Novel Trends for Use of Microbial Tannases

Abstract

Tannases, mainly produced by microorganisms, are able to hydrolyze gallotannins, ellagitannins, complex tannins, and gallic acid esters into gallic acid, ellagic acid, glucose, or alcohols, and also synthesize gallic acid esters using tannic acid or gallic acid with a variety of alcohols in nonaqueous media. Microbial tannases have been widely applied especially in beverage processing, pharmaceutics, and brewing. However, many factors, especially high production costs, severely limit the use of microbial tannases at the industrial level. In this minireview, we aim to provide an overview of the advances in applications of microbial tannases during the last 15 years, mainly including the following respects: hydrolysis of tea cream, modification of green tea catechins, production of gallic acid, debittering of fruit juices, degradation of tannery effluents, and synthesis of propyl gallate, trying to know the trends and prospects for the future in applications of microbial tannases.

Tannase improves gallic acid bioaccessibility and maintains the quality of mango juice

“…Hydrolysable gallotannins can be depolymerised by tannase (tannin acyl hydrolase E.C. 3.1.1.20), which acts on both ester and depside bonds to release GA (Raghuwanshi et al ., ; Zhang et al ., ). Tannase has been used in the food industry as a processing aid to resolve food and beverage quality issues caused by hydrolysable tannins including clarification of alcoholic and coffee beverages (Belmares et al ., ), prevention of tea creaming along with colour and flavour enhancement (Lu et al ., ) and as a debittering agent in fruit juice preparations (Sharma et al ., ).…”

Biotransformation of industrial tannins by filamentous fungi

“…Despite a direct inhibiting effect cannot be associated with the tannin concentration in the effluent, a lower specific growth rates of ammonium and nitrite oxidising bacteria indicates a strong environmental pressure due to the tannery wastewater (Munz et al 2009). In this regard, the WWTP implementation with a fungal treatment could be useful to achieve better depuration results (Zhang et al 2015).…”

“…Fungal treatment aimed to the tannin removal can be based on three mechanisms: adsorption (Natarajant and Manivasang, 2018), degradation (Zhang et al 2015), and precipitation induced by extracellular enzymatic polymerisation (Yamaguchi et al 1998). These mechanisms could run at the same time or be sequential (Song and Burns 2005).…”

Tannery mixed liquors from an ecotoxicological and mycological point of view: Risks vs potential biodegradation application

“…As a consequence, a last comment is addressed to the use of dewater excess sludge and treated wastewaters in agriculture. This procedure is seen as a desirable option, in the light of Directive 2008/98/EC, which gives added value to wastes through their integrated management, moved by the aspiration to the reduction of mineral fertilizer use (Zhang et al, 2015). The hypothesized multiple benefits for agriculture and the environment are actually to be confirmed, by evaluating also the toxicity of these wastes.…”

“…Recently, the literature has pointed out a consistent presence of autochthonous mycoflora in the activated sludge of WWTPs treating paper mill, vinery or municipal wastewaters (Grabinskaloniewska et al, 1993; Awad Tannery wastewaters, regardless of the type of industrial process (chromium or vegetable), are among the most difficult to treat, basically on account of their recalcitrance and/or their toxicity towards bacteria (Lofrano et al, 2013). On the contrary, the ability of fungi in the degradation of tannery pollutants has been already demonstrated (Sharma and Malaviya, 2016;Zhang et al, 2015).…”