Abstract
Tannase (Tannin acyl hydrolase EC 3.1.1.20) is produced in high yield by Aspergillus niger LCF 8. Optimal conditions of production were determined. Induction of the strain, pH and aeration are the main parameters influencing the production yield. A pure enzyme sample (1,980 nKat/mg protein) was obtained by physical disruption of the mycelium, ultrafiltration and high pressure size exclusion chromatography (HPSEC). The biochemical properties of the enzyme were investigated. It is a glycoprotein of about 186,000 Dal, containing 43% sugars. The pI is 4.3. The optimal temperature for activity was 35°C. Esterase activity peaked at pH 5.0 while tannase activity was optimal at pH 6.0. The tannase was stable between pH 3.5 and 8.0 at temperature below 50°C. An in situ immobilized enzyme was also obtained. This was highly active towards gallotannins and ellagitannins. Since A. niger is officially approved in numerous countries for enzyme production in the food industry, the in situ immobilised tannase can be used for removing tannins responsible for unwanted effects in food or cosmetology processing.
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