Chemopreventive potential of the tannase-mediated biotransformation of green tea

Potentialities of Tannase-Treated Green Tea Extract in Nutraceutical and Therapeutic Applications

Green tea has garnered widespread interest in the past decades due to its content of health-beneficial polyphenols and catechins, besides reportedly exhibiting activities for the prevention, and possibly treatment, of many modern-life-associated afflictions. Hence, the functional food potential of health-beneficial beverages such as green tea is widely and commercially promoted. Biotransformation of green tea extract using enzymes such as tannase ostensibly enhances its beneficial well-being properties and disease-preventing functionalities. The tannase-treated green tea catechins may exhibit enhanced, amongst others, antioxidant, anti-tumour, anti-wrinkle, anti-inflammatory, anti-obesity and anti-sarcopenia properties compared to native green tea extract. Nonetheless, the health benefits and therapeutic and toxicological effects associated with these compounds, before and after tannase treatment, present a scientific gap for detailed studies. Accordingly, the review surveys the literature from the late twentieth century until the year 2023 related to the aforementioned important aspects.

Effects of Fermentation on Bioactivity and the Composition of Polyphenols Contained in Polyphenol-Rich Foods: A Review

Polyphenols, as common components with various functional activities in plants, have become a research hotspot. However, researchers have found that the bioavailability and bioactivity of plant polyphenols is generally low because they are usually in the form of tannins, anthocyanins and glycosides. Polyphenol-rich fermented foods (PFFs) are reported to have better bioavailability and bioactivity than polyphenol-rich foods, because polyphenols are used as substrates during food fermentation and are hydrolyzed into smaller phenolic compounds (such as quercetin, kaempferol, gallic acid, ellagic acid, etc.) with higher bioactivity and bioavailability by polyphenol-associated enzymes (PAEs, e.g., tannases, esterases, phenolic acid decarboxylases and glycosidases). Biotransformation pathways of different polyphenols by PAEs secreted by different microorganisms are different. Meanwhile, polyphenols could also promote the growth of beneficial bacteria during the fermentation process while inhibiting the growth of pathogenic bacteria. Therefore, during the fermentation of PFFs, there must be an interactive relationship between polyphenols and microorganisms. The present study is an integration and analysis of the interaction mechanism between PFFs and microorganisms and is systematically elaborated. The present study will provide some new insights to explore the bioavailability and bioactivity of polyphenol-rich foods and greater exploitation of the availability of functional components (such as polyphenols) in plant-derived foods.

Effects of enzyme-assisted extraction on the profile and bioaccessibility of isoflavones from soybean flour

The effects of enzymatic extraction strategies on extractability, bioconversion, and bioaccessibility of biologically active isoflavone aglycones, total phenolic content, and antioxidant activity of aqueous extracts from full-fat soy flour were evaluated. Protease, tannase, and cellulase enzymes were used individually or in combination. Except for the protease treatment, all enzymatic treatments increased the extraction of biologically active isoflavones (daidzein and genistein) compared with the control. The use of a mixture of protease, tannase, and cellulase resulted in increased extractability and/or bioconversion of aglycones from soy flour, indicating a synergistic effect amongst the enzymes. Daidzein and genistein concentrations increased from 29.0 to 158.2 μg/g and from 27.0 to 156.5 μg/g (compared to the control), respectively. Furthermore, enzymatic extraction followed by in vitro gastrointestinal digestion significantly increased the bioaccessibility of isoflavone aglycones, total phenolic content (by 22-45%), and antioxidant activity (by 15-22%) of the extracts. These results demonstrate that enzyme selection is an efficient strategy to maximize the extraction, bioconversion, and bioaccessibility of bioactive isoflavones from soy flour, which could contribute to health benefits associated with the consumption of soy-rich products.

Effects of bioactive components of Pu-erh tea on gut microbiomes and health: A review

Pu-erh tea is a post-fermentation tea with unique flavor and multiple health benefits. Due to the various microorganisms involved in the post-fermentation process, Pu-erh tea contains highly complex components, which have rich interactions with the gut microbiomes (GMs). Because the structure and homeostasis of GMs are closely related to human wellness and the various diseases progress, the beneficial effects of Pu-erh tea on GMs have a great potential for application in health care. However, there is no systematic summary of the bioactive components of Pu-erh tea, and their effects on the GMs. Here, we review the current studies on the effects of Pu-erh tea and its bioactive components on the structure of GMs as well as on health improvement, and further discuss the relevant quality indicators. This "components - function - indicators" clue will hopefully stimulate the standardization of Pu-erh tea fermentation process and the development of its functional products.

In-vitro biotransformation of tea using tannase produced by Enterobacter cloacae 41

Tannase is a widely used enzyme that improves the quality of tea by facilitating the release of water-soluble polyphenolic compounds, as well as reduces the formation of tea creams. The microbial tannase enzymes are often employed for tea biotransformation by hydrolyses esters of phenolic acids, including the gallated polyphenols found in blacks teas. The study was focused to investigate the tannase enzyme mediated biotransformation of black tea such as CTC-(Crush, tear, curl) & Kangra orthodox which are commonly used by the south Indian peoples. HPLC spectral analysis revealed that tannase treatment on tea cream formation (CTC & Kangra orthodox tea) allows the hydrolysis of the EGC, GA, ECG, and EGCG. A significant reduction in the formation of tea cream and increased antioxidant activity has been observed in the CTC (1.62 fold) and Kangra orthodox (1.55 fold). The results revealed that tannase treatment helps to improve the quality of black tea infusions with respect to cream formation, the intensity of colour, and sensory characteristics of tea. The result of this study indicates that E. cloacae 41 produced tannase can be used to improve the quality of both tea samples.

High Performance Liquid Chromatography and Metabolomics Analysis of Tannase Metabolism of Gallic Acid and Gallates in Tea Leaves

Tannase (E.C. 3.1.1.20) is hypothesized to be involved in the metabolism of gallates and gallic acid (GA) in pu-erh tea fermentation. In this work, we measured tannase in Aspergillus niger fermented tea leaves and confirmed the production of fungal tannase during pu-erh tea fermentation. A decrease in catechin and theaflavin gallates and a significant increase in GA content and the relative peak areas of ethyl gallate, procyanidin A2, procyanidin B2, procyanidin B3, catechin-catechin-catechin, epiafzelechin, and epicatechin-epiafzelechin [variable importance in the projection (VIP) > 1.0, p < 0.05, and fold change (FC) > 1.5] were observed using high performance liquid chromatography (HPLC) and metabolomics analysis of tea leaves fermented or hydrolyzed by tannase. In vitro assays showed that hydrolysis by tannase or polymerization of catechins increased the antioxidant activity of tea leaves. In summary, we identified a metabolic pathway for gallates and their derivatives in tea leaves hydrolyzed by tannase as well as associated changes in gallate and GA concentrations caused by fungal tannase during pu-erh tea fermentation.

Changes in the Biotransformation of Green Tea Catechins Induced by Different Carbon and Nitrogen Sources in Aspergillus niger RAF106

Biotransformation of green tea catechins mediated by microbes and/or enzymes could increase their bioavailability and improve their health benefits, but the regulatory mechanism remains unclear. Here, Aspergillus niger RAF106 isolated from Pu-erh tea was proved to be capable of degrading gradually ester-catechins into non-ester-catechins with higher bioavailability and gallic acid (GA) in aqueous solution only containing green tea catechins, and the products displayed similar radical-scavenging activity in vitro with the control. Meanwhile, the degradation was mediated by inducible enzymes as the extracellular form, and tannase might be an important enzyme among the extracellular enzymes. Moreover, it was found for the first time that the biotransformation was accelerated significantly by the addition of different nitrogen sources (i.e., yeast extract, peptone, NaNO3, and NH4Cl) and lactose through stimulating the hyphal growth and the tannase activities but was inhibited by glucose effect. Furthermore, nitrogen sources continued to promote the degradation of GA and/or non-ester-catechins by up-regulating the transcriptional expression of two dioxygenases and 10 monooxygenases. Besides, the addition of different nutrient sources except yeast extract did not alter the radical-scavenging activity of green tea catechins during the whole fermentation. These results provide a global insight into the roles of A. niger RAF106 and different nutrient sources in mediating the biotransformation of green tea catechins and modifying the radical-scavenging activity of biotransformed catechins.

Simultaneous Optimal Production of Flavonol Aglycones and Degalloylated Catechins from Green Tea Using a Multi-Function Food-Grade Enzyme

(1) Background: Green tea (GT) contains well-known phytochemical compounds; namely, it is rich in flavan-3-ols (catechins) and flavonols comprising all glycoside forms. These compounds in GT might show better biological activities after a feasible enzymatic process, and the process on an industrial scale should consider enzyme specificity and cost-effectiveness. (2) Methods: In this study, we evaluated the most effective method for the enzymatic conversion of flavonoids from GT extract. One enzyme derived from Aspergillus niger (molecular weight 80–90 kDa) was ultimately selected, showing two distinct but simultaneous activities: intense glycoside hydrolase activity via deglycosylation and weak tannin acyl hydrolase activity via degalloylation. (3) Results: The optimum conditions for producing flavonol aglycones were pH 4.0 and 50 °C. Myricetin glycosides were cleaved 3.7–7.0 times faster than kaempferol glycosides. Flavonol aglycones were produced effectively by both enzymatic and hydrochloride treatment in a time-course reaction. Enzymatic treatment retained 80% (w/w) catechins, whereas 70% (w/w) of catechins disappeared by hydrochloride treatment. (4) Conclusions: This enzymatic process offers an effective method of conditionally producing flavonol aglycones and de-galloylated catechins from conversion of food-grade enzyme.

Novel optimization strategy for tannase production through a modified solid-state fermentation system

BACKGROUND

High amounts of insoluble substrates exist in the traditional solid-state fermentation (SSF) system. The presence of these substrates complicates the determination of microbial biomass. Thus, enzyme activity is used as the sole index for the optimization of the traditional SSF system, and the relationship between microbial growth and enzyme synthesis is always ignored. This study was conducted to address this deficiency. All soluble nutrients from tea stalk were extracted using water. The aqueous extract was then mixed with polyurethane sponge to establish a modified SSF system, which was then used to conduct tannase production. With this system, biomass, enzyme activity, and enzyme productivity could be measured rationally and accurately. Thus, the association between biomass and enzyme activity could be easily identified, and the shortcomings of traditional SSF could be addressed.

RESULTS

Different carbon and nitrogen sources exerted different effects on microbial growth and enzyme production. Single-factor experiments showed that glucose and yeast extract greatly improved microbial biomass accumulation and that tannin and (NH₄)₂SO₄ efficiently promoted enzyme productivity. Then, these four factors were optimized through response surface methodology. Tannase activity reached 19.22 U/gds when the added amounts of tannin, glucose, (NH₄)₂SO₄, and yeast extract were 7.49, 8.11, 9.26, and 2.25%, respectively. Tannase activity under the optimized process conditions was 6.36 times higher than that under the initial process conditions. The optimized parameters were directly applied to the traditional tea stalk SSF system. Tannase activity reached 245 U/gds, which is 2.9 times higher than our previously reported value.

CONCLUSIONS

In this study, a modified SSF system was established to address the shortcomings of the traditional SSF system. Analysis revealed that enzymatic activity and microbial biomass are closely related, and different carbon and nitrogen sources have different effects on microbial growth and enzyme production. The maximal tannase activity was obtained under the optimal combination of nutrient sources that enhances cell growth and tannase accumulation. Moreover, tannase production through the traditional tea stalk SSF was markedly improved when the optimized parameters were applied. This work provides an innovative approach to bioproduction research through SSF.

Influence of rye flour enzymatic biotransformation on the antioxidant capacity and transepithelial transport of phenolic acids

Enzymatic biotransformation enhanced the release of phenolic acids and Caco-2 transepithelial transport of vanillic acid.

Biotransformation of catechin and extraction of active polysaccharide from green tea leaves via simultaneous treatment with tannase and pectinase

BACKGROUND

Green tea is a dietary source of bioactive compounds for human health. Enzymatic treatments induce the bioconversion of bioactive components, which can improve biological activities. In this study, we investigated the effect of simultaneous treatment with tannase and Rapidase on biotransformation of catechins and extraction of polysaccharide from green tea extract (GTE).

RESULTS

Tannase and pectinase treatments induced the biotransformation of catechins and altered tea polysaccharide () content. The addition of GTE to the enzyme reaction resulted in a significant increase in degallated catechins, including gallic acid, a product of the tannase reaction (314.5-4076.0 µg mL(-1)) and a reduction in epigallocatechin gallate (EGCG). Biotransformation of catechins improved the radical scavenging activity of GTE. Pectinase treatment led to change of TPS composition in GTE by hydrolyzing polysaccharides. In addition, pectinase-driven hydrolysis in polysaccharides significantly increased TPS-induced Interleukin 6 (IL-6) production in macrophages. In particular, treatment of Rapidase (TPS-Ra) led to the highest IL-6 production among TPS samples, similar to treatment of highly purified pectinase (TPS-GTE), a positive control.

CONCLUSION

Simultaneous processing with tannase and Rapidase can be an efficient method for the extraction of bioactive polysaccharides and biotransformation of catechins with enhanced radical scavenging activity from green tea.

Novel trends for use of microbial tannases

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.

Bioactive compounds produced by gut microbial tannase: implications for colorectal cancer development

The microorganisms in the human gastrointestinal tract have a profound influence on the transformation of food into metabolites which can impact human health. Gallic acid (GA) and pyrogallol (PG) are bioactive compounds displaying diverse biological properties, including carcinogenic inhibiting activities. However, its concentration in fruits and vegetables is generally low. These metabolites can be also generated as final products of tannin metabolism by microbes endowed with tannase, which opens up the possibility of their anti-cancer potential being increased. Patients with colorectal cancer (CRC) display an imbalanced gut microbiota respect to healthy population. The recent use of next generation sequencing technologies has greatly improved knowledge of the identity of bacterial species that colonize non-tumorous and tumorous tissues of CRC patients. This information provides a unique opportunity to shed light on the role played by gut microorganisms in the different stages of this disease. We here review the recently published gut microbiome associated to CRC patients and highlight tannase as an underlying gene function of bacterial species that selectively colonize tumorous tissues, but not adjacent non-malignant tissues. Given the anti-carcinogenic roles of GA and PG produced by gut tannin-degrading bacteria, we provide an overview of the possible consequences of this intriguing coincidence for CRC development.

Simultaneous preparation of naturally abundant and rare catechins by tannase-mediated biotransformation combining high speed counter current chromatography

Simultaneous preparation of naturally rare catechins, EGC and EC, has been realized by tannase-mediated biotransformation combining high speed counter current chromatography. In addition, simultaneous preparation of the four catechins, EGCG, ECG, EGC, and EC in green tea extract has also been achieved by HSCCC under the normal phase and the reversed phase modes. The identity of the catechins was determined by HPLC-DAD-ESI-MS and quantification of the catechins was performed by HPLC-DAD. In a typical HSCCC separation, 27.2 mg 98.8% EGCG, 14.1 mg 94.7% EGC, and 9.3 mg 97.5% EC were obtained. This new method is efficient, time-saving and valuable for biological studies.