Poster Presentation 2-18

Production of Gallic Acid by Aspergillus niger in Submerged Fermentation: Effect of Culture Medium Filtration and Autoclavation

V.S. Onofre, L.M. Bruno, E.S. Brito and G.A.S. Pinto*

Brazilian Agricultural Research Corporation/EMBRAPA

Tropical Agroindustry Research Center

Dra. Sara Mesquita

2270 – Fortaleza/CE – Brazil - Zip Code: 60511-110

Phone: 55-85-299-1811

Fax: 55-85-299-1833

Email: gustavo@cnpat.embrapa.br

Gallic acid (3,4,5-trihydroxy benzoic acid) is applied in various fields, mainly for production of trimethoprim and propyl gallate. For microbial production of gallic acid a medium containing tannic acid, which is considered a thermolabile molecule, is utilized. This work evaluated the effect of two sterilization procedures on gallic acid production by Aspergillus niger. The medium containing: tannic acid, 20.0g.L^-1; NaNO₃, 3.0g.L^-1; KH₂PO₄, 1.0g.L^-1; KCl, 0.5g.L^-1 and MgSO₄, 0.5g.L^-1 was sterilized by filtration (Millipore 0,25mm membrane) and autoclavation (121^oC/15min and 121^oC/30min). The fermentation, conducted in 250mL erlenmeyer with 100mL of medium, was started with inoculation of 1x10⁵spores/mL and incubated at 30^oC and 150rpm for 96 hours. Tannic acid, gallic acid, total reducing sugars, pH, biomass and tannase activity were determined. After autoclaving, tannic acid in the media was reduced to 80.3 and 70.9% (15 and 30 min, respectively) of its initial value, followed by an increase in initial gallic acid level. Filtration did not affect tannic acid concentration in the medium. Filtered media presented the best gallic acid production (15.08g.L^-1) and productivity (0.314g.L^-1.h^-1). However, in the medium autoclaved at 121^oC/15min a 13.0g.L^-1 production at 72 hours of fermentation was observed. No extracellular tannase activity was detected in any media.