Sustainable enzymatic treatment of organic waste in a framework of circular economy

Unraveling Structural and Biochemical Insights into a Novel Thermo-Alkaline Pectate Lyase from Caldicellulosiruptor bescii for Sustainable Fabric Bioscouring

Pectate lyase (PL) holds significant potential for applications in various industries. However, the existing PL was unable to adapt to thermo-alkaline industrial environments. In this work, a PL from Caldicellulosiruptor bescii DSM 6725 (hereafter, CbPelD) was studied to disclose its structural and biochemical properties. CbPelD consisted of a putative signal peptide sequence, a short linker region, and a catalytic domain (PelD-II), along with an exoacting β-fructofuranosidase domain (PelD-I). In molecular dynamics simulation, PelD-II demonstrated significantly higher activity and thermal stability compared to other truncated enzymes of CbPelD. The optimal pH and temperature for PelD-II were 10.0 and 60 °C, respectively, with the specific activity increasing by 164-223% in the presence of Ca2+ or Ni2+. The exotype PelD-II exhibited efficient degradation of polygalacturonic acid (PGA) into unsaturated galacturonic acid (uG1), digalacturonic acid (uG2), and trigalacturonic acid (uG3). In the bioscouring assay, PelD-II exhibited a significant increase in the wetted fabric area to 6.072 ± 0.684 cm2, which was about 7.9 times higher than untreated fabric. Scanning electron microscopy further revealed that treatment with PelD-II resulted in a smoother fiber surface, providing direct visual confirmation of the enzyme's action. These results highlight the potential of PelD-II for applications in the textile industries.

Graphing the Green route: Enzymatic hydrolysis in sustainable decomposition

This graphical review article explores how sustainable decomposition contributes to environmental sustainability in waste management with a focus on enzymatic hydrolysis. Methods such as composting and anaerobic digestion efficiently break down organic waste and reduce landfill use and greenhouse gas emissions, while producing valuable resources such as compost and biogas. In particular, enzymatic hydrolysis offers advantages over chemical methods because it operates under mild conditions, targets specific substrates precisely, and yields purer products with fewer side reactions. Its renewable and biodegradable nature aligns with sustainability goals, making it suitable for waste decomposition, biorefining, and resource recovery. Enzymatic waste conversion reduces waste and pollution, conserves natural resources, and supports circular economy. Various ongoing studies have aimed to enhance the efficiency and environmental benefits of enzymatic hydrolysis, enabling innovative waste-to-value solutions that address environmental, economic, and social challenges. This article emphasizes the importance of its timely examination of enzymatic hydrolysis as a prominent method for sustainable waste decomposition, stressing its environmental, economic, and societal benefits. It distinguishes itself through its extensive analysis of chemical methods, its emphasis on the circular economy, and its delineation of future research directions and the need for interdisciplinary collaboration to advance this innovative technology.

Valorization of food waste: A comprehensive review of individual technologies for producing bio-based products

BACKGROUND

The escalating global concerns about food waste and the imperative need for sustainable practices have fuelled a burgeoning interest in the valorization of food waste. This comprehensive review delves into various technologies employed for converting food waste into valuable bio-based products. The article surveys individual technologies, ranging from traditional to cutting-edge methods, highlighting their respective mechanisms, advantages, and challenges.

SCOPE AND APPROACH

The exploration encompasses enzymatic processes, microbial fermentation, anaerobic digestion, and emerging technologies such as pyrolysis and hydrothermal processing. Each technology's efficacy in transforming food waste into bio-based products such as biofuels, enzymes, organic acids, prebiotics, and biopolymers is critically assessed. The review also considers the environmental and economic implications of these technologies, shedding light on their sustainability and scalability. The article discusses the role of technological integration and synergies in creating holistic approaches for maximizing the valorization potential of food waste. Key finding and conclusion: This review consolidates current knowledge on the valorization of food waste, offering a comprehensive understanding of individual technologies and their contributions to the sustainable production of bio-based products. The synthesis of information presented here aims to guide researchers, policymakers, and industry stakeholders in making informed decisions to address the global challenge of food waste while fostering a circular and eco-friendly economy.

Advanced anaerobic digestion of household food waste pretreated by in situ-produced mixed enzymes via solid-state fermentation: Feasibility and application perspectives

Enzymatic pretreatment is an effective method which can improve the anaerobic digestion (AD) efficiency of household food waste (HFW). As an alternative to expensive commercial enzymes, mixed enzymes (MEs) produced in situ from HFW by solid-state fermentation (SSF) can greatly promote the hydrolysis rate of HFW and achieve advanced anaerobic digestion (AAD) economically sustainable. In this paper, strategies for improving the efficiency of the enzyme-production process and the abundance of MEs are briefly discussed, including SSF, fungal co-cultivation, and stepwise fermentation. The feasibility of using HFW as an applicable substrate for producing MEs (amylase, protease, and lignocellulose-degrading enzymes) and its potential advantages in HFW anaerobic digestion are comprehensively illustrated. Based on the findings, an integrated AAD process of HFW pretreated with MEs produced in situ was proposed to maximise bioenergy recovery. The mass balance results showed that the total volatile solids removal rate could reach 98.56%. Moreover, the net energy output could reach 2168.62 MJ/t HFW, which is 9.79% higher than that without in situ-produced MEs and pretreatment. Finally, perspectives for further study are presented.

The gain effect of microbial consortia induced by adaptive domestication for efficient conversion of Chinese cabbage waste by anaerobic fermentation

The resource-based treatment of Chinese cabbage waste by anaerobic fermentation can effectively mitigate air, soil, and groundwater pollution. However, the compatibility between fermentative microorganisms and the environment might be a crucial limiting factor for the resource recycling of Chinese cabbage waste. Therefore, the gain effect of microbial consortia (JMRS, JMRST, JMRSZ, JCCW, JCCWT and JCCWZ) induced by adaptive domestication for efficient conversion of Chinese cabbage waste by anaerobic fermentation were explored in this study. A total of 42 single subsamples with same weights were randomly divided into seven treatments: sterile deionized water (Control); anaerobic fermentation inoculated with JMRS (MRS); anaerobic fermentation inoculated with JMRST (MRST); anaerobic fermentation inoculated with JMRSZ (MRSZ); anaerobic fermentation inoculated with JCCW (CCW); anaerobic fermentation inoculated with JCCWT (CCWT); anaerobic fermentation inoculated with JCCWZ (CCWZ) and samples were taken on days 30 and 60 after anaerobic fermentation. The results exhibited that all the treatments contributed to high levels of lactic acid (178.77-201.79 g/kg dry matter) and low levels of ammonia-N (12.99-21.03 g/kg total nitrogen). Meanwhile, MRSZ enhanced (p < 0.05) acetic acid levels (1.53 g/kg dry matter) and resulted in the lowest yeast counts. Microbiologically, the addition of microbial consortia decreased the linear discriminant analysis (LDA) scores of Massilia and Stenotrophomonas maltophilia. Moreover, MRSZ enriched (p < 0.05) Lactobacillus hilgardii, and decreased (p < 0.05) the abundance of bacteria containing mobile elements and potentially pathogenic bacteria. In conclusion, JMRSZ improved the efficient conversion of Chinese cabbage waste for resource utilization.

Tackling municipal solid waste crisis in India: Insights into cutting-edge technologies and risk assessment

Municipal Solid Waste (MSW) management is a pressing global concern, with increasing interest in Waste-to-Energy Technologies (WTE-T) to divert waste from landfills. However, WTE-T adoption is hindered by financial uncertainties. The economic benefits of MSW treatment and energy generation must be balanced against environmental impact. Integrating cutting-edge technologies like Artificial Intelligence (AI) can enhance MSW management strategies and facilitate WTE-T adoption. This review paper explores waste classification, generation, and disposal methods, emphasizing public awareness to reduce waste. It discusses AI's role in waste management, including route optimization, waste composition forecasting, and process parameter optimization for energy generation. Various energy production techniques from MSW, such as high-solids anaerobic digestion, torrefaction, plasma pyrolysis, incineration, gasification, biodegradation, and hydrothermal carbonization, are examined for their advantages and challenges. The paper emphasizes risk assessment in MSW management, covering chemical, mechanical, biological, and health-related risks, aiming to identify and mitigate potential adverse effects. Electronic waste (E-waste) impact on human health and the environment is thoroughly discussed, highlighting the release of hazardous substances and their contribution to air, soil, and water pollution. The paper advocates for circular economy (CE) principles and waste-to-energy solutions to achieve sustainable waste management. It also addresses complexities and constraints faced by developing nations and proposes strategies to overcome them. In conclusion, this comprehensive review underscores the importance of risk assessment, the potential of AI and waste-to-energy solutions, and the need for sustainable waste management to safeguard public health and the environment.

Tunnel engineering of gas-converting enzymes for inhibitor retardation and substrate acceleration

Carbon monoxide dehydrogenase (CODH), formate dehydrogenase (FDH), hydrogenase (H2ase), and nitrogenase (N2ase) are crucial enzymatic catalysts that facilitate the conversion of industrially significant gases such as CO, CO2, H2, and N2. The tunnels in the gas-converting enzymes serve as conduits for these low molecular weight gases to access deeply buried catalytic sites. The identification of the substrate tunnels is imperative for comprehending the substrate selectivity mechanism underlying these gas-converting enzymes. This knowledge also holds substantial value for industrial applications, particularly in addressing the challenges associated with separation and utilization of byproduct gases. In this comprehensive review, we delve into the emerging field of tunnel engineering, presenting a range of approaches and analyses. Additionally, we propose methodologies for the systematic design of enzymes, with the ultimate goal of advancing protein engineering strategies.

Recent applications and future prospects of magnetic biocatalysts

Magnetic biocatalysts combine magnetic properties with the catalytic activity of enzymes, achieving easy recovery and reuse in biotechnological processes. Lipases immobilized by magnetic nanoparticles dominate. This review covers an advanced bibliometric analysis and an overview of the area, elucidating research advances. Using WoS, 34,949 publications were analyzed and refined to 450. The prominent journals, countries, institutions, and authors that published the most were identified. The most cited articles showed research hotspots. The analysis of the themes and keywords identified five clusters and showed that the main field of research is associated with obtaining biofuels derived from different types of sustainable vegetable oils. The overview of magnetic biocatalysts showed that these materials are also employed in biosensors, photothermal therapy, environmental remediation, and medical applications. The industry shows a significant interest, with the number of patents increasing. Future studies should focus on immobilizing new lipases in unique materials with magnetic profiles, aiming to improve the efficiency for various biotechnological applications.

Preparation of water-insoluble lignin nanoparticles by deep eutectic solvent and its application as a versatile and biocompatible support for the immobilization of α-amylase

As one of the most abundant biopolymers, lignin is a widely available resource. However, its potential largely remains untapped, with most of it ending up as waste from industries like paper production, pulp processing, and bio-refining. The research undertaken in this study focused on the extraction of lignin from agroforestry waste using a deep eutectic solvent (DES) as a carrier for α-amylase immobilization, resulting in high stability and reusability. Several techniques, including Nuclear Magnetic Resonance (NMR), Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDS), and the Brunauer-Emmett-Teller (BET) method were employed to examine the structure and morphology of both the extracted lignin and the immobilized enzyme. The temperature used to recover lignin by DES would affect immobilization efficiency and enzyme loading by influencing its specific surface area, pore size, and volume distribution. Investigations using Nuclear Overhauser Effect Spectroscopy (NOESY) uncovered that the hydroxyl groups in G, H, and S units and the β-O-4 structure of lignin primarily serve as binding sites for enzyme molecules. Immobilized α-amylase demonstrated a higher pH and thermal stability level, with an optimal pH of 7.0 and temperature of 100 °C, compared to the free enzyme, which exhibited optimal activity at a pH of 6.5 and temperature of 90 °C. Importantly, immobilized α-amylase retained >80 % of its initial activity even after 28 days at room temperature, and it maintained 70 % of its activity after being reused 12 times. These findings strongly suggest that lignin derived from agroforestry residues holds promising potential as a future versatile immobilization material, a prospect integral to society's sustainable development.

A strategic review on sustainable approaches in municipal solid waste management andenergy recovery: Role of artificial intelligence,economic stability andlife cycle assessment

The consumption of energy levels has increased in association with economic growth and concurrently increased the energy demand from renewable sources. The need under Sustainable Development Goals (SDG) intends to explore various technological advancements for the utilization of waste to energy. Municipal Solid Waste (MSW) has been reported as constructive feedstock to produce biofuels, biofuel carriers and biochemicals using energy-efficient technologies in risk freeways. The present review contemplates risk assessment and challenges in sorting and transportation of MSW and different aspects of conversion of MSW into energy are critically analysed. The circular bioeconomy of energy production strategies and management of waste are also analysed. The current scenario on MSW and its impacts on the environment are elucidated in conjunction with various policies and amendments equipped for the competent management of MSW in order to fabricate a sustained environment.

Emerging contaminants bioremediation by enzyme and nanozyme-based processes - A review

Due to their widespread occurrence and the inadequate removal efficiencies by conventional wastewater treatment plants, emerging contaminants (ECs) have recently become an issue of great concern. Current ongoing studies have focused on different physical, chemical, and biological methods as strategies to avoid exposing ecosystems to significant long-term risks. Among the different proposed technologies, the enzyme-based processes rise as green biocatalysts with higher efficiency yields and lower generation of toxic by-products. Oxidoreductases and hydrolases are among the most prominent enzymes applied for bioremediation processes. The present work overviews the state of the art of recent advances in enzymatic processes during wastewater treatment of EC, focusing on recent innovations in terms of applied immobilization techniques, genetic engineering tools, and the advent of nanozymes. Future trends in the enzymes immobilization techniques for EC removal were highlighted. Research gaps and recommendations on methods and utility of enzymatic treatment incorporation in conventional wastewater treatment plants were also discussed.

Grape Waste Materials-An Attractive Source for Developing Nanomaterials with Versatile Applications

In the last decade, researchers have focused on the recycling of agro-food wastes for the production of value-added products. This eco-friendly trend is also observed in nanotechnology, where recycled raw materials may be processed into valuable nanomaterials with practical applications. Regarding environmental safety, replacing hazardous chemical substances with natural products obtained from plant wastes is an excellent opportunity for the "green synthesis" of nanomaterials. This paper aims to critically discuss plant waste, with particular emphasis on grape waste, methods of recovery of active compounds, and nanomaterials obtained from by-products, along with their versatile applications, including healthcare uses. Moreover, the challenges that may appear in this field, as well as future perspectives, are also included.