Fungal tannase: Recent advances and industrial applications

Abstract

Tannin acyl hydrolase (E.C.3.1.1.20) universally known as tannase is an inducible enzyme that predominantly acts on tannins. Tannins have been documented as high molecular weight polyphenolic compounds possessing molecular weight in the range (500-3000 kDa). Tannins are the second most abundant polyphenolic compounds existing in nature after lignin. Tannins are water-soluble secondary metabolites existing in abundance in plants. Apparently, tannins exist in plants as the fourth most bountiful constituents behind cellulose, hemicellulose, and lignin. Tannins possess acrid properties and have the inherent capability of binding with proteins, cellulose, gelatin, and pectin thereby forming insoluble complexes. Tannases derived from microbial sources have enormous applications in various industries. This tremendous biocatalytic potential of tannase is attributed to their higher stability and feasibility. Tannases have a vast range of applications in various industrial bioprocesses ranging from food, feed to chemical as well as pharma sector. Furthermore, tannery effluentsare loaded with surplus amount of tannins, predominantly polyphenols, which are life-threatening pollutants and pose severe environmental and health hazards. As a matter of fact, tannases can be substantially utilized for degrading the tannins that predominantly exist in the tannery effluents, thus offering a much cheaper treatment for the eviction of these compounds. The enzyme also finds significant utilization in cosmetic industries to so as to lessen the extensive turbidity of plant extracts. Tannase can also be predominantly used for high-grade leather tannins preparation in the leather industry. The present chapter is an attempt to emphasize on microbial sources, substrates for maximal tannase production, factors governing tannase production, mechanism of action, purification, immobilization, inhibitors as well as widespread applications of tannases. The advancements in molecular tools and techniques have enabled a better understanding of tannase structure, underlying mechanism of its action as well as the more precise understanding of various process parameters governing tannase production. Over the years, tannases have witnessed a significant rise in their utilization in commercial sector; thus, there is always an opportunity for researchers to search out novel tannases with better and improved characteristics.