A Review on the Utilization of Lignin as a Fermentation Substrate to Produce Lignin-Modifying Enzymes and Other Value-Added Products

Lignocellulosic biomass as promising substrate for polyhydroxyalkanoate production: Advances and perspectives

The depletion of fossil resources, coupled with global warming and adverse environmental impact of traditional petroleum-based plastics, have necessitated the discovery of renewable resources and innovative biodegradable materials. Lignocellulosic biomass (LB) emerges as a highly promising, sustainable and eco-friendly approach for accumulating polyhydroxyalkanoate (PHA), as it completely bypasses the problem of "competition for food". This sustainable and economically efficient feedstock has the potential to lower PHA production costs and facilitate its competitive commercialization, and support the principles of circular bioeconomy. LB predominantly comprises cellulose, hemicellulose, and lignin, which can be converted into high-quality substrates for PHA production by various means. Future efforts should focus on maximizing the value derived from LB. This review highlights the momentous and valuable research breakthroughs in recent years, showcasing the biosynthesis of PHA using low-cost LB as a potential feedstock. The metabolic mechanism and pathways of PHA synthesis by microbes, as well as the key enzymes involved, are summarized, offering insights into improving microbial production capacity and fermentation metabolic engineering. Life cycle assessment and techno-economic analysis for sustainable and economical PHA production are introduced. Technological hurdles such as LB pretreatment, and performance limitations are highlighted for their impact on enhancing the sustainable production and application of PHA. Meanwhile, the development direction of co-substrate fermentation of LB and with other carbon sources, integrated processes development, and co-production strategies were also proposed to reduce the cost of PHA and effectively valorize wastes.

Optimized production of laccase from Pseudomonas stutzeri and its biodegradation of lignin in biomass

Laccases are multi-copper oxidases that play an important role in the biodegradation of phenolic compounds, lignin, dye, and wastes. Here, we report the screening of potential laccase-producing indigenous bacterial isolates and subsequent optimization of laccase production using crop residues as cheap supplementary energy sources. Among 16 bacterial isolates, seven were selected based on the appearance of reddish-brown bacterial colonies and guaiacol oxidation assay after 10 days of incubation at 37 °C. The maximum laccase activity (2.755 U/mL) was observed for bacterial isolate WR2. Response surface methodology (RSM) was used to maximize laccase production from WR2, identified as Pseudomonas stutzeri. Plackett-Burman design (PBD) was employed to design production runs involving various factors including time, pH, inoculum, wheat straw, cotton stalk, wheat bran, rice straw, copper sulfate, sugarcane bagasse, yeast extract, and peptone. The interactions of different factors were analyzed from the responses (laccase enzyme activity, etc.) in 12 experimental runs. In experimental run 4, the maximum laccase enzymatic activity (1.86 U/mL) was achieved after a 10-day incubation with wheat straw (1%) and cotton stalk (1%) at pH 6.8 and 37 °C, and high-degree lignin degradation was evident from a substantial reduction in the FTIR aromatic stretching peak of the degraded biomass.

A comprehensive review on biological funnel mechanism in lignin valorization: Pathways and enzyme dynamics

Lignin, a significant byproduct of the paper and pulp industry, is attracting interest due to its potential utilization in biomaterial-based sectors and biofuel production. Investigating biological methods for converting lignin into valuable products is crucial for effective utilization and has recently gained growing attention. Several microorganisms effectively decomposed low molecular weight lignins, transforming them into intermediate compounds via upper and lower metabolic pathways. This review focuses on assessing bacterial metabolic pathways involved in the breakdown of lignin into aromatic compounds and their subsequent utilization by different bacteria through various metabolic pathways. Understanding these pathways is essential for developing efficient synthetic metabolic systems to valorize lignin and obtain valuable industrial aromatic chemicals. The concept of "biological funneling," which involves examining key enzymes, their interactions, and the complex metabolic pathways associated with lignin conversion, is crucial in lignin valorization. By manipulating lignin metabolic pathways and utilizing biological routes, many aromatic compounds can be synthesized within cellular factories. Although there is insufficient evidence regarding the complete metabolism of polyaromatic hydrocarbons by particular microorganisms, understanding lignin-degrading enzymes, regulatory mechanisms, and interactions among various enzyme systems is essential for optimizing lignin valorization. This review highlights recent advancements in lignin valorization, bio-funneling, multi-omics, and analytical characterization approaches for aromatic utilization. It provides up-to-date information and insights into the latest research findings and technological innovations. The review offers valuable insights into the future potential of biological routes for lignin valorization.

Aqueous Phase Hydrogenation of 4-(2-Furyl)-3-buten-2-one over Different Re Phases

4-(2-furyl)-3-buten-2-one (FAc) is obtained by aldol condensation of furfural and acetone and has been used in hydrodeoxygenation reactions to obtain fuel products using noble metal catalysts. The hydrogenation of FAc in the aqueous phase using metallic- and Re oxide-supported catalysts on graphite was studied, within a temperature range of 200-240 °C, in a batch reactor over a 6 h reaction period. The catalysts were characterized using N2 adsorption-desorption, TPR-H2, TPD-NH3, XRD, and XPS analyses. Catalytic reactions revealed that metallic rhenium and rhenium oxide-supported catalysts are active for the hydrogenation and Piancatelli rearrangement of FAc. Notably, metallic rhenium exhibited a fourfold higher initial rate than rhenium oxide, which was attributed to the higher dispersion of Re in the Re/G catalyst over graphite. Re/G and ReOx/G catalysts tended to rearrange and hydrogenate FAc to 2-(2-oxopropyl)cyclopenta-1-one in water.

Unlocking the potential: Evolving role of technical lignin in diverse applications and overcoming challenges

Recent advancements have transformed lignin from a byproduct into a valuable raw material for polymers, dyes, adhesives, and fertilizers. However, its structural heterogeneity, variable reactive group content, impurities, and high extraction costs pose challenges to industrial-scale adoption. Efficient separation technologies and selective bond cleavage are crucial. Advanced pretreatment methods have enhanced lignin purity and reduced contamination, while novel catalytic techniques have improved depolymerization efficiency and selectivity. This review compares catalytic depolymerization methodologies, highlighting their advantages and disadvantages, and noting challenges in comparing yield values due to variations in isolation methods and lignin sources. Recognizing "technical lignin" from pulping processes, the review emphasizes its diverse applications and the necessity of understanding its structural characteristics. Emerging trends focus on bio-based functional additives and nanostructured lignin materials, promising enhanced properties and functionalities. Innovations open possibilities in sustainable agriculture, high-performance foams and composites, and advanced medical applications like drug delivery and wound healing. Leveraging lignin's biocompatibility, abundance, and potential for high-value applications, it can significantly contribute to sustainable material development across various industries. Continuous research in bio-based additives and nanostructured materials underscores lignin's potential to revolutionize material science and promote environmentally friendly industrial applications.

Metabolic complexity drives divergence in microbial communities

Microbial communities are shaped by environmental metabolites, but the principles that govern whether different communities will converge or diverge in any given condition remain unknown, posing fundamental questions about the feasibility of microbiome engineering. Here we studied the longitudinal assembly dynamics of a set of natural microbial communities grown in laboratory conditions of increasing metabolic complexity. We found that different microbial communities tend to become similar to each other when grown in metabolically simple conditions, but they diverge in composition as the metabolic complexity of the environment increases, a phenomenon we refer to as the divergence-complexity effect. A comparative analysis of these communities revealed that this divergence is driven by community diversity and by the assortment of specialist taxa capable of degrading complex metabolites. An ecological model of community dynamics indicates that the hierarchical structure of metabolism itself, where complex molecules are enzymatically degraded into progressively simpler ones that then participate in cross-feeding between community members, is necessary and sufficient to recapitulate our experimental observations. In addition to helping understand the role of the environment in community assembly, the divergence-complexity effect can provide insight into which environments support multiple community states, enabling the search for desired ecosystem functions towards microbiome engineering applications.

Engineering a coenzyme-independent dioxygenase for one-step production of vanillin from ferulic acid

Vanillin is one of the world's most important flavor and fragrance compounds used in foods and cosmetics. In plants, vanillin is reportedly biosynthesized from ferulic acid via the hydratase/lyase-type enzyme VpVAN. However, in biotechnological and biocatalytic applications, the use of VpVAN limits the production of vanillin. Although microbial enzymes are helpful as substitutes for plant enzymes, synthesizing vanillin from ferulic acid in one step using microbial enzymes remains a challenge. Here, we developed a single enzyme that catalyzes vanillin production from ferulic acid in a coenzyme-independent manner via the rational design of a microbial dioxygenase in the carotenoid cleavage oxygenase family using computational simulations. This enzyme acquired catalytic activity toward ferulic acid by introducing mutations into the active center to increase its affinity for ferulic acid. We found that the single enzyme can catalyze not only the production of vanillin from ferulic acid but also the synthesis of other aldehydes from p-coumaric acid, sinapinic acid, and coniferyl alcohol. These results indicate that the approach used in this study can greatly expand the range of substrates available for the dioxygenase family of enzymes. The engineered enzyme enables efficient production of vanillin and other value-added aldehydes from renewable lignin-derived compounds.

IMPORTANCE

The final step of vanillin biosynthesis in plants is reportedly catalyzed by the enzyme VpVAN. Prior to our study, VpVAN was the only reported enzyme that directly converts ferulic acid to vanillin. However, as many characteristics of VpVAN remain unknown, this enzyme is not yet suitable for biocatalytic applications. We show that an enzyme that converts ferulic acid to vanillin in one step could be constructed by modifying a microbial dioxygenase-type enzyme. The engineered enzyme is of biotechnological importance as a tool for the production of vanillin and related compounds via biocatalytic processes and metabolic engineering. The results of this study may also provide useful insights for understanding vanillin biosynthesis in plants.

Lignin bioconversion based on genome mining for ligninolytic genes in Erwinia billingiae QL-Z3

BACKGROUND

Bioconversion of plant biomass into biofuels and bio-products produces large amounts of lignin. The aromatic biopolymers need to be degraded before being converted into value-added bio-products. Microbes can be environment-friendly and efficiently degrade lignin. Compared to fungi, bacteria have some advantages in lignin degradation, including broad tolerance to pH, temperature, and oxygen and the toolkit for genetic manipulation.

RESULTS

Our previous study isolated a novel ligninolytic bacterial strain Erwinia billingiae QL-Z3. Under optimized conditions, its rate of lignin degradation was 25.24% at 1.5 g/L lignin as the sole carbon source. Whole genome sequencing revealed 4556 genes in the genome of QL-Z3. Among 4428 protein-coding genes are 139 CAZyme genes, including 54 glycoside hydrolase (GH) and 16 auxiliary activity (AA) genes. In addition, 74 genes encoding extracellular enzymes are potentially involved in lignin degradation. Real-time PCR quantification demonstrated that the expression of potential ligninolytic genes were significantly induced by lignin. 8 knock-out mutants and complementary strains were constructed. Disruption of the gene for ELAC_205 (laccase) as well as EDYP_48 (Dyp-type peroxidase), ESOD_1236 (superoxide dismutase), EDIO_858 (dioxygenase), EMON_3330 (monooxygenase), or EMCAT_3587 (manganese catalase) significantly reduced the lignin-degrading activity of QL-Z3 by 47-69%. Heterologously expressed and purified enzymes further confirmed their role in lignin degradation. Fourier transform infrared spectroscopy (FTIR) results indicated that the lignin structure was damaged, the benzene ring structure and groups of macromolecules were opened, and the chemical bond was broken under the action of six enzymes encoded by genes. The abundant enzymatic metabolic products by EDYP_48, ELAC_205 and ESOD_1236 were systematically analyzed via liquid chromatography-mass spectrometry (LC-MS) analysis, and then provide a speculative pathway for lignin biodegradation. Finally, The activities of ligninolytic enzymes from fermentation supernatant, namely, LiP, MnP and Lac were 367.50 U/L, 839.50 U/L, and 219.00 U/L by orthogonal optimization.

CONCLUSIONS

Our findings provide that QL-Z3 and its enzymes have the potential for industrial application and hold great promise for the bioconversion of lignin into bioproducts in lignin valorization.

Transcriptomic and metabolomic analysis reveals the influence of carbohydrates on lignin degradation mediated by Bacillus amyloliquefaciens

Introduction

Ligninolytic bacteria can secrete extracellular enzymes to depolymerize lignin into small-molecular aromatics that are subsequently metabolized and funneled into the TCA cycle. Carbohydrates, which are the preferred carbon sources of bacteria, influence the metabolism of lignin-derived aromatics through bacteria.

Methods

In this study, untargeted metabolomics and transcriptomics analyses were performed to investigate the effect of carbohydrates on lignin degradation mediated by Bacillus amyloliquefaciens MN-13, a strain with lignin-degrading activity that was isolated in our previous work.

Results

The results demonstrated that the cell growth of the MN-13 strain and lignin removal were promoted when carbohydrates such as glucose and sodium carboxymethyl cellulose were added to an alkaline lignin-minimal salt medium (AL-MSM) culture. Metabolomics analysis showed that lignin depolymerization took place outside the cells, and the addition of glucose regulated the uptake and metabolism of lignin-derived monomers and activated the downstream metabolism process in cells. In the transcriptomics analysis, 299 DEGs were screened after 24 h of inoculation in AL-MSM with free glucose and 2 g/L glucose, respectively, accounting for 8.3% of the total amount of annotated genes. These DEGs were primarily assigned to 30 subcategories, including flagellar assembly, the PTS system, RNA degradation, glycolysis/gluconeogenesis, the TCA cycle, pyruvate metabolism, and tryptophan metabolism. These subcategories were closely associated with the cell structure, generation of cellular energy, and precursors for biosynthetic pathways, based on a - log 10 (P adjust) value in the KEGG pathway analysis.

Conclusion

In summary, the addition of glucose increased lignin degradation mediated by the MN-13 strain through regulating glycolysis, TCA cycle, and central carbon metabolism.

Lytic polysaccharide monooxygenase synergized with lignin-degrading enzymes for efficient lignin degradation

Even though the discovery of lytic polysaccharide monooxygenases (LPMOs) has fundamentally shifted our understanding of biomass degradation, most of the current studies focused on their roles in carbohydrate oxidation. However, no study demonstrated if LPMO could directly participate to the process of lignin degradation in lignin-degrading microbes. This study showed that LPMO could synergize with lignin-degrading enzymes for efficient lignin degradation in white-rot fungi. The transcriptomics analysis of fungi Irpex lacteus and Dichomitus squalens during their lignocellulosic biomass degradation processes surprisingly highlighted that LPMOs co-regulated with lignin-degrading enzymes, indicating their more versatile roles in the redox network. Biochemical analysis further confirmed that the purified LPMO from I. lacteus CD2 could use diverse electron donors to produce H2O2, drive Fenton reaction, and synergize with manganese peroxidase for lignin oxidation. The results thus indicated that LPMO might uniquely leverage the redox network toward dynamic and efficient degradation of different cell wall components.

Polymeric Materials Obtained by Extrusion and Injection Molding from Lignocellulosic Agroindustrial Biomass

This review presents the advances in polymeric materials achieved by extrusion and injection molding from lignocellulosic agroindustrial biomass. Biomass, which is derived from agricultural and industrial waste, is a renewable and abundant feedstock that contains mainly cellulose, hemicellulose, and lignin. To improve the properties and functions of polymeric materials, cellulose is subjected to a variety of modifications. The most common modifications are surface modification, grafting, chemical procedures, and molecule chemical grafting. Injection molding and extrusion technologies are crucial in shaping and manufacturing polymer composites, with precise control over the process and material selection. Furthermore, injection molding involves four phases: plasticization, injection, cooling, and ejection, with a focus on energy efficiency. Fundamental aspects of an injection molding machine, such as the motor, hopper, heating units, nozzle, and clamping unit, are discussed. Extrusion technology, commonly used as a preliminary step to injection molding, presents challenges regarding fiber reinforcement and stress accumulation, while lignin-based polymeric materials are challenging due to their hydrophobicity. The diverse applications of these biodegradable materials include automotive industries, construction, food packaging, and various consumer goods. Polymeric materials are positioned to offer even bigger contributions to sustainable and eco-friendly solutions in the future, as research and development continues.

Evolution of genetic architecture and gene regulation in biphenyl/PCB-degrading bacteria

A variety of bacteria in the environment can utilize xenobiotic compounds as a source of carbon and energy. The bacterial strains degrading xenobiotics are suitable models to investigate the adaptation and evolutionary processes of bacteria because they appear to have emerged relatively soon after the release of these compounds into the natural environment. Analyses of bacterial genome sequences indicate that horizontal gene transfer (HGT) is the most important contributor to the bacterial evolution of genetic architecture. Further, host bacteria that can use energy effectively by controlling the expression of organized gene clusters involved in xenobiotic degradation will have a survival advantage in harsh xenobiotic-rich environments. In this review, we summarize the current understanding of evolutionary mechanisms operative in bacteria, with a focus on biphenyl/PCB-degrading bacteria. We then discuss metagenomic approaches that are useful for such investigation.

Structural insights, biocatalytic characteristics, and application prospects of lignin-modifying enzymes for sustainable biotechnology-A review

Lignin modifying enzymes (LMEs) have gained widespread recognition in depolymerization of lignin polymers by oxidative cleavage. LMEs are a robust class of biocatalysts that include lignin peroxidase (LiP), manganese peroxidase (MnP), versatile peroxidase (VP), laccase (LAC), and dye-decolorizing peroxidase (DyP). Members of the LMEs family act on phenolic, non-phenolic substrates and have been widely researched for valorization of lignin, oxidative cleavage of xenobiotics and phenolics. LMEs implementation in the biotechnological and industrial sectors has sparked significant attention, although its potential future applications remain underexploited. To understand the mechanism of LMEs in sustainable pollution mitigation, several studies have been undertaken to assess the feasibility of LMEs in correlating to diverse pollutants for binding and intermolecular interactions at the molecular level. However, further investigation is required to fully comprehend the underlying mechanism. In this review we presented the key structural and functional features of LMEs, including the computational aspects, as well as the advanced applications in biotechnology and industrial research. Furthermore, concluding remarks and a look ahead, the use of LMEs coupled with computational frameworks, built upon artificial intelligence (AI) and machine learning (ML), has been emphasized as a recent milestone in environmental research.

Lignin-Degrading Bacteria in Paper Mill Sludge

The effluents generated in the paper industry, such as black liquor, have a high content of lignin and other toxic components; however, they represent a source of lignin-degrading bacteria with biotechnological potential. Therefore, the present study aimed to isolate and identify lignin-degrading bacteria species in paper mill sludge. A primary isolation was carried out from samples of sludge present in environments around a paper company located in the province of Ascope (Peru). Bacteria selection was made by the degradation of Lignin Kraft as the only carbon source in a solid medium. Finally, the laccase activity (Um-L^-1) of each selected bacteria was determined by oxidation of 2,2'-azinobis-(3-etilbencenotiazolina-6-sulfonate) (ABTS). Bacterial species with laccase activity were identified by molecular biology techniques. Seven species of bacteria with laccase activity and the ability to degrade lignin were identified. The bacteria Agrobacterium tumefasciens (2), Klebsiella grimontii (1), and Beijeinckia fluminensis (1) were reported for first time. K. grimowntii and B. fluminensis presented the highest laccase activity, with values of 0.319 ± 0.005 UmL^-1 and 0.329 ± 0.004 UmL^-1, respectively. In conclusion, paper mill sludge may represent a source of lignin-degrading bacteria with laccase activity, and they could have potential biotechnological applications.

Cellulose Nanocrystals (CNCs) and Cellulose Nanofibers (CNFs) as Adsorbents of Heavy Metal Ions

The isolation of nanocellulose has been extensively investigated due to the growing demand for sustainable green materials. Cellulose nanocrystals (CNCs) and cellulose nanofibers (CNFs), which have the same chemical composition but have different morphology, particle size, crystallinity, and other properties depending on the precursor and the synthesis method used. In comparison, CNC particles have a short rod-like shape and have smaller particle dimensions when compared to CNF particles in the form of fibers. CNC synthesis was carried out chemically (hydrolysis method), and CNF synthesis was carried out mechanically (homogenization, ball milling, and grinding), and both can be modified because they have a large surface area and are rich in hydroxyl groups. Modifications were made to increase the adsorption ability of heavy metal ions. The Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric (TG), and dynamic light scattering (DLS) can reveal the characteristics and morphology of CNCs and CNFs. The success and effectiveness of the heavy metal adsorption process are influenced by a few factors. These factors include adsorbent chemical structure changes, adsorbent surface area, the availability of active sites on the adsorbent’s surface, adsorption constants, heavy metal ionic size differences, pH, temperature, adsorbent dosage, and contact time during the adsorption process. In this review, we will discuss the characteristics of CNCs and CNFs synthesized from various precursors and methods, the modification methods, and the application of CNCs and CNFs as heavy metal ion adsorbents, which includes suitable isotherm and kinetics models and the effect of pH on the selectivity of various types of heavy metal ions.

Hollow CoS2 anchored on hierarchically porous carbon derived from Pien Tze Huang for high-performance supercapacitors

The development of electrode materials with a high specific capacitance, power density, and long-term stability is essential and remains a challenge for developing supercapacitors. Cobalt sulfides (CoS₂) are considered one of the most promising and widely studied electrode materials for supercapacitors. Herein, CoS₂ and hierarchical porous carbon derived from Pien Tze Huang waste are assembled into a cobalt sulfide/carbon (CoS₂/PZH) matrix composite using a one-step hydrothermal method to resolve the challenges of supercapacitors. The resulting CoS₂/PZH composite material exhibits a hierarchical porous structure with hollow CoS₂ embedded in a PZH framework. The uniform dispersion of the hierarchical porous structure CoS₂/PZH is achieved due to the PZH framework, while the uniform decoration of the porous PZH with the hollow CoS₂ prevents the PZH from stacking easily. Moreover, the excellent synergistic effect of the hierarchical porous and hollow structure of CoS₂/PZH can shorten the electron/ion diffusion channels, expose additional active sites, and provide stable structures for subsequent reactions. As a result, the CoS₂/PZH composite material displays a high initial specific capacity of 447.5 F g^-1 at 0.5 A g^-1, a high energy density of 22.38 W h kg^-1, and long-term cycling stability (a retention rate of 92.3% over 10 000 cycles at 5 A g^-1).

Integrating 1G with 2G Bioethanol Production by Using Distillers’ Dried Grains with Solubles (DDGS) as the Feedstock for Lignocellulolytic Enzyme Production

First-generation (1G) bioethanol is one of the most used liquid biofuels in the transport industry. It is generated by using sugar- or starch-based feedstocks, while second-generation (2G) bioethanol is generated by using lignocellulosic feedstocks. Distillers’ dried grains with solubles (DDGS) is a byproduct of first-generation bioethanol production with a current annual production of 22.6 million tons in the USA. DDGS is rich in fiber and valuable nutrients contents, which can be used to produce lignocellulolytic enzymes such as cellulases and hemicellulases for 2G bioethanol production. However, DDGS needs a pretreatment method such as dilute acid, ammonia soaking, or steam hydrolysis to release monosaccharides and short-length oligosaccharides as fermentable sugars for use in microbial media. These fermentable sugars can then induce microbial growth and enzyme production compared to only glucose or xylose in the media. In addition, selection of one or more suitable microbial strains, which work best with the DDGS for enzyme production, is also needed. Media optimization and fermentation process optimization strategies can then be applied to find the optimum conditions for the production of cellulases and hemicellulases needed for 2G bioethanol production. Therefore, in this review, a summary of all such techniques is compiled with a special focus on recent findings obtained in previous pieces of research conducted by the authors and by others in the literature. Furthermore, a comparison of such techniques applied to other feedstocks and process improvement strategies is also provided. Overall, dilute acid pretreatment is proven to be better than other pretreatment methods, and fermentation optimization strategies can enhance enzyme production by considerable folds with a suitable feedstock such as DDGS. Future studies can be further enhanced by the technoeconomic viability of DDGS as the on-site enzyme feedstock for the manufacture of second-generation bioethanol (2G) in first-generation (1G) ethanol plants, thus bridging the two processes for the efficient production of bioethanol using corn or other starch-based lignocellulosic plants.

Pineapple Agro-Industrial Biomass to Produce Biomedical Applications in a Circular Economy Context in Costa Rica

Pineapple is a highly demanded fruit in international markets due to its unique appearance and flavor, high fiber content, vitamins, folic acid, and minerals. It makes pineapple production and processing a significant source of income for producing countries, such as Costa Rica. This review collects bibliographic information dating back to the beginnings of pineapple production in Costa Rica to the state of the market today. It details the impacts of its production chain and proposes a biorefinery as a solution to environmental problems. Besides the potentiality of new sustainable markets to contribute to the post-COVID-19 economy in Costa Rica is highlighted. The general characteristics of pineapple by-products -cellulose, hemicellulose, lignin, and other high-value products like bromelain y saponin- are described, as well as the primary processes for their ex-traction via biorefinery and main applications in the medical field. Finally, a brief description of the main works in the literature involving modeling and simulation studies of pineapple by-products properties is included.

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.

Endophytes in Lignin Valorization: A Novel Approach

Lignin, one of the essential components of lignocellulosic biomass, comprises an abundant renewable aromatic resource on the planet earth. Although 15%––40% of lignocellulose pertains to lignin, its annual valorization rate is less than 2% which raises the concern to harness and/or develop effective technologies for its valorization. The basic hindrance lies in the structural heterogeneity, complexity, and stability of lignin that collectively makes it difficult to depolymerize and yield common products. Recently, microbial delignification, an eco-friendly and cheaper technique, has attracted the attention due to the diverse metabolisms of microbes that can channelize multiple lignin-based products into specific target compounds. Also, endophytes, a fascinating group of microbes residing asymptomatically within the plant tissues, exhibit marvellous lignin deconstruction potential. Apart from novel sources for potent and stable ligninases, endophytes share immense ability of depolymerizing lignin into desired valuable products. Despite their efficacy, ligninolytic studies on endophytes are meagre with incomplete understanding of the pathways involved at the molecular level. In the recent years, improvement of thermochemical methods has received much attention, however, we lagged in exploring the novel microbial groups for their delignification efficiency and optimization of this ability. This review summarizes the currently available knowledge about endophytic delignification potential with special emphasis on underlying mechanism of biological funnelling for the production of valuable products. It also highlights the recent advancements in developing the most intriguing methods to depolymerize lignin. Comparative account of thermochemical and biological techniques is accentuated with special emphasis on biological/microbial degradation. Exploring potent biological agents for delignification and focussing on the basic challenges in enhancing lignin valorization and overcoming them could make this renewable resource a promising tool to accomplish Sustainable Development Goals (SDG’s) which are supposed to be achieved by 2030.

Recent Biotechnology Advances in Bio-Conversion of Lignin to Lipids by Bacterial Cultures

The complexity and recalcitrance of the lignin structure is a major barrier to its efficient utilization and commercial production of high-value products. In recent years, the “bio-funneling” transformation ability of microorganisms has provided a significant opportunity for lignin conversion and integrated biorefinery. Based on the chemical structure of lignin, this mini-review introduces the recent advances of lignin depolymerization by bacterial strains and the application of microbial lignin degradation in lipids production. Furthermore, the current challenges, future trends and perspectives for microbe-based lignin conversion to lipids are discussed.

Microbial valorization of lignin: Prospects and challenges

Lignin is the world's second most prevalent biomaterial, but its effective value-added product valorization methods are still being developed. The most common preparation processes for converting lignin to platform chemicals and biofuels are fragmentation and depolymerization. Due to its structural diversity, fragmentation generally produces a variety of products, necessitating tedious separation and purifying methods to isolate the desired products. Bacterial-based techniques are commonly utilized for lignin fragmentation due to their high metabolitic activity. Recent advancements in lignin valorization utilizing bacteria, such as lignin decomposing microbes and major pathways involved that can breakdown lignin into various valuable products namely lipids, furfural, vanillin, polyhydroxybutyrate, poly lactic acid blends were discussed in this review. This review also covers the genetic and fermentation methodologies to enhance lignin decomposition, challenges and future trends of microbe based lignin valorization.