev. colomb. biotecnol [online]. 2010, vol.12, n.2, pp.139-150. ISSN 0123-3475.

There is a great interest for the use of lignocellulolytic enzymes in several industries and in biomass degradation for production of biofuels and other applications. Among the microbial sources of enzymes, Aspergillus niger is one of the most used microorganisms in the production of industrial enzymes due to its high levels of protein secretion and its GRAS (generally regarded as safe) condition. The aim of the present study was to evaluate the influence of A. niger inoculum concentration in the morphology and production of cellulases and xylanases in submerged cultures. For this, 250 mL flasks containing 40 mL culture medium were inoculated with a 3% (v/v) of either 104 or 108 spores per milliliter suspension and incubated at 28 ^o C and 175 rpm during 120 hours. Lactose (10 g*L^-1) was used as the carbon source. In each case, the amount of biomass, the extracellular soluble protein, residual lactose, total celullase activity and xylanase activity were determined every 24 hours. Even thought there was not a notorious effect on the growth morphology, except in color and diameter of pellets; µmax was affected (0.06 and 0.03 h^-1 for 104 and 108 spores*mL^-1, respectively) as well as maximum biomass concentration. In addition, while the volumetric productivity of cellulase (8.2 and 8.0 UI*L^-1*h^-1 for 104 and 108 spores*mL^-1, respectively) were similar for both inocula, the productivity of xylanase was greater for the more concentrated inoculum (29.7 and 33.4 UI*L^-1*h^-1 for 104 and 108 spores*mL^-1, respectively).The results show that cellulase and xylanase productivities are closely related to the inoculum concentration.

Palavras-chave : Cellulase; xylanase; submerged culture; morphology; Aspergillus niger.

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