Abstract
Filamentous fungi of the group are native soil saprophytic fungi. Industrial strains of this group have been extensively used for the production of plant degrading enzymes for the food and beverage, animal feed and paper-and-pulp industries. Recombinant DNA technology allows for the overproduction of these enzymes in copious amounts. The advantages and limitations of A. niger as recombinant host for enzyme production are briefly discussed. Specific attention is devoted to the overproduction of several cellulases and hemicellulases to high homogeneity in the protease-deficient strain A. niger D15. The size, temperature and pH optima of the heterologous enzymes were shown to be similar to that of their natively produced counter parts. The optimization of enzyme production in dilute sugar cane molasses, using a recombinant strain producing the xylanase II of Trichoderma reesei as example, was also demonstrated.
Highlights
Filamentous fungi belonging to the genus Aspergillus are commonly associated with biomass degradation and produce a wide range of secreted hydrolases, including native endoand exo-acting enzymes involved in the degradation of plant cell walls
The A. niger D15[pGT], A. niger D15[xyn2] and A. niger D15[xyn2]PyrG+ strains were inoculated to a spore concentration of 1x106 spores/ml in 20 ml of 20% molasses at pH 6.5 and cultivated under optimal conditions in order to determine if the uridine dependency of A. niger D15[xyn2] plays a significant role in the -xylanase activity or biomass production
The strain A. niger D15 have previously proven to be an excellent host for the production of heterologous proteins [31]
Summary
Filamentous fungi belonging to the genus Aspergillus are commonly associated with biomass degradation and produce a wide range of secreted hydrolases, including native endoand exo-acting enzymes involved in the degradation of plant cell walls. We explored the impact of cultivation conditions and strain properties on growth and production of recombinant Xyn2 -xylanase produced by A. niger D15 in a medium consisting solely of diluted molasses (diluted to 20% molasses in water). The optimal concentration of the molasses required for optimal Xyn2 production, was determined by using flasks containing 20 ml of 10, 20, 30, 40 and 50% molasses (v/v) inoculated with 1x105 spores/ml of the A. niger D15[pGT] and A. niger D15[xyn2] strains, respectively.
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