Main By-product Research Articles

Comparison of different technologies using organic acid and mineral acid solvents on pectin extraction from apple pomace

Pectin is one of the most widely used functional polysaccharide, which is extensively used in food, biotechnological, chemical, cosmetic, and pharmaceutical industries. Pectin can be suitably extracted from apple pomace which is the main by-product of apple juice industry. In this study, pectin obtained from microwave assisted extraction (MAE) and conventional extraction (CE) were compared in terms of extraction yield, extraction time and extraction temperature. The type of acids namely organic acids and mineral acids were also compared, in which pectin from apple pomace was extracted using different concentration of organic acid (citric acid, 0.1 M and 0.05 M) and mineral acid (hydrochloric acid, 0.1 M and 0.05 M). The best extraction condition of the extraction process was found to be higher in yield by using citric acid at microwave power of 180 W, solid-to-liquid ratio of (1:25), concentration of citric acid of 0.1 M for 90 s. Under these conditions, the extraction yield of pectin reached 19.1 ± 0.2%, methoxyl content (5.27%), anhydroglacturonic acid (43.38%) and degree of esterification (68.97%). The current work showed that critic acid is a ‘green’ and safe acidic solvent that could be used to extract pectin from apple pomace that was highly competitive and environmentally friendly process. The microwave Assisted extraction method is considered to be a potential alternative conventional (traditional) extraction method. The obtained data undertakes that apple pomace obtained by the green extraction has a great potential to be a valuable source of pectin, while preserving similar quality to conventional sources of pectin.

Value-Added Application of Bourbon Spent Grain and Proso Millet for High-Fiber Extruded Product

Highlights Distillers spent grain (DSG) constitutes a major disposal problem for the bourbon industry. The impact of DSG particle size and addition level on the quality attributes of extruded products was evaluated. Particle size and addition level modulated the extrusion of DSG-proso millet-based extrudate. Some quality of extrudates with up to 10% DSG addition level and 300 µm particle size compared favorably with the control. Abstract. Bourbon is an important export for the US, especially in the state of Kentucky, which accounts for 95% of global production. The disposal of the main byproduct of bourbon distilling is a major problem for the industry. Distiller’s spent grain (DSG) produced contains insoluble and soluble fibers and protein, making it an attractive option as a health-promoting functional ingredient in food production. The objective of this research was to determine the DSG properties needed for the development of high-fiber extruded products with millet as the base-starch ingredient. Samples were produced using a co-rotating twin-screw extruder. A two-way factorial design was used to test the effect of DSG particle size (180, 300, and 500 µm) and addition levels (5%, 10%, and 15%) on some physico-functional properties of the extrudates, such as specific mechanical energy, water solubility index, water absorption index, radial expansion ratio, fracturability, hardness, porosity, degree of gelatinization, and pasting properties. In general, higher DSG addition levels resulted in decreased radial expansion and porosity, and created harder, bulkier, and darker color products. However, samples produced with medium particle size DSG (300 µm) at 5% addition level saw no significant decrease in expansion or hardness compared to the control (0% DSG). Similarly, at 10% DSG addition level and coarse (500 µm) particle size, there was no significant difference in porosity compared to the control group. This study shows that optimized particle size and DSG addition level allow the incorporation of bourbon spent grain into an extruded-expanded product without significant loss of attributes but with higher dietary fiber content. Keywords: Bourbon, Distillers Spent Grain, Extrusion, High-fiber, Proso Millet.

Antioxidant Dietary Fiber Sourced from Agroindustrial Byproducts and Its Applications

Agroindustrial activities generate various residues or byproducts which are inefficiently utilized, impacting the environment and increasing production costs. These byproducts contain significant amounts of bioactive compounds, including dietary fiber with associated phenolic compounds, known as antioxidant dietary fiber (ADF). Phenolic compounds are related to the prevention of diseases related to oxidative stress, such as neurodegenerative and cardiovascular diseases. The mechanism of ADF depends on its chemical structure and the interactions between the dietary fiber and associated phenolic compounds. This work describes ADF, the main byproducts considered sources of ADF, its mechanisms of action, and its potential use in the formulation of foods destined for human consumption. ADF responds to the demand for low-cost, functional ingredients with great health benefits. A higher intake of antioxidant dietary fiber contributes to reducing the risk of diseases such as type II diabetes, colon cancer, obesity, and kidney stones, and has bile-acid retention-excretion, gastrointestinal laxative, hypoglycemic, hypocholesterolemic, prebiotic, and cardioprotective effects. ADF is a functional, sustainable, and profitable ingredient with different applications in agroindustry; its use can improve the technofunctional and nutritional properties of food, helping to close the cycle following the premise of the circular economy.

Protease-Assisted Mild Extraction of Soluble Fibre and Protein from Fruit By-Products: A Biorefinery Perspective.

By-products from the fruit supply chain, especially seeds/kernels, have shown great potential to be valorised, due to their high content of macronutrients, such as lipids, protein, and fibre. A mild enzymatic assisted extraction (EAE) involving the use of a protease was tested to evaluate the feasibility of a cascade approach to fractionate the main fruit by-products components. Protease from Bacillus licheniformis (the enzyme used in the AOAC 991.43 official method for dietary fibre quantification) was used, and besides protein, the conditions of hydrolysis (60 °C, neutral pH, overnight) allowed us to dissolve a portion of soluble fibres, which was then separated from the solubilized peptide fraction through ethanol precipitation. Good protein extraction yields, in the range 35-93%, were obtained. The soluble fibre extraction yield ranged from 1.6% to 71% depending on the by-product, suggesting its applicability only for certain substrates, and it was found to be negatively correlated with the molecular weight of the fibre. The monosaccharide composition of the soluble fibres extracted was also diverse. Galacturonic acid was present in a low amount, indicating that pectin was not efficiently extracted. However, a predominance of arabinose and galactose monomers was detected in many fractions, indicating the isolation of a fruit soluble fibre portion with potential similarity with arabinogalactans and gum arabic, opening up perspectives for technological applications. The residual solid pellet obtained after protease assisted extraction was found to be an excellent fibre-rich substrate, suitable for being subjected to more "hard" processing (e.g., sequential pectin and hemicellulose extraction) with the objective to derive other fractions with potential great added economic value.

Flavonoid Composition and Antibacterial Properties of Crocus sativus L. Petal Extracts.

Saffron petals, which are the main by-products of Crocus sativus L. (Iridaceae family), are produced in large quantities and are known for their many beneficial properties. In this regard, this study aims to investigate the phenolic composition and antibacterial properties of hydroethanolic extracts from Crocus sativus L. petals collected from Serghina (province of Boulmane) in Morocco. The phenolic profiles were characterized using high-performance liquid chromatography coupled to a photodiode array and electrospray ionization mass spectrometry (HPLC-PDA-ESI/MS). The antibacterial potential was evaluated against four bacterial strains potentially causing food-borne disease (Staphylococcus aureus, Salmonella typhimurium, Escherichia coli, and Listeria monocytogenes) using disc diffusion and broth micro-dilution assays. Results showed that a total of 27 phenolic compounds was detected in the Crocus sativus L. petal extracts, which were assigned to flavonoids (kaempferol, quercetin, isorhamnetin, and myricetin derivatives). The most abundant compound was represented by kaempferol-sophoroside isomer (20.82 mg/g ± 0.152), followed by kaempferol-sophoroside-hexoside (2.63 mg/g ± 0.001). The hydroethanolic extracts of Crocus sativus L. petals demonstrated bactericidal effects against Staphylococcus aureus and Listeria monocetogenes and bacteriostatic effects against Escherichia coli and Salmonella typhimurium. Therefore, the by-product Crocus sativus L. petal extracts might be considered as valuable sources of natural antibacterial agents with potential applications in the food and pharmaceutical industries.

Application of magnetite supplementation for enhancing biohydrogen production using Gelidium amansii hydrolysate

Acid hydrolysis of biomass generates a high concentration of hydrolysis by-products, which must be removed. Magnetite (Fe3O4) supplementation can reduce the amount of powdered activated carbon (PAC) input required for detoxification by increasing hydrogen productivity and alleviating the inhibitory effects of hydrolysis by-products. In this study, sugars were extracted by acid hydrolysis of Gelidium amansii, and hydrogen production using this was quantified with the magnetite supplementation. The total sugar concentration of 0.5 % H2SO4 hydrolysate was 24.4 g/L, including 3.7 g/L of glucose, 18.9 g/L galactose, and 1.7 g/L of arabinose, as well as hydrolysis by-products of 0.9 g/L of formic acid, 1.2 g/L of levulinic acid, and 11.4 g/L of 5-hydroxymethylfurfural (5-HMF). Magnetite supplementation at a concentration of 1.3 g/L or less in 5-HMF, the main by-product, increased hydrogen production by an average of 11.4 %. This strategy will optimize future biohydrogen production processes using Gelidium amansii and reduce detoxification costs.

Evaluating Compost from Digestate as a Peat Substitute in Nursery for Olive and Hazelnut Trees

This study deals jointly with three aspects of environmental, agricultural and energy sustainability: (a) Biogas is a booming energy source worldwide, resulting in an increasing production of digestate, its main by-product; (b) The extraction of peat, mainly used for nursery substrates, is being banned due to the destruction of natural habitats and release of GHGs; (c) Compost can represent a replacement of peat and contributes to the containment of GHGs. This study has verified how a compost obtained from digestate can be used as a substitute for peat in the nursery sector. While previous studies have evaluated compost use on just one species at a time, this study compared the same compost on two very different species: olive tree and hazelnut tree, both with growing interest for new tree plantings. Two concentrations of compost in the potting substrate of nursery seedlings were evaluated: 30% and 45% by weight, measuring the effect on some growth parameters during the growing season. The trials showed responses positive for olive and substantially negative for hazelnut: olive trees manifested better growth parameters with 45% compost, as opposed to hazelnut, where the addition of 45% compost worsened all growth parameters. A general conclusion can be drawn: in the nursery sector, compost can be used to replace peat, but this replacement can almost never be 100 percent, having instead to calibrate the percentage of replacement according to the characteristics of the compost and the individual edaphic needs of the plant species.

Combined Neutrase-Alcalase Protein Hydrolysates from Hazelnut Meal, a Potential Functional Food Ingredient.

Consumers' interest in functional foods has significantly increased in the past few years. Hazelnut meal, the main valuable byproduct of the hazelnut oil industry, is a rich source of proteins and bioactive peptides and thus has great potential to become a valuable functional ingredient. In this study, hazelnut protein hydrolysates obtained by a single or combined hydrolysis by Alcalase and Neutrase were mainly characterized for their physicochemical properties (SDS-PAGE, particle size distribution, Fourier-transform infrared (FTIR) spectroscopy, molecular weight distribution, etc.) and potential antiobesity effect (Free fatty acid (FFA) release inhibition), antioxidant activity (DPPH and ABTS methods), and emulsifying properties. The impact of a microfluidization pretreatment was also investigated. The combination of Alcalase with Neutrase permitted the highest degree of hydrolysis (DH; 15.57 ± 0.0%) of hazelnut protein isolate, which resulted in hydrolysates with the highest amount of low-molecular-weight peptides, as indicated by size exclusion chromatography (SEC) and SDS-PAGE. There was a positive correlation between the DH and the inhibition of FFA release by pancreatic lipase (PL), with a significant positive effect of microfluidization when followed by Alcalase hydrolysis. Microfluidization enhanced the emulsifying activity index (EAI) of protein isolates and hydrolysates. Low hydrolysis by Neutrase had the best effect on the EAI (84.32 ± 1.43 (NH) and 88.04 ± 2.22 m2/g (MFNH)), while a negative correlation between the emulsifying stability index (ESI) and the DH was observed. Again, the combined Alcalase-Neutrase hydrolysates displayed the highest radical scavenging activities (96.63 ± 1.06% DPPH and 98.31 ± 0.46% ABTS). FTIR results showed that the application of microfluidization caused the unfolding of the protein structure. The individual or combined application of the Alcalase and Neutrase enzymes caused a switch from the β-sheet organization of the proteins to α-helix structures. In conclusion, hazelnut meal may be a good source of bioactive and functional peptides. The control of its enzymatic hydrolysis, together with an appropriate pretreatment such as microfluidization, may be crucial to achieve the best suitable activity.

Optimizing lactic acid production for agricultural wastes revalorization via sugars hydrothermal conversion with zirconia-based catalysts: response surface methodology

The hydrothermal conversion of a complex sugars solution comprising glucose, arabinose, and xylose with zirconia-based catalysts to produce lactic acid (LA) was studied. Catalysts were synthesized by a simple template-assisted sol–gel method. Alternative template removal procedures, such as refluxing ethanol extraction, were compared to the conventional direct calcination. The catalyst obtained after ethanol extraction (Z-Ex) reported the highest specific surface area (323 m2 g−1), total pore volume (0.21 cm3 g−1) and density of acid sites (1.111 µmol m−2), with a significant contribution of strong acid sites. On the other hand, template removal by thermal treatment transformed the hydrous zirconia into crystalline tetragonal phase, reducing the specific surface area and removing most of the acid sites. Catalytic tests were carried out in a stirred batch reactor, resulting Z-Ex the most selective towards LA production. A four-factor experimental design was performed for Z-Ex catalyst by varying temperature, reaction time, initial pressure, and catalyst/reactants ratio. Results were analyzed using the response surface methodology (RSM) to maximize the LA production. A molar yield of 61.2% towards LA and complete sugars conversion were reached at optimized operating conditions: 189 °C, 208 min, 0.5 g catalyst g−1 reactants, and 10 bar N2. Additionally, fitting models for main by-products molar yields (furans, glyceraldehyde, glycolic, formic, acetic, and levulinic acids) were obtained with good accuracy prediction. All responses were jointly studied to understand the reaction mechanisms involved in generation of intermediaries and undesired degradation products.Graphical Abstract

Thiourea as a Stabilizer of Reduced Forms of Technetium─Tc(III) and Tc(IV): Experimental and Theoretical Studies of Complexes

This paper presents synthetic methods for the preparation of Tc(III) and Tc(IV) coordination compounds with thiourea. We have shown that the main product of the synthesis is the complex [TcTu5X]X2, (Tu = (NH2)2CS, X = Cl, Br) and not [TcTu6]Cl3·4H2O, as previously thought. Tu2[TcX6]X2·3H2O is the main technetium-containing byproduct of the reaction. All reaction products, including byproducts, were characterized by X-ray diffraction analysis. We also measured the solubility for the obtained Tc(III) complexes. This research work considers the process of thermolysis of the obtained Tc(III) complexes and shows that the presence of sulfur atoms in the coordination sphere can inhibit the process of metal formation in an argon-hydrogen medium. The analysis of nonvalent interactions in Tc(III) complexes showed that the main contribution is made by van der Waals interactions of the H···H type (40.8-42.3%) and hydrogen bonds Hal···H/H···Hal and H···S/S···H, which are 41.6-44.5% in total. As the temperature decreases, the proportion of H···H contacts and H bonds decreases, and when the halogen (Cl by Br) is replaced, the proportion of H bonds increases and the proportion of van der Waals interactions decreases.

Nutritional Attributes and Phenolic Composition of Flower and Bud of Sophora japonica L. and Robinia pseudoacacia L.

Sophora japonica L. (SJL) and Robinia pseudoacacia L. (RPL) are widely cultivated in China. However, the utilization of their main by-products are limited due to a lack of comprehensive nutritional attributes. Herein, the proximate composition, mineral elements, fatty acids, amino acids, monosaccharides, and phenolics were analyzed to investigate the nutritional attributes of SJL and RPL. Dietary fiber was the main ingredient in SJL and RPL, followed by protein and lipids. The content of Fe in SJL and RPL was highest, especially in flowers of SJL, reaching about 1179.51 mg/kg. The total unsaturated fatty acids accounted for 89.67% of the bud of SJL. Meanwhile, the essential amino acids contents of the flower and bud of SJL and RPL accounted for 35.95-40.59% of total amino acids. The flower of SJL (373.75 mg/g) exhibited the most abundant monosaccharides. Meanwhile, the total phenolics and flavonoid contents in the buds of SJL and RPL were significantly higher than that of the flower, implying the buds possessed better biological activity. Moreover, the bud of SJL possessed the most abundant phenolics. The results provided a reference for the development of functional food derived from SJL and RPL.

Consumer perception and physicochemical characterization of a new product made from lactic acid fermented orange peels

A new product made from orange peels discarded from juice making has been characterized during the present study. In order to reduce its bitterness, orange peel was fermented during 10 days in two different sugary brines (2% or 5% NaCl content) using a Lactiplantibacillus plantarum strain. The lactic acid fermentation process was characterized by determining pH, sucrose, and the organic acids content. The original peel and the final products were characterized by instrumental texture and color determination, and total flavonoids content. In addition, consumers' expectations and perception of the new products were also studied using an online survey and a consumer study in which acceptance and perceived bitterness were assessed. Results suggested that the 2% NaCl-fermentation process allowed a greater bacteria development (with a higher lactic acid production and larger differences in color parameters with the original peel than the 5% NaCl-fermented samples) although both fermented samples were significantly different from the original peel in their physicochemical characteristics. Total flavonoids content, which has been related to bitterness perception, was significatively lower in the fermented samples than in the raw orange peel (50% reduction). Spanish consumers’ expectations and perception of the new product were similar, and the snack made with the peel fermented in the 2% NaCl-brine was more liked than the same snack made with the original peel, or the 5% NaCl-fermented one. Using a lactic acid fermentation in a sugary brine was useful to decrease the bitterness perception and increase liking of the orange peel, meaning a potential valorization for this orange juice by-product.Implications for gastronomy.The present study includes the physico-chemical characterization and consumers’ perception of a new product developed with one of the main citrus by-products: orange peels. A new ingredient for the Spanish gastronomy is proposed, showing a potential use for one of the main HORECA (HOtels REstaurants Catering sector) and juices industry by-products. A simple lactic-acid fermentation process, inspired in the North-African gastronomy culture, is described, and the consumer perception of the new product, presented as a freeze-dried snack is shown, proposing a new way of decreasing this food waste in Spain. In addition, some ideas about how to decrease bitterness perception on flavonoids-rich materials are shown, contributing to the knowledge on other new foods development.

Development of Rigid Polyurethane Foams Based on Kraft Lignin Polyol Obtained by Oxyalkylation Using Propylene Carbonate

This study aimed to develop new rigid polyurethane foams (RPUFs) for thermal insulation based on kraft lignin, the main by-product of the pulp and paper industry. Crude lignin-based polyol (LBP) was obtained via the oxyalkylation of kraft lignin using propylene carbonate (PC). A design of experiments (DoE) was used to evaluate the effect of the isocyanate (NCO)-to-hydroxyl (OH)-group’s ratio, the content of crude LBP, the blowing agent (BA), and catalyst on the thermal conductivity and density of RPUFs. Statistical analysis revealed that the increase in crude LBP and BA content in the formulation decreases the thermal conductivity and density of the foams. In addition, the fact that LBP is a viscous polyol containing PC-oligomers appears to affect the cellular structure of RPUFs, and consequently reduces their mechanical and thermal properties. The main novelty of this study consisted in the careful optimization of the formulation, namely, with regard to the type of blowing agent and with the high content of crude LBP obtained from the oxyalkylation of LignoBoost kraft lignin without purification to obtain good quality RPUF that meets market requirements for insulation materials.

Effective gossypol removal from cottonseed meal through optimized solid-state fermentation by Bacillus coagulans

BackgroundCottonseed meal (CSM) is the main by-product of the cottonseed oil extraction process with high protein content, which is an important protein source for feed industry. However, CSM contains free gossypol (FG), a toxic substance that is detrimental to animal health and greatly limits its application. Microbial fermentation is currently considered to be one of the most effective methods to reduce FG and other anti-nutritional factors in CSM. Previously, yeast and bacteria species are used for degradation of FG in CSM, but showing less detoxification efficiency. Bacillus coagulans combines the properties of both lactic acid bacteria and Bacillus, producing both lactic acid and spores, and is considered a potential probiotic. In this study, we aimed to evaluate and optimize the effect of the solid-state fermentation process using a Bacillus coagulans to gossypol removal contained cottonseed meal.Results36 B. coagulans strains were isolated and found to have the ability to remove free gossypol. Through the evaluation of strains and optimization of fermentation conditions including fermentation temperature, ratio of material to water, inoculation amount, fermentation time and pH, we have established a solid-state fermentation process using a Bacillus coagulans strain S17 on CSM substrate with 1:1 of the material-to-water ratio, 15% (v/w) seed inoculation, 2% expanded corn flour, 1% bran, and 0.3%-0.8% metal irons at 40 °C for 52 h. After fermentation, the FG content in CSM was reduced from 923.80 to 167.90 mg/kg with 81.83% detoxification efficiency. Meanwhile, the crude protein content in CSM increased from 47.98 to 52.82%, and importantly, the spore concentration of strain S17 reached 1.68 × 1010 CFU/g dry material.ConclusionThe study showed that B. coagulans have the potential strong ability to degrade free gossypol through cottonseed meal fermentation. This study presents a feasible process for improving the resource utilization rate and nutritional value of CSM via solid-state fermentation through B. coagulans S17.

Treatment of Sugarcane Vinasse Using Heterogeneous Photocatalysis with Zinc Oxide Nanoparticles

Vinasse is the main by-product of the ethanol industry; for each liter of ethanol, 13 to 18 L of vinasse is generated. Vinasse is composed of 93% water and 7% organic and inorganic solids and has an acidic pH and a high concentration of macro- and micronutrients used by plants, which is the reason for its widespread application in soil fertigation. However, over time, excessive direct discharge of vinasse into the soil causes damage, such as salinization and groundwater contamination. In this study, we used heterogeneous photocatalysis with zinc oxide nanoparticles (ZnO-NPs) to reduce chemical oxygen demand (COD) and biochemical oxygen demand (BOD) and as an antimicrobial treatment. ZnO-NPs were synthesized by the precipitation of zinc sulfate heptahydrate and sodium hydroxide, resulting in nanoparticles with a size of 21.6 ± 0.3 nm and an energy bandgap of 2.6 eV. Microscopic examinations revealed that Saccharomyces cerevisiae microorganisms are present in vinasse and that the minimum inhibitory concentration for the ZnO-NPs is 1.56 g/L. Photocatalysis with 40 mg/L of ZnO-NPs for 4 h of exposure to sunlight resulted in COD and BOD reduction efficacies of 17.1% and 71.7%, respectively. This study demonstrates the viability of using ZnO-NPs in vinasse treatment, contributing to sustainable applications and reducing the environmental impacts of fertigation.

Recovery of gold from e-waste via food waste byproducts

Global materials’ and energy constraints and environmental issues call for a holistic approach to waste upcycling. We propose a chemically rational, cost-effective and environmentally friendly recovery of non-leaching gold from e-waste using aqueous chemistry with hydrogen peroxide, an environmentally benign oxidant, and lactic acid, a food chain byproduct. The oxidation of the base metals enables the release of gold in its metallic state in the form of flakes subsequently separated via filtration. Our main byproduct is a precursor of Cu2O, a relevant metal oxide for solar energy conversion applications. The recovered gold was characterized by scanning electron microscopy, energy dispersive spectroscopy and x-ray photoelectron spectroscopy to gain insight into the morphology of the flakes and their chemical composition. Furthermore, recovered gold was used to successfully fabricate the source and drain electrodes in organic field-effect transistors.

Evaluation of Chemical Constituents of Litchi Pericarp Extracts and Its Antioxidant Activity in Mice.

Litchi pericarp is the main byproduct of litchi processing and contains several polyphenols. However, the chemical constituents and the antioxidant effect in litchi pericarp extracts (LPE) have been rarely studied. The result of the quantitative analyses of the major monomers in LPE indicated that procyanidin A2, procyanidin B2, epicatechin, rutin, and catechin were the major polyphenol compounds of LPE. The LPE exhibited high radical scavenging activity, as indicated by the results of the 1,1-diphenyl-2-picrylhydrazyl (DPPH) and ascorbic acid, 2,2'-Azinobis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) tests. Moreover, administrating D-galactose in mice led to the reduced activity of antioxidant enzymes, aggravated lipid peroxidation, and induced protein oxidation. The results were improved in the aging mice after the LPE treatment was performed. The above results suggest that LPE has an excellent antioxidant effect. Accordingly, litchi pericarp can serve as a promising source of dietary antioxidants.

Establishment of a Sonotrode Ultrasound-Assisted Extraction of Phenolic Compounds from Apple Pomace.

Apple pomace is the main by-product from apple processing in the juice industry and is considered a source of polyphenols with several health bioactivities. Thus, this research focuses on the establishment of the ultrasound-assisted extraction of total phenolic compounds, focusing on phloretin and phloridzin, with high antioxidant activity from apple pomace, using a sonotrode. We used a Box-Behnken design of 15 experiments with 3 independent factors (ethanol (%), time (min) and amplitude (%)). The responses evaluated were the sum of phenolic compounds, phloretin and phloridzin measured by HPLC-MS-ESI-TOF, and antioxidant activity measured by DPPH, ABTS and FRAP. The validity of the model was confirmed by ANOVA. Further, it was carried out using a comparison between different apple pomaces with or without seeds extracted by the optimal conditions. Phloretin and phloridzin accounted for 7 to 32% of the total phenolic compounds in the apple pomaces. Among all the apple pomace analyzed, that of the variety Gala had the highest phenolic content and antioxidant activity. The presence of the cyanogenic compound amygdalin was detected in apple pomaces that contained seeds accompanied with a higher content of phloretin and phloridzin but a lower content of flavan-3-ols.

Characterization of Bioactive Compounds in Lees from New Zealand Wines with Different Vinification Backgrounds.

Wine lees are one of the main by-products produced during winemaking. Little is known about the effect of the vinification technique on the phenolic compounds and the biological activity of wine lees extracts. Wine lees collected at varying vinification sources of two grape varieties, Riesling (RL) and Pinot Noir (PN), were analyzed for total phenolic content (TPC), tannin content (TTC), their anthocyanin and phenolic profile, and the antioxidant and antimicrobial activities of their extracts. The results showed a low TPC and TTC in RL lees, which could be attributed to the varietal characteristic of RL grapes and to less skin contact during vinification. Vinification techniques modified the composition of the phenolic compounds in the lees. The results showed a good linear relationship between the antioxidant activities and the TPC and TTC, indicating that PN lees were better sources of phenolics and antioxidant activity than RL lees. The antimicrobial activity of wine lees was related to the phenolic composition rather than the quantity of total phenolics. Knowing the grape and wine processing conditions can provide some insights into the potential composition of wine lees and, hence, determine the potential economic use of the by-product.

Enhancing erythritol production from crude glycerol in a wild-type Yarrowia lipolytica by metabolic engineering.

Background: Erythritol is a zero-calorie sweetener that is widely used in the food, pharmaceutical, and medical industries. Crude glycerol is the main by-product of biodiesel, and the effective utilization of crude glycerol will help to improve biodiesel viability. Previous studies on the production of erythritol from Y. lipolytica using crude glycerol as a carbon source have focused on optimizing the fermentation process of the mutant Y. lipolytica Wratislavia K1, while metabolic engineering has not been successfully applied. Results: To this end, we engineered the yeast Y. lipolytica to increase the productivity of this strain. Wild strains tolerant to high concentrations of crude glycerol were screened and identified. A series of rational metabolic approaches were employed to improve erythritol production. Among them, the engineered strain Y-04, obtained by tandem overexpression of GUT1 and GUT2, significantly increased glycerol assimilation by 33.3%, which was consistent with the results of RT-qPCR analysis. The effects of tandem overexpression of GUT1, GUT2, TKL1, and TAL1 on erythritol synthesis were also evaluated. The best results were obtained using a mutant that overexpressed GUT1, GUT2, and TKL1 and knocked out EYD1. The final Y-11 strain produced 150 g/l erythritol in a 5-L bioreactor with a yield and productivity of 0.62 g/g and 1.25 g/l/h, respectively. To the best of our knowledge, this is the highest erythritol yield and productivity from crude glycerol ever reported in Y. lipolytica. Conclusion: This work demonstrated that overexpression of GUT1, GUT2, and TKL1 and knockdown of EYD1 could be used to improve crude glycerol utilization and erythritol synthesis in Y. lipolytica. The process parameters such as erythritol yield and productivity were significantly elevated, which is valuable for industrial applications. Crude glycerol, as a carbon source, could efficiently restrict the synthesis of by-products while enhancing the generation of erythritol, compared to glucose. This indicates considerable potential for synthesizing value-added products from crude glycerol by Y. lipolytica.