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Phytase production by Aspergillus niger and Aspergillus terreus in solid state fermentation using wheat bran
Acceso Abierto
Phytase, Solid State Fermentation, Wheat Bran
Phytases have been one of the focal enzymes for animal nutrition during the past two decades. In this work, the use of wheat bran as substrate for phytase production in Solid State Fermentation (SSF) was studied. In order to find the best fermentation conditions for phytase production using a laboratory strain indentified as Aspergillus niger, three different pretreatments (1: wheat bran without wash and autoclaved, 2: wheat bran washed and autoclaved, and 3: wheat bran without wash and UV exposed for 2h); and two different impregnation media (A (g/L): sucrose 5, MnSO4 0.1, MgSO4 0.5, Fe2(SO4)2 0.1, KCl 0.5, yeast extract 2; and B (g/L): glucose 5, starch 5, MnSO4 0.1, MgSO4 0.5, Fe2(SO4)2 0.1, KCl 0.5, CaCl2 0.5, NH4NO3 2) were tested. Fermentations (pH 6.5, 60% moisture at 30°C) were carried out for 12 days in 15 mL tubes containing 2.5 g of solid culture media (SCM). Subsequently, the best pretreatment and impregnation media were used to investigate the phytase production in column reactors containing 25 g of the formulated SCM, using two strains identified as Aspergillus niger and Aspergillus terreus. The fermentations (pH 6.5, 60% moisture at 30°C) were monitored for 8 days. The best fermentation conditions found using 15 mL tubes as reactor were: wheat bran without wash and UV exposed for 2h and culture media A; reaching a maximum phytase activity of 1.91±0.25 U/gdm (gram of dry matter) at 192h of fermentation. The other wheat bran pretreatments as well as culture media B do not present significant phytase activity. Maximum phytase activity reached using column reactors were: 4.2±0.71 U/gdm at 96h of culture for Aspergillus niger and 0.49±0.005 U/gdm at 96h for Aspergillus terreus. The use of 15 mL tubes fermentation system; show to be an easy and practical way to assay different fermentation conditions at the same time, obtaining rapid and reliable results. UV sterilization is an excellent process for using wheat bran as substrate for phytase production. Moreover the column reactors fermentation increased significantly the phytase productivity. The fermentation conditions obtained in this research can be used to find the best phytase producing strain for future experiments.
Asociación Mexicana de Ciencias de los Alimentos
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