Extraction of phenolic compounds from grape pomace using ohmic heating: Chemical composition, bioactivity and bioaccessibility

This study addresses the effectiveness of ohmic heating technology (OH) for the sustainable recovery of phenolic compounds from Grape Pomace (GP) by hydroethanolic extraction. GP extracts biological potential was evaluated in terms of antioxidant activity, cytotoxicity and preventive effect against reactive oxygen species (ROS). To understand if GP extracts can be used as a functional ingredient, simulated gastrointestinal digestion was performed to evaluate the bioaccessibility. OH-assisted hydroethanolic extraction proved to be an effective process for the recovery of GP phenolic compounds with high antioxidant capacity. The digestion process increased the concentration of total phenolics and the biotransformation of high-molecular phenolics (anthocyanins, flavonoids and resveratrol) in simpler phenolic acids, improving bioaccessibility. GP extract displayed a selective action against cancer cells (Caco-2 and HeLa) and promoted ROS prevention. The results highlighted the ability of OH to extract bioactives from GP and its potential application as a nutraceutical or for functional food formulations.

Integrated biorefinery development using winery waste streams for the production of bacterial cellulose, succinic acid and value-added fractions

An integrated biorefinery has been developed using winery wastes (grape pomace-GP, stalks-GS, wine lees-WL). Bacterial cellulose was produced from GP extracted free sugars. Grape-seed oil and polyphenols were extracted from GP. Experimental design was employed to optimize lignin removal (50.8%) from mixtures of remaining GP solids and GS via NaOH (1.19% w/v) treatment at 70°C for 30 min. Delignification liquid contained condensed tannins with 76% Stiasny number. Enzymatic hydrolysis produced a sugar-rich hydrolysate (40.2 g/L sugars). Ethanol, antioxidants, tartaric acid and nutrient-rich hydrolysate were produced from WL. The crude hydrolysates were used in fed-batch Actinobacillus succinogenes cultures for 37.2 g/L succinic acid production. The biorefinery produces 42.65 g bacterial cellulose, 24.3 g oil, 40.3 g phenolic-rich extract with 1.41 Antioxidant Activity Index, 80.2 g ethanol, 624.8 g crude tannin extract, 20.03 g tartaric acid and 157.8 g succinic acid from 1 kg of each waste stream.

Revisiting the production of L( +)-lactic acid from vine shoots: bioconversion improvements by employing thermotolerant bacteria

Vine shoots (Vitis vinifera L.) constitute an abundant lignocellulosic source which is frequently underutilised. Alkaline and acidic pretreatments (with and without washing steps) were compared and optimised to release fermentable sugars from vine shoots. An acidic pretreatment using 1.72% H₂SO₄ at 134 °C for 17 min (with 10% w/w solid biomass), followed by an enzymatic hydrolysis, offered the most cost-effective results, releasing 40.21 g/L sugars. Three thermotolerant strains, namely, Bacillus coagulans DSM 2314, Geobacillus stearothermophilus DSM 2313, and G. stearothermophilus DSM 494, were assessed to produce lactic acid from vine-shoot hydrolysates under aerobic and non-sterile conditions, without the need of detoxification steps. In addition, wine lees were satisfactorily employed as nitrogen sources for the fermentation, providing similar results to yeast extract and being the only nutrient added to vine-shoot hydrolysates. Under optimal conditions, B. coagulans DSM 2314 produced 29.21 ± 0.23 g/L lactic acid in 24 h, with a sugar consumption of 98.74 ± 0.07% and a yield of 96.38 ± 0.76%, when supplemented with red wine lees. The purity of the isomer L( +) reached 97.59 ± 1.35% of the total lactic acid produced. Although G. stearothermophilus was able to transform the hexoses from vine-shoot hydrolysates into lactic acid, it proved to be inefficient for metabolising pentoses, thus obtaining lower lactic acid values (16-18 g/L).

Changes in the nutrient dynamics and microbiological properties of grape marc in a continuous-feeding vermicomposting system

Finding strategies to reuse and treat organic wastes is of utmost need. Biological processes offer the possibility to transform them into safer end products with benefits for both agriculture and the environment. Moreover, it represents an ecologically-sound and economically attractive alternative to landfill disposal and incineration. In this work, we evaluated the feasibility of vermicomposting to treat and process grape marc, the main solid by-product of the wine industry. The long-term changes in grape marc derived from both white and red winemaking processes were assessed throughout the process of vermicomposting from a physico-chemical and microbiological perspective. New layers of fresh marc were added sequentially in the presence and absence of earthworms (Eisenia andrei) forming an age gradient during a 42-week period. An optimal moisture level of 70% was maintained over the course of the process. The pH fell within weak-alkaline levels through the layerś profile and the electrical conductivity was between 200 and 300 µS cm^-1, providing optimum conditions for earthworm growth. The mass loss caused by earthworm activity led to an increased content of macro- and micronutrients at the end of the trial. An overall decrease in microbial biomass and its activity, indicative of a stabilised material, was also recorded with depth of layer. Altogether, this points to vermicomposting as a suitable management system for processing grape marc with a dual purpose, that is fertilizer production and environment protection. This is especially relevant in the current attempts to reach a fully circular economy.

Burkholderia thailandensis E264 as a promising safe rhamnolipids' producer towards a sustainable valorization of grape marcs and olive mill pomace

Within the circular economy framework, our study aims to assess the rhamnolipid production from winery and olive oil residues as low-cost carbon sources by nonpathogenic strains. After evaluating various agricultural residues from those two sectors, Burkholderia thailandensis E264 was found to use the raw soluble fraction of nonfermented (white) grape marcs (NF), as the sole carbon and energy source, and simultaneously, reducing the surface tension to around 35 mN/m. Interestingly, this strain showed a rhamnolipid production up to 1070 mg/L (13.37 mg/g of NF), with a higher purity, on those grape marcs, predominately Rha-Rha C14-C14, in MSM medium. On olive oil residues, the rhamnolipid yield of using olive mill pomace (OMP) at 2% (w/v) was around 300 mg/L (15 mg/g of OMP) with a similar CMC of 500 mg/L. To the best of our knowledge, our study indicated for the first time that a nonpathogenic bacterium is able to produce long-chain rhamnolipids in MSM medium supplemented with winery residues, as sole carbon and energy source. KEY POINTS: • Winery and olive oil residues are used for producing long-chain rhamnolipids (RLs). • Both higher RL yields and purity were obtained on nonfermented grape marcs as substrates. • Long-chain RLs revealed stabilities over a wide range of pH, temperatures, and salinities.

Hazardous impact of vinasse from distilled winemaking by-products in terrestrial plants and aquatic organisms

Vinasses obtained from the distillation of winemaking by-products (WDV) are complex effluents with variable physicochemical properties. Frequently, WDVs are used to irrigate agricultural soil, and/or discharged into aquatic bodies, which may result in serious environmental pollution, due to the presence of organic acids and recalcitrant compounds (polyphenols, tannins and metals). The present study aimed to evaluate the toxicity impact of an untreated WDV on terrestrial and aquatic organisms, at different levels of biological organization. The effluent was collected at the distillation column exit and characterized according to several physicochemical properties. The WDV potential phytotoxicity was assessed by germination inhibition assays on six agricultural crops, and its acute toxicity was assessed on Aliivibrio fisheri (microtox assay), Daphnia magna neonates (freshwater crustacean), and zebrafish Danio rerio (fish embryo toxicity test, FET). The WDV presented a low pH (3.88), high levels of electrical conductivity, ECond (6.36 dS m^-1) and salinity (3.3 ppt), besides high level of potassium (2.1 g L^-1) and organic compounds (TOC = 17.7 g L^-1), namely polyphenols (1.7 g L^-1). The diluted WDV displayed variable inhibitory effects on the plant endpoints (percentage of inhibition of germination and radicle elongation and germination index). Overall, plants' susceptibility to increasing concentrations of WDV were differential (onion ≈ garden cress ≥ tomato > lettuce > maize > green beans) and the germination index EC₅₀ varied from 10.9 to 64.4% v/v. Also, the acute negative effects toward aquatic organisms were determined, decreasing from the more complex organism to the simpler one: zebrafish embryos (96 h-LC₅₀ = 0.34% v/v)>D. magna (48 h-LC₅₀ = 4.8% v/v)>A. fisheri (30min-EC₅₀ = 7.0% v/v). In conclusion, the findings suggest that WDVs might have a high toxicological impact on both terrestrial plants and aquatic organisms, even at high dilution levels, reinforcing the need for appropriate treatments before considering its discharge or reuse.

Strategies for recycling and valorization of grape marc

Grapes are one of the most cultivated fruit crops worldwide. Either for wine or juice production, grape processing generates a large amount of residues that must be treated, disposed of or reused properly to reduce their pollution load before being applied to the soil. In this review, a special focus is given to the treatment and valorization of the winemaking by-product like grape marc via anaerobic digestion, composting and vermicomposting at laboratory, pilot, and industrial scales. The impact of the final products (digestates, composts, and vermicomposts) on soil properties is briefly addressed. Moreover, the role of grape marc and seeds as a valuable source of natural phytochemicals that include polyphenols and other bioactive compounds of interest for pharmaceutical, cosmetic, and food industries is also discussed. This is of paramount importance given the fact that sustainability requires the use of management and valorization strategies that allow the recovery of valuable compounds (e.g. antioxidants) with minimum disposal of waste streams.

Assessing the potential phytotoxicity of digestate from winery wastes

In this study, digestate from winery wastes was investigated focusing on phytotoxicity using macrophytes and evaluating the potential contribution of ammonium and copper. Spreading of digestate on soil could represent a suitable approach to recycle nutrients and organic matter, creating an on site circular economy. In this study, digestate quality was evaluated considering both chemical-physical characteristics and biological toxicity applying germination test. The effluent did not meet the entire amendment quality standard defined by Italian law (Decree 75/2010 germination index > 60% with solution of 30% v/v of digestate), but bio-stimulation was observed at low doses (3.15-6.25% v/v) for S. alba and S. saccharatum. The beneficial concentration agreed with Nitrate Directive dose and suggested that limited addition of digestate could have several positive effects on soil characteristics and on crop growth. Specific test using ammonium and copper solutions showed that these pollutants were not directly correlated to observed phytotoxicity.

Mesophilic and thermophilic anaerobic co-digestion of winery wastewater sludge and wine lees: An integrated approach for sustainable wine production

In this work, winery wastes generated by a cellar producing approximately 300,000 hL of wine per year was monitored for a period of one year. On average, 196 L of wastewater, 0.1 kg of waste activated sludge (dry matter) and 1.6 kg of wine lees were produced per hectoliter of wine produced. Different winery wastes, deriving from different production steps, namely waste activated sludge from wastewater treatment and wine lees, were co-treated using an anaerobic digestion process. Testing was conducted on a pilot scale for both mesophilic and thermophilic conditions. The process was stable for a long period at 37 °C, with an average biogas production of 0.386 m³/kg COD_fed. On the other hand, for thermophilic conditions, volatile fatty acids accumulated in the reactor and the process failed after one hydraulic retention time (23 days). In order to fix the biological process, trace elements (iron, cobalt and nickel) were added to the feed of the thermophilic reactor. Metals augmentation improved process stability and yields at 55 °C. The pH ranged between 7.8 and 8.0, and specific gas production was 0.450 m³/kg COD_fed, which corresponded to dry matter and COD removals of 34% and 88%, respectively. Although the observed performances in terms of biogas production were good, the thermophilic process exhibited some limitations related to both the necessity of metals addition and the worse dewaterability properties. In fact, while the mesophilic digestates reached a good dewatering quality via the addition of 6.5 g of polymer per kg of dry matter, the required dosage for the thermophilic sludge was greater than 10 g/kg of dry matter.