Ligninolytic Enzymes Mediated Ligninolysis: An Untapped Biocatalytic Potential to Deconstruct Lignocellulosic Molecules in a Sustainable Manner

Mycotransformation of Commercial Grade Cypermethrin Dispersion by Aspergillus terreus PDB-B Strain Isolated from Lake Sediments of Kulamangalam, Madurai

A fungal isolate Aspergillus terreus PDB-B (accession number: MT774567.1), which could tolerate up to 500 mg/L of cypermethrin, was isolated from the lake sediments of Kulamangalam tropical lake, Madurai, and identified by internal transcribed spacer (ITS) sequencing followed by phylogenetic analysis. The biotransformation potential of the strain was compared with five other strains (A, J, UN2, M1 and SM108) as a consortium, which were tentatively identified as Aspergillus glaucus, Aspergillus niger, Aspergillus flavus, Aspergillus terreus, and Aspergillus flavus, respectively. Batch culture and soil microcosm studies were conducted to explore biotransformation using plate-based enzymatic screening and GC-MS. A mycotransformation pathway was predicted based on a comparative analysis of the transformation products (TPs) obtained. The cytotoxicity assay revealed that the presence of (3-methylphenyl) methanol and isopropyl ether could be relevant to the high rate of lethality.

Mechanistic insights into the cinnamaldehyde modification of lignin for sustainable anti-fungal reagent

The limited anti-fungal activity of enzymatic hydrolysis lignin (EHL) has been a challenge in its direct application as a bamboo preservative. To address this issue, the cinnamaldehyde modification of EHL was carried out to introduce anti-fungal structures into the lignin matrix, effectively enhancing its anti-fungal activity. The results demonstrated that the minimal inhibitory concentrations of the modified lignin (EHL-DC) against Aspergillus niger significantly improved from 16 mg/mL to 1 mg/mL, with comparable enhancements in anti-fungal activity against other fungi. As a result of the modification, the EHL-DC is more prone to interact with fungal cell membranes, contributing to a roughened, shrunken hyphal surface and a decrease in mycelial biomass. Multiple characterization methods were employed to better grapple with the EHL-DC chemical changes. The nitrogen content increased from 2.3 % to 8.3 %, and alterations in elemental compositions further support the proposed reaction mechanism and its role in enhancing EHL's anti-fungal activity. This study offers novel insights into the high-value utilization of enzymatic hydrolysis lignin based on green chemistry principles.

Improved biotransformation of lignin-valorized vanillin into vanillylamine in a sustainable bioreaction medium

Lignin is a critical biopolymer for creating a large number of highly valuable biobased compounds. Vanillin, one of lignin-derived aromatics, can be used to synthesize vanillylamine that is a key fine chemical and pharmaceutical intermediate. To produce vanillylamine, a productive whole-cell-catalyzed biotransformation of vanillin was developed in deep eutectic solvent - surfactant - H2O media. One newly created recombinant E. coli 30CA cells expressing ω-transaminase and L-alanine dehydrogenase was employed to transform 50 mM and 60 mM vanillin into vanillylamine in the yield of 82.2% and 8.5% under 40 °C, respectively. The biotransamination efficiency was enhanced by introducing surfactant PEG-2000 (40 mM) and deep eutectic solvent ChCl:LA (5.0 wt%, pH 8.0), and the highest vanillylamine yield reached 90.0% from 60 mM vanillin. Building an effective bioprocess was utilized for transamination of lignin-derived vanillin to vanillylamine with newly created bacteria in an eco-friendly medium, which had potential application for valorization of lignin to value-added compounds.

Endo-Exoglucanase Synergism for Cellulose Nanofibril Production Assessment and Characterization

A study to produce cellulose nanofibrils (CNF) from kraft cellulose pulp was conducted using a centroid simplex mixture design. The enzyme blend contains 69% endoglucanase and 31% exoglucanase. The central composite rotational design (CCRD) optimized the CNF production process by achieving a higher crystallinity index. It thus corresponded to a solid loading of 15 g/L and an enzyme loading of 0.974. Using the Segal formula, the crystallinity index (CrI) of the CNF was determined by X-ray diffraction to be 80.87%. The average diameter of the CNF prepared by enzymatic hydrolysis was 550-600 nm, while the one produced by enzymatic hydrolysis and with ultrasonic dispersion was 250-300 nm. Finally, synergistic interactions between the enzymes involved in nanocellulose production were demonstrated, with Colby factor values greater than one.

Agro waste as a potential carbon feedstock for poly-3-hydroxy alkanoates production: Commercialization potential and technical hurdles

The enormous production and widespread applications of non -biodegradable plastics lead to their accumulation and toxicity to animals and humans. The issue can be addressed by the development of eco-friendly strategies for the production of biopolymers by utilization of waste residues like agro residues. This will address two societal issues - waste management and the development of an eco-friendly biopolymer, poly-3-hydroxy alkanoates (PHAs). Strategies adopted for utilization of agro-residues, challenges and future perspectives are discussed in detail in this comprehensive review. The possibility of PHA properties improvements can be increased by preparation of blends.

Sugarcane bagasse into value-added products: a review

Strategic valorization of readily available sugarcane bagasse (SB) is very important for waste management and sustainable biorefinery. Conventional SB pretreatment methods are ineffective to meet the requirement for industrial adaptation. Several past studies have highlighted different pretreatment procedures which are lacking environmentally benign characteristics and effective SB bioconversion. This article provides an in-depth review of a variety of environmentally acceptable thermochemical and biological pretreatment techniques for SB. Advancements in the conversion processes such as pyrolysis, liquefaction, gasification, cogeneration, lignin conversion, and cellulose conversion via fermentation processes are critically reviewed for the formation of an extensive array of industrially relevant products such as biofuels, bioelectricity, bioplastics, bio adsorbents, and organic acids. This article would provide comprehensive insights into several crucial aspects of thermochemical and biological conversion processes, including systematic perceptions and scientific developments for value-added products from SB valorization. Moreover, it would lead to determining efficient pretreatment and/or conversion processes for sustainable development of industrial-scale sugarcane-based biorefinery.

Green Biotechnology of Oyster Mushroom (Pleurotus ostreatus L.): A Sustainable Strategy for Myco-Remediation and Bio-Fermentation

The field of biotechnology presents us with a great chance to use many organisms, such as mushrooms, to find suitable solutions for issues that include the accumulation of agro-wastes in the environment. The green biotechnology of mushrooms (Pleurotus ostreatus L.) includes the myco-remediation of polluted soil and water as well as bio-fermentation. The circular economy approach could be effectively achieved by using oyster mushrooms (Pleurotus ostreatus L.), of which the substrate of their cultivation is considered as a vital source for producing biofertilizers, animal feeds, bioenergy, and bio-remediators. Spent mushroom substrate is also considered a crucial source for many applications, including the production of enzymes (e.g., manganese peroxidase, laccase, and lignin peroxidase) and bioethanol. The sustainable management of agro-industrial wastes (e.g., plant-based foods, animal-based foods, and non-food industries) could reduce, reuse and recycle using oyster mushrooms. This review aims to focus on the biotechnological applications of the oyster mushroom (P. ostreatus L.) concerning the field of the myco-remediation of pollutants and the bio-fermentation of agro-industrial wastes as a sustainable approach to environmental protection. This study can open new windows onto the green synthesis of metal-nanoparticles, such as nano-silver, nano-TiO2 and nano-ZnO. More investigations are needed concerning the new biotechnological approaches.

Ligninolytic enzymes in Basidiomycetes and their application in xenobiotics degradation

Variety of microorganisms have already proven their capabilities for degradation of wide range of wastes with anthropogenic nature. These pollutants, both liquid and solids, also include so called xenobiotics like phenol and its derivatives, PAHs, dyes, pesticides, pharmaceuticals, etc. Xenobiotics as bisphenol A (BPA), chlorhexidine (CHX), octenidine (OCT), other disinfectants and antiseptics have high ecotoxicological impact. Moreover, they can also impair our quality of life and our health interfering different metabolic and hormone receptors pathways in human body. Chemical treatment of such wastes is not a viable option because of its poor socio-economics and environmental merits. Therefore, applying effective, ecofriendly and cheap treatment methods is of great importance. Basidiomycetes are extensively investigated for their abilities to degrade numerous pollutants and xenobiotics. Through their extracellular ligninolytic enzymes they are capable of reducing or completely removing wide range of hazardous compounds. These enzymes can be categorized in two groups: oxidases (laccase) and peroxidases (manganese peroxidase, lignin peroxidase, versatile peroxidase). Due to the broad substrate specificity of the secreted enzymes Basidiomycetes can be applied as a powerful tool for bioremediation of diverse xenobiotics and recalcitrant compounds.

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.

Bioengineered microbial platforms for biomass-derived biofuel production - A review

Global warming issues, rapid fossil fuel diminution, and increasing worldwide energy demands have diverted accelerated attention in finding alternate sources of biofuels and energy to combat the energy crisis. Bioconversion of lignocellulosic biomass has emerged as a prodigious way to produce various renewable biofuels such as biodiesel, bioethanol, biogas, and biohydrogen. Ideal microbial hosts for biofuel synthesis should be capable of using high substrate quantity, tolerance to inhibiting substances and end-products, fast sugar transportation, and amplified metabolic fluxes to yielding enhanced fermentative bioproduct. Genetic manipulation and microbes' metabolic engineering are fascinating strategies for the economical production of next-generation biofuel from lignocellulosic feedstocks. Metabolic engineering is a rapidly developing approach to construct robust biofuel-producing microbial hosts and an important component for future bioeconomy. This approach has been widely adopted in the last decade for redirecting and revamping the biosynthetic pathways to obtain a high titer of target products. Biotechnologists and metabolic scientists have produced a wide variety of new products with industrial relevance through metabolic pathway engineering or optimizing native metabolic pathways. This review focuses on exploiting metabolically engineered microbes as promising cell factories for the enhanced production of advanced biofuels.

The enzyme interactome concept in filamentous fungi linked to biomass valorization

Biomass represents an abundant and inexpensive source of sugars and aromatic compounds that can be used as raw materials for conversion into value-added bioproducts. Filamentous fungi are sources of plant cell wall degrading enzymes in nature. Understanding the interactions between enzymes is crucial for optimizing biomass degradation processes. Herein, the concept of the interactome is presented as a holistic approach that depicts the interactions among enzymes, substrates, metabolites, and inhibitors. The interactome encompasses several stages of biomass degradation, starting with the sensing of the substrate and the subsequent synthesis of hydrolytic and oxidative enzymes (fungus-substrate interaction). Enzyme-enzyme interactions are exemplified in the complex processes of lignocellulosic biomass degradation. The enzyme-substrate-metabolite-inhibitor interaction also provides a better understanding of biomass conversion, allowing bioproduct production from recalcitrant agro-industrial residues, thus bringing greater value to residual biomass. Finally, technological applications are presented for optimizing the interactome at various levels.

Bioprospection of ligninolytic enzymes from marine origin filamentous fungi

Fungi are excellent producers of extracellular enzymes. Therefore, the present study aimed to investigate the screening of marine fungi, which are laccase and manganese peroxidase potential producers, in solid fermentation for future applications in bioremediation processes of contaminated sites. For this purpose, two-level factorial planning was adopted, using time (6 and 15 days) and the absence or presence of oil (0 and 1%) as factors. The semi-quantitative evaluation was carried out by calculating radial growth, enzyme activity and enzyme index by measuring phenol red or syringaldazine oxidation halo. The results showed that all the studied strains showed a positive result for manganese peroxidase production, with an enzymatic activity in solid medium less than 0.61, indicating a strongly positive activity. Through the enzyme index, the study also showed prominence for Penicillium sp. strains, with values > 2. The enzyme index increase in oil presence and the inexpressive use of the genera studied for ligninolytic enzymes production from crude oil demonstrated these data importance for fermentative processes optimization. Considering the ability of these strains to develop into recalcitrant compounds and the potential for manganese peroxidase production, they are indicated for exploitation in various bioremediation technologies, as well as other biotechnological applications.

Harnessing microbial wealth for lignocellulose biomass valorization through secretomics: a review

The recalcitrance of lignocellulosic biomass is a major constraint to its high-value use at industrial scale. In nature, microbes play a crucial role in biomass degradation, nutrient recycling and ecosystem functioning. Therefore, the use of microbes is an attractive way to transform biomass to produce clean energy and high-value compounds. The microbial degradation of lignocelluloses is a complex process which is dependent upon multiple secreted enzymes and their synergistic activities. The availability of the cutting edge proteomics and highly sensitive mass spectrometry tools make possible for researchers to probe the secretome of microbes and microbial consortia grown on different lignocelluloses for the identification of hydrolytic enzymes of industrial interest and their substrate-dependent expression. This review summarizes the role of secretomics in identifying enzymes involved in lignocelluloses deconstruction, the development of enzyme cocktails and the construction of synthetic microbial consortia for biomass valorization, providing our perspectives to address the current challenges.

Lignin peroxidase in focus for catalytic elimination of contaminants - A critical review on recent progress and perspectives

Lignin peroxidase (LiP) seems to be a catalyst for cleaving high-redox potential non-phenolic compounds with an oxidative cleavage of CC and COC bonds. LiP has been picked to seek a practical and cost-effective alternative to the sustainable mitigation of diverse environmental contaminants. LiP has been an outstanding tool for catalytic cleaning and efficient mitigation of environmental pollutants, including lignin, lignin derivatives, dyes, endocrine-disrupting compounds (EDCs), and persistent organic pollutants (POPs) for the past couple of decades. The extended deployment of LiP has proved to be a promising method for catalyzing these environmentally related hazardous pollutants of supreme interest. The advantageous potential and capabilities to act at different pH and thermostability offer its working tendencies in extended environmental engineering applications. Such advantages led to the emerging demand for LiP and increasing requirements in industrial and biotechnological sectors. The multitude of the ability attributed to LiP is triggered by its stability in xenobiotic and non-phenolic compound degradation. However, over the decades, the catalytic activity of LiP has been continuing in focus enormously towards catalytic functionalities over the available physiochemical, conventional, catalyst mediated technology for catalyzing such molecules. To cover this literature gap, this became much more evident to consider the catalytic attributes of LiP. In this review, the existing capabilities of LiP and other competencies have been described with recent updates. Furthermore, numerous recently emerged applications, such as textile effluent treatment, dye decolorization, catalytic elimination of pharmaceutical and EDCs compounds, have been discussed with suitable examples.

Nanostructured materials for harnessing the power of horseradish peroxidase for tailored environmental applications

High catalytic efficiency, stereoselectivity, and sustainability outcomes of enzymes entice chemists for considering biocatalytic transformations to supplant conventional synthetic routes. As a green and versatile enzyme, horseradish peroxidase (HRP)-based enzymatic catalysis has been widely employed in a range of biological and chemical transformation processes. Nevertheless, like many other enzymes, HRP is likely to denature or destabilize in harsh realistic conditions due to its intrinsic fragile nature, which results in inevitably shortened lifespan and immensely high bioprocess cost. Enzyme immobilization has proven as a prospective strategy for improving their biocatalytic performance in continuous industrial processes. Nanostructured materials with huge accessible surface area, abundant porous structures, exceptional functionalities, and high chemical and mechanical stability have recently garnered intriguing research interests as novel kinds of supporting matrices for HRP immobilization. Many reported immobilized biocatalytic systems have demonstrated high catalytic performances than that to the free form of enzymes, such as enhanced enzyme efficiency, selectivity, stability, and repeatability due to the protective microenvironments provided by nanostructures. This review delineates an updated overview of HRP immobilization using an array of nanostructured materials. Furthermore, the general physicochemical aspects, improved catalytic attributes, and the robust practical implementations of engineered HRP-based catalytic cues are also discussed with suitable examples. To end, concluding remarks, challenges, and worthy suggestions/perspectives for future enzyme immobilization are also given.

Bio-based active food packaging materials: Sustainable alternative to conventional petrochemical-based packaging materials

In food industry, a growing concern is the use of suitable packaging material (i.e., biodegradable coatings and films) with enhanced thermal, mechanical and barrier characteristics to prevent from contamination and loss of foodstuff. Biobased polymer resources can be used for the development of biodegradable bioplastics. To achieve this goal, biopolymers should be economic, renewable and abundantly available. Bioplastic packaging materials based on renewable biomass could be used as sustainable alternative to petrochemically-originated plastic materials. This review summarizes the recent advancements in biopolymer-based coatings and films for active food packaging applications. Microbial polymers (PHA and PLA), wood-based polymers (cellulose, hemicellulose, starch & lignin), and protein-based polymers (gelatin, keratin, wheat gluten, soy protein and whey protein isolates) were among the materials most widely exploited for the development of smart packaging films. These biopolymers are able to synthesize coatings and films with good barrier properties against food borne pathogens and the transport of gases. Biobased reinforcements e.g., plant essential oils and natural additives to bioplastic films improve oxygen barrier, antibacterial and antifungal properties. To induce the desired functionality the simultaneous utilization of different synthetic and biobased polymers in the form of composites/blends is also an emerging area of research. Nanoscale reinforcements into bioplastic packaging have also been reported to improve packaging characteristics ultimately increasing food shelf life. The development of bioplastic/biocomposite and nanobiocomposites exhibits high potential to replace nonbiodegradable materials with characteristics comparable to fossil-based plastics, additionally, giving biodegradable and compostable characteristics. The idea of utilization of renewable biomass and the implications of biotechnology can firstly reduce the burden from fossil-resources, while secondly promoting biobased economy.

Modalities for conversion of waste to energy - Challenges and perspectives

The United Nation is achieving its sustainable development objectives by focusing on the greener technologies for waste to energy (WTE) conversion. This necessitates the exploration of every conceivable sustainable route in different sectors. Among these, sustainable bio-economy, electricity, and waste management are the most dynamic areas. However, till now sustainability judgments for the generation of electricity from waste-to-energy supply chain (WTE-SC) technologies have been restricted in scale with respect to the three-dimensional sustainability structure (social, environmental, and economic). In most of the cases, the assessments were controlled by various environmental factors/indicators, via overlooking the economic and social indicators. In this review, we have tried to summarize a variety of state-of-the-art WTE technologies including biological and thermal treatment, landfill gas utilization and biorefineries technologies etc. These technologies can be implemented by various policy makers and agencies to deal with the communities fear before spreading and executing the relevant rules and regulations. The implementation of these rules and regulations for WTE-SC were scheduled to decide the barriers and challenges from the perspective of finance, institution, technology, and regulation.

Environmental impact of lignocellulosic wastes and their effective exploitation as smart carriers - A drive towards greener and eco-friendlier biocatalytic systems

In recent years, lignocellulosic wastes have gathered much attention due to increasing economic, social, environmental apprehensions, global climate change and depleted fossil fuel reserves. The unsuitable management of lignocellulosic materials and related organic wastes poses serious environmental burden and causes pollution. On the other hand, lignocellulosic wastes hold significant economic potential and can be employed as promising catalytic supports because of impressing traits such as surface area, porous structure, and occurrence of many chemical moieties (i.e., carboxyl, amino, thiol, hydroxyl, and phosphate groups). In the current literature, scarce information is available on this important and highly valuable aspect of lignocellulosic wastes as smart carriers for immobilization. Thus, to fulfill this literature gap, herein, an effort has been made to signify the value generation aspects of lignocellulosic wastes. Literature assessment spotlighted that all these waste materials display high potential for immobilizing enzyme because of their low cost, bio-renewable, and sustainable nature. Enzyme immobilization has gained recognition as a highly useful technology to improve enzyme properties such as catalytic stability, performance, and repeatability. The application of carrier-supported biocatalysts has been a theme of considerable research, for the past three decades, in the bio-catalysis field. Nonetheless, the type of support matrix plays a key role in the immobilization process due to its influential impact on the physicochemical characteristics of the as-synthesized biocatalytic system. In the past, an array of various organic, inorganic, and composite materials has been used as carriers to formulate efficient and stable biocatalysts. This review is envisioned to provide recent progress and development on the use of different agricultural wastes (such as coconut fiber, sugarcane bagasse, corn and rice wastes, and Brewers' spent grain) as support materials for enzyme immobilization. In summary, the effective utilization of lignocellulosic wastes to develop multi-functional biocatalysts is not only economical but also reduce environmental problems of unsuitable management of organic wastes and drive up the application of biocatalytic technology in the industry.