Catechins are antioxidants known to exhibit beneficial biological activities. Five main catechins are found in green tea and each catechin has its own biological features. In order to fully exploit prominent biological activities of specific catechins and to develop new pharmaceuticals based on catechins, it is necessary to obtain pure catechin preparations by isolation from natural sources, or by chemical synthesis, or by biotransformation reactions with high yield and specificity. This study shows that epigallocatechin gallate (EGCG) can be hydrolysed to epigallocatechin (EGC) by a hydrolase produced by Aspergillus niger after induction by addition of EGCG to the fungal cultures. Cultures without EGCG induction and cultures, to which olive oil had been added as an inducer, did not show any EGCG hydrolysis activity. The yield of EGC could reach at least 56%. Methods based on thin-layer chromatography and high performance liquid chromatography, were used for separation and quantification of EGCG and EGC. Enzymatic conversion is an environmentally friendly and efficient approach to produce non-ester catechins.