Emerging technologies for the pretreatment of lignocellulosic biomass

A detailed sensitivity analysis identifies the key factors influencing the enzymatic saccharification of lignocellulosic biomass

Corn stover is the most abundant form of crop residue that can serve as a source of lignocellulosic biomass in biorefinery approaches, for instance for the production of bioethanol. In such biorefinery processes, the constituent polysaccharide biopolymers are typically broken down into simple monomeric sugars by enzymatic saccharification, for further downstream fermentation into bioethanol. However, the recalcitrance of this material to enzymatic saccharification invokes the need for innovative pre-treatment methods to increase sugar conversion yield. Here, we focus on experimental glucose conversion time-courses for corn stover lignocellulose that has been pre-treated with different acid-catalysed processes and intensities. We identify the key parameters that determine enzymatic saccharification dynamics by performing a Sobol's sensitivity analysis on the comparison between the simulation results from our complex stochastic biophysical model, and the experimental data that we accurately reproduce. We find that the parameters relating to cellulose crystallinity and those associated with the cellobiohydrolase activity are predominantly driving the enzymatic saccharification dynamics. We confirm our computational results using mathematical calculations for a purely cellulosic substrate. On the one hand, having identified that only five parameters drastically influence the saccharification dynamics allows us to reduce the dimensionality of the parameter space (from nineteen to five parameters), which we expect will significantly speed up our fitting algorithm for comparison of experimental and simulated saccharification time-courses. On the other hand, these parameters directly highlight key targets for experimental endeavours in the optimisation of pre-treatment and saccharification conditions. Finally, this systematic and two-fold theoretical study, based on both mathematical and computational approaches, provides experimentalists with key insights that will support them in rationalising their complex experimental results.

Fermentative Production of β-Carotene from Sugarcane Bagasse Hydrolysate by Rhodotorula glutinis CCT-2186

Β-Carotene is a red-orange pigment that serves as a precursor to important pharmaceutical molecules like vitamin A and retinol, making it highly significant in the industrial sector. Consequently, there is an ongoing quest for more sustainable production methods. In this study, glucose and xylose, two primary sugars derived from sugarcane bagasse (SCB), were utilized as substrates for β-carotene production by Rhodotorula glutinis CCT-2186. To achieve this, SCB underwent pretreatment using NaOH, involved different concentrations of total solids (TS) (10%, 15%, and 20%) to remove lignin. Each sample was enzymatically hydrolyzed using two substrate loadings (5% and 10%). The pretreated SCB with 10%, 15%, and 20% TS exhibited glucose hydrolysis yields (%wt) of 93.10%, 91.88%, and 90.77%, respectively. The resulting hydrolysate was employed for β-carotene production under batch fermentation. After 72 h of fermentation, the SCB hydrolysate yielded a β-carotene concentration of 118.56 ± 3.01 mg/L. These findings showcase the robustness of R. glutinis as a biocatalyst for converting SCB into β-carotene.

Biomass gasification, catalytic technologies and energy integration for production of circular methanol: New horizons for industry decarbonisation

The Intergovernmental Panel on Climate Change (IPCC) recognises the pivotal role of renewable energies in the future energy system and the achievement of the zero-emission target. The implementation of renewables should provide major opportunities and enable a more secure and decentralised energy supply system. Renewable fuels provide long-term solutions for the transport sector, particularly for applications where fuels with high energy density are required. In addition, it helps reducing the carbon footprint of these sectors in the long-term. Information on biomass characteristics feedstock is essential for scaling-up gasification from the laboratory to industrial-scale. This review deals with the transformation biogenic residues into a valuable bioenergy carrier like biomethanol as the liquid sunshine based on the combination of modified mature technologies such as gasification with other innovative solutions such as membranes and microchannel reactors. Tar abatement is a critical process in product gas upgrading since tars compromise downstream processes and equipment, for this, membrane technology for upgrading syngas quality is discussed in this paper. Microchannel reactor technology with the design of state-of-the-art multifunctional catalysts provides a path to develop decentralised biomethanol synthesis from biogenic residues. Finally, the development of a process chain for the production of (i) methanol as an intermediate energy carrier, (ii) electricity and (iii) heat for decentralised applications based on biomass feedstock flexible gasification, gas upgrading and methanol synthesis is analysed.

Enhancing deep eutectic solvent systems for efficient fermentable sugar recovery from lignocellulosic fiber

Efficient conversion of sugars into fermentable sugars is a critical challenge in the cost-effective production of lignocellulosic biopolymers and biofuels. This study focuses on various sugar quantification techniques applied to Furcraea Foetida (Mauritius Hemp) samples, utilizing natural deep eutectic solvents (NADES) and deep eutectic solvents (DES) like urea, glycerol, citrates, pyrogallol (PY), and cetyltrimethylammonium bromide (CTAB). Employing a Taguchi-designed experiment, operational conditions were fine-tuned to evaluate the influence of time, concentration, and temperature on each deep eutectic solvent-based process. The emerging green solvent extraction approach demonstrated significant results, achieving notably high sugar yields compared to traditional techniques such as alkali, hot-water, and acid-mediated extraction. At a CTAB:PY molar ratio of 1:3, optimized for 60 min at 50 °C, the highest fermentable sugar (FS) yield of 0.6891 ± 0.0123 g FS/g LCB was attained-2 to 6 times higher than non-optimized values and 0.2 to 0.3 times higher than optimized traditional methods. In light of this, this research study emphasizes the pivotal significance of efficient sugar conversion through optimized deep eutectic solvent-based extraction methods, with a particular focus on Furcraea Foetida fibers, offering promising outcomes for the biofuel and biopolymer production industry.

Renewable Energy Potential: Second-Generation Biomass as Feedstock for Bioethanol Production

Biofuels are clean and renewable energy resources gaining increased attention as a potential replacement for non-renewable petroleum-based fuels. They are derived from biomass that could either be animal-based or belong to any of the three generations of plant biomass (agricultural crops, lignocellulosic materials, or algae). Over 130 studies including experimental research, case studies, literature reviews, and website publications related to bioethanol production were evaluated; different methods and techniques have been tested by scientists and researchers in this field, and the most optimal conditions have been adopted for the generation of biofuels from biomass. This has ultimately led to a subsequent scale-up of procedures and the establishment of pilot, demo, and large-scale plants/biorefineries in some regions of the world. Nevertheless, there are still challenges associated with the production of bioethanol from lignocellulosic biomass, such as recalcitrance of the cell wall, multiple pretreatment steps, prolonged hydrolysis time, degradation product formation, cost, etc., which have impeded the implementation of its large-scale production, which needs to be addressed. This review gives an overview of biomass and bioenergy, the structure and composition of lignocellulosic biomass, biofuel classification, bioethanol as an energy source, bioethanol production processes, different pretreatment and hydrolysis techniques, inhibitory product formation, fermentation strategies/process, the microorganisms used for fermentation, distillation, legislation in support of advanced biofuel, and industrial projects on advanced bioethanol. The ultimate objective is still to find the best conditions and technology possible to sustainably and inexpensively produce a high bioethanol yield.

Sustainable utilization of fruit and vegetable waste bioresources for bioplastics production

Nowadays, rapidly increasing production, use and disposable of plastic products has become one of the utmost environmental issues. Our current circumstances in which the food supply chain is demonstrated as containing plastic particles and other plastic-based impurities, represents a significant health risk to humans, animals, and environmental alike. According to this point of view, biodegradable plastic material aims to produce a more sustainable and greener world with a lower ecological impact. Bioplastics are being investigated as an environmentally friendly candidate to address this problem and hence global bioplastic production has seen significant growth and expansion in recent years. This article focuses on a few critical issues that must be addressed for bioplastic production to become commercially viable. Although the reduction of fruit and vegetable waste biomass has an apparent value in terms of environmental benefits and sustainability, commercial success at industrial scale has remained flat. This is due to various factors, including biomass feedstocks, pretreatment technologies, enzymatic hydrolysis, and scale-up issues in the industry, all of which contribute to high capital and operating costs. This review paper summarizes the global overview of bioplastics derived from fruit and vegetable waste biomass. Furthermore, economic and technical challenges associated with industrialization and diverse applications of bioplastics in biomedical, agricultural, and food-packaging fields due to their excellent biocompatibility properties are reviewed.HighlightsReview of the diverse types and characteristics of sustainability of biobased plasticsImproved pretreatment technologies can develop to enhance greater yieldEnzyme hydrolysis process used for bioplastic extraction & hasten industrial scale-upFocus on technical challenges facing commercialized the bioplasticsDetailed discussion on the application for sustainability of biodegradable plastics.

Lignocellulosic biomass pretreatment: Industrial oriented high-solid twin-screw extrusion method to improve biogas production from forestry biomass resources

Forestry lignocellulosic waste is an important, largely untapped source of biomass for producing clean energy. In this study, a high-solids twin-screw extrusion approach is developed as a novel pretreatment method to effectively increase the biogas production rate to better fit commercial requirements. Multiple screw designs are progressively introduced with increasingly intensified mechanical shear. The experiments also looked at the impact of feed solids content and several cost-effective processing aids along with these screw designs. Various characterization methods were used to relate the physical state of the biomass based on its specific surface area and volatile fraction, to the rate of biomethane generation possible from a 14- and 31-day biomethane potential test. An increase in biomethane production over this period by up to 190% was possible with the optimal screw design compared to a benchmark sample. This is a promising finding for the industrialization of biomethane production from forestry lignocellulosic biomass.

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.

Cellulose nanocrystals extracted from rice husk using the formic/peroxyformic acid process: isolation and structural characterization

Cellulose derived from biomass is a renewable resource with numerous applications. Using formic/peroxyformic acid at atmospheric pressure, cellulose nanocrystals (CNC) were isolated from rice husk (RH) in this study. This method was an excellent way to get rid of lignin and hemicelluloses from RH. The cellulose was subsequently acid hydrolyzed by H2SO4 (64%) for 30 minutes at 45 °C. The chemical and microstructure analysis showed that the lignin and hemicellulose contents of raw RH had been eliminated, and the crystallinity content of CNC was 67.16%. According to transmission electron microscopy (TEM) morphological analysis, CNC measured 19 ± 3.3 nm in diameter, 195 ± 24 nm in length, and 10.2 ± 6.8 in aspect ratio. The thermal stability of RH and CNC was also investigated using thermogravimetric analysis (TGA). These encouraging findings demonstrated the potential for reusing RH agricultural waste to create CNC and include nanocomposites as a reinforcing material.

Biodegradable UV-Protective Composite Film from Cellulosic Waste: Utilisation of Cotton Gin Motes as Biocomponent

With an increase in environmental pollution and microplastic problems, it is more urgent now to replace non-biodegradable films with biodegradable films that are low-cost and from renewable resources. Cotton gin motes (GM), a type of cellulosic waste that is generated from cotton ginning, is an excellent candidate for fabricating biodegradable films due to its properties and abundance. In this study, GM was first mechanically milled into a fine powder, followed by compounding with polycaprolactone (PCL) and extruded to produce composite pellets which were then compress-moulded into composite films. This environmentally friendly process used physical processing and all the materials were consumed in the process without generating any waste residue. To improve the compatibility and mixing properties between GM and PCL, the use of a plasticiser (polyethylene glycol) was considered. A high content of GM powder (up to 50%) was successfully compounded with the polymer. The SEM images of the composite films showed smooth surface morphology and well-distributed GM powder in the PCL matrix. The added advantage of compounding GM with the polymer matrix was that the composite film developed UV-shielding properties due to the presence of lignin in the GM powder. This property will be critical for films used in UV-resistance applications. Furthermore, the composite even with high GM content (50%), showed good mechanical properties, with 9.5 MPa yield strength and 442% elongation, which was only a 50% decrease in elongation when compared with clear PCL film. The soil biodegradation of GM composite films under controlled temperature (20 °C) and humidity (50%) for 1 month showed around 41% weight loss. Overall, this study demonstrates the potential of GM to be used as a biodegradable and UV-protective composite film for a wide array of applications, such as packaging and UV-protective coverings.

Optimization of biogas production from straw wastes by different pretreatments: Progress, challenges, and prospects

Lignocellulosic biomass (LCB) presents a promising feedstock for carbon management due to enormous potential for achieving carbon neutrality and delivering substantial environmental and economic benefit. Bioenergy derived from LCB accounts for about 10.3 % of the global total energy supply. The generation of bioenergy through anaerobic digestion (AD) in combination with carbon capture and storage, particularly for methane production, provides a cost-effective solution to mitigate greenhouse gas emissions, while concurrently facilitating bioenergy production and the recovery of high-value products during LCB conversion. However, the inherent recalcitrant polymer crystal structure of lignocellulose impedes the accessibility of anaerobic bacteria, necessitating lignocellulosic residue pretreatment before AD or microbial chain elongation. This paper seeks to explore recent advances in pretreatment methods for LCB biogas production, including pulsed electric field (PEF), electron beam irradiation (EBI), freezing-thawing pretreatment, microaerobic pretreatment, and nanomaterials-based pretreatment, and provide a comprehensive overview of the performance, benefits, and drawbacks of the traditional and improved treatment methods. In particular, physical-chemical pretreatment emerges as a flexible and effective option for methane production from straw wastes. The burgeoning field of nanomaterials has provoked progress in the development of artificial enzyme mimetics and enzyme immobilization techniques, compensating for the intrinsic defect of natural enzyme. However, various complex factors, such as economic effectiveness, environmental impact, and operational feasibility, influence the implementation of LCB pretreatment processes. Techno-economic analysis (TEA), life cycle assessment (LCA), and artificial intelligence technologies provide efficient means for evaluating and selecting pretreatment methods. This paper addresses current issues and development priorities for the achievement of the appropriate and sustainable utilization of LCB in light of evolving economic and environmentally friendly social development demands, thereby providing theoretical basis and technical guidance for improving LCB biogas production of AD systems.

Versatile Applications of Brewer's Spent Grain: Solid-State Fermentation and Nutritional Added Value

Brewer's spent grain (BSG) is a major by-product in the beer-brewing process which contributes to 85% of the entire generated by-product in the brewing process. BSG is rich in proteins, and most of the malt proteins (74-78%) remain insoluble in BSG after the mashing process. Solid-state fermentation (SSF) is a promising bioprocess that enables microorganisms to survive in environments with minimal water and has shown to enhance the nutritional composition of BSG. In this review, the potential application of protein, amino acids (proline, threonine, and serine), phenolic contents, and soluble sugars (glucose, fructose, xylose, arabinose, and cellobiose) extracted from BSG by various microorganisms using SSF is explored. Incorporation of BSG into animal feed, human diets, and as a substrate for microorganisms are the prospects that could be implemented in the industrial scale. This review also discussed various advances to improve the fermentation yield such as symbiotic fermentation, the addition of nitrogen supplements, and an optimal mixture of the agro-industrial waste substrate. Future perspectives on SSF are also addressed to provide important ideas for immediate and future studies. However, challenges include optimizing SSF conditions and design of bioreactors, and operational costs must be addressed in the future to overcome current obstacles. Overall, this mini review highlights the potential benefits of BSG utilization and SSF in a sustainable way.

Green and chemical-free pretreatment of corn straw using cold isostatic pressure for methane production

In this study, the effect of cold isostatic pressure (CIP) pretreatment on the physicochemical properties and subsequent anaerobic digestion (AD) performance of corn straw (CS) was explored. The CS was subjected to CIP pretreatment by pressures of 200, 400 and 600 MPa, respectively, while AD was carried out at medium temperature (35 ± 2 °C). The results showed that CIP pretreatment disrupted the dense structure of the CS and altered the crystallinity index and surface hydrophobicity of the CS, thereby affecting the AD process. The presence of CIP pretreatment increased the initial reducing sugar concentration by 0.11-0.27 g/L and increased the maximum volatile fatty acids content by 112.82-436.64 mg/L, which facilitated the process of acidification and hydrolysis of the AD. It was also observed that the CIP pretreatment maintained the pH in the range of 6.37-7.30, maintaining the stability of the overall system. Moreover, the cumulative methane production in the CIP pretreatment group increased by 27.17 %-64.90 % compared to the control group. Analysis of the microbial results showed that CIP pretreatment increased the abundance of cellulose degrading bacteria Ruminofilibacter from 21.50 % to 27.53 % and acetoclastic methanogen Methanosaeta from 45.48 % to 56.92 %, thus facilitating the hydrolysis and methanogenic stages. The energy conversion analysis showed that CIP is a green and non-polluting pretreatment strategy for the efficient AD of CS to methane.

Chemobiocatalytic transfromation of biomass into furfurylamine with mixed amine donor in an eco-friendly medium

Biobased furfurylamine (FAM) is a versatile platform molecule for producing additives, pharmaceuticals, and pesticides. Recombinant E. coli HNND-AlaDH was created by co-expressing L-alanine dehydrogenase (AlaDH) and mutated Aspergillus terreus ω-transaminase (HNND), aiming to convert furfural (FUR) into FAM using inexpensive L-alanine and isopropylamine as mixed amine donors. In ChCl:FA:OA (10 wt%), pineapple peel, bagasse, barley shell, peanut shell, and corn stalk could be efficiently transformed into FUR under 170 °C for 10 min. Pineapple peel produced a high titer of FUR (183.3 mM). Additionally, the viscosity, surface tension and polarity of ChCl:FA:OA were explored. The biomass-derived FUR was fully transformed to FAM by HNND-AlaDH with amine donor (1:1:1 of L-Ala/isopropylamine/FUR mol/mol/mol) within 300 min. Accordingly, the FAM productivity was 0.58 g/(g xylan in pineapple peel). This chemobiocatalytic strategy established through the combination of chemocatalysis and biocatalysis could be applied to convert renewable biomass into valuable organic amines.

From waste to food and bioinsecticides: An innovative system integrating Tenebrio molitor bioconversion and pyrolysis bio-oil production

To achieve a waste-free clean production, the present study aimed to valorize an underused agroindustrial byproduct (rice bran) by mealworms bioconversion and produce bio-oil from pyrolysis of insect excreta (frass) as bioinsecticide. To reach the first goal, the suitability of rice bran (RB) versus standard diet, wheat bran (WB), was examined by determining feed conversion, growth performance, and nutritional profile of T. molitor larvae. RB diet was an appropriate feed substrate for breeding mealworms, as evidenced by their high survival rates, optimal feed conversion parameters, and its capability to support the growth and life cycle of this insect. Besides, RB did not affect soluble larval protein content but modified crude fat content and fatty acid profile. In order to address the second aim, egested frass from RB and WB were subjected to pyrolysis to obtain bio-oils. The main compound was acetic acid (≈37%) followed by 1,6-anhydro-β-d-glucopyranose (from 16 to 25%), as measured by GC-MS analysis. Nitrogen-containing chemicals accounted for ≈10%. Frass bio-oils could represent a novel source of bioinsecticides due to their bioeffectiveness in insect pests of economic importance (Plodia interpunctella and Tribolium castaneum) and medical interest (Culex pipiens pipiens). For P. interpunctella adults, frass bio-oils produced insecticidal activity by fumigant and contact exposure whereas for T. castaneum adults, just fumigant. By a miniaturized model that simulates semireal storage conditions, it was seen that, on T. castaneum, frass RB bio-oil generated higher repellent effect than frass WB. Finally, bio-oils proved to have larvicidal activity against Cx. p. pipiens.

Lignocellulosic Biomass for the Fabrication of Triboelectric Nano-Generators (TENGs)-A Review

Growth in population and increased environmental awareness demand the emergence of new energy sources with low environmental impact. Lignocellulosic biomass is mainly composed of cellulose, lignin, and hemicellulose. These materials have been used in the energy industry for the production of biofuels as an eco-friendly alternative to fossil fuels. However, their use in the fabrication of small electronic devices is still under development. Lignocellulose-based triboelectric nanogenerators (LC-TENGs) have emerged as an eco-friendly alternative to conventional batteries, which are mainly composed of harmful and non-degradable materials. These LC-TENGs use lignocellulose-based components, which serve as electrodes or triboelectric active materials. These materials can be derived from bulk materials such as wood, seeds, or leaves, or they can be derived from waste materials from the timber industry, agriculture, or recycled urban materials. LC-TENG devices represent an eco-friendly, low-cost, and effective mechanism for harvesting environmental mechanical energy to generate electricity, enabling the development of self-powered devices and sensors. In this study, a comprehensive review of lignocellulosic-based materials was conducted to highlight their use as both electrodes and triboelectric active surfaces in the development of novel eco-friendly triboelectric nano-generators (LC-TENGs). The composition of lignocellulose and the classification and applications of LC-TENGs are discussed.

Systematic identification of CAZymes and transcription factors in the hypercellulolytic fungus Penicillium funiculosum NCIM1228 involved in lignocellulosic biomass degradation

BACKGROUND

Penicillium funiculosum NCIM1228 is a filamentous fungus that was identified in our laboratory to have high cellulolytic activity. Analysis of its secretome suggested that it responds to different carbon substrates by secreting specific enzymes capable of digesting those substrates. This phenomenon indicated the presence of a regulatory system guiding the expression of these hydrolyzing enzymes. Since transcription factors (TFs) are the key players in regulating the expression of enzymes, this study aimed first to identify the complete repertoire of Carbohydrate Active Enzymes (CAZymes) and TFs coded in its genome. The regulation of CAZymes was then analysed by studying the expression pattern of these CAZymes and TFs in different carbon substrates-Avicel (cellulosic substrate), wheat bran (WB; hemicellulosic substrate), Avicel + wheat bran, pre-treated wheat straw (a potential substrate for lignocellulosic ethanol), and glucose (control).

RESULTS

The P. funiculosum NCIM1228 genome was sequenced, and 10,739 genes were identified in its genome. These genes included a total of 298 CAZymes and 451 TF coding genes. A distinct expression pattern of the CAZymes was observed in different carbon substrates tested. Core cellulose hydrolyzing enzymes were highly expressed in the presence of Avicel, while pre-treated wheat straw and Avicel + wheat bran induced a mixture of CAZymes because of their heterogeneous nature. Wheat bran mainly induced hemicellulases, and the least number of CAZymes were expressed in glucose. TFs also exhibited distinct expression patterns in each of the carbon substrates. Though most of these TFs have not been functionally characterized before, homologs of NosA, Fcr1, and ATF21, which have been known to be involved in fruiting body development, protein secretion and stress response, were identified.

CONCLUSIONS

Overall, the P. funiculosum NCIM1228 genome was sequenced, and the CAZymes and TFs present in its genome were annotated. The expression of the CAZymes and TFs in response to various polymeric sugars present in the lignocellulosic biomass was identified. This work thus provides a comprehensive mapping of transcription factors (TFs) involved in regulating the production of biomass hydrolyzing enzymes.

Kinetic model derived from machine learning for accurate prediction of microalgal hydrogen production via conversion from low thermally pre-treated palm kernel expeller waste

The depletion of fossil fuel sources and increase in energy demands have increased the need for a sustainable alternative energy source. The ability to produce hydrogen from microalgae is generating a lot of attention in both academia and industry. Due to complex production procedures, the commercial production of microalgal biohydrogen is not yet practical. Developing the most optimum microalgal hydrogen production process is also very laborious and expensive as proven from the experimental measurement. Therefore, this research project intended to analyse the random time series dataset collected during microalgal hydrogen productions while using various low thermally pre-treated palm kernel expeller (PKE) waste via machine learning (ML) approach. The analysis of collected dataset allowed the derivation of an enhanced kinetic model based on the Gompertz model amidst the dark fermentative hydrogen production that integrated thermal pre-treatment duration as a function within the model. The optimum microalgal hydrogen production attained with the enhanced kinetic model was 387.1 mL/g microalgae after 6 days with 1 h thermally pre-treated PKE waste at 90 °C. The enhanced model also had better accuracy (R2 = 0.9556) and net energy ratio (NER) value (0.71) than previous studies. Finally, the NER could be further improved to 0.91 when the microalgal culture was reused, heralding the potential application of ML in optimizing the microalgal hydrogen production process.

Simultaneous saccharification of hemicellulose and cellulose of corncob in a one-pot system using catalysis of carbon based solid acid from lignosulfonate

The drive towards sustainable chemistry has inspired the development of active solid acids as catalysts and ionic liquids as solvents for an efficient release of sugars from lignocellulosic biomass for future biorefinery practices. Carbon-based solid acid (SI-C-S-H2O2) prepared from sodium lignosulfonate, a waste of the paper industry, was used with water or ionic liquid to hydrolyze corncob in this study. The effects of various reaction parameters were investigated in different solvent systems. The highest xylose yield of 83.4% and hemicellulose removal rate of 90.6% were obtained in an aqueous system at 130 °C for 14 h. After the pretreatment, cellulase was used for the hydrolysis of residue and the enzymatic digestibility of 92.6% was obtained. Following these two hydrolysis steps in the aqueous systems, the highest yield of total reducing sugar (TRS) was obtained at 88.1%. Further, one-step depolymerization and saccharification of corncob hemicellulose and cellulose to reducing sugars in an IL-water system catalyzed by SI-C-S-H2O2 was conducted at 130 °C for 10 h, with a high TRS yield of 75.1% obtained directly. After recycling five times, the solid acid catalyst still showed a high catalytic activity for sugar yield in different systems, providing a green and effective method for lignocellulose degradation.

Valorization of dragon fruit waste to value-added bioproducts and formulations: A review

Owing to the increasing worldwide population explosion, managing waste generated from the food sector has become a cross-cutting issue globally, leading to environmental, economic, and social issues. Circular economy-inspired waste valorization approaches have been increasing steadily, generating new business opportunities developing valuable bioproducts using food waste, especially fruit wastes, that may have several applications in energy-food-pharma sectors. Dragon fruit waste is one such waste resource, which is rich in several value-added chemicals and oils, and can be a renewable resource to produce several value-added compounds of potential applications in different industries. Pretreatment and extraction processes in biorefineries are important strategies for recovering value-added biomolecules. There are different methods of valorization, including green extractions and biological conversion approaches. However, microbe-based conversion is one of the advanced technologies for valorizing dragon fruit waste into bioethanol, bioactive products, pharmaceuticals, and other valued products by reusing or recycling them. This state-of-the-art review briefly overviews the dragon fruit waste management strategies and advanced eco-friendly and cost-effective valorization technologies. Furthermore, various applications of different valuable bioactive components obtained from dragon fruit waste have been critically discussed concerning various industrial sectors. Several industrial sectors, such as food, pharmaceuticals, and biofuels, have been critically reviewed in detail.

Analytical Pyrolysis of Pinus radiata and Eucalyptus globulus: Effects of Microwave Pretreatment on Pyrolytic Vapours Composition

Pinus radiata (PR) and Eucalyptus globulus (EG) are the most planted species in Chile. This research aims to evaluate the pyrolysis behaviour of PR and EG from the Bío Bío region in Chile. Biomass samples were subjected to microwave pretreatment considering power (259, 462, 595, and 700 W) and time (1, 2, 3, and 5 min). The maximum temperature reached was 147.69 °C for PR and 130.71 °C for EG in the 700 W-5 min condition, which caused the rearrangement of the cellulose crystalline chains through vibration and an increase in the internal energy of the biomass and the decomposition of lignin due to reaching its glass transition temperature. Thermogravimetric analysis revealed an activation energy (Ea) reduction from 201.71 to 174.91 kJ·mol-1 in PR and from 174.80 to 158.51 kJ·mol-1 in EG, compared to the untreated condition (WOT) for the 700 W-5 min condition, which indicates that microwave pretreatment improves the activity of the components and the decomposition of structural compounds for subsequent pyrolysis. Functional groups were identified by Fourier transform infrared spectroscopy (FTIR). A decrease in oxygenated compounds such as acids (from 21.97 to 17.34% w·w-1 and from 27.72 to 24.13% w·w-1) and phenols (from 34.41 to 31.95% w·w-1 and from 21.73 to 20.24% w·w-1) in PR and EG, respectively, was observed in comparison to the WOT for the 700 W-5 min condition, after analytical pyrolysis. Such results demonstrate the positive influence of the pretreatment on the reduction in oxygenated compounds obtained from biomass pyrolysis.

Strategic biomodification for raw plant-based pretreatment biorefining toward sustainable chemistry

Plant-based pretreatment biorefining is the initial triggering process in biomass-conversion to bio-based chemical products. In view of chemical sustainability, the raw plant-based pretreatment biorefining process is more favorable than the fossil-based one. Its direct use contributes to reducing CO2 emissions and the production cost of the target products by eliminating costly steps, such as the separation and purification of intermediates. Three types of feedstock plant resources have been utilized as raw plant feedstock sources, such as: lignocellulosic, starchy, and inulin-rich feedstock plants. These plant sources can be directly used for bio-based chemical products. To enhance the efficiency of their pretreatment biorefining process, well-designed biomodification schemes are discussed in this review to afford important information on useful biomodification approaches. For lignocellulosic feedstock plants, the enzymes and regulatory elements involved in lignin reduction are discussed using: COMT, GAUT4, CSE, PvMYB4 repressor, etc. For inulin-rich feedstock plants, 1-SST, 1-FFT, 1-FEH, and endoinulinase are illustrated in relation with the reduction of chain length of inulin polymer. For starchy feedstock plants, their biomodification is targeted to enhancing the depolymerization efficiency of starch to glucose monomer units. For this biomodification target, six candidates are discussed. These are SBE I, SBE IIa, SBE IIb, GBSS I, PTSTI, GWD 1, and PTSTI. The biomodification strategies discussed here promise to be conducive to enhancing the efficiency of the plant-based pretreatment biorefining process.

Production and applications of pullulan from lignocellulosic biomass: Challenges and perspectives

Pullulan is an exopolysaccharide produced by Aureobasidium pullulans, with interesting characteristics which lead to its application in industries such as pharmaceuticals, cosmetics, food, and others. To reduce production costs for industrial applications, cheaper raw materials such as lignocellulosic biomass can be utilized as a carbon and nutrient source for the microbial process. In this study, a comprehensive and critical review was conducted, encompassing the pullulan production process and the key influential variables. The main properties of the biopolymer were presented, and different applications were discussed. Subsequently, the utilization of lignocellulosics for pullulan production within the framework of a biorefinery concept was explored, considering the main published works that deal with materials such as sugarcane bagasse, rice husk, corn straw, and corn cob. Next, the main challenges and future prospects in this research area were highlighted, indicating the key strategies to favor the industrial production of pullulan from lignocellulosic biomasses.

Environment friendly emerging techniques for the treatment of waste biomass: a focus on microwave and ultrasonication processes

In the recent past, an increasing interest is mostly observed in using microwave and ultrasonic irradiation to aid the biological conversion of waste materials into value-added products. This study is focused on various individual impacts of microwaves and ultrasonic waves for the treatment of biomass before the synthesis of value-added products. Following, a comprehensive review of the mechanisms governing microwaves and ultrasonication as the treatment methods, their effects on biomass disruption, solubilization of organic matter, modification of the crystalline structure, enzymatic hydrolysis and production of reducing sugars was performed. However, based on the lab-scale experiments evaluated, microwaves and ultrasonication were studied to be economically and energetically ineffective despite their beneficial effects on the waste biomass. This article reviews some of the difficulties associated with using microwaves and ultrasonic irradiation for the efficient processing of waste biomasses and identified some potential directions for future study.

`A critical review on current status and environmental sustainability of pre-treatment methods for bioethanol production from lignocellulose feedstocks

Lignocellulosic biomass resource has been widely used as a natural resource for the synthesis of biofuels and bio-based products through pre-treatment, saccharification and fermentation processes. In this review, we delve into the environmental implications of bioethanol production from the widely utilized lignocellulosic biomass resource. The focus of our study is the critical stage of pre-treatment in the synthesis process, which also includes saccharification and fermentation. By collecting scientific data from the available literature, we conducted a comprehensive life cycle analysis. Our findings revealed substantial differences in the environmental burdens associated with diverse pre-treatment methods used for lignocellulosic biomass. These results highlight the importance of selecting environmentally benign pre-treatment techniques to promote the sustainability of bioethanol production. Future research directions are suggested, emphasizing the optimization of pre-treatment processes to further mitigate their environmental impact.

Advances in enzymatic conversion of biomass derived furfural and 5-hydroxymethylfurfural to value-added chemicals and solvents

The progress of versatile chemicals and bio-based fuels using renewable biomass has gained ample importance. Furfural and 5-hydroxymethylfurfural are biomass-derived compounds that serve as the cornerstone for high-value chemicals and have a myriad of industrial applications. Despite the significant research into several chemical processes for furanic platform chemicals conversion, the harsh reaction conditions and toxic by-products render their biological conversion an ideal alternative strategy. Although biological conversion confers an array of advantages, these processes have been reviewed less. This review explicates and evaluates notable improvements in the bioconversion of 5-hydroxymethylfurfural and furfural to comprehend the current developments in the biocatalytic transformation of furan. Enzymatic conversion of HMF and furfural to furanic derivative have been explored, while the latter has substantially overlooked a foretime. This discrepancy was reviewed along with the outlook on the potential usage of 5-hydroxymethylfurfural and furfural for the furan-based value-added products' synthesis.

Microbial tolerance engineering for boosting lactic acid production from lignocellulose

Lignocellulosic biomass is an attractive non-food feedstock for lactic acid production via microbial conversion due to its abundance and low-price, which can alleviate the conflict with food supplies. However, a variety of inhibitors derived from the biomass pretreatment processes repress microbial growth, decrease feedstock conversion efficiency and increase lactic acid production costs. Microbial tolerance engineering strategies accelerate the conversion of carbohydrates by improving microbial tolerance to toxic inhibitors using pretreated lignocellulose hydrolysate as a feedstock. This review presents the recent significant progress in microbial tolerance engineering to develop robust microbial cell factories with inhibitor tolerance and their application for cellulosic lactic acid production. Moreover, microbial tolerance engineering crosslinking other efficient breeding tools and novel approaches are also deeply discussed, aiming to providing a practical guide for economically viable production of cellulosic lactic acid.

Cellulosic Ethanol Production from Weed Biomass Hydrolysate of Vietnamosasa pusilla

Lignocellulosic biomass can be used as a renewable and sustainable energy source to help reduce the consequences of global warming. In the new energy age, the bioconversion of lignocellulosic biomass into green and clean energy displays remarkable potential and makes efficient use of waste. Bioethanol is a biofuel that can diminish reliance on fossil fuels while minimizing carbon emissions and increasing energy efficiency. Various lignocellulosic materials and weed biomass species have been selected as potential alternative energy sources. Vietnamosasa pusilla, a weed belonging to the Poaceae family, contains more than 40% glucan. However, research on the applications of this material is limited. Thus, here we aimed to achieve maximum fermentable glucose recovery and bioethanol production from weed biomass (V. pusilla). To this end, V. pusilla feedstocks were treated with varying concentrations of H₃PO₄ and then subjected to enzymatic hydrolysis. The results indicated that after pretreatment with different concentrations of H₃PO₄, the glucose recovery and digestibility at each concentration were markedly enhanced. Moreover, 87.5% of cellulosic ethanol was obtained from V. pusilla biomass hydrolysate medium without detoxification. Overall, our findings reveal that V. pusilla biomass can be introduced into sugar-based biorefineries to produce biofuels and other valuable chemicals.

Lignocellulosic biomass conversion via greener pretreatment methods towards biorefinery applications

Lignocellulose biomass during pretreatment releases various compounds, among them the most important is reducing sugars, which can be utilized for the production of biofuels and some other products. Thereby, innovative greener pretreatment techniques for lignocellulosic materials have been considered to open a new door in the aspects of digestibility of the rigid carbohydrate-lignin matrix to reduce the particle size and remove hemicellulose/lignin contents to successfully yield valid bioproducts. This article reviews about the composition of lignocelluloses and emphasizes various green pretreatments viz novel green solvent-based IL and DES steam explosion, supercritical carbon dioxide explosion (Sc-CO2) and co-solvent enhanced lignocellulosic fractionation (CELF) along with suitable mechanistic pathway of LCB pretreatment process. Finally, this article concludes that the existing pretreatments should be redesigned to conquer the demands by large scale production and suggests combined pretreatment methods to carry out various biomass pre-processing.

An efficient chemoenzymatic cascade strategy for transforming biomass into furfurylamine with lobster shell-based chemocatalyst and mutated ω-transaminase biocatalyst in methyl isobutyl ketone-water

To date, an efficient process for manufacturing valuable furan compounds from available renewable resources has gained great attention via a chemoenzymatic route. In this study, a sulfonated tin-loaded heterogeneous catalyst CLUST-Sn-LS using lobster shell as biobased carrier was prepared to convert corncob (75.0 g/L) into furfural (122.5 mM) at 170 °C for 30 min in methyl isobutyl ketone (MIBK)-H₂O biphasic system (2:1, v/v). To improve furfurylamine yield, a novel recombinant E. coli TFTS harboring robust mutant Aspergillus terreus ω-transaminase [hydrophilic threonine (T) at position 130 was site-directed mutated to hydrophobic phenylalanine (F)] was constructed to transform 300-500 mM furfural into furfurylamine (90.1-93.6 % yield) at 30 °C and pH 7.5 in MIBK-H₂O. Corncob was converted to furfurylamine in MIBK-H₂O with a high productivity of 0.461 g furfurylamine/(g xylan). This constructed chemoenzymatic method coupling bio-based chemocatalyst CLUST-Sn-LS and mutant ω-transaminase biocatalyst in a biphasic system could efficiently convert lignocellulose into furfurylamine.

High solids loading pretreatment: The core of lignocellulose biorefinery as an industrial technology - An overview

Pretreatment is the first and most determinative, yet the least mature step of lignocellulose biorefinery chain. The current stagnation of biorefinery commercialization indicates the barriers of the existing pretreatment technologies are needed to be unlocked. This review focused on one of the core factors, the high lignocellulose solids loading in pretreatment. The high solids loading of pretreatment significantly reduces water input, energy requirement, toxic compound discharge, solid/liquid separation costs, and carbon dioxide emissions, improves the titers of sugars and biproducts to meet the industrial requirements. Meanwhile, lignocellulose feedstock after high solids loading pretreatment is compatible with the existing logistics system for densification, packaging, storage, and transportation. Both the technical-economic analysis and the cellulosic ethanol conversion performance suggest that the solids loading in the pretreatment step need to be further elevated towards an industrial technology and the effective solutions should be proposed to the technical barriers in high solids loading pretreatment operations.

Recent advances on physical technologies for the pretreatment of food waste and lignocellulosic residues

The complete deployment of a bio-based economy is essential to meet the United Nations' Sustainable Development Goals from the 2030 Agenda. In this context, food waste and lignocellulosic residues are considered low-cost feedstocks for obtaining industrially attractive products through biological processes. The effective conversion of these raw materials is, however, still challenging, since they are recalcitrant to bioprocessing and must be first treated to alter their physicochemical properties and ease the accessibility to their structural components. Among the full pallet of pretreatments, physical methods are recognised to have a high potential to transform food waste and lignocellulosic residues. This review provides a critical discussion about the recent advances on milling, extrusion, ultrasound, and microwave pretreatments. Their mechanisms and modes of application are analysed and the main drawbacks and limitations for their use at an industrial scale are discussed.

Advances in physicochemical pretreatment strategies for lignocellulose biomass and their effectiveness in bioconversion for biofuel production

The inherent recalcitrance of lignocellulosic biomass is a significant barrier to efficient lignocellulosic biorefinery owing to its complex structure and the presence of inhibitory components, primarily lignin. Efficient biomass pretreatment strategies are crucial for fragmentation of lignocellulosic biocomponents, increasing the surface area and solubility of cellulose fibers, and removing or extracting lignin. Conventional pretreatment methods have several disadvantages, such as high operational costs, equipment corrosion, and the generation of toxic byproducts and effluents. In recent years, many emerging single-step, multi-step, and/or combined physicochemical pretreatment regimes have been developed, which are simpler in operation, more economical, and environmentally friendly. Furthermore, many of these combined physicochemical methods improve biomass bioaccessibility and effectively fractionate ∼96 % of lignocellulosic biocomponents into cellulose, hemicellulose, and lignin, thereby allowing for highly efficient lignocellulose bioconversion. This review critically discusses the emerging physicochemical pretreatment methods for efficient lignocellulose bioconversion for biofuel production to address the global energy crisis.

Prospects for utilizing microbial consortia for lignin conversion

Naturally occurring microbial communities are able to decompose lignocellulosic biomass through the concerted production of a myriad of enzymes that degrade its polymeric components and assimilate the resulting breakdown compounds by members of the community. This process includes the conversion of lignin, the most recalcitrant component of lignocellulosic biomass and historically the most difficult to valorize in the context of a biorefinery. Although several fundamental questions on microbial conversion of lignin remain unanswered, it is known that some fungi and bacteria produce enzymes to break, internalize, and assimilate lignin-derived molecules. The interest in developing efficient biological lignin conversion approaches has led to a better understanding of the types of enzymes and organisms that can act on different types of lignin structures, the depolymerized compounds that can be released, and the products that can be generated through microbial biosynthetic pathways. It has become clear that the discovery and implementation of native or engineered microbial consortia could be a powerful tool to facilitate conversion and valorization of this underutilized polymer. Here we review recent approaches that employ isolated or synthetic microbial communities for lignin conversion to bioproducts, including the development of methods for tracking and predicting the behavior of these consortia, the most significant challenges that have been identified, and the possibilities that remain to be explored in this field.

Effect of pretreatment strategies on halophyte Atriplex crassifolia to improve saccharification using thermostable cellulases

Bioethanol is believed to be an influential revolutionary gift of biotechnology, owing to its elevating global demand and massive production. Pakistan is home to a rich diversity of halophytic flora, convertible into bounteous volumes of bioethanol. On the other hand, the accessibility to the cellulosic part of biomass is a major bottleneck in the successful application of biorefinery processes. The most common pre-treatment procedures existent include physicochemical and chemical approaches, which are not environmentally benign. To overcome these problems, biological pre-treatment has gained importance but the drawback is the low yield of the extracted monosaccharides. The current research was aimed at exploring the best pre-treatment method for the bioconversion of halophyte Atriplex crassifolia into saccharides using three thermostable cellulases. Atriplex crassifolia was subjected to acid, alkali and microwave pre-treatments, followed by compositional analysis of the pre-treated substrates. Maximum delignification i.e. 56.6% was observed in the substrate pre-treated using 3% HCl. Enzymatic saccharification using thermostable cellulases also validated the results where the highest saccharification yield i.e. 39.5% was observed for the sample pre-treated using same. Maximum enzymatic hydrolysis of 52.7% was obtained for 0.40 g of the pre-treated halophyte Atriplex crassifolia where Endo-1,4- β -glucanase (300U), Exo-1,4- β -glucanase (400U) and β -1,4-glucosidase (1000U) were simultaneously added and incubated for 6 h at 75°C. The reducing sugar slurry obtained after optimization of saccharification was utilized as glucose in submerged fermentation for bioethanol production. The fermentation medium was inoculated with Saccharomyces cerevisiae, incubated at 30°C and 180 rpm for 96 h. Ethanol production was estimated using potassium dichromate method. Maximum production of bioethanol i.e. 16.33% was noted at 72 h. It can be concluded from the study that Atriplex crassifolia owing to its high cellulosic content after pre-treatment using dilute acid method, yields substantial amount of reducing sugars and high saccharification rates when subjected to enzymatic hydrolysis using thermostable cellulases, under optimized reaction conditions. Hence, the halophyte Atriplex crassifolia is a beneficial substrate that can be utilized to extract fermentable saccharides for bioethanol production.

Recent advances in lignocellulosic and algal biomass pretreatment and its biorefinery approaches for biochemicals and bioenergy conversion

As the global demand for sustainable energy increases, lignocellulosic (such as agricultural residues, forest biomass, municipal waste, and dedicated energy crops) and algal (including macroalgae and microalgae) biomass have attracted considerable attention, because of their high availability of carbohydrates. This is a potential feedstock to produce biochemical and bioenergy. Pretreatment of biomass can disrupt their complex structure, increasing conversion efficiency and product yield. Therefore, this review comprehensively discusses recent advances in different pretreatments (physical, chemical, physicochemical, and biological pretreatments) for lignocellulosic and algal biomass and their biorefining methods. Life cycle assessment (LCA) which enables the quantification of the environmental impact assessment of a biorefinery also be introduced. Biorefinery processes such as raw material acquisition, extraction, production, waste accumulation, and waste conversion are all monitored under this concept. Nevertheless, there still exist some techno-economic barriers during biorefinery and extensive research is still needed to develop cost-effective processes.

Bioethanol Production from Lignocellulosic Biomass-Challenges and Solutions

Regarding the limited resources for fossil fuels and increasing global energy demands, greenhouse gas emissions, and climate change, there is a need to find alternative energy sources that are sustainable, environmentally friendly, renewable, and economically viable. In the last several decades, interest in second-generation bioethanol production from non-food lignocellulosic biomass in the form of organic residues rapidly increased because of its abundance, renewability, and low cost. Bioethanol production fits into the strategy of a circular economy and zero waste plans, and using ethanol as an alternative fuel gives the world economy a chance to become independent of the petrochemical industry, providing energy security and environmental safety. However, the conversion of biomass into ethanol is a challenging and multi-stage process because of the variation in the biochemical composition of biomass and the recalcitrance of lignin, the aromatic component of lignocellulose. Therefore, the commercial production of cellulosic ethanol has not yet become well-received commercially, being hampered by high research and production costs, and substantial effort is needed to make it more widespread and profitable. This review summarises the state of the art in bioethanol production from lignocellulosic biomass, highlights the most challenging steps of the process, including pretreatment stages required to fragment biomass components and further enzymatic hydrolysis and fermentation, presents the most recent technological advances to overcome the challenges and high costs, and discusses future perspectives of second-generation biorefineries.

Sustainable production of biohydrogen from algae biomass: Critical review on pretreatment methods, mechanism and challenges

The production of chemicals and energy from sustainable biomass with an important objective decreasing carbon impressions has recently become one of the key areas of attention. Algae biomass have been recognized and researched as a potential renewable biomass of biohydrogen production attributed to their limited multiplying time, fast growing qualities and ability of lipid accumulation. This review additionally envelops various key perspectives such as composition and properties of algae biomass and pretreatment strategies such as physical, chemical and biological methods adopted for the algae biomass. This review is mainly focused on pretreatment strategies which have been developed to enhance biohydrogen production. The present review deals with methods and mechanism, enzymes involved and factors influencing on biohydrogen production which help to grasp various bottlenecks, challenges and constraints. Finally, the significant progressions and economical perspective on improving biohydrogen yield because of the expansion of co-substrates and the current trends are examined.

Alcoholysis kinetics and mechanism studies of ethyl levulinate production from ball milled corn stover

Alcoholysis of ball-milled biomass over catalysts with Brønsted and Lewis acid sites provides an efficient and sustainable scheme to produce versatile biobased chemicals under mild conditions; however, optimizing the process parameters is challenged by the complexity of reaction pathways and the multiplicity of ball milling and combination catalyst gains. To address these challenges, we present kinetic analysis of ethyl levulinate (EL) production from ball-milled corn stover catalyzed by Brønsted (B) acidic ionic liquid [Bmim-SO3H][HSO4] (SO3H-IL) and Lewis (L) acidic Al2(SO4)3. Product analysis shows that cellulosic substrates can form EL either through the intermediate ethyl-d-glycopyranoside (EDGP) or levoglucosenone (LGO), with the former leading the alcoholysis reaction. Kinetics results reveal that ball milling accelerates the reaction rate by promoting the formation of EDGP and LGO from cellulose. Pure SO3H-IL gives high selectivity towards EDGP from ball-milled corn stover and promotes the LGO production, whereas addition of Al2(SO4)3 substantially facilitates their further conversion to EL. Our findings contribute to the rational design of efficient catalytic strategies for sustainable and profitable biorefinery.

Hydrothermal and photocatalytic synergistic pretreatment to improve the full utilization of corn stalk

In this study, the hydrothermal and photocatalytic synergistic pretreatment for improving the full component utilization of corn stalk based on lignin first biorefining was employed to generate carbohydrates and obtain modified lignin. The results showed that the highest lignin removal ratio (40.70 %) and cellulose retention ratio (92.64 %) were obtained due to the smallest energy gap (6.05 eV) and the largest penetration distance (1.73 Å) between GVL and the lignin. And the yield of carbohydrates increased from 1.95 % to 58.17 % after hydrothermal pretreatment at 180 ℃. Furthermore, the modified lignin enhanced the flocculation effect, resulting in the increase of the removal of safranine-T by 6 times. In addition, the chemical and physical properties of modified lignin were studied and the mechanism of photocatalysis modification was explored. The research provides a new pretreatment method for the utilization of biomass and simultaneously achieves carbohydrate enrichment in bio-oil and purification of dye wastewater.

Lignocellulose biohydrogen towards net zero emission: A review on recent developments

This review mainly determines novel and advance physical, chemical, physico-chemical, microbiological and nanotechnology-based pretreatment techniques in lignocellulosic biomass pretreatment for bio-H2 production. Further, aim of this review is to gain the knowledge on the lignocellulosic biomass pretreatment and its priority on the efficacy of bio-H2 and positive findings. The influence of various pretreatment techniques on the structure of lignocellulosic biomass have presented with the pros and cons, especially about the cellulose digestibility and the interference by generation of inhibitory compounds in the bio-enzymatic technique as such compounds is toxic. The result implies that the stepwise pretreatment technique only can ensure eventually the lignocellulosic biomass materials fermentation to yield bio-H2. Though, the mentioned pretreatment steps are still a challenge to procure cost-effective large-scale conversion of lignocellulosic biomass into fermentable sugars along with low inhibitory concentration.

Review of Functional Aspects of Nanocellulose-Based Pickering Emulsifier for Non-Toxic Application and Its Colloid Stabilization Mechanism

In the past few years, the research on particle-stabilized emulsion (Pickering emulsion) has mainly focused on the usage of inorganic particles with well-defined shapes, narrow size distributions, and chemical tunability of the surfaces such as silica, alumina, and clay. However, the presence of incompatibility of some inorganic particles that are non-safe to humans and the ecosystem and their poor sustainability has led to a shift towards the development of materials of biological origin. For this reason, nano-dimensional cellulose (nanocellulose) derived from natural plants is suitable for use as a Pickering material for liquid interface stabilization for various non-toxic product formulations (e.g., the food and beverage, cosmetic, personal care, hygiene, pharmaceutical, and biomedical fields). However, the current understanding of nanocellulose-stabilized Pickering emulsion still lacks consistency in terms of the structural, self-assembly, and physio-chemical properties of nanocellulose towards the stabilization between liquid and oil interfaces. Thus, this review aims to provide a comprehensive study of the behavior of nanocellulose-based particles and their ability as a Pickering functionality to stabilize emulsion droplets. Extensive discussion on the characteristics of nanocelluloses, morphology, and preparation methods that can potentially be applied as Pickering emulsifiers in a different range of emulsions is provided. Nanocellulose's surface modification for the purpose of altering its characteristics and provoking multifunctional roles for high-grade non-toxic applications is discussed. Subsequently, the water-oil stabilization mechanism and the criteria for effective emulsion stabilization are summarized in this review. Lastly, we discuss the toxicity profile and risk assessment guidelines for the whole life cycle of nanocellulose from the fresh feedstock to the end-life of the product.

The Disposition of Bioactive Compounds from Fruit Waste, Their Extraction, and Analysis Using Novel Technologies: A Review

Fruit waste contains several bioactive components such as polyphenols, polysaccharides, and numerous other phytochemicals, including pigments. Furthermore, new financial opportunities are created by using fruit ‘leftovers’ as a basis for bioactivities that may serve as new foods or food ingredients, strengthening the circular economy’s properties. From a technical standpoint, organic phenolic substances have become more appealing to industry, in addition to their application as nutritional supplements or functional meals. Several extraction methods for recovering phenolic compounds from fruit waste have already been published, most of which involve using different organic solvents. However, there is a growing demand for eco-friendly and sustainable techniques that result in phenolic-rich extracts with little ecological impact. Utilizing these new and advanced green extraction techniques will reduce the global crisis caused by fruit waste management. Using modern techniques, fruit residue is degraded to sub-zero scales, yielding bio-based commodities such as bioactive elements. This review highlights the most favorable and creative methods of separating bioactive materials from fruit residue. Extraction techniques based on environmentally friendly technologies such as bioreactors, enzyme-assisted extraction, ultrasound-assisted extraction, and their combination are specifically covered.

Pretreatment of lignocellulosic biomass from sugar bagasse under microwave assisted dilute acid hydrolysis for biobutanol production

Alternative renewable energy sources are the future potential energy that will benefit the country's overall energy shortage and demand. The efficient biofuel production depends on the viability of the raw material used. The holistic approach of this study is to establish an integrated bioprocess from lignocellulosic material for biofuel synthesis. Sugar bagasse as one of the waste material, can be economically process for sugar extraction used in biofuel production. In this study, the optimum saccharification rate obtained was 43.62% when the biomass was pretreated at microwave temperature of 100 °C for 15 min with 2.5 g catalyst concentration. The results attained shows that hydrolysis time reduces to approximately 40-50% in compare with other traditional heating method. The sample was analyzed by using UV spectrophotometer and HPLC and computed by using Response Surface Method in MINITAB 17, whereas the structural changes of the residue was detected by using ATR-FTIR and ESEM.

Rapid decomposition of rice straw by application of a novel microbial consortium and study its microbial community dynamics

Rice straw decomposition is an attractive solution to open-field burning but the traditional method has slow kinetics and takes 60-90 days to obtain mature compost. In this study, we propose to boost up the decomposition process by addition of a novel microbial consortium rich in lignocellulolytic microbes. C: N ratio of the compost reached 11.69% and degradation efficiency of cellulose and hemicellulose was found to be 64 and 87% respectively within 25 days. Lignocellulolytic activity of the microbial consortium was confirmed by plate and activity assay. These parameters clearly indicated that a mature compost was obtained in 25 days. The 16S rRNA gene amplicon sequencing and functional analysis of predicted genes indicated amino acid and carbohydrate metabolism as the major metabolic pathway during composting. The tertiary level of functional analysis revealed the major metabolic pathways in the bacterial communities as pentose phosphate pathway, glycolysis and tricarboxylic acid cycle.

Valorization of lignocellulosic biomass for polyhydroxyalkanoate production: Status and perspectives

With the increasing concerns regarding climate, energy, and plastic crises, bio-based production of biodegradable polymers has become a dire necessity. Significant progress has been made in biotechnology for the production of biodegradable polymers from renewable resources to achieve the goal of zero plastic waste and a net-zero carbon bioeconomy. In this review, an overview of polyhydroxyalkanoate (PHA) production from lignocellulosic biomass (LCB) was presented. Having established LCB-based biorefinery with proper pretreatment techniques, various PHAs could be produced from LCB-derived sugars, hydrolysates, and/or aromatic mixtures employing microorganisms. This provides a clue for addressing the current environmental crises because "biodegradable polymers" could be produced from one of the most abundant resources that are renewable and sustainable in a "carbon-neutral process". Furthermore, the potential future of LCB-to-non-natural PHA production was discussed with particular reference to non-natural PHA biosynthesis methods and LCB-derived aromatic mixture biofunnelling systems.

Adaptation on xylose improves glucose-xylose co-utilization and ethanol production in a carbon catabolite repression (CCR) compromised ethanologenic strain

BACKGROUND

Sugar hydrolysates from lignocellulosic biomass are majorly composed of glucose and xylose that can be fermented to biofuels. Bacteria, despite having the natural ability to consume xylose are unable to consume it in presence of glucose due to a carbon catabolite repression (CCR) mechanism. This leads to overall reduced productivity as well as incomplete xylose utilization due to ethanol build-up from glucose utilization. In our effort to develop a strain for simultaneous fermentation of glucose and xylose into ethanol, we deleted ptsG in ethanologenic E. coli SSK42 to make it deficient in CCR and performed adaptive laboratory evolution to achieve accelerated growth rate, sugar consumption and ethanol production. Finally, we performed proteomics study to identify changes that might have been responsible for the observed improved phenotype of the evolved strain.

RESULTS

The parental strain of SSK42, i.e., wild-type E. coli B, did not co-utilize glucose and xylose as expected. After deleting the ptsG gene encoding the EIIBC^Glc subunit of PTS system, glucose consumption is severely affected in wild-type E. coli B. However, the ethanologenic, SSK42 strain, which was evolved in our earlier study on both glucose and xylose, didn't show such a drastic effect of EIIBC^Glc deletion, instead consumed glucose first, followed by xylose without delay for switching from one sugar to another. To improve growth on xylose and co-utilization capabilities, the ptsG deleted SSK42 was evolved on xylose. The strain evolved for 78 generations, strain SCD78, displayed significant co-utilization of glucose and xylose sugars. At the bioreactor level, the strain SCD78 produced 3-times the ethanol titer of the parent strain with significant glucose-xylose co-utilization. The rate of glucose and xylose consumption also increased 3.4-fold and 3-fold, respectively. Proteome data indicates significant upregulation of TCA cycle proteins, respiration-related proteins, and some transporters, which may have a role in increasing the total sugar consumption and co-utilization of sugars.

CONCLUSION

Through adaptive evolution, we have obtained a strain that has a significant glucose-xylose co-utilization phenotype with 3-fold higher total sugar consumption rate and ethanol production rate compared to the unevolved strain. This study also points out that adaptation on xylose is enough to impart glucose-xylose co-utilization property in CCR compromised ethanologenic strain SSK42.

Isolation and Characterization of Cellulose Nanocrystals from Date Palm Waste

This study presents the isolation, characterization, and kinetic analyses of cellulose nanocrystals (CNCs) from date palm waste in the United Arab Emirates. After bleaching date palm stem waste with acidified NaClO₂ and delignification via NaOH treatments, cellulose was extracted. Mineral acid hydrolysis (62 wt % H₂SO₄) was performed at 45 °C for 45 min to produce crystalline nanocellulose. Fourier transform infrared (FTIR) and chemical composition analysis confirmed the removal of noncellulosic constituents. The crystallinity index increased gradually with chemical treatments, according to the obtained X-ray diffraction (XRD) results. Thermogravimetric analysis and differential scanning calorimetry results revealed that the CNC has high thermal stability. The Coats-Redfern method was used to determine the kinetic parameters. The kinetic analysis confirmed that CNC has more activation energy than cellulose and thus confirms its compact and resistive crystalline structure. This has been attributable to the stronger hydrogen bonding in CNC crystalline domains than that in cellulose crystalline domains. Scanning electron microscopy revealed that lignin and hemicellulose were eliminated after chemical pretreatments, and CNC with a rodlike shape was obtained after hydrolysis. Moreover, transmission electron microscopy confirmed the nanoscale of crystalline cellulose. ζ potential analysis indicated that the CNC afforded a stable suspension (-29.27 mV), which is less prone to flocculation. Kinetic analyses of cellulose and cellulose nanocrystals isolated from date palm waste are useful for making composites and designing selective pyrolysis reactors.

Production of butanol from lignocellulosic biomass: recent advances, challenges, and prospects

Due to energy and environmental concerns, biobutanol is gaining increasing attention as an alternative renewable fuel owing to its desirable fuel properties. Biobutanol production from lignocellulosic biomass through acetone-butanol-ethanol (ABE) fermentation has gained much interest globally due to its sustainable supply and non-competitiveness with food, but large-scale fermentative production suffers from low product titres and poor selectivity. This review presents recent developments in lignocellulosic butanol production, including pretreatment and hydrolysis of hemicellulose and cellulose during ABE fermentation. Challenges are discussed, including low concentrations of fermentation sugars, inhibitors, detoxification, and carbon catabolite repression. Some key process improvements are also summarised to guide further research and development towards more profitable and commercially viable butanol fermentation.

Isolation and Characterization Cellulose Nanosphere from Different Agricultural By-Products

Cellulose nanospheres (CN) have been considered a leading type of nanomaterial that can be applied as a strengthening material in the production of nanocomposites. This work aimed to isolate and characterize the properties of CN from different agricultural by-products. CNs were successfully isolated from rice straw, corncob, Phulae pineapple leaf and peel using acid hydrolysis (60% H2SO4) combined with homogenization-sonication (homogenized at 12,000 rpm for 6 min and ultrasonicated for 10 min). The results showed that the CN from rice straw (RS-CN) and corncob (CC-CN) exhibited high yields (22.27 and 22.36%) (p < 0.05). All hydrolyzed CNs exhibited a spherical shape with a diameter range of 2 to 127 nm. After acid hydrolysis, Fourier transform infrared (FTIR) results showed no impurities. X-ray diffraction (XRD) showed that the structure of cellulose was changed from cellulose-I to cellulose-II. However, cellulose-I remained in pineapple peel cellulose nanosphere (PP-CN). The crystalline index (CI) ranged from 43.98 to 73.58%, with the highest CI obtained in the CC-CN. The CN from all sources presented excellent thermal stability (above 300 °C). The functional properties, including water absorption Index (WAI), water solubility index (WSI) and swelling capacity were investigated. PP-CN showed the highest WAI and swelling capacity, while the PL-CN had the highest WSI (p < 0.05). Among all samples, CC-CN showed the highest extraction yield, small particle size, high CI, and desirable functional properties to be used as a material for bio-nanocomposites film.