Degradation Of Tannins Research Articles

Bacterial Degradation of Bacteriostatic Polyphenols, Tannins

Tannin degradation by bacteria has not been studied much as tannins are commonly known to be bacteriostatic due to enzyme inhibition, substrate deprivation, and the enzyme activity on the bacterial cell wall. However, about a handful of bacteria have been found to tolerate certain concentrations of tannin. This study focuses on isolating and identifying bacteria from decaying portions of tree bark for tannase production and effective catalysis of ester bond hydrolysis in tannins. Different concentrations of commercial tannic acid were used as the sole carbon source on mineral salt medium (MSM) agar plates, to test the maximum tolerable concentrations (MTCs) by the isolates. Tannin degradation was confirmed by a visual reading method and bacterial tannase activity and the biodegradation percentage were determined. One particular isolate was identified to have 50 g/L MTC of tannin, with a tannase activity of 51.61 U/mL that is optimum after 96 hours of incubation. The 16s rRNA sequencing results showed that the isolate belonged to Bacillus genus and the resulting bacterial strain isolate was found to be a new strain of Bacillus subtilis which was submitted to GenBank under the accession number MH330408.

Degradation of epigallocatechin and epicatechin gallates by a novel tannase TanHcw from Herbaspirillum camelliae

BackgroundHerbaspirillum camelliae is a gram-negative endophyte isolated from the tea plant. Both strains WT00C and WT00F were found to hydrolyze epigallocatechin-3-gallate (EGCG) and epicatechin-3-gallate (ECG) to release gallic acid (GA) and display tannase activity. However, no tannase gene was annotated in the genome of H. camelliae WT00C.ResultsThe 39 kDa protein, annotated as the prolyl oligopeptidase in the NCBI database, was finally identified as a novel tannase. Its gene was cloned, and the enzyme was expressed in E. coli and purified to homogeneity. Moreover, enzymatic characterizations of this novel tannase named TanHcw were studied. TanHcw was a secretary enzyme with a Sec/SPI signal peptide of 48 amino acids at the N-terminus, and it catalyzed the degradation of tannin, methyl gallate (MG), epigallocatechin-3-gallate (EGCG) and epicatechin-3-gallate (ECG). The optimal temperature and pH of TanHcw activities were 30 °C, pH 6.0 for MG and 40 °C, pH 7.0 for both EGCG and ECG. Na+, K+ Mn2+ and Triton-X100, Tween80 increased the enzyme activity of TanHcw, whereas Zn2+, Mg2+, Hg2+, EMSO, EDTA and β-mercaptoethanol inhibited enzyme activity. Km, kcat and kcat /Km of TanHcw were 0.30 mM, 37.84 s−1, 130.67 mM−1 s−1 for EGCG, 0.33 mM, 34.59 s−1, 105.01 mM−1 s−1 for ECG and 0.82 mM, 14.64 s−1, 18.17 mM−1 s−1 for MG, respectively.ConclusionA novel tannase TanHcw from H. camelliae has been identified and characterized. The biological properties of TanHcw suggest that it plays a crucial role in the specific colonization of H. camelliae in tea plants. Discovery of the tannase TanHcw in this study gives us a reasonable explanation for the host specificity of H. camelliae. In addition, studying the characteristics of this enzyme offers the possibility of further defining its potential in industrial application.

Kinetic of polyphenol losses during convection drying of cashew (Anacardium occidentale L.) apples

Lowering manufacturing costs and utilization of by-products are urgent requirements to improve the competitiveness of Vietnamese cashew nuts in the world market. Heat treatment strategies such as drying are common techniques to process waste sources into a food source. The degradation of polyphenol, vitamin C, and tannins in the process represent a major obstacle in maintaining the nutritional quality of cashew pulp as well as in de-acridization of raw materials. This work firstly attempted to determine the optimal convection drying conditions that gave the highest nutritional quality contents in cashew apples. Then, the polyphenol degradation kinetic of cashew apple material during the drying process was examined in zero-order and first-order kinetic models. The results suggested the best contents of polyphenol, vitamin C and tannin could be attained at the drying process at 55°C for 275 mins. In addition, the first-order kinetic model was used to describe the decomposition of polyphenols during the drying process and the equation to predict the residual polyphenol content in cashew apple was formed to optimize the process. Research parameters provide a database for the following processing processes in the production of cashew-derived food products.

A comprehensive review on tannase: Microbes associated production of tannase exploiting tannin rich agro-industrial wastes with special reference to its potential environmental and industrial applications

Microorganisms have been used for the production of various enzymes, including inducible tannase for various industrial and environmental applications. Tannases have lot of potential to convert hydrolysable tannins to gallic acid, which is one of the important industrial and therapeutic significant molecules whose demand is over 10000 tons per year. Tannins invariably occur in angiosperms, gymnosperms and pteridophytes, and predominantly present in various parts of plants such as, leaves, roots, bark and fruit. Furthermore, tannery effluents are frequently loaded with significant levels of tannic acid. Tannase can be effectively used to decrease tannin load in the toxic tannery effluent thus providing the opportunity to minimize the operational cost. Over the past three decades, tannase from microbial sources has been proposed for the degradation of natural tannins. The availability of various agro-industrial residues paves a way for maximum utilization of tannase production for the degradation of tannin and eventually the production of gallic acid. In this review, an illustrative and comprehensive account on tannase from microbial source for current day applications is presented. The present review emphasises on up-to-date microbial sources of tannases, biochemical properties, optimization of tannase production in solid state and submerged fermentation and its industrial and environmental applications.

Assessing Lignin Decomposition and Soil Organic Carbon Contents Across a Tropical Savannah-Rainforest Boundary in Guyana

The soils beneath the rainforest of Guyana have the potential to hold, and release, large stores of carbon under land use and climate change. Little is known about soil carbon stocks or molecular dynamics in this region. This study therefore aims to elucidate differences in the molecular (lignin and tannin) and bulk soil organic carbon (SOC) stocks in different ‘sub-environments’ along a rainforest-savannah boundary, setting a framework for further investigation into the soil carbon dynamics of the region. Bulk SOC analysis shows that Gleysols have the highest stocks, particularly those under rainforest vegetation (swamp and island forests surrounded by savannah), whereas Plinthosols have significantly lower SOC stocks. Texture and soil water content analysis indicates that predominantly clay soils play a role in high SOC stocks, whilst predominantly sandy soils prevent SOC stocks from accumulating. Clay and sand are present in both Gleysols and Plinthosols, to different extents. Analysis of lignin and tannin in surface soils of the sub-environments reveals clear differences in molecular composition. Heavily degraded lignin signatures in rainforest Gleysols suggests a surrounding physio-chemical environment which promotes their degradation. Conversely, Plinthosols beneath woodland within the savannah have the greatest amount of lignin and tannin products. The presence of the clay mineral kaolinite and iron oxide strengite in these soils indicates a low ability for protection or complexing of organic matter. Therefore, water content and microbial activity may play a more important role in the degradation of lignin and tannin, as well as the SOC stock. With the potential for future deforestation due to land use or climate change, the high lignin degradation of Gleysols indicates a vulnerability to savannah encroachment. Forest Islands isolated from the main forest biome are the most vulnerable to change, and could lose a significant proportion of their SOC stock in a transition to savannah.

APLIKASI FOSFAT PADA PROSES EKSTRAKSI TEH HIJAU UNTUK MINUMAN TEH HIJAU SIAP MINUM

Color is one of quality parameters that affects consumer intention to purchase ready to drink (RTD) green tea. Consumers expect RTD green tea to have yellow greenish color, however the color becomes brown and darker during the shelf life. This study aimed to evaluate the effect of phosphate mix addition to water prior to green tea leaves extraction on pH, color, and the tannin in tea extract, pre-RTD, and RTD during incubation period at 60°C for 2 days. The pre-RTD contained tea extract, sugar, and ascorbic acid. Addition of sodium bicarbonate was done in pre-RTD to obtain RTD with pH of 6.1±0.2. The type of phos-phate used was sodium acid pyrophosphate (SAPP) and phosphoric acid. The concentrations of SAPP were 650 and 1300 mg/L, while those of phosphoric acid were 125, 250, and 500 mg/L.The total phospho-rous added from the combination of SAPP and phosphoric acid was 221-521 mg/L. Meanwhile, green tea extracted without phosphate was used as a control. The results showed that phosphate addition to water prior to green tea extraction caused decrease in pH of tea extract from 5.83±0.18 to 2.8-3.8, decrease in browning intensity, and reduced tannin degradation during the incubation period. Sugar and ascorbic acid added to the tea extract resulted in pH in all samples <4.0 and maintained the lightness of the pre-RTD. Phosphate application was not able to retain the color of RTD after incubation period. This study showed that addition of phosphorous as a combination of SAPP and phosphoric acid to water at concentrations of 221-521 mg/L prior to green tea extraction had positive impact in reducing browning intensity of RTD green tea with pH of lower than 4.0.

Evaluation of the aerobic and anaerobic degradation of an industrial effluent from vegetable tannery processing of leather on batch reactors

<p>In this study, the aerobic and anaerobic biodegradability of the industrial wastewater from the vegetable tanning process were evaluated. Water from a food wastewater treatment system was used as seed inoculum for the aerobic process and mature granular methanogenic sludge from a brewery industrial wastewater plant was used for the anaerobic process. The water from the tanning industry had a biological to chemical oxygen demand ratio of 33% with values of total chemical oxygen demand (COD) in the range of 342000 mg O2/L and total dissolved solids of 506595 mg/L. The assay of the tannery effluent under aerobic conditions resulted in a decrease of COD of 39.2% and a degradation of tannins lower than 12% after 26 days, while the anaerobic degradation showed a COD reduction of 65% with a 39% of degradation of tannins. The production of methane and Volatile Fatty Acids, during the anaerobic treatment, suggests a potential adaptation of biological organisms present in the mature anaerobic granular methanogenic sludge.</p>

Photo-catalytic degradation of polyphenolic tannins in continuous-flow reactor using titanium dioxide immobilized on a cellulosic material.

Tannins are recalcitrant polyphenolic molecules that resist microbial attack. Their main environmental damage is due to their low biodegradability. This work aims to investigate the photo-catalytic degradation of two commercial tannin extracts, chestnut (hydrolysable tannin) and mimosa (condensed tannin). The experiments were carried out under UV-light irradiation in a continuous-flow reactor using titanium dioxide (TiO2) immobilized on cellulosic fibers. It was highlighted that photo-catalytic degradation is unfavourable in acidic medium and when the pH is too high (pH above 12); it reaches its maximum efficiency at pH 7.5 (99 and 97% for chestnut and mimosa, respectively). Nearly complete degradation of tannins requires an irradiation period of 6 h. The process efficiency is inversely affected by the concentration of tannins essentially above 75 mg/L for chestnut and 60 mg/L for mimosa. Above 240 mL/min, any increase in feed flow negatively affects the performance of the process. Furthermore, a significant decrease of treatment efficiency was seen when increasing the concentration of ethanol and salts in the medium. Obtained results suggest that UV-light irradiation in a continuous-flow photo-reactor using immobilized TiO2 may be considered as an adequate process for the treatment of water containing recalcitrant tannin molecules.

Efficiency of tannase enzyme for degradation of tannin from cashew apple juice: Modeling and optimization of process using artificial neural network and response surface methodology

AbstractThe study was conducted on tannase‐assisted extraction of cashew apple juice at different combinations of tannase concentration (0.01–0.1% wt/wt), incubation time (20–120 min), and incubation temperature (30–50°C) for the maximum reduction of tannin from the juice. The modeling and optimization of process parameters were performed using response surface methodology (RSM) and artificial neural network (ANN). The RSM proposed an optimum process condition of 0.079% tannase concentration, 85 min incubation time, and 46°C incubation temperature, whereas the ANN model proposed 0.085% tannase concentration, 89 min incubation time, and 39°C incubation temperature as the optimum conditions. The reduction in tannin content achieved using the optimum conditions proposed by RSM and ANN models were 63.93 and 68.85%, respectively. Statistical parameters such as absolute average deviation (AAD), mean squared error (MSE), and determination coefficient (R2) indicated the superiority of the ANN model with high R2 and low AAD and MSE values.Practical applicationAstringency due to tannin content is the primary reason behind the low consumer acceptability of the cashew apple juice. The application of tannase enzyme during juice extraction has a potential to decrease the tannin content of cashew apple juice. However, the effect of tannase enzyme, on tannin degradation in cashew apple juice has not been systematically studied in details. Hence, a study was conducted to optimize the process parameters of tannase‐assisted juice extraction from cashew apple for maximum reduction of tannin content. More than 68% reduction in tannin content was achieved using the optimized process conditions. This study will help food industries to develop juice from highly nutritious cashew apple with minimum astringency and better consumer acceptability.

Review on some cereal and legume based composite biscuits

The major determinants of malnutrition in Africa are low availability of nutritious foods and inadequate consumption of protein-rich diets. Consumption of nutritious snacks could help to reduce protein-energy malnutrition in children and adults. Biscuits are a ready-to-eat, convenient and cheap snack that is consumed by all age group in many countries. It can be produced from cereal and legume flour blends. A proximate composition such as protein, ash, crude fiber, and fat content of some cereal-legume based biscuit increased with increase in the percentage substitution of legumes flour. Carbohydrate content of biscuits decreased as legume substitution increased. The Ash (total mineral) content of some cereal and legume-based composite biscuits increased as the level of legume flour incorporation increased. The increased in some nutrient composition of the biscuit in cereal and legume blends could be due to the significant quantity of nutrients in legumes. Anti-nutritional factors (ANF) such as tannin and phytic acid affect digestibility and nutrient bioavailability for absorption. Substitution of malted cereal flour with legume flour resulted decreased in the level of both tannin and phytate in the composite biscuits and vice versa. Lower tannin and phytate content observed could be due to degradation of tannin and phytate during malting. Sensory attributes such as color, texture, aroma, taste, and overall acceptability of some cereal and legume-based biscuits were highly rated (in acceptable ranges).

Influence of tannase from Serratia marcescens strain IMBL5 on enhancing antioxidant properties of green tea

Abstract The present study was focused on the isolation and screening of potential tannase producing gut microbes from dung beetle Onthophagus babirussa IMBL, further optimized and characterized for industrial applications. Serratia marcescens strain IMBL5 was found to be the most potent tannase producer out of 36 isolates. The adjusted process parameters for maximum tannase yield were pH 4.5 at 45 °C and 96 h incubation. The tannase production was increased 4.46 fold i.e. 120.13 U/mL, by varying the concentration of media components using Response surface methodology. The molecular weight of purified tannase was resolved at ~40 kDa through SDS-PAGE analysis. Several functional groups including carboxyl, hydroxyl and amide groups were detected in FT-IR analysis whilst the occurrence of epicatechin gallate peaks detected from HPLC chromatogram signifying the tannin degradation. Tannase also potentially induce the antioxidant properties of green tea extract which was determined through in-vitro analysis. There was no hemolytic activity exhibited in hemolysis assay using human red blood cells which corroborated that tannase derived from S. marcescens strain IMBL5 might be a safe and promising agent in food industry.

Proximate, Anti - Nutrients and Sensorial Acceptability of Some Cereal and Legume Based Composite Biscuits: Review

The major determinants of malnutrition in Africa are low availability of nutritious foods and inadequate consumption of protein-rich diets. Consumption of nutritious snacks could help to reduce protein-energy malnutrition in children and adults. Biscuits are a ready-to-eat, convenient and cheap snack that is consumed by all age group in many countries. It can be produced from cereal and legume flour blends. A proximate composition such as protein, ash, crude fiber, and fat content of some cereal-legume based biscuit increased with increase in the percentage substitution of legumes flour. Carbohydrate content of biscuits decreased as legume substitution increased. The Ash (total mineral) content of some cereal and legume-based biscuits increased as the level of legume flour incorporation increased. The increased in some nutrient composition of the biscuit in cereal and legume blends could be due to the significant quantity of nutrients in legumes. Anti - nutritional factors (ANF) such as tannin and phytic acid affect digestibility and nutrient bioavailability for absorption. Substitution of malted cereal flour with legume flour resulted decreased in the level of both tannin and phytate in the composite biscuits and vice versa. Lower tannin and phytate content observed could be due to degradation of tannin and phytate during malting. Sensory attributes such as color, texture, aroma, taste, and overall acceptability of some cereal and legume-based biscuits were highly rated (in acceptable ranges). Keywords: Nutrient composition, Cereal, Anti-nutritional factors, Biscuits, Legume, Sensory acceptability, composite flour DOI: 10.7176/FSQM/98-03 Publication date: June 30 th 2020

Role of bacterivorous organisms on fungal-based systems for natural tannin degradation

Tannery wastewater presents high concentrations of organic load and pollutant recalcitrant molecules (e.g. tannins), which reduce the efficiency of biological treatment processes. Recent studies showed that several fungal species and strains are effective in the degradation of tannins. However, high bacterial load can negatively affect fungal growth, reducing system stability and degradation performances.The aim of the present study was to evaluate the effects of the introduction of bacterivorous grazers (ciliates and/or rotifers) in batch scale experiments using fungi to remove Tara tannin, i.e. to check the potential synergistic effect between fungi and bacterivorous grazers in the degradation of recalcitrant compounds. In this context, the ciliated grazers Paramecium calkinsi, Tetrahymena sp., Pseudovorticella sp., and the rotifer Lecane inermis, preliminary selected according to their ability to grow in a solution prepared with Tara tannin, were separately tested. Activated sludge, including a complex mixture of native grazers, was used as experimental control. The following parameters were monitored: bacterial load, number of grazers/mL and Soluble Chemical Oxygen Demand (SCOD). Colony Forming Unit (CFU)/grazers ratio was also calculated. Particular attention was paid to: i) bacterial load reduction and ii) enhancement of recalcitrant compounds degradation, and we observed that in all experimental conditions where grazers occurred bacterial load was significantly reduced and the system achieved a higher SCOD removal in a shorter time. Our findings provide useful insights for the stabilization of fungal-based systems in non-sterile conditions.

Exploring the formaldehyde reactivity of tannins with different molecular weight distributions: bayberry tannins and larch tannins

Abstract In recent years, tannin degradation has been used to obtain tannin materials with an optimal molecular weight distribution (MWD) for synthesizing tannin-formaldehyde (TF) resin with high performance, but the optimal MWD of tannins is still unknown. The excellent formaldehyde reactivity of tannins is the basis for the synthesis of high-performance TF resin. Based on the formaldehyde reactivity of tannins, bayberry tannins and larch tannins were used to explore the optimal MWD of tannins for TF resin synthesis. Progressive solvent precipitation (PSP) was used to obtain tannin fractions with different MWDs. The formaldehyde reactivity of tannins was determined using the modified Stiansy method combined with the standard curve method (GB/T 17657-2013). The bayberry tannin fraction [weight-average molecular weight (Mw) of acetylated tannin: 4115, mean degree of polymerization (mDP): 6.64] and the larch tannin fraction (Mw of acetylated tannin: 3906, mDP: 5.84) had the best formaldehyde reactivity. Furthermore, significant differences in the formaldehyde reactivity of condensed tannins (CTs) with different MWDs were observed. The obtained results can be used to purposefully degrade tannins to achieve an optimal MWD, which is beneficial for the production of TF adhesives with high performance.

Integrated Approaches to Reveal Genes Crucial for Tannin Degradation in Aureobasidium melanogenum T9.

Tannins biodegradation by a microorganism is one of the most efficient ways to produce bioproducts of high value. However, the mechanism of tannins biodegradation by yeast has been little explored. In this study, Aureobasidium melanogenum T9 isolated from red wine starter showed the ability for tannins degradation and had its highest biomass when the initial tannic acid concentration was 20 g/L. Furthermore, the genes involved in the tannin degradation process were analyzed. Genes tan A, tan B and tan C encoding three different tannases respectively were identified in the A. melanogenum T9. Among these genes, tan A and tan B can be induced by tannin acid simultaneously at both gene transcription and protein expression levels. Our assay result showed that the deletion of tanA and tanB resulted in tannase activity decline with 51.3 ± 4.1 and 64.1 ± 1.9 U/mL, respectively, which is much lower than that of A. melanogenum T9 with 91.3 ± 5.8 U/mL. In addition, another gene coding gallic acid decarboxylase (gad) was knocked out to better clarify its function. Mutant Δgad completely lost gallic acid decarboxylase activity and no pyrogallic acid was seen during the entire cultivation process, confirming that there was a sole gene encoding decarboxylase in the A. melanogenum T9. These results demonstrated that tanA, tanB and gad were crucial for tannin degradation and provided new insights for the mechanism of tannins biodegradation by yeast. This finding showed that A. melanogenum has potential in the production of tannase and metabolites, such as gall acid and pyrogallol.

Tannin degradation by phytopathogen's tannase: A Plant's defense perspective

Abstract Tannins are plant secondary metabolites and characterized as plant defensive molecules. They impose a barrier against phytopathogens invasion in plants and thus oppose diseases occurrence in them. Tannase is an enzyme known for its ability to degrade plant tannins. Important plant pathogens also possess tannase coding sequence in their genome. Researches on tannase are till date focused on its applications in animal nutrition, in bioremediation and in food industries etc. The information about tannase role with respect to pathogen's virulence is very scanty or almost nil in scientific literature. The presence of tannase in pathogen's genome is an adaptive feature which may be a part of its strategy to overcome the negative effects of plants tannins. The present review summarizes important aspects of tannase and its possible role in disease causing ability of pathogens in plants.

Identification of phenolic compounds and antioxidant activity of guava dehydrated by different drying methods

The influence of different drying techniques on guava was investigated, including phenolic components and antioxidant activities. Through drying processes, total phenolic content (TPC) increased and formation of small molecular phenolic acids (multi-methoxy benzoic acid and sinapic acid) was promoted. UPLC-ESI-QTOF-MS determination showed flavanol compounds, hydrolyzable tannins, ellagic acid conjugates and cinnamic acid derivatives were four predominant phenolics of guava. Drying treatments caused degradation of catechin and its derivatives. Contrarily, drying treatments contributed to higher contents of procyanidin trimers. Moreover, thermal drying treatments led to degradation of macromolecular tannins and formation of smaller molecular tannins and ellagic acid conjugates, while simultaneously reduced the stabilities of most intrinsic ellagic acid conjugates. Furthermore, drying processes increased the yield of cinnamic acid dihexose, probably generating from lignin or phenolics–carbohydrate complex. Freeze drying and hot air drying showed better performance on retention of TPC and enhancement of antioxidant activity (AA).

A Mass Spectrometric Study on Tannin Degradation within Dyed Woolen Yarns.

Natural tannins from various plants have been used throughout human history in textile dyeing, often as mordant dyes. The ageing behavior of these dyes is a challenge in conservation science, requiring a thorough knowledge of the textile–mordant-dye system. In this work, we analyzed reference wool yarns dyed with natural tannins from oak gallnuts, walnut (Juglans regia), and catechu (Acacia catechu), after artificial ageing. To gain insights on the composition of the dyestuffs and on how they aged, an analytical procedure based on extraction with Na2EDTA/DMF (ethylenediaminetetraacetic acid/dimethylformamide) and high-performance liquid chromatography (HPLC) analysis using high-resolution mass spectrometry detection was used. Since conventional reversed-phase (RP) columns usually show poor retention efficiency of highly polar compounds such as tannins, an RP-amide embedded polar group stationary phase was used to achieve optimal retention of the most polar compounds. Tannins from oak gallnuts showed little degradation after ageing, while a significant increase in the content of hydroxybenzoic acids was observed for tannins from walnut and catechu. Finally, the analytical procedure was applied to characterize the tannin dyes in historical tapestries from the 15th to 16th century, and the results were discussed in comparison with the reference yarns.

Effect of Mixed Inoculums Volume and pH on Anti Nutritional Level in Cabbage Fermentation using Saccharomyces cerevisiae and Lactobacillus plantarum

Cabbage (Brassica oleracea var. capitata) that is one of the widely consumed vegetables, contains significant amounts of anti-nutritional components, such as tannin. This component can be reduced by fermentation, where bacterial tannase activity is able to degrade tannin into glucose and gallic acid. A simultaneously mixed cultures fermentation using Saccharomyces cerevisiae and Lactobacillus plantarum has been developed because they possess some mutualism interaction that can be beneficial in the fermentation process. Therefore, this research was focused on the effect of mixed inoculums volume of S. cerevisiae and L. plantarum and initial culture pH on the tannin and glucose level during cabbage fermentation. The sliced cabbage was inoculated with simultaneously mixed cultures (volume ratio of yeast and bacteria used was 1:1) at a different volume range 5%-25% (v/v) and also various pH range from 4 to 7, and then incubated at room temperature in anaerobic condition for 4 days. Tannin and glucose level in fermented cabbage (both biomass and filtrate) were determined using Folin-Denis and phenol-sulphuric method, respectively. The using of 5% mixed inoculums volume and initial pH around 7 were found to be the optimum condition for tannin degradation in cabbage. The remained tannin level in these fermented cabbage decreased up to 18.58% (54.061 mg/100 g FW). This experiment reveals that the amounts of inoculums and initial culture pH affected tannin degradation during cabbage fermentation using mixed cultures of yeast and lactic acid bacteria.

The role of cosubstrate and mixing on fungal biofilm efficiency in the removal of tannins

ABSTRACT Tannins are polyphenolic compounds produced by plants and they are used in industrial vegetable tanning of leather. Tannins represent one of the low biodegradability substances in tannery wastewaters with high recalcitrant soluble chemical oxygen demand, furthermore high concentration of tannins can inhibit biological treatment. In the present study, four novel rotating submerged packed bed reactors were inoculated with a selected fungal strain to reach a biological degradation of tannins in non-sterile conditions. The selected fungal strain, Aspergillus tubingensis MUT 990, was immobilised in polyurethane foam cubes carriers and inserted inside a submerged rotating cage reactors. The reactors were feed with a solution composed of four tannins: Quebracho (Schinopsis spp.), Wattle (Mimosa spp.), Chestnut (Castanea spp.) and Tara (Caesalpinia spp.). Four reactors with a volume of 4 L each were used, the co-substrate was pure malt extract, the hydraulic retention time was 24 h and the pH setpoint was 5.5. The reactors configuration was chosen to allow the study of the effect of rotation and the co-substrate addition on tannins removal. The experiment lasted two months and it was achieved 80% of chemical oxygen demand and up to 90% dissolved organic carbon removal, furthermore it was detected an important tannase activity.