Purification and characterization of a novel tannase produced by Kluyveromyces marxianus using olive pomace as solid support, and its promising role in gallic acid production

Stress response and adaptation mechanisms in Kluyveromyces marxianus

Kluyveromyces marxianus is a non-Saccharomyces yeast that has gained importance due to its great potential to be used in the food and biotechnology industries. In general, K. marxianus is a known yeast for its ability to assimilate hexoses and pentoses; even this yeast can grow in disaccharides such as sucrose and lactose and polysaccharides such as agave fructans. Otherwise, K. marxianus is an excellent microorganism to produce metabolites of biotechnological interest, such as enzymes, ethanol, aroma compounds, organic acids, and single-cell proteins. However, several studies highlighted the metabolic trait variations among the K. marxianus strains, suggesting genetic diversity within the species that determines its metabolic functions; this diversity can be attributed to its high adaptation capacity against stressful environments. The outstanding metabolic characteristics of K. marxianus have motivated this yeast to be a study model to evaluate its easy adaptability to several environments. This chapter will discuss overview characteristics and applications of K. marxianus and recent insights into the stress response and adaptation mechanisms used by this non-Saccharomyces yeast.

Evaluation of antibacterial, antifungal and antibiofilm activities of A. baumannii-derived tannase and gallic acid against uropathogenic microorganisms

One of the most prevalent infectious diseases and a key driver of antibiotic prescriptions in pediatrics is urinary tract infection (UTI). Due to the emergence of more resistant uropathogenic bacterial and fungal strains, current treatments are no longer effective, necessitating the urgent development of novel antibacterial and antifungal drugs. In this study, the antifungal, antibacterial, and anti-biofilm capabilities of compounds, such as tannase (TN) and gallic acid (GA), which were produced from a novel natural source, Acinetobacter baumannii (AB11) bacteria, were assessed for the inactivation of uropathogenic microorganisms (UMs). Ammonium sulphate precipitation, ion exchange, high-performance liquid chromatography, and gel filtration were used to purify TN and GA that were isolated from A. baumannii. A 43.08 % pure TN with 1221.2 U/mg specific activity and 10.51 mg/mL GA was obtained. The antibacterial, antifungal and anti-biofilm activities of TN and GA were evaluated against UMs and compared to those of commercially available antibiotics including sulfamethoxazole (SXT), levofloxacin (LEV), ciprofloxacin (CIP), amikacin (Ak), and nitrofurantoin (F). The results showed that TN and GA were superior to commercial antibiotics in their ability to inactivate UMs and considerably reduced biofilms formation. Additionally, the GA emerges as the top substitute for currently available medications, demonstrating superior antibacterial and antibiofilm properties against all UMs evaluated in this study. The results of this investigation showed that A. baumannii-derived TN and GA could be utilized as an alternative medication to treat UTIs.

In vitro and in vivo evaluation of tannic acid as an antibacterial agent in broilers infected with Salmonella Typhimurium

This study was conducted to evaluate tannic acid (TA) as an antibacterial agent against Salmonella Typhimurium in in vitro and in vivo chicken models. The TA formed an inhibitory zone against Salmonella enterica serotypes including S. Typhimurium, S. Enteritidis, and S. Infantis. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of TA against Salmonella Typhimurium nalidixic acid resistant strain (STNR) were determined as 40 and 700 μg/mL, respectively. Sublethal doses of TA (5, 10, and 20 μg/mL) restricted swimming and swarming motility and biofilm formation of STNR compared to the control group (0 μg/mL) (P < 0.05). The TA-bovine serum albumin (BSA) complex formed at simulated gastric pH (pH 3.75) was hydrolyzed at pH 6.75 and 7.25 (P < 0.05), and the hydrolysis of the TA-BSA complex was stronger at pH 7.25 compared to the pH 6.75 (P < 0.05). The inhibitory zone of the TA-BSA complex against STNR at pH 6.75 was lower than TA without BSA at 30 and 60 min (P < 0.05), but not at 120 min (P > 0.1). The inhibitory zone of the TA-BSA complex against STNR at pH 7.25 was not decreased at 0, 30, and 60 min compared to TA without BSA (P > 0.1). The recovery rate of TA was 83, 54.8, 10.5, and 19.6% in the gizzard, jejunum, ileum, and ceca, respectively, in broiler chickens. The STNR-infected broilers fed 0.25 g/kg of TA had significantly lower unweighted beta diversity distance compared to the sham-challenged control (SCC) and challenged controlled (CC) group on D 21. TA supplementation linearly (P < 0.05) and quadratically (tendency; P = 0.071) reduced relative abundance of the family Peptostreptococcaceae in broilers infected with STNR on D 7. TA supplementation linearly (P < 0.05) and quadratically (tendency; P = 0.06) increased the relative abundance of the family Erysipelotrichaceae in broilers infected with STNR on D 21. Therefore, TA has potential to be used as an antibacterial agent against the S. Typhimurium infection in broilers.

Biotransformation of gallate esters by a pH-stable tannase of mangrove-derived yeast Debaryomyces hansenii

Introduction: Tannase is a crucial enzyme that finds wide applications in the pharmaceutical industry, feed processing, and beverage manufacturing. Although extensive studies have been conducted on tannases from fungi and bacteria, reports on tannases exhibiting favorable pH stability are relatively limited. Methods: In this study, a tannin-degrading strain Debaryomyces hansenii was screened to induce tannase production, and the corresponding tannase coding gene TANF was successfully cloned and expressed in Yarrowia lipolytica. SDS-PAGE analysis revealed that the purified TanF tannase had a molecular weight of approximately 70 kDa. Results and Discussion: The enzyme demonstrated optimal activity at 40°C and retained over 80% of its activity in the range of 35°C-60°C. Of particular interest, TanF exhibited remarkable enzyme activity at pH 5.0 and retained more than 70% of its relative activity across a wide pH range of 3.0-8.0. Furthermore, TanF exhibited broad substrate specificity for gallate esters. The final gallic acid production by TanF from tannic acid achieved 18.32 g/L. Therefore, the excellent properties TanF has been demonstrated to be an efficient tool for the preparation of gallic acid.

Qualitative Screening of Yeast Biodiversity for Hydrolytic Enzymes Isolated from the Gastrointestinal Tract of a Coprophage “Gymnopleurus sturmi” and Dung of Ruminants

In this study, thirty yeast strains isolated from the gut of coprophagous “Gymnopleurus sturmi” and twenty-four from the dung of ruminants were shown to be producers of cellulases. Cellulolytic yeast isolates could also produce other hydrolytic enzymes such as pectinase, lipase, β-glucosidase, catalase, inulinase, urease, gelatinase, and protease. The oroduction of amylase was present in only one isolate of dung of ruminants. On the other hand, the production of tannase was absent in these isolates. All the yeasts isolated from two sources could utilize various carbon sources, including sorbitol, sucrose, and raffinose, and withstand high concentrations of glucose (300 g/L), salt (100 g/L), and exogenous ethanol. They could grow in a wide pH range of 3 to 11. The growth was stable up to a temperature of 40 °C for isolates from the gut of coprophage and 37 °C for the yeast from the dung of ruminants. These activities and growing conditions were similar to the diet of coprophagous insects and the composition of ruminant manure, likely because the adaptation and distribution of these microorganisms depend on the phenology and trophic preferences of these insects.

Production, Purification and Characterization of Extracellular Tannase from a Newly Isolated Yeast, Geotrichum cucujoidarum

With an aim to isolate a tannase positive organism, the microbial mat growing on the stored areca extract leachate surface was screened. Once the tannase positive organism was isolated, it was identified by ITS/18S rRNA gene sequencing. Further, the enzyme was purified and examined for its biochemical properties. A potent extracellular tannase-producing yeast was isolated and was identified as Geotrichum cucujoidarum. After the shake flask studies, the enzyme activity of 4.42 U/ml and specific activity of 29.86 U/mg were achieved in a medium with tannic acid as an inducer. Later, ethanol (70%) precipitation followed by purification through FPLC using SEC 650 column resulted in 166.37 U/mg specific activity and a recovery of 50.54%. The purified enzyme was a monomer with a molecular weight of 63 kDa. The optimum pH and the temperature of the enzyme were found to be 5.0 and 30°C, respectively. The Michaelis-Menten constant (Km) was found to be 2.9 mM, and the turn over number (kcat) and catalytic efficiency (kcat/km) of the purified tannase were 102 S-1 and 35.17 mM-1S-1 respectively. Temperature and pH stability profiles of the enzyme, influence of various metal ions, chelators and surfactants on enzyme activity and kinetic constants of enzyme shows that the tannase produced from Geotrichum cucujoidarum is unique and is a potential candidate for further studies.

Molecular mechanism of high-production tannase of Aspergillus carbonarius NCUF M8 after ARTP mutagenesis: revealed by RNA-seq and molecular docking

BACKGROUND

Tannase is an enzyme produced by microbial fermentation and is widely used in the food industry; however, the molecular mechanism of tannase production by Aspergillus has not yet been studied. This study was conducted to reveal the differences in Aspergillus carbonarius tannase enzymatic characterization, secondary structures and molecular mechanisms after treatment of the strain with atmospheric and room temperature plasma (ARTP).

RESULTS

The results showed that the specific activity of tannase was improved by ARTP treatment, and it showed higher thermostability and tolerance to metal ions and additives. The enzymatic characterization and molecular docking results indicated that tannase had a higher affinity and catalytic rate with tannic acid as a substrate after ARTP treatment. In addition, the docking results indicated that Aspergillus tannases may catalyze tannic acid by forming two hydrogen-bonding networks with neighboring residues. RNA-seq analysis indicated that changes in steroid biosynthesis, glutathione metabolism, glycerolipid metabolism, oxidative phosphorylation pathway and mitogen-activated protein kinase signaling pathways might be crucial reasons for the high production of tannase.

CONCLUSION

ARTP enhanced the yield and properties of A. carbonarius tannase by changing the enzyme structure and cell metabolism. This study provides a theoretical basis for elucidating the molecular mechanism underlying high production of Aspergillus tannases. © 2022 Society of Chemical Industry.

Improving the Acid Resistance of Tannase TanBLp (AB379685) from Lactobacillus plantarum ATCC14917T by Site-Specific Mutagenesis

Tannin acyl hydrolase referred commonly as tannase catalyzes the hydrolysis of the galloyl ester bond of tannin to release gallic acid. The tannase TanBLp which cloned from Lactobacillus plantarum ATCC14917^T has high activity in the pH range (7.0-9.0) at 40 °C, it would be detrimental to the utilization at acidic environment. The catalytic sites and stability of TanBLp were analyzed using bioinformatics and site-specific mutagenesis. The results reiterated that the amino acid residues Ala164, Lys343, Glu357, Asp421 and His451 had played an important role in maintaining the activity. The optimum pH of mutants V75A, G77A, N94A, A164S and F243A were shifted from 8.0 to 6.0, and mutant V75A has the highest pH stability and activity at acidic conditions than other mutants, which was more suitable for industrial application to manufacture gallic acid. This study was of great significance to promote the industrialization and efficient utilization of tannase TanBLp.

Characterization and Secretory Expression of a Thermostable Tannase from Aureobasidium melanogenum T9: Potential Candidate for Food and Agricultural Industries

Being a key industrial enzyme, tannase is extensively applied in various fields. Despite the characterizations of a large number of tannases, there are hardly a few tannases with exceptional thermostability. In this detailed study, a tannase-encoding gene named tanA was identified from Aureobasidium melanogenum T9 and heterologously expressed in Yarrowia lipolytica host of food grade. The purified tannase TanA with a molecular weight of above 63.0 kDa displayed a specific activity of 941.4 U/mg. Moreover, TanA showed optimum activity at 60°C and pH 6.0. Interestingly, TanA exhibited up to 61.3% activity after incubation for 12 h at 55°C, signifying its thermophilic property and distinguished thermostability. Additionally, TanA was a multifunctional tannase with high specific activities to catalyze the degradation of various gallic acid esters. Therefore, this study presents a novel tannase, TanA, with remarkable properties, posing as a potential candidate for food and agricultural processing.

Bioprospecting Kluyveromyces marxianus as a Robust Host for Industrial Biotechnology

Kluyveromyces marxianus is an emerging non-conventional food-grade yeast that is generally isolated from diverse habitats, like kefir grain, fermented dairy products, sugar industry sewage, plants, and sisal leaves. A unique set of beneficial traits, such as fastest growth, thermotolerance, and broad substrate spectrum (i.e., hemi-cellulose hydrolysates, xylose, l-arabinose, d-mannose, galactose, maltose, sugar syrup molasses, cellobiose, and dairy industry) makes this yeast a particularly attractive host for applications in a variety of food and biotechnology industries. In contrast to Saccharomyces cerevisiae, most of the K. marxianus strains are apparently Crabtree-negative or having aerobic-respiring characteristics, and unlikely to endure aerobic alcoholic fermentation. This is a desirable phenotype for the large-scale biosynthesis of products associated with biomass formation because the formation of ethanol as an undesirable byproduct can be evaded under aerobic conditions. Herein, we discuss the current insight into the potential applications of K. marxianus as a robust yeast cell factory to produce various industrially pertinent enzymes, bioethanol, cell proteins, probiotic, fructose, and fructo-oligosaccharides, and vaccines, with excellent natural features. Moreover, the biotechnological improvement and development of new biotechnological tools, particularly CRISPR-Cas9-assisted precise genome editing in K. marxianus are delineated. Lastly, the ongoing challenges, concluding remarks, and future prospects for expanding the scope of K. marxianus utilization in modern biotechnology, food, feed, and pharmaceutical industries are also thoroughly vetted. In conclusion, it is critical to apprehend knowledge gaps around genes, metabolic pathways, key enzymes, and regulation for gaining a complete insight into the mechanism for producing relevant metabolites by K. marxianus.

Strategies to Increase the Value of Pomaces with Fermentation

The generation of pomaces from juice and olive oil industries is a major environmental issue. This review aims to provide an overview of the strategies to increase the value of pomaces by fermentation/biotransformation and explore the different aspects reported in scientific studies. Fermentation is an interesting solution to improve the value of pomaces (especially from grape, apple, and olive) and produce high-added value compounds. In terms of animal production, a shift in the fermentation process during silage production seems to happen (favoring ethanol production rather than lactic acid), but it can be controlled with starter cultures. The subsequent use of silage with pomace in animal production slightly reduces growth performance but improves animal health status. One of the potential applications in the industrial context is the production of enzymes (current challenges involve purification and scaling up the process) and organic acids. Other emerging applications are the production of odor-active compounds to improve the aroma of foods as well as the release of bound polyphenols and the synthesis of bioactive compounds for functional food production.

Acid Stable Yeast Cell-Associated Tannase with High Capability in Gallated Catechin Biotransformation

Previously, nine tannin-tolerant and tannase-producing yeasts were isolated from Miang; all produced cell-associated tannase (CAT) during growth in tannin substrate. Among which, only CAT from Sporidiobolus ruineniae showed better stability than its purified form. Yet, it is of particular interest to directly characterize CATs from the latter yeasts. In this study, four CATs from yeasts, namely Cyberlindnera rhodanensis A22.3, Candida sp. A39.3, Debaryomyces hansenii A45.1, and Cy. rhodanensis A45.3 were characterized. The results indicate that all CATs were produced within the same production yield (11 mU/mL). Most CATs exhibited similar pH and temperature optima and stabilities, except for CAT from Cy. rhodanensis A22.3. This CAT was assigned as acid-stable tannase due to its unusual optimum pH of 2.0 with pH stability and half-life thermostability in the range of pH 2.0-4.0, and 70 °C, respectively. All CATs demonstrated high substrate specificity toward epigallocatechin gallate and epicatechin gallate, thus forming epigallocatechin and epicatechin, respectively. Moreover, they showed operational stability to repeated use for up to five cycles without loss of the initial activity. Therefore, CATs from these yeasts could be useful for the extraction and biotransformation of tea catechins and related applications.

Chitosan Activated with Genipin: A Nontoxic Natural Carrier for Tannase Immobilization and Its Application in Enhancing Biological Activities of Tea Extract

In this work, a non-toxic chitosan-based carrier was constructed via genipin activation and applied for the immobilization of tannase. The immobilization carriers and immobilized tannase were characterized using Fourier transform infrared spectroscopy and thermogravimetric analysis. Activation conditions (genipin concentration, activation temperature, activation pH and activation time) and immobilizations conditions (enzyme amount, immobilization time, immobilization temperature, immobilization pH, and shaking speed) were optimized. The activity and activity recovery rate of the immobilized tannase prepared using optimal activation and immobilization conditions reached 29.2 U/g and 53.6%, respectively. The immobilized tannase exhibited better environmental adaptability and stability. The immobilized tannase retained 20.1% of the initial activity after 12 cycles and retained 81.12% of residual activity after 30 days storage. The catechins composition analysis of tea extract indicated that the concentration of non-ester-type catechins, EGC and EC, were increased by 1758% and 807% after enzymatic treatment. Biological activity studies of tea extract revealed that tea extract treated with the immobilized tannase possessed higher antioxidant activity, higher inhibitory effect on α-amylase, and lower inhibitory effect on α-glucosidase. Our results demonstrate that chitosan activated with genipin could be an effective non-toxic carrier for tannase immobilization and enhancing biological activities of tea extract.

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.

Characterization of a Robust and pH-Stable Tannase from Mangrove-Derived Yeast Rhodosporidium diobovatum Q95

Tannase plays a crucial role in many fields, such as the pharmaceutical industry, beverage processing, and brewing. Although many tannases derived from bacteria and fungi have been thoroughly studied, those with good pH stabilities are still less reported. In this work, a mangrove-derived yeast strain Rhodosporidium diobovatum Q95, capable of efficiently degrading tannin, was screened to induce tannase, which exhibited an activity of up to 26.4 U/mL after 48 h cultivation in the presence of 15 g/L tannic acid. The tannase coding gene TANRD was cloned and expressed in Yarrowia lipolytica. The activity of recombinant tannase (named TanRd) was as high as 27.3 U/mL. TanRd was purified by chromatography and analysed by SDS-PAGE, showing a molecular weight of 75.1 kDa. The specific activity of TanRd towards tannic acid was 676.4 U/mg. Its highest activity was obtained at 40 °C, with more than 70% of the activity observed at 25–60 °C. Furthermore, it possessed at least 60% of the activity in a broad pH range of 2.5–6.5. Notably, TanRd was excellently stable at a pH range from 3.0 to 8.0; over 65% of its maximum activity remained after incubation. Besides, the broad substrate specificity of TanRd to esters of gallic acid has attracted wide attention. In view of the above, tannase resources were developed from mangrove-derived yeasts for the first time in this study. This tannase can become a promising material in tannin biodegradation and gallic acid production.

Kluyveromyces marxianus: An emerging yeast cell factory for applications in food and biotechnology

Several yeasts, which are eukaryotic microorganisms, have long been used in different industries due to their potential applications, both for fermentation and for the production of specific metabolites. Kluyveromyces marxianus is one of the most auspicious nonconventional yeasts, generally isolated from wide-ranging natural habitats such as fermented traditional dairy products, kefir grain, sewage from sugar industries, sisal leaves, and plants. This is a food-grade yeast with various beneficial traits, such as rapid growth rate and thermotolerance that make it appealing for different industrial food and biotechnological applications. K. marxianus is a respiro-fermentative yeast likely to produce energy by either respiration or fermentation pathways. It generates a wide-ranging specific metabolites and could contribute to a variety of different food and biotechnological industries. Although Saccharomyces cerevisiae is the most widely used dominant representative in all aspects, many applications of K. marxianus in biotechnology, food and environment have only started to emerge nowadays; some of the most promising applications are reviewed here. The general physiology of K. marxianus is outlined, and then the different applications are discussed: first, the applications of K. marxianus in biotechnology, and then the recent advances and possible applications in food, feed and environmental industries. Finally, this review provides a discussion of the main challenges and some perspectives for targeted applications of K. marxianus in the modern food technology and applied biotechnology in order to exploit the full potential of this yeast which can be used as a cell factory with great efficiency.

Co-production of gallic acid and a novel cell-associated tannase by a pigment-producing yeast, Sporidiobolus ruineniae A45.2

BACKGROUND

Gallic acid has received a significant amount of interest for its biological properties. Thus, there have been recent attempts to apply this substance in various industries and in particular the feed industry. As opposed to yeasts, fungi and bacteria and their tannases have been well documented for their potential bioconversion and specifically for the biotransformation of tannic acid to gallic acid. In this research, Sporidiobolus ruineniae A45.2 is introduced as a newly pigment-producing and tannase-producing yeast that has gained great interest for its use as an additive in animal feed. However, there is a lack of information on the efficacy of gallic acid production from tannic acid and the relevant tannase properties. The objective of this research study is to optimize the medium composition and conditions for the co-production of gallic acid from tannic acid and tannase with a focus on developing an integrated production strategy for its application as a feed additive.

RESULTS

Tannase produced by S. ruineniae A45.2 has been classified as a cell-associated tannase (CAT). Co-production of gallic acid obtained from tannic acid and CAT by S. ruineniae A45.2 was optimized using response surface methodology and then validated with the synthesis of 11.2 g/L gallic acid from 12.3 g/L tannic acid and the production of 31.1 mU/mL CAT after 48 h of cultivation in a 1-L stirred tank fermenter. Tannase was isolated from the cell wall, purified and characterized in comparison with its native form (CAT). The purified enzyme (PT) revealed the same range of pH and temperature optima (pH 7) as CAT but was distinctively less stable. Specifically, CAT was stable at up to 70 °C for 60 min, and active under its optimal conditions (40 °C) at up to 8 runs.

CONCLUSION

Co-production of gallic acid and CAT is considered an integrated and green production strategy. S. ruineniae biomass could be promoted as an alternative source of carotenoids and tannase. Thus, the biomass, in combination with gallic acid that was formed in the fermentation medium, could be directly used as a feed additive. On the other hand, gallic acid could be isolated and purified for food and pharmaceutical applications. This paper is the first of its kind to report that the CAT obtained from yeast can be resistant to high temperatures of up to 70 °C.

Thermostable Tannase from Aspergillus Niger and Its Application in the Enzymatic Extraction of Green Tea

Tannase is widely used in tea beverage processing because of its ability to catalyze the hydrolysis of hydrolysable tannins or gallic acid esters and effectively improve the quality of tea extracts through enzymatic extraction. A new thermophilic tannase was cloned from Aspergillus niger FJ0118 and characterized. The tannase exhibited an optimal reaction temperature of 80 °C and retained 89.6% of the initial activity after incubation at 60 °C for 2 h. The enzymatic extraction of green tea at high temperature (70 °C) for a short time (40 min) was devised on the basis of the superior thermal stability of tannase. The enzymatic reaction significantly increased the total polyphenol content of green tea extract from 137 g·kg⁻¹ to 291 g·kg⁻¹. The enzymatic reaction effectively degraded the ester catechins into non-ester catechins compared with the water extraction method. Results suggested that the thermally stable tannase exhibited potential applications in the enzymatic extraction of green tea beverage.

Expression and biochemical characterization of a new alkaline tannase from Lactobacillus pentosus

Lactobacillus pentosus BA-7 and L. pentosus QA1-5 are tannin-tolerant lactic acid bacteria that were isolated from Miang, a traditional fermented tea-leaf found in northern Thailand and a tannin-rich substrate. Tannase encoding genes were isolated, cloned and overexpressed in Escherichia coli BL21(DE3). The recombinant tannase was produced with production yields of 40 and 39 KU/L for LpTanBA-7 and LpTanQA1-5, respectively. Both revealed the same molecular weight of 50 kDa as estimated by SDS-PAGE and were optimally active under alkaline pH conditions LpTanQA1-5 revealed optimal temperatures in a range of 37-40 °C as is typically found in lactic acid bacteria, while LpTanBA-7 was active at higher temperatures with an optimum temperature range of 45-55 °C. LpTanBA-7 was found to be more stable within the same range of temperatures than LpTanQA1-5. Furthermore, it was active and stable toward various organic solvents and produced 50 mg/mL of gallic acid from 100 mg/mL tannic acid. Based on the results, LpTanBA-7 is considered a new alkali-moderately thermophilic tannase obtained from lactic acid bacterium that may be capable of a feasible production capacity of gallic acid and its esters. Furthermore, tannase that is active at high temperatures could also be used in tea products in order to develop a sweet aftertaste, as well as to improve levels of antioxidant activity.

Solid state fermentation of Bacillus gottheilii M2S2 in laboratory-scale packed bed reactor for tannase production

Production of tannase was performed in packed bed reactor filled with an inert support polyurethane foam (PUF) using Bacillus gottheilii M2S2. The influence of process parameters such as fermentation time (24-72 h), tannic acid concentration (0.5-2.5% w/v), inoculum size (7-12% v/v), and aeration rate (0-0.2 L/min) on tannase production with PUF were analyzed using one variable at a time (OVAT) approach. The outcome of OVAT was optimized by central composite design. Based on the statistical investigation, the proposed mathematical model recommends 1% (w/v) of tannic acid, 10% (v/v) of inoculum size and 0.13 L/min of aeration rate for maximum production (76.57 ± 1.25 U/L). The crude enzyme was purified using ammonium sulfate salt precipitation method followed by dialysis. The biochemical properties of partially purified tannase were analyzed and found the optimum pH (4.0), temperature (40 °C) for activity, and K_m (1.077 mM) and V_max (1.11 µM/min) with methyl gallate as a substrate. Based on the SDS-PAGE analysis, tannase exhibited two bands with molecular weights of 57.5 and 42.3 kDa. Briefly, the partially purified tannase showed 4.2 fold increase (63 ± 1.60 U/L) in comparison to the submerged fermentation and the production of tannase was validated by using NMR spectrometer.

Antioxidant and anticancer efficacy of therapeutic bioactive compounds from fermented olive waste

Olive pomace, which is considered as one of the worst agro-industrial wastes in Mediterranean countries was tested for bioactive compounds production through the solid state fermentation of Kluyveromyces marxianus. Because they present potent biological activities, phenolic compounds from both unfermented and fermented pomace were extracted with simultaneous evaluation of their antioxidant and anticancer activities. Conditions for optimum total phenolic recovery with maximum antioxidant activity were optimized using methanol as the extracting solvent with a sample to solvent ratio of 1:10 at 50 °C for 2 hours. The in-vitro anticancer activity of both extracts was assessed against different human cancer cell lines. The results revealed that both extracts exerted anticancer effects close to the value of doxorubicin drug against liver HepG2 and breast MCF-7 cell lines, and moderate activity against prostate PC3 and colon HCT116 cell lines. Nevertheless, the fermented extract was more potent than the unfermented one. No effect against lung A549, cervix Hela cancer cell lines or normal HFB4 cells was observed for both extracts. A GC/MS analysis was carried out to determine the compounds responsible for antioxidant and anticancer activities. The results showed the presence of methyl palmitate, methyl oleate, and ethyl oleate in the methanolic extract of unfermented olive pomace, while that of the fermented one showed the production of carvacrol, thymol, eugenol, caryophyllene oxide and methyl isopalmitate.