Tannases and other fungal enzymes applicable to the transformation of tannins and their potential for the bioremediation of effluents from the leather industry

Abstract

The use of fungal enzymes, such as tannases and oxidative enzymes, in the tannin bioconversion process offers great advantages over other biological and chemical technologies in terms of safety, reuse, and better control of process parameters, and is also a profitable and environmentally friendly method. Some reports have shown that different fungi can remove tannins from effluents, transforming them and/or detoxifying them, and using them, in some cases, as their only source of carbon. By means of different enzymes, these fungi trigger reactions that lead to the elimination of water-soluble tannins, which are the cause of toxicity in surface water bodies. Thus, these microorganisms are attractive to obtain enzyme cocktails applicable to the bioremediation of effluents rich in tannins such as those derived from the leather industry. This review aims to provide updated information on fungal sources of enzymes able to transform tannins, with emphasis on tannases, and to show alternatives to culture tannase-producing fungi and obtain the enzymes and their activity in immobilization matrices. The inducible nature of the fungal synthesis of tannases reveals the importance of acquiring basic knowledge about the physiology of tannase-producing fungi and the need for studies in different culture and scaling systems.