Valorization Of Agro-industrial Wastes Research Articles

Ashbya gossypii as a versatile platform to produce sabinene from agro-industrial wastes

BackgroundAshbya gossypii is a filamentous fungus widely utilized for industrial riboflavin production and has a great potential as a microbial chassis for synthesizing other valuable metabolites such as folates, biolipids, and limonene. Engineered strains of A. gossypii can effectively use various waste streams, including xylose-rich feedstocks. Notably, A. gossypii has been identified as a proficient biocatalyst for producing limonene from xylose-rich sources. This study aims to investigate the capability of engineered A. gossypii strains to produce various plant monoterpenes using agro-industrial waste as carbon sources.ResultsWe overexpressed heterologous terpene synthases to produce acyclic, monocyclic, and bicyclic monoterpenes in two genetic backgrounds of A. gossypii. These backgrounds included an NPP synthase orthogonal pathway and a mutant erg20F95W allele with reduced FPP synthase activity. Our findings demonstrate that A. gossypii can synthesize linalool, limonene, pinene, and sabinene, with terpene synthases showing differential substrate selectivity for NPP or GPP precursors. Additionally, co-overexpression of endogenous HMG1 and ERG12 with heterologous NPP synthase and terpene synthases significantly increased sabinene yields from xylose-containing media. Using mixed formulations of corn-cob lignocellulosic hydrolysates and either sugarcane or beet molasses, we achieved limonene and sabinene productions of 383 mg/L and 684.5 mg/L, respectively, the latter representing a significant improvement compared to other organisms in flask culture mode.ConclusionsEngineered A. gossypii strains serve as a suitable platform for assessing plant terpene synthase functionality and substrate selectivity in vivo, which are crucial to understand monoterpene bioproduction. The NPP synthase pathway markedly enhances limonene and sabinene production in A. gossypii, achieving levels comparable to those of other industrial microbial producers. Furthermore, these engineered strains offer a novel approach for producing monoterpenes through the valorization of agro-industrial wastes.

Simultaneous optimization of activation conditions of alperujo (two-phase olive mill waste) using a desirability function: Production of porous carbons for adsorption and energy storage

Valorization of agro-industrial waste is considered an essential step towards a circular economy. The potential reuse of these byproducts in practical applications requires feasibility assessments and optimization of variables in order to be profitable. In the present study, an abundant and problematic residue from the olive oil industry, “alperujo” (two-phase olive mill waste), was used as precursor material for activated carbons. A simultaneous optimization methodology was applied to maximize two response variables: energy storage capacity and lead (Pb) removal efficiency. The simultaneous optimum conditions were 3.66 g of KOH per g of carbonized residue and a temperature of 650 °C for 120 min. The result was a microporous activated carbon with an energy storage capacity of 252 F/g and a lead removal from aqueous solutions of 68.8 %. These values are comparable with those offered by commercial activated carbons, evidencing that porous materials obtained from alperujo using unique activating conditions for both applications present a remarkable performance. The novelty of the present study lies in the application of a useful statistical methodology for simultaneous optimization through the “desirability function”, resulting in a reduction in cost and time. Our results have demonstrated that it is possible to generate activated carbons with the highest performance for two different applications using the same combination of activation variables.

Pentagalloyl Glucose and Gallotannins from Mangifera Indica L. Seed Kernel Extract as A Promising Antifungal Feed Additive, In Vitro, and In Silico Studies

Recently, the valorization of agro-industrial wastes through their exploration of their bioactive compounds has become a necessary trend to maximize their applications in various production sectors, particularly animal feeding. In the study, mango seed kernels were used as agro-industrial wastes to extract gallotannins fraction (GF) and pentagalloyl glucose (PGG). The GF and PGG were mixed with poultry feeds to investigate their potential ability to control Aspergillus flavus (A. flavus) growth and inhibit its production of aflatoxins (AFs). Ketoconazole was used as an antifungal standard. GF and PGG combat the growth of A. flavus, with minimum inhibition concentration (MIC) of 21.7 ± 1.7 and 20 ± 0 mg/mL, respectively. Moreover, GF and PGG showed promising results in preventing the production of AFs (AFB1, AFB2, AFG1, and AFG2) at 5 and 10 mg/100-gram feed. Furthermore, to explain the mode of action of PGG as an antifungal agent, a molecular docking study has been performed against Type 1 Polyketide Synthase (PKS), which is found in many toxigenic Aspergillus species and has a highly active Acyl Carrier Protein (ACP) domain that is implicated in thiol ester-bound intermediates involved in fungal polyketides, fatty acids, and other non-ribosomal peptide formation, which are highly implicated in the construction of aflatoxin biosynthesis. The promising results prompt us to use mango seed extract as a cheap source of gallotannin components as a safe feed additive for reducing fungal and mycotoxin contamination in animal feeds.

Enhanced productivity of nutrient-rich single cell protein from Paradendryphiella arenariae PG1 through valorization of agro-industrial waste: A Green symphony from Waste-to-Protein Approach

The rise in global population strains agro-industrial waste management, positioning single-cell protein (SCP) production as a cost-effective solution. Evaluating eight agro-waste residues identified wheat bran with a high solid recovery rate (67.15 %). SCP production increased from 1.29 ± 0.23 gL−1 to 21.05 ± 0.33 gL−1, achieving a microbial conversion efficiency of 90.88 % by Paradendryphiella arenariae (PG1). Nucleic acid content in SCP was reduced by 31 % using NaOH and 36 % via heat shock, significantly enhancing SCP quality, digestibility, and safety. SCP's impact on Caenorhabditis elegans (C. elegans) revealed a maximum lifespan of 18 ± 0.2 days, notable pharyngeal pumping rates (117 ± 2.541 and 67 ± 3.473 min−1 on days 5 and 10), and body bending rates (115.3 ± 0.86 and 44.8 ± 0.28 min−1 on days 5 and 10). This comprehensive approach demonstrates the promise of SCP production in sustainable waste management, resource optimization, and detailed toxicity analysis in C. elegans, broadening the potential applications of SCP in various fields.

Bio-synthesis, purification and structural analysis of Cyclosporine-A produced by Tolypocladium inflatum with valorization of agro-industrial wastes

Cyclosporine A (CyA) holds significant importance as a strategic immunosuppressive drug for organ transplant patients. In this study, we aimed to produce pure and cost-effective Cyclosporine A (CyA) by fermenting a culture medium containing dairy sludge, using Tolypocladium inflatum PTCC 5253. Following the fermentation stage, ethyl acetate extraction and fast protein liquid chromatography were employed for sample purification. The initial evaluation of the effectiveness of CyA obtained from these processes was performed through bioassay, wherein the antimicrobial clear zone diameter was found to be larger compared to the sample obtained from the fermentation culture. The concentration of CyA was determined using high-performance liquid chromatography, yielding values of 334 mg/L, 456 mg/L, and 578 mg/L for the fermented, extracted, and purified samples, respectively. Further analysis utilizing liquid chromatography tandem mass spectrometry (LC/MS/MS) confirmed a purity of 91.9% and proper agreement with the standard sample based on the ion intensity of Z/m 1205. To validate the structure of CyA, nuclear magnetic resonance spectroscopy, Fourier-transform infrared (FT-IR), and Raman spectroscopy were employed. X-ray diffraction and differential scanning calorimetry analyses demonstrated that the purified CyA exhibited a crystal structure similar to the standard sample, characterized by two broad peaks at 2θ = 9° and 20°, and comparable glass transition temperatures (57–68 °C for the purified sample; 53–64 °C for the standard sample). Dynamic light scattering analysis confirmed a uniform particle size distribution in both the purified and standard samples. The zeta potentials of the purified and standard samples were determined to be − 25.8 ± 0.16 and − 23.63 ± 0.12 mV, respectively. Our results demonstrate that dairy sludge can serve as a suitable culture medium for the production of (CyA).

Valorization of Silybum marianum seed shells waste as biosorbent for basic fuchsin dye removal from water: kinetics, isotherms, and thermodynamic studies

Over the last decades, the valorization of agro-industrial wastes into adsorbents has received a lot of attention due to the low-cost, high performance and sustainability factors. This work aims to valorize Silybum marianum seed shells (SMSS) as biosorbent for the removal of basic fuchsin dye (BF) from water. The prepared biosorbent from SMSS was characterized to check the morphological and structural proprieties using several techniques including FTIR, XRD, SEM, TGA-DTA, and BET. It was found that SMSS has a fibrous semi-amorphous structure typical of lignocellulosic materials. The study also investigated the impact of numerous operational parameters on basic fuchsin biosorption efficiency, including particle size, biosorbent mass, stirring speed, initial dye concentration, temperature, and pH of solution. Additionally, the research explored the influence of natural water matrices on dye removal. The adsorption performance was found to be higher at basic pH values, reaching 97.50%. The adsorption process was analyzed using different kinetic models, and it was found that the process follows a pseudo-second-order model. The experimental data was thoroughly scrutinized using the Freundlich and Langmuir isotherm models. The results confirm that Langmuir model fits well the BF dye adsorption on SMSS surface. The thermodynamic study revealed that the adsorption process of BF dye onto SMSS was endothermic. Overall, SMSS shows great adsorption ability which might be a good candidate for real wastewater treatment, by considering low-cost and availability of the original waste.

Valorization of agro-industrial wastes using fungi for industrial enzymes production

Huge quantities of the agricultural wastes are produced from practices related to industrial processing, which are mainly burned and thrown in landfills, becoming a threat to the human health and causing environmental pollution. Agro-industrial residues, such as sugarcane bagasse, orange peel, wheat bran, corn straw, barley, rice straw, corn cob, husk, soy bran, and coffee husk were considered as valuable raw materials that can be converted into products of biotechnological interest using microorganisms. Agro-industrial wastes rich in nutrients, such as proteins, minerals, and sugars that, used as possible low cost substrates, for the fungal cultivation, thus considered as an alternative eco-friendly tool for many biological products of economic value, such as enzymes. Fungi organisms are capable of synthesizing a wide range of relevant oxidative and hydrolytic extracellular enzymes, such as peroxidases, laccases, xylanases, and cellulases. The enzymes secreted fungi, are proteins that function as bio-catalysts, responsible for carrying out various biochemical reactions, which applied in food, detergent, cellulose, paper, cosmetics and textile industries, etc. Thus, the replacement of raw materials with lignocellulosic-sources can result in reducing environmental problems and resolving the pollution associated with their disposal, in addition a higher investment will be gained. Therefore, a review was carried out on the important value of agro-industrial wastes, and the cultivation of fungal isolates for economic production of the industrially important enzymes, based on submerged and solid-state fermentation processes, as well as the important application of these enzymes.

Valorization of agro-industrial waste from the cassava industry as esterified cellulose butyrate for polyhydroxybutyrate-based biocomposites.

The aim of this study was to utilize cassava pulp to prepare biocomposites comprising microcrystalline cellulose from cassava pulp (CP-MCC) as a filler and polyhydroxybutyrate (PHB) synthesized in-house by Cupriavidus necator strain A-04. The CP-MCC was extracted from fresh cassava pulp. Next, the CP-MCC surface was modified with butyryl chloride (esterified to CP-MCC butyrate) to improve dissolution and compatibility with the PHB. FTIR results confirmed that the esterified CP-MCC butyrate had aliphatic chains replacing the hydroxyl groups; this substitution increased the solubilities in acetone, chloroform, and tetrahydrofuran. Biocomposite films were prepared by varying the composition of esterified CP-MCC butyrate as a filler in the PHB matrix at 0, 5, 10, 15, 20 and 100 wt%. The results for the 95:5 and 90:10 CP-MCC butyrate biocomposite films showed that esterification led to improvements in the thermal properties and increased tensile strengths and elongations at break. All prepared biocomposite films maintained full biodegradability.

Valorization of agro-industrial waste in composite films for sustainable packaging applications

The increase in general awareness about environmental hazards caused by petrochemical plastics has substantially increased the necessity of eco-friendly substitutes for plastics. Conventional plastics in addition to being non-biodegradable are also derived from depleting non-renewable resources. Therefore, the production of packaging films utilizing agro-industrial waste has gained widespread attention as a sustainable alternative to conventional non-degradable plastic. The underutilized compounds from agro-industrial waste such as by-products of fruit and vegetable industries or the waste from sugar industries can serve as a great alternative for plastics owing to their low cost, availability and abundance of raw materials. They possess significant physical and chemical properties which make them good sources for producing biopolymers as well as cellulosic fillers. The processing and production of food products by agro-industries generate waste or by-products such as husks of various grains, leaves, gums, bagasse, offal and seeds, which contain an ample amount of plant-derived fibrous proteins such as pectin, starch and cellulose. They also have nutritional properties and peculiar sensory properties which are obliged to the bioactive compounds found in them. Therefore, these waste materials can be reutilized for recycling along with high value-added purposes which will reduce environmental stress and empower sustainable greener approaches. This review will provide a discussion on the usage of agro-industrial wastes for fabricating sustainable composite films with several reinforcements. Additionally, the significance of waste-derived biopolymers as films having value-added functional packaging properties over conventional packaging films will also be discussed. This usage of agro-industrial waste material in turn would aid in the circular economy flow, waste reduction along with generation of high-end usage and recycling of waste.

Formulation Study on Edible Film from Waste Grape and Red Cabbage.

(1) Background: Recent research on the valorization of agro-industrial waste has attempted to obtain new products. Grape residue is a waste product used in the grape wine industry that is rich in anthocyanins, as well as leaves and waste parts from red cabbage processing. Anthocyanins, thanks to their various functionalities, can be recovered and used as active and intelligent agents in food packaging. Anthocyanins have antioxidant properties that help to prevent cardiovascular disease. (2) Methods: In this study, the process of extracting waste was studied using solvent and supercritical CO2 extraction. The obtained anthocyanins were used in starch-based food film formulations. Several formulations were studied using rheometric techniques and the effect of adding anthocyanins on optimal film formulation was investigated. (3) Results: Solvent extractions resulted in a maximum extraction yield. The extracts obtained were used for the preparation of coating and edible films, optimized in the formulation. (4) Conclusions: The addition of anthocyanins to films resulted in increased sample structuring and mechanical properties that are valid for applications, like dipping using coverage methods. The packaging is also attractive and pH-sensitive.

Valorization of Agro-Industrial Wastes and Residues through the Production of Bioactive Compounds by Macrofungi in Liquid State Cultures: Growing Circular Economy

Vast quantities of side streams produced worldwide by the agricultural and food industry present an environmental challenge and an opportunity for waste upcycling in the frame of the circular bioeconomy. Fungi are capable of transforming lignocellulosic residues and wastes into a variety of added-value compounds with applications in functional food products, pharmaceuticals, chemicals, enzymes, proteins, and the emerging sector of nutraceuticals. The liquid state culture of fungi is an efficient and potentially scalable and reproducible biotechnological tool that allows the optimized production of fungal metabolites. Particularly, the utilization of agro-industrial by-products, residues, and wastes as a substrate for the liquid culture of macrofungi is suggested as an attainable solution in the management of these streams, contributing to climate change mitigation. This review presents recently published literature in the field of liquid state cultures of macrofungi using agro-industrial side streams, the different substrates, methods, and factors affecting their growth and metabolite production, as well as their applications, focusing on the variety of natural valuable compounds produced.

Valorization of agro-industrial wastes into polyhydroxyalkanoates-rich single-cell proteins to enable a circular waste-to-feed economy

Recovering and converting carbon and nutrients from waste streams into healthy single-cell proteins (SCPs) can be an effective strategy to address costly waste management and support the increasing animal feed demand for the global food supply. Recently, SCPs rich in polyhydroxybutyrate (PHB) have been identified as an effective biocontrol healthy feed to replace conventional antibiotics-supplemented aquaculture feed. PHB, an intercellular polymer of short-chain-length (SCL) hydroxy-fatty acids, is a common type of polyhydroxyalkanoates (PHA) that can be microbially produced from various organics, including agro-industrial wastes. The complex chemical properties of agro-industrial wastes might produce SCPs containing PHA with SCL and/or medium chain-length (MCL) hydroxy-fatty acids. However, the effects of MCL-PHA-containing SCPs on aqua species' health and disease-fighting ability remains poorly understood. This study investigated the feasibility of producing various PHA-containing SCPs from renewable agro-industrial wastes/wastewaters, the effectiveness of SCL- and MCL-PHA as biocontrol agents, and the effects of these PHA-rich SCPs on the growth and disease resistance of an aquaculture animal model, brine shrimp Artemia. Zobellella denitrificans ZD1 and Pseudomonas oleovorans were able to grow on different pure substrates and agro-industrial wastes/wastewaters to produce various SCL- and/or MCL-PHA-rich SCPs. Low doses of MCL-fatty acids (i.e., PHA intermediates) efficiently suppressed the growth of aquaculture pathogens. Moreover, MCL-PHA-rich SCPs served as great food/energy sources for Artemia and improved Artemia's ability to fight pathogens. This study offers a win-win approach to address the challenges of wastes/wastewater management and feed supply faced by the aquaculture industry.

Valorization of Agro-Industrial Wastes by Ultrasound-Assisted Extraction as a Source of Proteins, Antioxidants and Cutin: A Cascade Approach.

The use of agro-industrial wastes to obtain compounds with a high added-value is increasing in the last few years in accordance with the circular economy concept. In this work, a cascade extraction approach was developed based on ultrasound-assisted extraction (UAE) for tomato, watermelon, and apple peel wastes. The protein and antioxidant compounds were obtained during the first extraction step (NaOH 3 wt.%, 98.6 W, 100% amplitude, 6.48 W/cm2, 6 min). The watermelon peels (WP) showed higher proteins and total phenolic contents (857 ± 1 mg BSA/g extract and 107.2 ± 0.2 mg GAE/100 g dm, respectively), whereas the highest antioxidant activity was obtained for apple peels (1559 ± 20 µmol TE/100 g dm, 1767 ± 5 µmol TE/100 g dm, and 902 ± 16 µmol TE/100 g dm for ABTS, FRAP and DPPH assays, respectively). The remaining residue obtained from the first extraction was subsequently extracted to obtain cutin (ethanol 40 wt.%, 58 W, 100% amplitude, 2 W/cm2, 17 min, 1/80 g/mL, pH 2.5). The morphological studies confirmed the great efficiency of UAE in damaging the vegetal cell walls. WP showed a higher non-hydrolysable cutin content (55 wt.% of the initial cutin). A different monomers’ profile was obtained for the cutin composition by GC-MS, with the cutin from tomato and apple peels being rich in polyhydroxy fatty acids whereas the cutin extracted from WP was mainly based on unsaturated fatty acids. All of the cutin samples showed an initial degradation temperature higher than 200 °C, presenting an excellent thermal stability. The strategy followed in this work has proved to be an effective valorization methodology with a high scaling-up potential for applications in the food, pharmaceutical, nutraceutical, cosmetics and biopolymer sectors.

An overview of sustainable approaches for bioenergy production from agro-industrial wastes

Biofuels are perfect replacements for conventional fossil fuels, as they are environmentally friendly, non-polluting, locally available, sustainable, renewable, and accessible. The biomass, available abundantly on the earth's crust can be used for the production of biofuels via the circular economy concept. The presence of high organic content, chemical oxygen demand (COD), biological oxygen demand (BOD), etc. makes them excellent candidates for bioenergy generation. Bioenergy generation from agro-industrial wastes, a major biomass feedstock, is considered to be a promising technology for overcoming fossil fuel depletion as well as environmental pollution. Also, the utilization of agro-industrial wastes as feedstocks in large quantities resolves the concerns associated with waste management, which otherwise piles up and causes severe environmental pollution and health-hazardous effects. Thus, the current review mainly focuses on bioenergy generation via valorization of agro-industrial wastes. It also discusses various methodologies employed for the production of different biofuels e.g., biogas, biohydrogen, bioethanol, biodiesel, etc. The review further highlights the production strategies, limitations, and prospects of agro-industrial wastes as feedstock for bioenergy generation and waste management. It gives detailed insight into the integrated depolymerization and hydrolysis of biomass where it can be effectively used as a “green tool” in various industries e.g., biorefinery applications, and be a step towards a “cleaner ecosystem and future”.

Digestión anaeróbica de residuos agroindustriales: Lagunas anaerobias en América Latina

The valorization of agro-industrial wastes (AW) by means of waste-to-energy strategies through anaerobic digestion (AD) is a reality in developed countries. In Latin America, there are different problems in the management of AW from intensive livestock farming. This study aims to provide a pseudo-radiography of AD management systems with a focus on anaerobic lagoons in Latin America (LATAM). Using data science, quantitative and qualitative data from 1003 scientific papers were synthesized and analyzed to form a database; which allowed evaluation of the congruence of the scientific research with the real problems of LATAM management. The results showed that anaerobic lagoons in the region are the main AW management systems (mainly bovine and swine manure) and that scientific research in this sector does not address the related problems. 38 types of inhibition phenomena with a total of 5264 mentions were addressed in the database. Nitrogen-related AR inhibition phenomena represented 21% of the incidences in this study, besides being the most significant phenomenon in anaerobic lagoons in LATAM

A comprehensive review on the properties and functionalities of biodegradable and semibiodegradable food packaging materials

The development of biodegradable food packaging with superior properties and functionalities compared to conventional food packaging is one of the emerging research interests. Immediate disposal of conventional single use nonbiodegradable food packaging results in adverse environmental impact. Utilization of either biomass-based, microorganism-derived, or biotechnologically synthesized biopolymers as biodegradable matrices is the common approach toward achieving sustainability. Consequently, starch and cellulose are being commonly used as biodegradable matrices. However, rather than being fully biodegradable, most of them can be considered as semibiodegradable. Majority of the review studies are based on matrices that have an origin in edible sources, which might result in food insecurity. Although development of bio-based polymers with sound packaging properties have been extensively studied, the potential agro-industrial waste as alternative, eco-friendly, and economically viable matrices have attracted little attention. Therefore, the approaches of developing biodegradable food packaging and the framework of converting agro-industrial waste into biodegradable packaging matrices are discussed comparatively in this paper. It also critiques the approaches and valorization of agro-industrial waste in biodegradable food packaging. Thereby, an overview of physicochemical, functional, and biodegradable properties of commonly used biodegradable food packaging materials are provided as an insight for agro-industrial waste-based food packaging. The potential use of agro-industrial waste-based biodegradable food packaging materials against commonly used biodegradable food packaging materials has been highlighted in this study. Thereby, the vital necessity of growing awareness about agro-industrial waste as biodegradable food packaging materials is emphasized through this comprehensive review.

Sustainable Production of Lignocellulolytic Enzymes in Solid-State Fermentation of Agro-Industrial Waste: Application in Pumpkin (Cucurbita maxima) Juice Clarification

Valorization of agro-industrial waste through greener and biotechnological processes are promising approaches to minimize the generation of agro-industrial waste. Therefore, the study aimed to produce lignocellulolytic enzymes from agro-industrial waste under solid-state fermentation (SSF) conditions and study their application in the clarification of pumpkin juice. The SSF was performed with three different combinations of wheat bran + rice bran (WBRB), wheat bran + wheat straw (WBWS), and rice bran + wheat straw (RBWS) as dry solid substrates (1:1) using Fusarium oxysporum (MTCC 7229). The protein, carboxymethyl cellulase (CMCase), and xylanase contents ranged from 0.98–3.90 mg/g, 5.89–6.84 U/g substrate, and 10.08–13.77 U/g substrate, respectively in different agro-industrial waste as substrates (WBRB, WBWS, RBWS, and control). The increase in enzyme concentration (0.50–2.40%) added to pumpkin juice exhibited an increased juice yield (16.30–55.60%), reduced browning index (1.03–0.70), and an increase in clarity (5.31–13.77 %T), which was further confirmed by a total variance of 84.83% by principal component analysis. Thus, the low-cost lignocellulolytic enzymes can be produced from agro-industrial waste that might have applications in food and beverage industries. Hence, this approach could be used as a long-term sustainable and circular source to valorize agro-industrial waste towards the greener future and the preservation of ecosystems.

Bioprospecting microbial hosts to valorize lignocellulose biomass – Environmental perspectives and value-added bioproducts

Current biorefinery approaches comprehend diverse biomass feedstocks and various conversion techniques to produce a variety of high-value biochemicals and biofuels. Lignocellulose is among the most abundant, bio-renewable, and sustainable bioresources on earth. It is regarded as a prodigious alternative raw feedstock to produce a large number of chemicals and biofuels. Producing biofuels and platform chemicals from lignocellulosic biomasses represent advantages in terms of energy and environmental perspectives. Lignocellulose is a main structural constituent of non-woody and woody plants consisting of lignin, cellulose, and hemicellulose. Efficient exploitation of all these components is likely to play a considerable contribution to the economic viability of the processes since lignocellulosic biomass often necessitate pretreatment for liberating fermentable sugars and added value products that might serve as feedstocks for microbial strains to produce biofuels and biochemicals. Developing robust microbial culture and advancements in metabolic engineering approaches might lead to the rapid construction of cell factories for the effective biotechnological transformation of biomass feedstocks to produce biorefinery products. In this comprehensive review, we discuss the recent progress in the valorization of agro-industrial wastes as prospective microbial feedstocks to produce a spectrum of high-value products, such as microbial pigments, biopolymers, industrial biocatalysts, biofuels, biologically active compounds, bioplastics, biosurfactants, and biocontrol agents with therapeutic and industrial potentialities. Lignocellulosic biomass architecture, compositional aspects, revalorization, and pretreatment strategies are outlined for efficient conversion of lignocellulosic biomass. Moreover, metabolic engineering approaches are briefly highlighted to develop cell factories to make the lignocellulose biorefinery platforms appealing.

Valorization of Agroindustrial Waste from Chestnut Production

In recent years, the consumption of fruits of European chestnut has considerably enhanced due to their positive health effects. However, the chestnut peeling process generates solid residues (inner and outer shells), which account for about 10–15% of the whole chestnut weight. In the present study, an integration between a chemical and a thermochemical process is proposed as a valorization route for the chestnut residues: the extraction of polyphenols, a class of strong natural antioxidants, and the slow pyrolysis for biochar production. The chestnut residues after the polyphenols extraction are used as pyrolysis feedstock, and the produced biochars are applied as adsorbing materials to simplify the recovery of the extracted polyphenols.The aim of this study is to evaluate how the physical and chemical characteristics of biochar from chestnut residues influence the adsorption of polyphenols. The biochar production was carried out in a slow pyrolysis reactor using two feedstocks (as received and post-extraction chestnut residues) and three pyrolysis temperatures (500 °C, 600 °C and 700 °C), thus resulting in six different biochars. Each biochar was used as an adsorbent material for the polyphenols in the aqueous extracting solution obtained from chestnut residues. Specific classes of polyphenols were considered, such as non-tannin polyphenols, hydrolysable tannins and condensed tannins. The adsorption efficiency of biochar increases in the char produced at 700 °C for both the considered feedstocks. The analysis of the specific polyphenols groups shows that, despite having an overall adsorption capacity much lower than activated carbon, biochars have a great selectivity for the adsorption of non-tannin polyphenols.

Hydroxytyrosol and Oleuropein-Enriched Extracts Obtained from Olive Oil Wastes and By-Products as Active Antioxidant Ingredients for Poly (Vinyl Alcohol)-Based Films.

Oxidative stability of food is one of the most important parameters affecting integrity and consequently nutritional properties of dietary constituents. Antioxidants are widely used to avoid deterioration during transformation, packaging, and storage of food. In this paper, novel poly (vinyl alcohol) (PVA)-based films were prepared by solvent casting method adding an hydroxytyrosol-enriched extract (HTyrE) or an oleuropein-enriched extract (OleE) in different percentages (5, 10 and 20% w/w) and a combination of both at 5% w/w. Both extracts were obtained from olive oil wastes and by-products using a sustainable process based on membrane technologies. Qualitative and quantitative analysis of each sample carried out by high performance liquid chromatography (HPLC) and nuclear resonance magnetic spectroscopy (NMR) proved that the main components were hydroxytyrosol (HTyr) and oleuropein (Ole), respectively, two well-known antioxidant bioactive compounds found in Olea europaea L. All novel formulations were characterized investigating their morphological, optical and antioxidant properties. The promising performances suggest a potential use in active food packaging to preserve oxidative-sensitive food products. Moreover, this research represents a valuable example of reuse and valorization of agro-industrial wastes and by-products according to the circular economy model.