Juan A. Ascacio-Valdés

Fungal biodegradation of pomegranate ellagitannins.

Ellagitannins (ETs) are phytochemicals derived from secondary metabolism associated to defense system, with complex chemical structures, which have high participation during all stages of protection against microbial infection. In this study, we report the fungal biodegradation of a bioactive ET, named punicaline which was recovered and purified from pomegranate peels and used as carbon source in solid‐state culture (SSC) using polyurethane as solid support. SSC was kinetically monitored during 36 h of incubation time. ETs and glycosides consumption were spectrophotometrically determined. Ellagic acid (EA) accumulation was analyzed by HPLC. Several enzymatic activities were assayed (cellulase, xylanase, β‐glucosydase, polyphenoloxidase, tannase, and ET hydrolyzing activities). The consumption levels of ETs and glycosides were 66 and 40%, while EA accumulation reached 42.02 mg g−1. A differential pattern of enzymatic activities was found; evidence from our studies suggests that the ET hydrolyzing activity is directly associated to EA accumulation, and production of this enzyme may represent the most critical step to successfully develop a bioprocess for production of an important bioactive compound, the EA.

Assessment of pomegranate wine lees as a valuable source for the recovery of (poly)phenolic compounds

Wine lees are the residue formed at the bottom of recipients containing wine after fermentation and are mainly composed of yeast. They can be applied for the recovery of value-added phytochemicals owing to the ability of yeast to form molecular interactions with (poly)phenolic compounds. This study aimed to evaluate the potential use of lees obtained as by-products after winemaking of pomegranate (Punica granatum L.) juice. Pomegranate wine lees showed high both phenolic content (about 30 mg GAE/g dry matter) and antioxidant capacity by DPPH and ABTS(+) assays. The phytochemical screening of this by-product by UHPLC-ESI-MS(n) allowed the identification of up to 39 chemicals, being hydrolysable tannins and anthocyanins the predominant structures. Ellagic acid and gallic acid were present in high amounts. In addition, mineral composition was also assessed. Overall, pomegranate wine lees resulted in a promising source for the recovery of bioactive polyphenols with potential applications in different industrial fields.

Euphorbia antisyphilitica residues as a new source of ellagic acid

In this study, a new source of ellagic acid (EA) is reported. Euphorbia antisyphilitica or “candelilla” was used to extract phenolic dilactone. Cereous layers and fibrous tissue were analyzed. A completely randomized experimental design with a treatment factorial arrangement was employed. The factors considered were: plant/extracting agent ratio, extraction temperature and time. Candelilla wax does not contain EA. Temperature and the ratio plant/extracting agent were determinant during the EA extraction process. Around 20 mg of free EA per gram of fibrous tissue were found. Residues of candelilla are a good source of EA.

Antifungal ellagitannin isolated from Euphorbia antisyphilitica Zucc

OBJECTIVE To study antifungal activity of a new ellagitannin isolated from the plant residues of Euphorbia antisyphilitica (E. antisyphilitica) Zucc in the wax extraction process. METHODS An extract was prepared from dehydrated and pulverized residues and fractionated by liquid chromatography on Amberilte XAD-16, until obtained an ellagitannin-rich ethanolic fraction which was treated by rotaevaporation to recover the ellagitannin as fine powder. An aqueous solution was prepared and treated through ionic exchange liquid chromatography (Q XL) and gel permeation chromatography (G 25). The ellagitannin-rich fraction was thermogravimetrically evaluated (TGA and DTA) to test the thermo-stability of ellagic acid (monomeric unit). Then ellagitannin powder was analyzed by infrared spectrospcopy to determinate the functional groups and, also mass spectroscopy was used to determine the molecular ion. RESULTS The principal functional groups of ellagitannin were determined, the molecular weight was 860.7 g/mol; and an effective antifungal activity against phytopathogenic fungi was demonstrated. CONCLUSIONS It can be concluded that the new ellagitannin (860.7 g/mol) isolated from E. antisyphilitica Zucc is an effective antifungal agent against Alternaria alternata, Fusarium oxyzporum, Colletotrichum gloeosporoides and Rhizoctnia solani.

Immobilization of metal–humic acid complexes in anaerobic granular sludge for their application as solid-phase redox mediators in the biotransformation of iopromide in UASB reactors

Metal-humic acid complexes were synthesized and immobilized by a granulation process in anaerobic sludge for their application as solid-phase redox mediators (RM) in the biotransformation of iopromide. Characterization of Ca- and Fe-humic acid complexes revealed electron accepting capacities of 0.472 and 0.556milli-equivalentsg(-1), respectively. Once immobilized, metal-humic acid complexes significantly increased the biotransformation of iopromide in upflow anaerobic sludge blanket (UASB) reactors. Control UASB reactor (without humic material) achieved 31.6% of iopromide removal, while 80% was removed in UASB reactors supplied with each metal-humic acid complex. Further analyses indicated multiple transformation reactions taking place in iopromide including deiodination, N-dealkylation, decarboxylation and deacetylation. This is the first successful application of immobilized RM, which does not require a supporting material to maintain the solid-phase RM in long term operation of bioreactors. The proposed redox catalyst could be suitable for enhancing the redox conversion of different recalcitrant pollutants present in industrial effluents.

The complete biodegradation pathway of ellagitannins by Aspergillus niger in solid‐state fermentation

Our research group has found preliminary evidences of the fungal biodegradation pathway of ellagitannins, revealing first the existence of an enzyme responsible for ellagitannins degradation, which hydrolyzes pomegranate ellagitannins and it was called ellagitannase or elagitannin acyl hydrolase. However, it is necessary to generate new and clear information in order to understand the ellagitannin degradation mechanisms. This work describes the distinctive and unique features of ellagitannin metabolism in fungi. In this study, hydrolysis of pomegranate ellagitannins by Aspergillus niger GH1 was studied by solid‐state culture using polyurethane foam as support and pomegranate ellagitannins as substrate. The experiment was performed during 36 h. Results showed that ellagitannin biodegradation started after 6 h of fermentation, reaching the maximal biodegradation value at 18 h. It was observed that ellagitannase activity appeared after 6 h of culture, then, the enzymatic activity was maintained up to 24 h of culture reaching 390.15 U/L, after this period the enzymatic activity decreased. Electrophoretic band for ellagitannase was observed at 18 h. A band obtained using non‐denaturing electrophoresis was identified as ellagitannase, then, a tandem analysis to reveal the ellagitannase activity was performed using Petri plate with pomegranate ellagitannins. The extracts were analyzed by HPLC/MS to evaluate ellagitannins degradation. Punicalin, gallagic acid, and ellagic acid were obtained from punicalagin. HPLC/MS analysis identified the gallagic acid as an intermediate molecule and immediate precursor of ellagic acid. The potential application of catabolic metabolism of ellagitannin hydrolysis for ellagic acid production is outlined.

Impact of extraction techniques on antioxidant capacities and phytochemical composition of polyphenol-rich extracts.

In this work, impact of extraction methods (maceration, decoction, MAE, and UAE) on TPC, antioxidant activity, and the mass fraction of phenolics in several plant extracts (Punica granatum, Juglans regia, Moringa oleifera, and Cassia fistula) was investigated. The results showed that, despite the nature of matrix, the highest values of TPC in all samples were obtained by MAE as follows: PP (18.92±0.11), ML (15.19±0.11), HL (12.69±0.16), and WS (12.80±0.11) mg GAEg-1 respectively, and exhibited potent antioxidant activity (from 0.28±0.01 to 5.34±0.02mgGAEg-1), representing sources of powerful antioxidants. The LC-MS2 analysis revealed a wide range of phenolics, highlighting their content in phenolic acids, flavonoids and lignans. The presence of different phenol molecules demonstrated that the extraction method had influence on phytochemical profile. Finally, due to its high extraction efficiency, MAE was the more effective extraction technique.

Rhizopus oryzae – Ancient microbial resource with importance in modern food industry

Filamentous fungi are microorganisms widely known for their diverse biochemical features. Fungi can efficiently invade a wide variety of substrates under operational conditions producing numerous bioproducts of interest, such as enzymes, organic acids, aromatic compounds and colorants. An additional interesting characteristic of some fungi is their safety classification for different uses, which guarantees that the bioproducts obtained from them do not contain any toxic component deleterious to humans. Rhizopus oryzae is among this group of fungi and is classified as a GRAS filamentous fungus, commonly used for production of some oriental traditional foods. It is mainly recognized as a good producer of lactic acid; however, its potential for other biotechnological processes is under study. This review analyzes and discusses the current scientific and technical contributions which may maximize the potential of R. oryzae as a producer of different compounds of industrial interest.

Enhanced Reduction of p-Nitrophenol by a Methanogenic Consortium Promoted by Metallic Nanoparticles

The present study reports the synthesis and characterization of metallic nanoparticles (NPs) of Pd and bimetallic alloys of PdCu NPs for their application as catalysts to achieve the microbial reduction of p-nitrophenol (PNP). Addition of bimetallic alloys of PdCu NPs to methanogenic sludge incubations increased up to threefold the rate of reduction of PNP. Moreover, their presence promoted a more efficient and selective reduction of PNP to the desired product (p-aminophenol) with negligible accumulation of toxic intermediates (p-nitroso-phenol and p-hydroxylamine-phenol), which prevailed in sludge incubations lacking nanocatalysts. PdCu NPs synthesized by adding precursors H2PdCl4 and H2CuCl4 independently and simultaneously to the synthesis vessel showed superior catalytic properties as compared to those produced by mixing the same precursors prior addition to the synthesis vessel. The enhanced catalytic properties of bimetallic NPs could be explained by higher physical stability and interfacial arrangement within PdCu alloys promoting a more efficient transfer of reducing equivalents derived from lactate/ethanol fermentation towards the target nitro group in PNP. A wastewater treatment technology, combining the microbial activity of methanogenic consortia and the catalytic activity of bimetallic NPs, is proposed as an alternative for the removal of recalcitrant pollutants from wastewaters.

Hydrolases of Halophilic Origin With Importance for the Food Industry

Abstract Currently, some enzymes used in the food industry do not have the same activity when they are exposed to extreme pH, high temperatures, low water activity, etc., Recently, there has been increased interest in finding enzymes with resistance to aggressive conditions to generate efficient and clean processes. Enzymes are used to reduce viscosity, improve extractions, perform bioconversions, produce separations, change functions, and modify flavors, among other uses. Enzymes produced by halophilic microorganisms are produced under high salt concentration environments, have a high percentage of amino acid acidic-residues, and low levels of lysine as well as high contents of hydrophobic residues, aspartic, and glutamic acid and a low content of aliphatic residues. Hydrolases act mainly on four families of molecules (carbohydrates, lipids, proteins, and nucleic acids). Some of these enzymes are amylases, proteases, pectinases, lipases, and DNAses, among others. In this chapter, we discuss the main discoveries on these enzymes as well as their properties, applications, and future trends.