Agro-industrial lignocellulosic biomass a key to unlock the future bio-energy: A brief review

Process Intensification of the Continuous Synthesis of Bio-Derived Monomers for Sustainable Coatings Using a Taylor Vortex Flow Reactor

We describe the optimization and scale-up of two consecutive reaction steps in the synthesis of bio-derived alkoxybutenolide monomers that have been reported as potential replacements for acrylate-based coatings (Sci. Adv.2020, 6, eabe0026). These monomers are synthesized by (i) oxidation of furfural with photogenerated singlet oxygen followed by (ii) thermal condensation of the desired 5-hydroxyfuranone intermediate product with an alcohol, a step which until now has involved a lengthy batch reaction. The two steps have been successfully telescoped into a single kilogram-scale process without any need to isolate the 5-hydroxyfuranone between the steps. Our process development involved FTIR reaction monitoring, FTIR data analysis via 2D visualization, and two different photoreactors: (i) a semicontinuous photoreactor based on a modified rotary evaporator, where FTIR and 2D correlation spectroscopy (2D-COS) revealed the loss of the methyl formate coproduct, and (ii) our fully continuous Taylor Vortex photoreactor, which enhanced the mass transfer and permitted the use of near-stoichiometric equivalents of O2. The use of in-line FTIR monitoring and modeling greatly accelerated process optimization in the Vortex reactor. This led to scale-up of the photo-oxidation in 85% yield with a projected productivity of 1.3 kg day-1 and a space-time yield of 0.06 mol day-1 mL-1. Higher productivities could be achieved while sacrificing yield (e.g., 4 kg day-1 at 40% yield). The use of superheated methanol at 200 °C in a pressurized thermal flow reactor accelerated the second step, the thermal condensation of 5-hydroxyfuranone, from a 20 h batch reflux reaction (0.5 L, 85 g) to a space time of <1 min in a reactor only 3 mL in volume operating with projected productivities of >700 g day-1. Proof of concept for telescoping the two steps was established with an overall two-step yield of 67%, producing a process with a projected productivity of 1.1 kg day-1 for the methoxybutenolide monomer without any purification of the 5-hydroxyfuranone intermediate.

Valorization of crop residues and animal wastes: Anaerobic co-digestion technology

To switch the over-reliance on fossil-based resources, curb environmental quality deterioration, and promote the use of renewable fuels, much attention has recently been directed toward the implementation of sustainable and environmentally benign 'waste-to-energy' technology exploiting a clean, inexhaustible, carbon-neutral, and renewable energy source, namely agricultural biomass. From this perspective, anaerobic co-digestion (AcoD) technology emerges as a potent and plausible approach to attain sustainable energy development, foster environmental sustainability, and, most importantly, circumvent the key challenges associated with mono-digestion. This review article provides a comprehensive overview of AcoD as a biochemical valorization pathway of crop residues and livestock manure for biogas production. Furthermore, this manuscript aims to assess the different biotic and abiotic parameters affecting co-digestion efficiency and present recent advancements in pretreatment technologies designed to enhance feedstock biodegradability and conversion rate. It can be concluded that the substantial quantities of crop residues and animal waste generated annually from agricultural practices represent valuable bioenergy resources that can contribute to meeting global targets for affordable renewable energy. Nevertheless, extensive and multidisciplinary research is needed to evolve the industrial-scale implementation of AcoD technology of livestock waste and crop residues, particularly when a pretreatment phase is included, and bridge the gap between small-scale studies and real-world applications.

Cellulolytic and Ethanologenic Evaluation of Heterotermes indicola's Gut-Associated Bacterial Isolates

Cellulose is the basic component of lignocellulosic biomass (LCB) making it a suitable substrate for bioethanol fermentation. Cellulolytic and ethanologenic bacteria possess cellulases that convert cellulose to glucose, which in turn yields ethanol subsequently. Heterotermes indicola is a subterranean termite that causes destructive damage by consuming wooden structures of infrastructure, LCB products, etc. Prospectively, the study envisioned the screening of cellulolytic and ethanologenic bacteria from the termite gut. Twenty six bacterial strains (H1-H26) based on varied colonial morphologies were isolated. Bacterial cellulolytic activity was tested biochemically. Marked gas production in the form of bubbles (0.1-4 cm) in Durham tubes was observed in H3, H7, H13, H15, H17, H21, and H22. Sugar degradation of all isolates was indicated by pink to maroon color development with the tetrazolium salt. Hallow zones (0.42-11 mm) by Congo red staining was exhibited by all strains except H2, H7, H8, and H19. Among the 26 bacterial isolates, 12 strains were identified as efficient cellulolytic bacteria. CMCase activity and ethanol titer of all isolates varied from 1.30 ± 0.03 (H13) to 1.83 ± 0.01 (H21) umol/mL/min and 2.36 ± 0.01 (H25) to 7.00 ± 0.01 (H21) g/L, respectively. Likewise, isolate H21 exhibited an ethanol yield of 0.40 ± 0.10 g/g with 78.38 ± 2.05% fermentation efficiency. Molecular characterization of four strains, Staphylococcus sp. H13, Acinetobacter baumanni H17, Acinetobacter sp. H21, and Acinetobacter nosocomialis H22, were based on the maximum cellulolytic index and the ethanol yield. H. indicola harbor promising and novel bacteria with a natural cellulolytic tendency for efficient bioconversion of LCB to value-added products. Hence, the selected cellulolytic bacteria can become an excellent addition for use in enzyme purification, composting, and production of biofuel at large.

The green novel approach in hydrolysis of pistachio shell into xylose by microwave-assisted high-pressure CO2 /H2 O

BACKGROUND

Pistachio shell is a valuable lignocellulosic biomass because almost 90% of its hemicellulose fraction is xylan, which can be converted into high value-added compounds such as xylooligosaccarides, xylose, xylitol and furfural. The present study represents a green and novel approach to produce xylose from lignocellulosic biomass. Microwave-assisted high-pressure CO2 /H2 O hydrolysis (MW-HPCO2 ) comprising a combination never previously used was performed to produce xylose from pistachio shell.

RESULTS

Response surface methodology with a Box-Behnken design was implemented to optimize microwave-assisted high-pressure CO2 /H2 O hydrolysis (MW-HPCO2 ). The effect of temperature, time and liquid-to-solid ratio was studied in the ranges of 180-210 °C, 10-30 min and 5-30 mL g-1 , respectively. A maximum xylose yield of 61.39% and minimum degradation compounds (5-hydroxymethyl furfural and furfural) of 11.07% were attained under reaction conditions of 190 °C, 30 min and 18 mL g-1 .

CONCLUSION

The results showed that hydrolysis temperature, time and liquid-to-solid ratio had a strong influence on the xylose yield, as well as on the formation of degradation compounds. MW-HPCO2 significantly increased accessibility to cellulose-derived products in the subsequent enzymatic hydrolysis. The results of the present study reveal that MW-HPCO2 can be a promising green technique for the hydrolysis of lignocellulosic biomass. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Exploring the potential of a new thermotolerant xylanase from Rasamsonia composticola (XylRc): production using agro-residues, biochemical studies, and application to sugarcane bagasse saccharification

Xylanases from thermophilic fungi have a wide range of commercial applications in the bioconversion of lignocellulosic materials and biobleaching in the pulp and paper industry. In this study, an endoxylanase from the thermophilic fungus Rasamsonia composticola (XylRc) was produced using waste wheat bran and pretreated sugarcane bagasse (PSB) in solid-state fermentation. The enzyme was purified, biochemically characterized, and used for the saccharification of sugarcane bagasse. XylRc was purified 30.6-fold with a 22% yield. The analysis using sodium dodecyl sulphate-polyacrylamide gel electrophoresis revealed a molecular weight of 53 kDa, with optimal temperature and pH values of 80 °C and 5.5, respectively. Thin-layer chromatography suggests that the enzyme is an endoxylanase and belongs to the glycoside hydrolase 10 family. The enzyme was stimulated by the presence of K+, Ca2+, Mg2+, and Co2+ and remained stable in the presence of the surfactant Triton X-100. XylRc was also stimulated by organic solvents butanol (113%), ethanol (175%), isopropanol (176%), and acetone (185%). The Km and Vmax values for oat spelt and birchwood xylan were 6.7 ± 0.7 mg/mL, 2.3 ± 0.59 mg/mL, 446.7 ± 12.7 µmol/min/mg, and 173.7 ± 6.5 µmol/min/mg, respectively. XylRc was unaffected by different phenolic compounds: ferulic, tannic, cinnamic, benzoic, and coumaric acids at concentrations of 2.5-10 mg/mL. The results of saccharification of PSB showed that supplementation of a commercial enzymatic cocktail (Cellic® CTec2) with XylRc (1:1 w/v) led to an increase in the degree of synergism (DS) in total reducing sugar (1.28) and glucose released (1.05) compared to the control (Cellic® HTec2). In summary, XylRc demonstrated significant potential for applications in lignocellulosic biomass hydrolysis, making it an attractive alternative for producing xylooligosaccharides and xylose, which can serve as precursors for biofuel production.

Non-fuel applications of bio-oil for sustainability in management of bioresources

Biomass valorization by thermochemical conversion method is a promising and intriguing pathway due to the flexibility of utilizing a diverse group of biomass and biowastes, specific product delivery mechanism through manipulation of process parameters, and wide applicability of the products. Pyrolysis has been viewed as an effective valorization technique to transform biowastes into pyrolytic oil, solid char, and syngas. Syngas is generally fed to the pyrolysis process to generate heat necessary for the pyrolysis process to sustain. Pyrolysis may also be a subsidiary component in a biorefinery system where it draws feedstocks from refinery process residues or the side streams of the refinery operation. In recent times, pyrolysis products have been under intense research for their usability and diverse applicability. Bio-oil's rich chemical makeup has promising potential to be used as an advanced biofuel and is considered as a storehouse of diverse chemical species ranging from green solvents to bioactive chemicals. The current review provides a state of knowledge on non-fuel uses of bio-oil and concludes that the pyrolysis process and products could be a part of the future bioeconomy if designed in a manner that biowastes are transformed into value-added products which replace products of petroleum origin.

Opuntia ficus indica cladode as fermentation feedstock for lactic acid production by Lactobacillus acidophilus LA 5

Opuntia ficus-indica cladodes are by-products which contain high amounts of fibres, bioactive and functional compounds. Given their high annual productivity per hectare, cladodes represent a cheap and suitable substrate, usable for fermentation processes. We investigated their potential as a substrate for the growth and production of lactic acid from Lactobacillus acidophilus LA-5. A separate hydrolysis and fermentation was performed. The concentration of reducing sugars obtained after the dilute acid and enzymatic hydrolysis was 28.45 g/L. The lactobacillus count ranged from 6.03 to 8.1 log CFU/mL, whereas lactic acid yield and productivity were 0.63 g/g and 0.73 g/L h, respectively. The maximum lactic acid concentration was found to be 17.5 g/L. This study reports the possibility of using the O. ficus indica cladode for lactic acid production by LA-5 aiming to reduce costs for sustainable industrial production.

Influence of Novel EnZolv Pretreatment on the Release of Reducing Sugar and Proximate Content of Banana Fiber

Lignocellulosic biomass (LCB) from agriculture residues has gained a lot of attention in recent years for its conversion to useful by-products. The one drawback that the conversion of biomass faces is its recalcitrant nature which can be overcome by effective pretreatment technology. One such process is the EnZolv, a novel pretreatment technique used for delignification of biomass and it was recognized as an eco-friendly approach. The main objective of our present study is to optimize the novel EnZolv process parameters for enhanced release of reducing sugar from banana fiber. Banana fiber pre-optimization for EnZolv pretreated at 100% moisture content, incubated at 40 °C temperature, with an enzyme load of 50 U·g-1 of biomass for an incubation time of 5 h at a shaking speed of 100 rpm yielded enhanced sugar release of 1.7 mg·mL-1. The effect of pretreatment on proximate composition results in a decrease in the volatile matter (53%) and moisture percentage (1.07%) and an increase in the other parameters such as ash content (12%) and fixed carbon content (34%) under the optimized condition. A significantly higher release of phenol content 1264 µg·mL-1 equivalent to gallic acid suggests that EnZolv pretreatment confirms the degradation of lignin content in the biomass.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12088-023-01130-4.

Nanocellulose-based aerogels for water purification: A review

Water purification using thin membranes at high pressures through adsorption and size exclusion is the widely used mechanism due to its simplicity and enhanced efficiency compared to other traditional water purification methods. Aerogels have the potential to replace conventional thin membranes considering their unmatched adsorption/absorption capacity and higher water flux due to their unique highly porous (99 %) 3D structure, ultra-low density (~1.1 to 500 mg/cm³), and very high surface area. The availability of a large number of functional groups, surface tunability, hydrophilicity, tensile strength and flexibility of nanocellulose (NC) makes it a potential candidate for aerogel preparation. This review discusses the preparation and employment of NC-based aerogels in the removal of dyes, metal ions and oils/organic solvents. It also offers recent updates on the effect of various parameters that enhance its adsorption/absorption performance. The future perspectives of NC aerogels and their performance with the emerging materials chitosan and graphene oxide are also compared.

Cellulose nanocrystals from agricultural residues (Eichhornia crassipes): Extraction and characterization

Extraction of cellulose nanocrystals (CNCs) from agro-residues has received much attention, not only for their unique properties supporting a wide range of potential applications, but also their limited risk to global climate change. This research was conducted to assess Nile roses (Eichhornia crassipes) fibers as a natural biomass to extract CNCs through an acid hydrolysis approach. Nile roses fibers (NRFs) were initially subjected to alkaline (pulping) and bleaching pretreatments. Microcrystalline cellulose (MCC) was used as control in comparison to Nile rose based samples. All samples underwent acid hydrolysis process at a mild temperature (45 °C). The impact of extraction durations ranging from 5 to 30 min on the morphology structure and crystallinity index of the prepared CNCs was investigated. The prepared CNCs were subjected to various characterization techniques, namely: X-ray diffraction (XRD), FT-IR analysis, Transmission electron microscopy (TEM), and X-ray Photoelectron spectroscopy (XPS). The outcomes obtained by XRD showed that the crystallinity index increased as the duration of acid hydrolysis was prolonged up to 10 min, and then decreased, indicating optimal conditions for the dissolution of amorphous zones of cellulose before eroding the crystallized domains. These data were confirmed by FT-IR spectroscopy. However, a minor effect of hydrolysis duration on the degree of crystallinity was noticed for MCC based samples. TEM images illustrated that a spherical morphology of CNCs was formed as a result of 30 min acid hydrolysis, highlighting the optimal 20 min acid hydrolysis to obtain a fibrillar structure. The XPS study demonstrated that the main constituents of extracted CNCs were carbon and oxygen.

Recovery of valuable metals from spent lithium-ion batteries using microbial agents for bioleaching: a review

Spent lithium-ion batteries (LIBs) are increasingly generated due to their widespread use for various energy-related applications. Spent LIBs contain several valuable metals including cobalt (Co) and lithium (Li) whose supply cannot be sustained in the long-term in view of their increased demand. To avoid environmental pollution and recover valuable metals, recycling of spent LIBs is widely explored using different methods. Bioleaching (biohydrometallurgy), an environmentally benign process, is receiving increased attention in recent years since it utilizes suitable microorganisms for selective leaching of Co and Li from spent LIBs and is cost-effective. A comprehensive and critical analysis of recent studies on the performance of various microbial agents for the extraction of Co and Li from the solid matrix of spent LIBs would help for development of novel and practical strategies for effective extraction of precious metals from spent LIBs. Specifically, this review focuses on the current advancements in the application of microbial agents namely bacteria (e.g., Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans) and fungi (e.g., Aspergillus niger) for the recovery of Co and Li from spent LIBs. Both bacterial and fungal leaching are effective for metal dissolution from spent LIBs. Among the two valuable metals, the dissolution rate of Li is higher than Co. The key metabolites which drive the bacterial leaching include sulfuric acid, while citric acid, gluconic acid and oxalic acid are the dominant metabolites in fungal leaching. The bioleaching performance depends on both biotic (microbial agents) and abiotic factors (pH, pulp density, dissolved oxygen level and temperature). The major biochemical mechanisms which contribute to metal dissolution include acidolysis, redoxolysis and complexolysis. In most cases, the shrinking core model is suitable to describe the bioleaching kinetics. Biological-based methods (e.g., bioprecipitation) can be applied for metal recovery from the bioleaching solution. There are several potential operational challenges and knowledge gaps which should be addressed in future studies to scale-up the bioleaching process. Overall, this review is of importance from the perspective of development of highly efficient and sustainable bioleaching processes for optimum resource recovery of Co and Li from spent LIBs, and conservation of natural resources to achieve circular economy.

Valorization of Food Waste Slurry as Potential Candidate for Lipid Accumulation: A Concept of Oleaginous Bio-Refinery

In the current state of huge waste production and energy crisis, there is a need to find additional alternate energy resources and options for waste management. The present study was designed to measure the potential of different fruit wastes to serve as substrate for lipid accumulation in oleaginous bacteria. For this purpose, three novel bacterial strains (AF3, KM1 and KM10) isolated from the crude oil samples were systematically compared for their lipid accumulation potential using three types of waste including orange waste (OW), mango waste (MW) and apple waste (AW). Using waste as sole substrate, it was observed that maximum lipid accumulation by each strain was above 20%, which confirms that the bacteria belong to the oleaginous group. However, each bacterial isolate represented differential accumulative capacity with varying organic matter removal efficiency. Maximum lipid accumulation was achieved by KM10 (>25%) with AW as substrate, and KM1 (>24%) with MW as substrate; however, AF3 represented only 21% lipid accumulation using AW as substrate. Similarly, the maximum removal efficiency was recorded for KM10 in AW, followed by OW, where >60% and >50% of volatile solids (VS) removal, respectively, were achieved over the period of 7 days of incubation. This showed that the oleaginous strains also exhibit excellent waste treatment efficiency. The 16s RNA gene sequencing results showed that these KM1 and KM10 strains were Serratia surfactantfaciens and Serratia liquefaciens. In the end, a circular economy model was presented to highlight the significance of the mechanisms, which offers dual benefits over the linear economy model. Overall, the findings of the present study revealed that the novel oleaginous strains not only provide considerable lipid accumulation, but are simultaneously capable of low-cost waste treatment.

Pretreatments of lignocellulosic and algal biomasses for sustainable biohydrogen production: Recent progress, carbon neutrality, and circular economy

Lignocellulosic and algal biomasses are known to be vital feedstocks to establish a green hydrogen supply chain toward achieving a carbon-neutral society. However, one of the most pressing issues to be addressed is the low digestibility of these biomasses in biorefinery processes, such as dark fermentation, to produce green hydrogen. To date, various pretreatment approaches, such as physical, chemical, and biological methods, have been examined to enhance feedstock digestibility. However, neither systematic reviews of pretreatment to promote biohydrogen production in dark fermentation nor economic feasibility analyses have been conducted. Thus, this study offers a comprehensive review of current biomass pretreatment methods to promote biohydrogen production in dark fermentation. In addition, this review has provided comparative analyses of the technological and economic feasibility of existing pretreatment techniques and discussed the prospects of the pretreatments from the standpoint of carbon neutrality and circular economy.

Molecular breeding of barley for quality traits and resilience to climate change

Barley grains are a rich source of compounds, such as resistant starch, beta-glucans and anthocyanins, that can be explored in order to develop various products to support human health, while lignocellulose in straw can be optimised for feed in husbandry, bioconversion into bioethanol or as a starting material for new compounds. Existing natural variations of these compounds can be used to breed improved cultivars or integrated with a large number of mutant lines. The technical demands can be in opposition depending on barley's end use as feed or food or as a source of biofuel. For example beta-glucans are beneficial in human diets but can lead to issues in brewing and poultry feed. Barley breeders have taken action to integrate new technologies, such as induced mutations, transgenics, marker-assisted selection, genomic selection, site-directed mutagenesis and lastly machine learning, in order to improve quality traits. Although only a limited number of cultivars with new quality traits have so far reached the market, research has provided valuable knowledge and inspiration for future design and a combination of methodologies to achieve the desired traits. The changes in climate is expected to affect the quality of the harvested grain and it is already a challenge to mitigate the unpredictable seasonal and annual variations in temperature and precipitation under elevated [CO₂] by breeding. This paper presents the mutants and encoded proteins, with a particular focus on anthocyanins and lignocellulose, that have been identified and characterised in detail and can provide inspiration for continued breeding to achieve desired grain and straw qualities.

Discovery of novel carbohydrate degrading enzymes from soda lakes through functional metagenomics

Extremophiles provide a one-of-a-kind source of enzymes with properties that allow them to endure the rigorous industrial conversion of lignocellulose biomass into fermentable sugars. However, the fact that most of these organisms fail to grow under typical culture conditions limits the accessibility to these enzymes. In this study, we employed a functional metagenomics approach to identify carbohydrate-degrading enzymes from Ethiopian soda lakes, which are extreme environments harboring a high microbial diversity. Out of 21,000 clones screened for the five carbohydrate hydrolyzing enzymes, 408 clones were found positive. Cellulase and amylase, gave high hit ratio of 1:75 and 1:280, respectively. A total of 378 genes involved in the degradation of complex carbohydrates were identified by combining high-throughput sequencing of 22 selected clones and bioinformatics analysis using a customized workflow. Around 41% of the annotated genes belonged to the Glycoside Hydrolases (GH). Multiple GHs were identified, indicating the potential to discover novel CAZymes useful for the enzymatic degradation of lignocellulose biomass from the Ethiopian soda Lakes. More than 73% of the annotated GH genes were linked to bacterial origins, with Halomonas as the most likely source. Biochemical characterization of the three enzymes from the selected clones (amylase, cellulase, and pectinase) showed that they are active in elevated temperatures, high pH, and high salt concentrations. These properties strongly indicate that the evaluated enzymes have the potential to be used for applications in various industrial processes, particularly in biorefinery for lignocellulose biomass conversion.

Sustainable biopolyol production via solvothermal liquefaction silvergrass saccharification residue: Experimental, economic, and environmental approach

With the rising environmental concern, sustainable chemistry should be accomplished by considering technical, economic, and environmental factors that guarantee the successful implementation of new alternative products. Hence, we performed the integrated techno-economic and life cycle assessment for two-step solvothermal liquefaction (two-pot synthesis) and simplified solvothermal liquefaction (one-pot synthesis) based on experiment results. Based on the itemized cost estimation, the unit biopolyol production costs obtained from the two-pot synthesis and one-pot synthesis were 10.0 $ kg^-1 and 2.89 $ kg^-1, respectively. To provide techno-economic guidelines for biopolyol production, profitability analysis, and uncertainty analysis were used to identify the economic feasibility of the proposed processes. In addition, the life cycle assessment results indicated that biopolyol production via the two-pot synthesis leads to a slightly lower greenhouse gas emission compared with the one-pot synthesis, which further required the use of an analytic hierarchy process to determine the best process for biopolyol production depending on the different weight points in the economic and environmental aspects. From these results, we can provide the technical performance, economic feasibility, and environmental impact of lab-scale biopolyol production from silvergrass residue, a low-cost waste of biomass saccharification.

Enhancement of healthful novel sugar contents in genetically engineered sugarcane juice integrated with molecularly characterized ThSyGII (CEMB-SIG2)

Enhancement of sugar contents and yielding healthful sugar products from sugarcane demand high profile scientific strategies. Previous efforts to foster manipulation in metabolic pathways or triggering sugar production through combating abiotic stresses fail to yield high sugar recovery in Saccharum officinarum L. Novel sucrose isomers trehalulose (TH) and isomaltulose (IM) are naturally manufactured in microbial sources. In pursuance of novel scientific methodology, codon optimized sucrose isomerase gene, Trehalulose synthase gene II(CEMB-SIG2) cloned under dual combined stem specific constitutive promoters in pCAMBIA1301 expression vector integrated with Vacuole targeted signal peptide (VTS) to concentrate gene product into the vacuole. The resultant mRNA expression obtained by Real Time PCR validated extremely increased transgene expression in sugarcane culms than leaf tissues. Overall sugar estimation from transgenic sugarcane lines was executed through refractometer. HPLC based quantifications of Trehalulose (TH) alongside different internodes of transgenic sugarcane confirmed the enhancement of boosted sugar concentrations in mature sugarcane culms. Trehalulose synthase gene II receptive sugarcane lines indicated the unprecedented impressions of duly combined constitutive stem regulated promoters. Transgenic sugarcane lines produce highest sugar recovery percentages, 14.9% as compared to control lines (8.5%). The increased sugar recovery percentage in transgenic sugarcane validated the utmost performance and expression of ThSyGII gene .High Profile Liquid chromatography based sugar contents estimation of Trehalulose (TH) and Isomaltulose (IM) yielded unprecedented improvement in the whole sugar recovery percentage as compared to control lines.⁠.

Potential of lignocellulose degrading microorganisms for agricultural residue decomposition in soil: A review

Lignocellulosic crop residues (LCCRs) hold a significant share of the terrestrial biomass, estimated at 5 billion Mg per annum globally. A massive amount of these LCCRs are burnt in many countries resulting in immense environmental pollution; hence, its proper disposal in a cost-effective and eco-friendly manner is a significant challenge. Among the different options for management of LCCRs, the use of lignocellulose degrading microorganisms (LCDMOs), like fungi and bacteria, has emerged as an eco-friendly and effective way for its on-site disposal. LCDMOs achieve degradation through various mechanisms, including multiple supportive enzymes, causing oxidative attacks by which recalcitrance of lignocellulose material is reduced, paving the way to further activity by depolymerizing enzymes. This improves the physical properties of soil, recycles plant nutrients, promotes plant growth and thus helps improve productivity. Rapid and proper microbial degradation may be achieved through the correct combination of the LCDMOs, supplementing nutrients and controlling different factors affecting microbial activity in the field. The review is a critical discussion of previous studies revealing the potential of individuals or a set of LCDMOs, factors controlling the rate of degradation and the key researchable areas for better understanding of the role of these decomposers for future use.

Biomass Valorization to Chemicals over Cobalt Nanoparticles on SBA-15

A series of heterogeneous catalysts based on cobalt supported on SBA-15 were prepared through wet impregnation and co-impregnation assisted by ethylene glycol (EG) methods. The cobalt oxide catalysts generated after the drying and calcination process were denoted as CoO/SBA-15w and CoO/SBA-15c for a wet- and co-impregnation method, respectively. Subsequent to the reduction process, the reduced cobalt catalysts were obtained and denoted as Co/SBA-15w and Co/SBA-15c. The TEM images revealed the catalysts prepared through these methods show very clear distinctions that the catalyst prepared by wet impregnation shows large aggregates of cobalt particles on the external surface of SBA-15 due to their inability to enter the channels. The catalysts were evaluated on the hydrocracking of pyrolyzed -cellulose as a biomass model. The results showed that the reduced cobalt-based catalysts are having higher conversion value and selectivity towards the 2-furancarboxaldehyde reached ca. 20%. Copyright © 2022 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA   License (https://creativecommons.org/licenses/by-sa/4.0). 

Prospects of soil microbiome application for lignocellulosic biomass degradation: An overview

Sustainable and practically viable biofuels production technology using lignocellulosic biomass is still seeking its way of implementation owing to some major issues involved therein. Unavailability of efficient microbial sources for the degradation of cellulosic biomass is one of the major roadblocks in biomass to biofuels production technology. In this context, utilization of microbiomes to degrade lignocellulaosic biomass is emerging as a rapid and effective approach that can fulfill the requirements of biomass based biofuels production technology. Therefore, the present review is targeted to explore soil metagenomic approach to improve the lignocellulosic biomass degradation processing for the cost-effective and eco-friendly application. Soil microbiomes consist of rich microbial community along with high probability of cellulolytic microbes, and can be identified by culture independent metagenomics method which can be structurally and functionally explored via genomic library. Therefore, in depth analysis and discussion have also been made via structural & functional metagenomics tools along with their contribution to genomic library. Additionally, the present review highlights currently existing bottlenecks along with their feasible solutions. This review will help to understand the basic research as well as industrial concept for the process improvement based on soil microbiome mediated lignocellulosic biomass degradation, and this may likely to implement for the low-cost commercial biofuels production technology.

Systematic review on lignin valorization in the agro-food system: From sources to applications

Lignocellulosic biomass is the most abundant renewable resource on earth and currently most of this biomass is considered a low-value waste. Specifically, lignin is an underrated bioresource that is mostly burned for energy production and few value-added products have been created. Since the agro-food industry produces large amounts of wastes that can be potential sources of high-quality lignin, scientific efforts should be directed to this industry. Thus, this review provides a systematic overview of the trends and evolution of research on agro-food system-derived lignin (from 2010 to 2020), including the extraction of lignin from various agro-food sources and emergent applications of lignin in the agro-food chain. Crops with the highest average production/year (n = 26) were selected as potential lignin sources. The extraction process efficiency (yield) and lignin purity were used as indicators of the raw material potential. Overall, it is notable that research interest on agro-food lignin has increased exponentially over the years, both as source (567%) and application (128%). Wheat, sugarcane, and maize are the most studied sources and are the ones that render the highest lignin yields. As for the extraction methods used, alkaline and organosolv methods are the most employed (∼50%). The main reported applications are related to lignin incorporation in polymers (∼55%) and as antioxidant (∼24%). Studies on agro-food system-derived lignin is of most importance since there are numerous possible sources that are yet to be fully valorized and many promising applications that need to be further developed.

Single Cell Protein Production Using Different Fruit Waste: A Review

The single cell protein (SCP) technique has become a popular technology in recent days, which addresses two major issues: increasing world protein deficiency with increasing world population and the generation of substantial industrial wastes with an increased production rate. Global fruit production has increased over the decades. The non-edible parts of fruits are discarded as wastes into the environment, which may result in severe environmental issues. These fruit wastes are rich in fermentable sugars and other essential nutrients, which can be effectively utilized by microorganisms as an energy source to produce microbial protein. Taking this into consideration, this review explores the use of fruit wastes as a substrate for SCP production. Many studies reported that the wastes from various fruits such as orange, sweet orange, mango, banana, pomegranate, pineapple, grapes, watermelon, papaya, and many others are potential substrates for SCP production. These SCPs can be used as a protein supplement in human foods or animal feeds. This paper discusses various aspects in regard to the potential of fruit wastes as a substrate for SCP production.

Effects of Bioliquid Recirculation on Hydrothermal Carbonization of Lignocellulosic Biomass

The characteristics of bioliquid produced through the hydrothermal carbonization (HTC) of wood wastes and the effects of recirculation on hydrochar production were analyzed. The organic acids and total organic carbon of bioliquid increased with progressive recirculation, whereas intermediate byproducts decreased. Hydrochar production by bioliquid recirculation increased mass yield, carbon content, caloric value, and energy yield of the former, while improving its quality as a solid refuse fuel. We concluded that bioliquid recirculation promoted HTC, as demonstrated by Fourier-transform infrared spectroscopy. Furthermore, contrary to predictions, a relatively constant quantity of bioliquid was generated in each step, indicating that its continuous reuse is feasible. Therefore, bioliquid recirculation can improve hydrochar production while simultaneously mitigating the environmental impact of wastewater generation. This method should be considered an important strategy toward the implementation of carbon-neutrality goals.

Biogas Production Potential of Thermophilic Anaerobic Biodegradation of Organic Waste by a Microbial Consortium Identified with Metagenomics

Anaerobic digestion (AD) is a widespread biological process treating organic waste for green energy production. In this study, wheat straw and corn stalks without any harsh preliminary treatment were collected as a renewable source to be employed in a laboratory-scale digester to produce biogas/biomethane. Processes parameters of temperature, pH, total solids, volatile solid, concentration of volatile fatty acids (VFA), and cellulose concentration, were followed. The volume of biogas produced was measured. The impact of organic loading was stated, showing that the process at 55 °C tolerated a higher substrate load, up to 45 g/L. Further substrate increase did not lead to biogas accumulation increase, probably due to inhibition or mass transfer limitations. After a 12-day anaerobic digestion process, cumulative volumes of biogas yields were 4.78 L for 1 L of the bioreactor working volume with substrate loading 30 g/L of wheat straw, 7.39 L for 40 g/L and 8.22 L for 45 g/L. The degree of biodegradation was calculated to be 68.9%, 74% and 72%, respectively. A fast, effective process for biogas production was developed from native wheat straw, with the highest quantity of daily biogas production occurring between day 2 and day 5. Biomethane concentration in the biogas was 60%. An analysis of bacterial diversity by metagenomics revealed that more than one third of bacteria belonged to class Clostridia (32.9%), followed by Bacteroidia (21.5%), Betaproteobacteria (11.2%), Gammaproteobacteria (6.1%), and Alphaproteobacteria (5%). The most prominent genera among them were Proteiniphilum, Proteiniborus, and Pseudomonas. Archaeal share was 1.37% of the microflora in the thermophilic bioreactor, as the genera Methanocorpusculum, Methanobacterium, Methanomassiliicoccus, Methanoculleus, and Methanosarcina were the most abundant. A knowledge of the microbiome residing in the anaerobic digester can be further used for the development of more effective processes in conjunction with theidentified consortium.

Efficiently unsterile polyhydroxyalkanoate production from lignocellulose by using alkali-halophilic Halomonas alkalicola M2

The alkali-halophilic Halomonas alkalicola M2 was isolated and developed for an open unsterile polyhydroxyalkanoate (PHA) fermentation from lignocellulose at pH 10.0 and NaCl 70 g/L. The alkaline pretreatment liquid (APL) was converted into PHA by the strain, which was significantly affected by the cultural conditions, including pH, NaCl concentration, nitrogen source, and APL concentration. The extracted PHA was composed of three monomers and similar in physicochemical properties to conventional short chain-length PHA. A record yield of 2.1 and 5.9 g of PHA was accumulated from 100 g dry bamboo powder (BP) by using APL and APL combined with hydrolysate during a 48-h open unsterile fermentation process, respectively. In summary, the alkali-halophilic H. alkalicola M2 achieved the open unsterile fermentation for lignocellulose efficient bioconversion into PHA under high alkalinity and salinity conditions and would be an ideal producer in the field.

Optimization of Liquid Hot Water Pretreatment and Fermentation for Ethanol Production from Sugarcane Bagasse Using Saccharomyces cerevisiae

Sugarcane bagasse can be considered a potential raw material in terms of quantity and quality for the production of alternative biofuels. In this research, liquid hot water (LHW) was studied as a pretreatment process to enhance the digestibility of pretreated material for further conversion into bioethanol. Different variables (temperature, residual time, and acid concentration) were determined to predict the optimized condition. LHW pretreatment showed an impact on the hemicellulose structure. The optimized condition at 160 °C for 60 min with 0.050 M acid concentration reached the highest glucose yield of 96.86%. Scanning electron microscopy (SEM) showed conspicuous modification of the sugarcane bagasse structure. The effect of LHW pretreatment was also demonstrated by the changes in crystallinity and surface area analysis. FTIR techniques revealed the chemical structure changes of pretreated sugarcane bagasse. The prepared material was further converted into ethanol production with the maximized ethanol concentration of 19.9 g/L.

Impact of Cultivation Substrate and Microbial Community on Improving Mushroom Productivity: A Review

Simple Summary

Lignocellulosic material and substrate formulations affect mushroom productivity. The microbial community in cultivation substrates affects the quality of the substrates and the efficiency of mushroom production. The elucidation of the key microbes and their biochemical function can serve as a useful guide in the development of a more effective system for mushroom cultivation.

Abstract

Lignocellulosic materials commonly serve as base substrates for mushroom production. Cellulose, hemicellulose, and lignin are the major components of lignocellulose materials. The composition of these components depends upon the plant species. Currently, composted and non-composted lignocellulosic materials are used as substrates in mushroom cultivation depending on the mushroom species. Different substrate compositions can directly affect the quality and quantity of mushroom production yields. Consequently, the microbial dynamics and communities of the composting substrates can significantly affect mushroom production. Therefore, changes in both substrate composition and microbial diversity during the cultivation process can impact the production of high-quality substrates and result in a high degree of biological efficiency. A brief review of the current findings on substrate composition and microbial diversity for mushroom cultivation is provided in this paper. We also summarize the advantages and disadvantages of various methods of mushroom cultivation by analyzing the microbial diversity of the composting substrates during mushroom cultivation. The resulting information will serve as a useful guide for future researchers in their attempts to increase mushroom productivity through the selection of suitable substrate compositions and their relation to the microbial community.

Investigating the Processing Potential of Ethiopian Agricultural Residue Enset/Ensete ventricosum for Biobutanol Production

The Enset plant is a potential food source for about 20 million Ethiopians. A massive amount of residual byproduct is discarded from traditional Ethiopian Enset food processing. This study shows a compositional analysis of Enset biomass and its use for biobutanol production. The Enset biomass was pretreated with 2% (w/v) NaOH or 2% (v/v) H₂SO₄ and subjected to enzymatic hydrolysis. The enzymatic hydrolysates were then fermented anaerobically by C. saccharoperbutylacetonicum DSM 14923. The majority of Enset biomass waste samples contained 36–67% cellulose, 16–20% hemicelluloses, and less than 6.8% lignin. In all alkali-pretreated Enset biomass samples, the enzyme converted 80–90% of the biomass to glucose within 24 h, while it took 60 h to convert 48–80% of the acid-pretreated Enset biomass. In addition, the alkali pretreatment method released more glucose than the acid pretreatment in all Enset biomass samples. After 72 h of ABE fermentation, 2.8 g/L acetone, 9.9 g/L butanol, and 1.6 g/L ethanol were produced from mixed Enset waste hydrolysate pretreated with alkali, achieving an ABE yield of 0.32 g/g and productivity of 0.2 g × L⁻¹ × h⁻¹, showing the first value of butanol produced from Enset biomass in the literature.

Bioethanol Production from Spent Sugar Beet Pulp—Process Modeling and Cost Analysis

Global economic development has led to the widespread use of fossil fuels, and their extensive use has resulted in increased environmental pollution. As a result, significantly more attention is being paid to environmental issues and alternative renewable energy sources. Bioethanol production from agro-industrial byproducts, residues, and wastes is one example of sustainable energy production. This research aims to develop a process and cost model of bioethanol production from spent sugar beet pulp. The model was developed using SuperPro Designer® v.11 (Intelligen Inc., Scotch Plains, NJ, USA) software, and determines the capital and production costs for a bioethanol-producing plant processing about 17,000 tons of spent sugar beet pulp per year. In addition, the developed model predicts the process and economic indicators of the analyzed biotechnological process, determines the share of major components in bioethanol production costs, and compares different model scenarios for process co-products. Based on the obtained results, the proposed model is viable and represents a base case for further bioprocess development.

Lytic polysaccharide monooxygenases (LPMOs) producing microbes: A novel approach for rapid recycling of agricultural wastes

Out of the huge quantity of agricultural wastes produced globally, rice straw is one of the most abundant ligno-cellulosic waste. For efficient utilization of these wastes, several cost-effective biological processes are available. The practice of field level in-situ or ex-situ decomposition of rice straw is having less degree of adoption due to its poor decomposition ability within a short time span between rice harvest and sowing of the next crop. Agricultural wastes including rice straw are in general utilized by using lignocellulose degrading microbes for industrial metabolite or compost production. However, bioconversion of crystalline cellulose and lignin present in the waste, into simple molecules is a challenging task. To resolve this issue, researchers have identified a novel new generation microbial enzyme i.e., lytic polysaccharide monooxygenases (LPMOs) and reported that the combination of LPMOs with other glycolytic enzymes are found efficient. This review explains the progress made in LPMOs and their role in lignocellulose bioconversion and the possibility of exploring LPMOs producers for rapid decomposition of agricultural wastes. Also, it provides insights to identify the knowledge gaps in improving the potential of the existing ligno-cellulolytic microbial consortium for efficient utilization of agricultural wastes at industrial and field levels.

Fungal biorefinery for sustainable resource recovery from waste

Depletion of natural resources and negative impact of fossil fuels on environment are becoming a global concern. The concept of biorefinery is one of the alternative platforms for the production of biofuels and chemicals. Valorisation of biological resources through complete utilization of waste, reusing secondary products and generating energy to power the process are the key principles of biorefinery. Agricultural residues and biogenic municipal solid wastes are getting importance as a potential feedstock for the generation of bioproducts. This communication reviews and highlights the scope of yeast and fungi as a potent candidate for the synthesis of gamut of bioproducts in an integrated approach addressing sustainability and circular bioeconomy. It also provides a close view on importance of microbes in biorefinery, feedstock pretreatment strategies for renewable sugar production, cultivation systems and yeast and fungi based products. Integrated closed loop approach towards multiple product generation with zero waste discharge is also discussed.

Effect of Zinc-Calcium on Xylose Consumption by Mucor circinelloides (MN128960): Xylitol and Ethanol Yield Optimization

Xylose is the second most abundant monomeric sugar on earth. Nevertheless, metabolizing xylose into ethanol is a complex process due to several biochemical reactions. Some microorganisms of the genus Mucor are suitable for this bioprocess. Using metal ions, such as zinc and calcium, allows some fungal species to increase their ethanol yield. In this work, the wild strain Mucor spp. (C1502) was molecularly identified via internal transcribed spacer (ITS) sequencing. Secondly, an optimization using response surface methodology (RSM) with a central composite experimental design (CCD) was carried out. The independent variables (X) were ZnSO4·7H2O (X1, 0.0–1.5 g/L) and CaCl2 (X2, 0.0–2.5 g/L) concentration in the fermentation broth in order to demonstrate the effect of these ions, xylose was used as the only carbon source. The dependent variables (Y) measured were ethanol yield (Y1, g ethanol/g xylose) and xylitol yield (Y2, g xylitol/g xylose). The identified strain, Mucor circinelloides, was given the accession number MN128960 by the NCBI. Once the optimal concentrations of zinc and calcium were calculated, experimental validation was performed, with the highest ethanol and xylitol yields reaching 0.36 g ethanol/g xylose and 0.35 g xylitol/g xylose, respectively. This study demonstrated that increasing the xylitol yield using the effect of the ions, zinc and calcium, increases the ethanol yield. Furthermore, M. circinelloides (C1502) can produce metabolites, such as ethanol and xylitol, from the xylose obtained from hemicellulose biomasses, which can be used as a carbon source at low cost and with great availability.

Advancements in the Conversion of Lipid-Rich Biowastes and Lignocellulosic Residues into High-Quality Road and Jet Biofuels Using Nanomaterials as Catalysts

At present, the majority of available road and jet biofuels are produced from oleochemical feedstocks that include vegetable oils and biowastes such as waste cooking oils and animal fats. Additionally, one of the most promising ways to achieve long-term environmental goals is to sustainably use lignocellulosic residues. These resources must be treated through a deoxygenation process and subsequent upgrading processes to obtain high-quality road and jet biofuels. Accordingly, in this review, we explore recent advancements in the deoxygenation of oleochemical and lignocellulosic feedstocks in the absence of hydrogen to produce high-quality road and jet biofuels, mainly focusing on the use of nanomaterials as catalysts and the valorization of lipid-rich biowastes and lignocellulosic residues. As a result, we found that regardless of the catalyst particle size, the coexistence of basic sites and weak/medium acid sites is highly important in catalytic systems. Basic sites can enhance the removal of oxygenates via decarboxylation and decarbonylation reactions and inhibit coke formation, while weak/medium acid sites can enhance the cracking reaction. Additionally, the extraction of value-added derivatives from lignocellulosic residues and their subsequent upgrade require the use of advanced methods such as the lignin-first approach and condensation reactions.

Recent Advances in the Development of Fire-Resistant Biocomposites—A Review

Biocomposites reinforced with natural fibers represent an eco-friendly and inexpensive alternative to conventional petroleum-based materials and have been increasingly utilized in a wide variety of industrial applications due to their numerous advantages, such as their good mechanical properties, low production costs, renewability, and biodegradability. However, these engineered composite materials have inherent downsides, such as their increased flammability when subjected to heat flux or flame initiators, which can limit their range of applications. As a result, certain attempts are still being made to reduce the flammability of biocomposites. The combustion of biobased composites can potentially create life-threatening conditions in buildings, resulting in substantial human and material losses. Additives known as flame-retardants (FRs) have been commonly used to improve the fire protection of wood and biocomposite materials, textiles, and other fields for the purpose of widening their application areas. At present, this practice is very common in the construction sector due to stringent fire safety regulations on residential and public buildings. The aim of this study was to present and discuss recent advances in the development of fire-resistant biocomposites. The flammability of wood and natural fibers as material resources to produce biocomposites was researched to build a holistic picture. Furthermore, the potential of lignin as an eco-friendly and low-cost FR additive to produce high-performance biocomposites with improved technological and fire properties was also discussed in detail. The development of sustainable FR systems, based on renewable raw materials, represents a viable and promising approach to manufacturing biocomposites with improved fire resistance, lower environmental footprint, and enhanced health and safety performance.

Influence of microbial inoculants on co-composting of lignocellulosic crop residues with farm animal manure: A review

The rapidly developing agro-industry generates huge amounts of lignocellulosic crop residues and animal manure worldwide. Although co-composting represents a promising and cost-effective method to treat various agricultural wastes simultaneously, poor composting efficiency prolongs total completion time and deteriorates the quality of the final product. However, supplementation of the feedstock with beneficial microorganisms can mitigate these negative effects by facilitating the decomposition of recalcitrant materials, enhancing microbial enzyme activity, and promoting maturation and humus formation during the composting process. Nevertheless, the influence of microbial inoculation may vary greatly depending on certain factors, such as start-up parameters, structure of the feedstock, time of inoculation, and composition of the microbial cultures used. The purpose of this contribution is to review recent developments in co-composting procedures involving different lignocellulosic crop residues and farm animal manure combined with microbial inoculation strategies. To evaluate the effectiveness of microbial additives, the results reported in a large number of peer-reviewed articles were compared in terms of composting process parameters (i.e., temperature, microbial activity, total organic carbon and nitrogen contents, decomposition rate of lignocellulose fractions, etc.) and compost characteristics (humification, C/N ratio, macronutrient content, and germination index). Most studies confirmed that the use of microbial amendments in the co-composting process is an efficient way to facilitate biodegradation and improve the sustainable management of agricultural wastes. Overall, this review paper provides insights into various inoculation techniques, identifies the limitations and current challenges of co-composting, especially with microbial inoculation, and recommends areas for further research in this field.

Integrated biorefinery processes for conversion of lignocellulosic biomass to value added materials: Paving a path towards circular economy

Lignocellulosic biomass is an effective and sustainable alternative for petroleum-derived fuels and chemicals to produce biofuels and bio-based products. Despite the high availability, the degradation of biomass is a substantial challenge. Hence, it is necessary to integrate several unit processes such as biochemical, thermochemical, physical, and catalytic conversion to produce wide range of bio-based products. Integrating these processes enhances the yield, reduces the reaction time, and can be cost-effective. Process integration could significantly lead to various outcomes which guides towards the circular economy. This review addresses integration of several biorefinery processes for the production of multifaceted products. In addition, modern and sustainable biorefinery technologies are discussed to pave the path towards circular economy through the closed-loop approach.

Comparative Evaluation of Adsorption of Major Enzymes in a Cellulase Cocktail Obtained from Trichoderma reesei onto Different Types of Lignin

Cellulase adsorption onto lignin decreases the productivity of enzymatic hydrolysis of lignocellulosic biomass. Here, adsorption of enzymes onto different types of lignin was investigated, and the five major enzymes—cellobiohydrolases (CBHs), endoglucanase (Cel7B), β-glucosidase (Cel3A), xylanase (XYNIV), and mannanase (Man5A)—in a cellulase cocktail obtained from Trichoderma reesei were individually analyzed through SDS-PAGE and zymogram assay. Lignin was isolated from woody (oak and pine lignin) and herbaceous (rice straw and kenaf lignin) plants. The relative adsorption of CBHs compared to the control was in the range of 14.15–18.61%. The carbohydrate binding motif (CBM) of the CBHs contributed to higher adsorption levels in oak and kenaf lignin, compared to those in pine and rice lignin. The adsorption of endoglucanase (Cel7B) by herbaceous plant lignin was two times higher than that of woody lignin, whereas XYNIV showed the opposite pattern. β-glucosidase (Cel3A) displayed the highest and lowest adsorption ratios on rice straw and kenaf lignin, respectively. Mannanase (Man5A) was found to have the lowest adsorption ratio on pine lignin. Our results showed that the hydrophobic properties of CBM and the enzyme structures are key factors in adsorption onto lignin, whereas the properties of specific lignin types indirectly affect adsorption.

Valorization of agro-industrial wastes for biorefinery process and circular bioeconomy: A critical review

Energy recovery from waste resources is a promising approach towards environmental consequences. In the prospect of environmental sustainability, utilization of agro-industrial waste residues as feedstock for biorefinery processes have gained widespread attention. In the agro-industry, various biomasses are exposed to different unit processes for offering value to various agro-industrial waste materials. Agro-industrial wastes can generate a substantial amount of valuable products such as fuels, chemicals, energy, electricity, and by-products. This paper reviews the methodologies for valorization of agro-industrial wastes and their exploitation for generation of renewable energy products. In addition, management of agro-industrial wastes and products from agro-industrial wastes have been elaborated. The waste biorefinery process using agro-industrial wastes does not only offer energy, it also offers environmentally sustainable modes, which address effective management of waste streams. This review aims to highlight the cascading use of biomass from agro-industrial wastes into the systemic approach for economic development.

Lignocellulosic Biomass Valorization for Bioethanol Production: a Circular Bioeconomy Approach

Lignocellulosic biomass generated from different sectors (agriculture, forestry, industrial) act as biorefinery precursor for production of second-generation (2G) bioethanol and other biochemicals. The integration of various conversion techniques on a single platform under biorefinery approach for production of biofuel and industrially important chemicals from LCB is gaining interest worldwide. The waste generated on utilization of bio-resources is almost negligible or zero in a biorefinery along with reduced greenhouse gas emissions, which supports the circular bioeconomy concept. The economic viability of a lignocellulosic biorefinery depends upon the efficient utilization of three major components of LCB-cellulose, hemicellulose and lignin. The heterogeneous structure and recalcitrant nature of LCB is main obstacle in its valorization into bioethanol and other value-added products. The success of bioconversion process depends upon methods used during pre-treatment, hydrolysis and fermentation processes. The cost involved in each step of the bioconversion process affects the viability of cellulosic ethanol. The lignocellulose biorefinery has ample scope, but much-focused research is required to fully utilize major parts of lignocellulosic biomass with zero wastage. The present review entails lignocellulosic biomass valorization for ethanol production, along with different steps involved in its production. Various value-added products produced from LCB components were also discussed. Recent technological advances and significant challenges in bioethanol production are also highlighted in addition to future perspectives.

High-rate biohydrogen production from xylose using a dynamic membrane bioreactor

This study aimed a high-rate dark fermentative H₂ production from xylose using a dynamic membrane module bioreactor (DMBR) with a 444-μm pore polyester mesh. 20 g xylose/L was fed continuously to the DMBR at different hydraulic retention times (HRTs) from 12 to 3 h at 37 °C. The maximum average H₂ yield (HY) and H₂ production rate (HPR) at 3 h HRT were found to be 1.40 ± 0.07 mol H₂/mol xylose_consumed and 30.26 ± 1.19 L H₂/L-d, respectively. The short HRT resulted in the maximum suspended biomass concentration (8.92 ± 0.40 g VSS/L) along with significant attached biomass retention (7.88 ± 0.22 g VSS/L). H₂ was produced by both butyric and acetic acid pathways. Low HY was concurrent with lactic acid production. The bacterial population shifted from non-H₂ producers, such as Lactobacillus and Sporolactobacillus spp., to Clostridium sp., when HY increased. Thus, xylose from lignocellulose is a feasible substrate for dark fermentative H₂ production using DMBR.

Thermochemical and Catalytic Conversion Technologies for the Development of Brazilian Biomass Utilization

The social, economic, and environmental impacts of climate change have been shown to affect poorer populations throughout the world disproportionally, and the COVID-19 pandemic of 2020–2021 has only exacerbated the use of less sustainable energy, fuel, and chemical sources. The period of economic and social recovery following the pandemic presents an unprecedented opportunity to invest in biorefineries based on the pyrolysis of agricultural residues. These produce a plethora of sustainable resources while also contributing to the economic valorization of first-sector local economies. However, biomass-derived pyrolysis liquid is highly oxygenated, which hinders its long-term stability and usability. Catalytic hydrogenation is a proposed upgrading method to reduce this hindrance, while recent studies on the use of nickel and niobium as low-cost catalysts, both abundant in Brazil, reinforce the potential synergy between different economic sectors within the country. This review gathers state-of-the-art applications of these technologies with the intent to guide the scientific community and lawmakers alike on yet another alternative for energy and commodities production within an environmentally sustainable paradigm.

Improvement of endoglucanase production by Aspergillus brasiliensis in solid-state fermentation using cupuaçu (Theobroma grandiflorum) residue as substrate

AIMS

Optimize the production of Aspergillus brasiliensis endoglucanase in a solid-phase bioprocess using cupuaçu shell as substrate.

METHODS AND RESULTS

The shells were supplemented with nitrogen and phosphorous and used as a substrate. The centesimal and inorganic composition of the residue was determined, and found to be rich in fibres, and possessed essential elements for fungal growth. In the initial cultivation of A. brasiliensis, endoglucanase activity of 7.35 U g^-1 was obtained. A factorial experimental design was used to determine the most significant variables for the bioprocess. The interactions between moisture, temperature and nitrogen source were noteworthy (p < 0.05). From the rotational central composite design, the optimization of temperature and nitrogen supplementation was obtained, and this reached 40.50 U g^-1 , which is an increase of more than five times the value obtained initially. The enzymatic extract was applied as the biocatalyst in the hydrolysis of cupuaçu shells and, after 48 h, it was possible to observe the production of reducing sugars.

CONCLUSIONS

Cupuaçu shell can be used as a substrate for endoglucanase production by A. brasiliensis. The process was optimized for the cultivation temperature and the nitrogen source. The enzymatic extract can be applied in the hydrolysis of lignocellulosic biomass.

SIGNIFICANCE AND IMPACT OF THE STUDY

Cupuaçu shells can be used to produce cellulases, a product of high added value that can generate economic and environmental benefits for communities and companies producing derivatives of the cupuaçu fruit.