Potential use of different agroindustrial by-products as supports for fungal ellagitannase production under solid-state fermentation

Recovery of Phenolic Compounds with Antioxidant Capacity Through Solid-State Fermentation of Pistachio Green Hull

Pistachio green hull (PGH) represents the non-edible fraction obtained after the seed is harvested and is an important source of phenolic compounds. Solid-state fermentation (SSF) is a viable biotechnological and economical technique for extracting phenolic compounds. This study aimed to evaluate the SSF with Aspergillus niger GH1 to recover total phenolic compounds (TPC) with antioxidant capacity (AC) from PGH. For this, the time of higher TPC and AC (DPPH [2,2-diphenyl-1-picrylhydrazyl], ABTS [2,2-azinobis-(3-ethylbenzothiazoline-6-sulfonate)], FRAP [ferric reducing antioxidant power]) was selected. Then, moisture, inoculum concentration, and aeration rate were evaluated. A. niger GH1 was able to grow and colonize the PGH, with the higher value of TPC (23.83 mg/g of dry mass (gdm)) obtained after 24 h of culture, which significantly correlated with AC (Pearson's R = 0.69). Moisture and aeration rate were the main factors influencing TPC. The highest values for both TPC and AC were achieved in treatment 8 (60% moisture, 5 × 106 spores/mL, and 1 L/Kgwm min), resulting in a 129% and 1039% increase, respectively. Gallic acid 4-O-glucoside and geranine were identified in the PGH extracts using high-performance liquid chromatography coupled with mass spectrometry. The SSF provides eco-friendly alternatives for releasing bioactive compounds from PGH, adding value to this waste.

Bioprospecting of endophytic fungi from semidesert candelilla (Euphorbia antisyphilitica Zucc): Potential for extracellular enzyme production

Endophytic microbial communities colonize plants growing under various abiotic stress conditions. Candelilla (Euphorbia antisyphilitica Zucc.) is a shrub that develops functionally in arid and semi-arid zones of Mexico; these conditions generate an association between the plant and the microorganisms, contributing to the production of enzymes as a defense mechanism for resistance to abiotic stress. The objective of this research was to isolate and identify endophyte fungi of candelilla and bioprospection of these endophytic fungi for enzyme production using candelilla by-products. Fungi were isolated and identified using ITS1/ITS4 sequencing. Their potency index (PI) was evaluated in producing endoglucanase, xylanase, amylase, and laccase. Fermentation was carried out at 30°C for 8 days at 200 rpm, with measurements every 2 days, using candelilla by-products as substrate. All fungi exhibited higher cellulase, amylase, and laccase activities on the 2nd, 6th, and 8th day of fermentation, respectively, of fermentation. The fungus Aspergillus niger ITD-IN4.1 showed the highest amylase activity (246.84 U/mg), the genus Neurospora showed the highest cellulase activity, reaching up to 13.45 FPU/mg, and the strain Neurospora sp. ITD-IN5.2 showed the highest laccase activity (3.46 U/mg). This work provides the first report on the endophytic diversity of E. antisyphilitica and its potential role in enzyme production.

Production of a Fungal Punicalagin-Degrading Enzyme by Solid-State Fermentation: Studies of Purification and Characterization

The present work describes the purification of an enzyme capable of degrading punicalagin. The enzyme was produced by Aspergillus niger GH1 by solid-state fermentation, and the enzyme production was induced by using ellagitannins as the sole carbon source. The purification steps included the concentration by lyophilization, desalting, anionic exchange, and gel filtration chromatography. The enzyme kinetic constants were calculated by using punicalagin, methyl gallate, and sugar beet arabinans. The molecular mass of the protein was estimated by SDS-PAGE. The identified bands were excised and digested using trypsin, and the peptides were submitted to HPLC-MS/MS analysis. The docking analysis was conducted, and a 3D model was created. The purification fold increases 75 times compared with the cell-free extract. The obtained Km values were 0.053 mM, 0.53% and 6.66 mM for punicalagin, sugar beet arabinans and methyl gallate, respectively. The optimal pH and temperature for the reaction were 5 and 40 °C, respectively. The SDS-PAGE and native PAGE analysis revealed the presence of two bands identified as α-l-arabinofuranosidase. Both enzymes were capable of degrading punicalagin and releasing ellagic acid.

Bioprocessing of pineapple waste biomass for sustainable production of bioactive compounds with high antioxidant activity

The effect of temperature, moisture content and pH during solid-state fermentation (SSF) of MD2 pineapple peel with Rhizopus oryzae (MUCL 28168) was evaluated on the release of bioactive compounds with antioxidant capacity. Applying a central composite design, it was found that temperature had a significant effect (p < 0.05) on the total phenolic content and DPPH antioxidant activity while for the ABTS radical elimination activity, the factor that presented a significant effect was the pH (p < 0.05); as this factor increases, the antioxidant activity enhances. The optimal conditions for fermentation process were 80% of moisture content, pH 5.5, temperature 37.3 °C and 24 h of process to maximize phenolic content and antioxidant activity. Gallic acid, chlorogenic acid, caffeic acid and cinnamic acid were identified in the extracts by HPLC analysis. These results permit to conclude that SSF of pineapple peel is an effective bioprocess for the release of phenolic compounds with antioxidant activity.

Graphical abstract

Solid-State Fermentation of Sorghum by Aspergillus oryzae and Aspergillus niger: Effects on Tannin Content, Phenolic Profile, and Antioxidant Activity

Sorghum contains antioxidants such as tannins. However, these are considered antinutritional factors since they are responsible for the low digestibility of proteins and carbohydrates. Nevertheless, these can be extracted by solid-state fermentation (SSF). Therefore, this study aimed to evaluate the effects of SSF from Aspergillus oryzae and Aspergillus niger Aa210 on the tannin contents, phenolic profiles determined by HPLC-MS, and antioxidant activities (ABTS, DPPH, and FRAP) of two genotypes of sorghum. The results showed that with SSF by A. niger Aa210, a higher tannin content was obtained, with yields of 70-84% in hydrolyzable tannins (HT) and 33-49% in condensed tannins (CT), while with SSF by A. oryzae the content of HT decreased by 2-3% and that of CT decreased by 6-23%. The extracts fermented by A. niger at 72 and 84 h exhibited a higher antioxidant activity. In the extracts, 21 polyphenols were identified, such as procyanidins, (+)-catechin, (-)-epicatechin, scutellarein, arbutin, and eriodictyol, among others. Therefore, SSF by A. niger was an efficient process for the release of phenolic compounds that can be used as antioxidants in different food products. It is also possible to improve the bioavailability of nutrients in sorghum through SSF. However, more studies are required.

Ellagic Acid: A Review on Its Natural Sources, Chemical Stability, and Therapeutic Potential

Ellagic acid (EA) is a bioactive polyphenolic compound naturally occurring as secondary metabolite in many plant taxa. EA content is considerable in pomegranate (Punica granatum L.) and in wood and bark of some tree species. Structurally, EA is a dilactone of hexahydroxydiphenic acid (HHDP), a dimeric gallic acid derivative, produced mainly by hydrolysis of ellagitannins, a widely distributed group of secondary metabolites. EA is attracting attention due to its antioxidant, anti-inflammatory, antimutagenic, and antiproliferative properties. EA displayed pharmacological effects in various in vitro and in vivo model systems. Furthermore, EA has also been well documented for its antiallergic, antiatherosclerotic, cardioprotective, hepatoprotective, nephroprotective, and neuroprotective properties. This review reports on the health-promoting effects of EA, along with possible mechanisms of its action in maintaining the health status, by summarizing the literature related to the therapeutic potential of this polyphenolic in the treatment of several human diseases.

Valorization of agro-industrial wastes for biorefinery process and circular bioeconomy: A critical review

Energy recovery from waste resources is a promising approach towards environmental consequences. In the prospect of environmental sustainability, utilization of agro-industrial waste residues as feedstock for biorefinery processes have gained widespread attention. In the agro-industry, various biomasses are exposed to different unit processes for offering value to various agro-industrial waste materials. Agro-industrial wastes can generate a substantial amount of valuable products such as fuels, chemicals, energy, electricity, and by-products. This paper reviews the methodologies for valorization of agro-industrial wastes and their exploitation for generation of renewable energy products. In addition, management of agro-industrial wastes and products from agro-industrial wastes have been elaborated. The waste biorefinery process using agro-industrial wastes does not only offer energy, it also offers environmentally sustainable modes, which address effective management of waste streams. This review aims to highlight the cascading use of biomass from agro-industrial wastes into the systemic approach for economic development.

Valorisation of food agro-industrial by-products: From the past to the present and perspectives

Food agro-industrial by-products mainly include peels, seeds, stems, bagasse, kernels, and husk, derived during food processing. Due to their overproduction and the lack of sustainable management, such by-products have been conventionally rejected and wasted in landfills, being the principal strategy for their treatment, but nowadays, this strategy has been associated with several environmental, social and economic issues. Hence, we focused on the use of different consolidated biotechnological processes and methodologies as suitable strategies for food by-products management and valorisation, highlighting them as potential bioresources because they still gather high compositional and nutritional value, owing to their richness in functional and bioactive molecules with human health benefits. Food by-products could be utilised for the development of new food ingredients or products for human consumption, promoting their integral valorisation and reincorporation to the food supply chain within the circular bioeconomy concept, creating revenue streams, business and job opportunities. In this review, the main goal was to provide a general overview of the food agro-industrial by-products utilised throughout the years, improving global sustainability and human nutrition, emphasising the importance of biowaste valorisation as well as the methodologies employed for the recovery of value-added molecules.

Euphorbia antisyphilitica Zucc: A Source of Phytochemicals with Potential Applications in Industry

Euphorbia antisyphilitica Zucc, better known as the candelilla plant, is one of the 10 non-timber forest products of greatest economic importance in the desert and semi-desert regions of Mexico. Moreover, it is a potential source of some functional phytochemicals such as polyphenolic compounds, wax and fiber, with potential applications in food, cosmetic and pharmaceutical industries. Thus, this review aims to describe these phytochemicals and their functional properties as antimicrobial, antioxidant, reinforcing and barrier agents. In addition, a suitable valorization of the candelilla plant and its byproducts is mandatory in order to avoid negative effects on the environment. This review provides, for the first time, an overview of the alternative methodologies for improving candelilla plant production, pointing out some of the agricultural aspects of the cultivation of this plant.

Solid-State Fermentation with Aspergillus niger GH1 to Enhance Polyphenolic Content and Antioxidative Activity of Castilla Rose (Purshia plicata)

This work was performed to study Castilla Rose (Purshia plicata) as a potential source of polyphenols obtained by solid-state fermentation (SSF)-assisted extraction using the microorganism Aspergillus niger GH1 and to evaluate the antioxidant activity of the extracted compounds. First, water absorption capacity (WAC) of the plant material, radial growth of the microorganism, determination of best fermentation conditions, and maximum accumulation time of polyphenols were tested. Then, a larger-scale fermentation, polyphenols isolation by column liquid chromatography (Amberlite XAD-16) and recovered compounds identification by HPLC-MS were made. Finally, the antioxidant activity of the recovered compounds was tested by ABTS, DPPH, and lipid oxidation inhibition assays. The best fermentation conditions were temperature 25 °C and inoculum 2 × 106 spores/g, while the maximum extraction time of polyphenols was 24 h (173.95 mg/g). The HPLC/MS analysis allowed the identification of 25 different polyphenolic compounds, and the antioxidant activity of the obtained polyphenols was demonstrated, showing ABTS assay the most effective with inhibition of 94.34%.

On-line monitoring of Aspergillus niger GH1 growth in a bioprocess for the production of ellagic acid and ellagitannase by solid-state fermentation

The present work describes the monitoring of CO₂ production by Aspergillus niger GH1 in a bioprocess for the production of ellagitannase (EAH) and ellagic acid by solid state fermentation. Pomegranate ellagitannins, mainly punicalagin, were used as carbon source and EAH inducer. A second condition, using ellagitannins and maltose as growth promoting carbon source, was tested. The ellagic acid production was quantified and the EAH activity was assayed. The accumulated metabolites were identified by HPLC-ESI-MS/MS. Higher CO₂ production (7.79mg/grams of dry material) was reached in media supplemented with maltose. Short-time lag phase (7.79h) and exponential phase (10.42h) were obtained using only ellagitannins, despite its lower CO₂ production (3.79mg/grams of dry material). Without the use of maltose lower ellagic acid (11.85mg/L/h) and EAH (21.80U/L/h) productivities were reached. The use of maltose enhances the productivity of EA (33.18mg/L/h) and EAH (33.70U/L/h). Besides of punicalin and ellagic acid, two unknown compounds with mass weight of 702 and 290g/mol (ions 701 and 289m/z in negative mode, respectively) were identified and characterized by HPLC-ESI-MS/MS analysis.

Solid state fermentation (SSF): diversity of applications to valorize waste and biomass

Solid state fermentation is currently used in a range of applications including classical applications, such as enzyme or antibiotic production, recently developed products, such as bioactive compounds and organic acids, new trends regarding bioethanol and biodiesel as sources of alternative energy, and biosurfactant molecules with environmental purposes of valorising unexploited biomass. This work summarizes the diversity of applications of solid state fermentation to valorize biomass regarding alternative energy and environmental purposes. The success of applying solid state fermentation to a specific process is affected by the nature of specific microorganisms and substrates. An exhaustive number of microorganisms able to grow in a solid matrix are presented, including fungus such as Aspergillus or Penicillum for antibiotics, Rhizopus for bioactive compounds, Mortierella for biodiesel to bacteria, Bacillus for biosurfactant production, or yeast for bioethanol.

Effect of different polyphenol sources on the efficiency of ellagic acid release by Aspergillus niger

Fungal hydrolysis of ellagitannins produces hexahydroxydiphenic acid, which is considered an intermediate molecule in ellagic acid release. Ellagic acid has important and desirable beneficial health properties. The aim of this work was to identify the effect of different sources of ellagitannins on the efficiency of ellagic acid release by Aspergillus niger. Three strains of A. niger (GH1, PSH and HT4) were assessed for ellagic acid release from different polyphenol sources: cranberry, creosote bush, and pomegranate used as substrate. Polyurethane foam was used as support for solid-state culture in column reactors. Ellagitannase activity was measured for each of the treatments. Ellagic acid was quantified by high performance liquid chromatography. When pomegranate polyphenols were used, a maximum value of ellagic acid (350.21 mg/g) was reached with A. niger HT4 in solid-state culture. The highest amount of ellagitannase (5176.81 U/l) was obtained at 8h of culture when cranberry polyphenols and strain A. niger PSH were used. Results demonstrated the effect of different polyphenol sources and A. niger strains on ellagic acid release. It was observed that the best source for releasing ellagic acid was pomegranate polyphenols and A. niger HT4 strain, which has the ability to degrade these compounds for obtaining a potent bioactive molecule such as ellagic acid.