using tannic acid as a carbon source [6]. Generally, the production of this enzyme occurs during the first steps of microbial growth because tannase is a primary metabolite [13,20]. According to Aguilar et al. [21], the maximal tannase production by Aspergillus sp. is attained between 1 to 3 days of cultivation, as observed for the Aspergillus sp. GM4 extracellular tannase. The decrease in the tan- nase production after three days of cultivation may be due to the reduction in substrate availability and the se- cretion of proteases that can act on secreted tannase.
Tannase can be produced either constitutively or un- der induction, depending on the strain and fermentation conditions. The enzyme production by Aspergillus sp. GM4 was induced in the presence of 2% (w/v) tannic acid, methyl gallate and gallic acid. However, a basal level of tannase production was observed when glucose was used as a carbon source. According to Bradoo et al. [19], the fungus A. japonicus produced tannase constitu- tively in culture medium containing simple or complex sugars, but the production is increased when tannic acid is the sole carbon source [19]. There is some controversy regarding the tannase regulation mechanism and the spe- cific roles of some compounds in the induction and re- pression of tannase expression. Tannic acid cannot act directly as an inducer because tannic acid is a large molecule that cannot cross the cell membrane, and there is no known tannic acid transporter. Therefore, the basal levels of tannase synthesis are important for initiating tannic acid
using tannic acid as a carbon source [6]. Generally, the production of this enzyme occurs during the first steps of microbial growth because tannase is a primary metabolite [13,20]. According to Aguilar et al. [21], the maximal tannase production by Aspergillus sp. is attained between 1 to 3 days of cultivation, as observed for the Aspergillus sp. GM4 extracellular tannase. The decrease in the tan- nase production after three days of cultivation may be due to the reduction in substrate availability and the se- cretion of proteases that can act on secreted tannase. Tannase can be produced either constitutively or un- der induction, depending on the strain and fermentation conditions. The enzyme production by Aspergillus sp. GM4 was induced in the presence of 2% (w/v) tannic acid, methyl gallate and gallic acid. However, a basal level of tannase production was observed when glucose was used as a carbon source. According to Bradoo et al. [19], the fungus A. japonicus produced tannase constitu- tively in culture medium containing simple or complex sugars, but the production is increased when tannic acid is the sole carbon source [19]. There is some controversy regarding the tannase regulation mechanism and the spe- cific roles of some compounds in the induction and re- pression of tannase expression. Tannic acid cannot act directly as an inducer because tannic acid is a large molecule that cannot cross the cell membrane, and there is no known tannic acid transporter. Therefore, the basal levels of tannase synthesis are important for initiating tannic acid
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