Tannin degrading enzymes: Catalytic properties and technological perspectives

Abstract

Tannins are an interesting group of natural compounds of a polyphenolic nature that can be found in the plant kingdom, principally in leaves, bark, stems, wood, flowers, fruits, and seeds; they are considered to be a plant's secondary metabolites and the second most abundant group of phenols present in nature. They have several important biological activities such as to participate in defense mechanisms in plants because they form complexes with different compounds, principally proteins; this last property is undesirable in tannin-rich foods and beverages; for this reason, the enzymatic hydrolysis of tannins is a key topic in the food industry. Tannases have been studied because they are versatile and complex enzymes with commercial importance. Tannases are capable of hydrolyzing complex tannins, hydrolyzable tannins, and gallic or ellagic acid esters. Also, mono-and dioxygenases can be used to biodegrade condensed tannins. Tannases play an important catalytical role in multiple reactions of tannins; however, the use of tannases is limited because production costs are elevated because of their physicochemical properties and regulation mechanisms are insufficiently understood. The present chapter describes and analyzes a wide variety of aspects of different microbial tannases, such as physicochemical and catalytic properties, and describes and discusses a variety of substrates used to produce different types of tannase. The chapter aims to show the possible uses of tannases in different industries, mainly the food industry, and emphasizes that it is necessary to carry out more in-depth and specific studies on metabolic regulation and new expression systems.