Two-Step Thermochemical Cellulose Hydrolysis With Partial Neutralization for Glucose Production

Sustainable media feedstocks for cellular agriculture

The global food system is shifting towards cellular agriculture, a second domestication marked by cultivating microorganisms and tissues for sustainable food production. This involves tissue engineering, precision fermentation, and microbial biomass fermentation to establish food value chains independent of traditional agriculture. However, these techniques rely on growth media sourced from agricultural, chemical (fossil fuels), and mining supply chains, raising concerns about land use competition, emissions, and resource depletion. Fermentable sugars, nitrogen, and phosphates are key ingredients derived from starch crops, energy-intensive fossil fuel based processes, and finite phosphorus resources, respectively. This review explores sustainable alternatives to reduce land use and emissions associated with cellular agriculture media ingredients. Sustainable alternatives to first generation sugars (lignocellulosic substrates, sidestreams, and gaseous feedstocks), sustainable nitrogen sources (sidestreams, green ammonia, biological nitrogen fixation), and efficient use of phosphates are reviewed. Especially cellulosic sugars, gaseous chemoautotrophic feedstocks, green ammonia, and phosphate recycling are the most promising technologies but economic constraints hinder large-scale adoption, necessitating more efficient processes and cost reduction. Collaborative efforts are vital for a biotechnological future grounded in sustainable feedstocks, mitigating competition with agricultural land and emissions.

Purification and Fractionation of Lignin via ALPHA: Liquid-Liquid Equilibrium for the Lignin-Acetic Acid-Water System

In order to effectively practice the Aqueous Lignin Purification with Hot Agents (ALPHA) process for lignin purification and fractionation, the temperatures and feed compositions where regions of liquid-liquid equilibrium (LLE) exist must be identified. To this end, pseudo-ternary phase diagrams for the lignin-acetic acid-water system were mapped out at 45-95 °C and various solvent: feed lignin mass ratios (S : F). For a given temperature, the accompanying SL (solid-liquid), SLL (solid-liquid-liquid), and one-phase regions were also located. For the first time, ALPHA using acetic acid (AcOH)-water solution was applied to a lignin recovered via the commercial LignoBoost process. In addition to determining tie-line compositions for the two regions of LLE that were discovered, the distribution of lignin and key impurities (the latter can negatively impact lignin performance for materials applications) between the two liquid phases was also measured. As a representative example, lignin isolated in the lignin-rich phase was reduced 7x in metals and 4x in polysaccharides by using ALPHA with a feed solvent composition of 50-55 % AcOH and an S : F of 6 : 1, with said lignin being obtained at a yield of 50-70 % of the feed lignin and having a molecular weight triple that of the feed.

Production of Water-Soluble Carbohydrates from Aspen Wood Flour with Hydrogen Chloride Gas

The aim of this study was to optimize the reaction conditions for concentrated acid hydrolysis of aspen wood flour by employing anhydrous hydrogen chloride gas to produce fermentable sugars. Gas hydrolysis with HCl was conducted both with and without temperature control during hydrolysis under a relatively low pressure of 0.1 MPa. Process parameters for HCl gas hydrolysis included the moisture content of aspen wood flour (0.7-50%) and reaction time under pressure (30 min to 24 h). In addition, liquid-phase hydrolysis with concentrated hydrochloric acid was conducted in concentrations of 32-42% and 15 min to 24 h reaction times for comparison with the gas-phase process. The highest yields (>90%) for water-soluble carbohydrates from aspen wood flour were achieved with temperature-controlled gas hydrolysis using 50% moisture content and 2 h total reaction time, which is in line with the previous research and comparable to hydrolysis with concentrated (42%) hydrochloric acid.

Degradation of cellulose polymorphs into glucose by HCl gas with simultaneous suppression of oxidative discoloration

As cellulose is the main polysaccharide in biomass, its degradation into glucose is a major undertaking in research concerning biofuels and bio-based platform chemicals. Here, we show that pressurized HCl gas is able to efficiently hydrolyze fibers of different crystalline forms (polymorphs) of cellulose when the water content of the fibers is increased to 30-50 wt%. Simultaneously, the harmful formation of strongly chromophoric humins can be suppressed by a simple addition of chlorite into the reaction system. 50-70 % glucose yields were obtained from cellulose I and II polymorphs while >90 % monosaccharide conversion was acquired from cellulose III_II after a mild post-hydrolysis step. Purification of the products is relatively unproblematic from a gas-solid mixture, and a gaseous catalyst is easier to recycle than the aqueous counterpart. The results lay down a basis for future practical solutions in cellulose hydrolysis where side reactions are controlled, conversion rates are efficient, and the recovery of products and reagents is effortless.

Ultrasonic cavitation: An effective cleaner and greener intensification technology in the extraction and surface modification of nanocellulose

With rising consumer demand for natural products, a greener and cleaner technology, i.e., ultrasound-assisted extraction, has received immense attention given its effective and rapid isolation for nanocellulose compared to conventional methods. Nevertheless, the application of ultrasound on a commercial scale is limited due to the challenges associated with process optimization, high energy requirement, difficulty in equipment design and process scale-up, safety and regulatory issues. This review aims to narrow the research gap by placing the current research activities into perspectives and highlighting the diversified applications, significant roles, and potentials of ultrasound to ease future developments. In recent years, enhancements have been reported with ultrasound assistance, including a reduction in extraction duration, minimization of the reliance on harmful chemicals, and, most importantly, improved yield and properties of nanocellulose. An extensive review of the strengths and weaknesses of ultrasound-assisted treatments has also been considered. Essentially, the cavitation phenomena enhance the extraction efficiency through an increased mass transfer rate between the substrate and solvent due to the implosion of microbubbles. Optimization of process parameters such as ultrasonic intensity, duration, and frequency have indicated their significance for improved efficiency.

Effect of microwave pretreatment on catalytic gasification of spirit-based distillers' grains to hydrogen-rich syngas

Steam gasification of spirit-based distillers' grains (SDGs) was performed in a fixed-bed reactor under different microwave pretreatment (MWP) approaches with or without addition of red mud (RM). The effects of MWP on the gasification rate, total gas yield, H₂/CO, and gasification mechanism of action were investigated. The results showed that RM could enhance the effect of MWP. The gasification rate, total gas yield and H₂/CO increased by 21.29%, 8.23% and 16.08%, respectively. In addition, RM and MWP had a synergistic effect on the catalytic gasification reaction. This was because MWP disrupted the complete ordered surface structure of the SDGs, allowing a large number of inherent alkali and alkaline earth metal ions to dissolve onto the surface and combine with the catalytically active material in RM to form a uniformly dispersed bimetallic catalyst. The catalytic mechanism consisted of an active-site catalytic mechanism and a bimetallic synergistic catalytic mechanism. Therefore, the combination of MWP and SDGs steam gasification is a promising, clean, efficient hydrogen-rich synthesis gas technology.

Land-Use Change Depletes Quantity and Quality of Soil Organic Matter Fractions in Ethiopian Highlands

The depletion of soil organic matter (SOM) reserve after deforestation and subsequent management practices are well documented, but the impacts of land-use change on the persistence and vulnerability of storage C and N remain uncertain. We investigated soil organic C (SOC) and N stocks in a landscape of chrono-sequence natural forest, grazing/crop lands and plantation forest in the highlands of North-West Ethiopia. We hypothesized that in addition to depleting total C and N pools, multiple conversions of natural forest significantly change the relative proportion of labile and recalcitrant C and N fractions in soils, and thus affect SOM quality. To examine this hypothesis, we estimated depletion of SOC and N stocks and labile (1 & 2) and recalcitrant (fraction 3) C and N pools in soil organic matter following the acid hydrolysis technique. Our studies showed the highest loss of C stock was in grazing land (58%) followed by cropland (50%) and eucalyptus plantation (47%), while on average ca. 57% N stock was depleted. Eucalyptus plantation exhibited potential for soil C recovery, although not for N, after 30 years. The fractionation of SOM revealed that depletions of labile 1 C stocks were similar in grazing and crop lands (36%), and loss of recalcitrant C was highest in grazing soil (56%). However, increases in relative concentrations of labile fraction 1 in grazing land and recalcitrant C and N in cropland suggest the quality of these pools might be influenced by management activities. Also, the C:N ratio of C fractions and recalcitrant indices (RIC and RIN) clearly demonstrated that land conversion from natural forest to managed systems changes the inherent quality of the fractions, which was obscured in whole soil analysis. These findings underscore the importance of considering the quality of SOM when evaluating disturbance impacts on SOC and N stocks.

A review on enzymes and pathways for manufacturing polyhydroxybutyrate from lignocellulosic materials

Currently, major focus in the biopolymer field is being drawn on the exploitation of plant-based resources grounded on holistic sustainability trends to produce novel, affordable, biocompatible and environmentally safe polyhydroxyalkanoate biopolymers. The global PHA market, estimated at USD 62 Million in 2020, is predicted to grow by 11.2 and 14.2% between 2020-2024 and 2020-2025 correspondingly based on market research reports. The market is primarily driven by the growing demand for PHA products by the food packaging, biomedical, pharmaceutical, biofuel and agricultural sectors. One of the key limitations in the growth of the PHA market is the significantly higher production costs associated with pure carbon raw materials as compared to traditional polymers. Nonetheless, considerations such as consumer awareness on the toxicity of petroleum-based plastics and strict government regulations towards the prohibition of the use and trade of synthetic plastics are expected to boost the market growth rate. This study throws light on the production of polyhydroxybutyrate from lignocellulosic biomass using environmentally benign techniques via enzyme and microbial activities to assess its feasibility as a green substitute to conventional plastics. The novelty of the present study is to highlight the recent advances, pretreatment techniques to reduce the recalcitrance of lignocellulosic biomass such as dilute and concentrated acidic pretreatment, alkaline pretreatment, steam explosion, ammonia fibre explosion (AFEX), ball milling, biological pretreatment as well as novel emerging pretreatment techniques notably, high-pressure homogenizer, electron beam, high hydrostatic pressure, co-solvent enhanced lignocellulosic fractionation (CELF) pulsed-electric field, low temperature steep delignification (LTSD), microwave and ultrasound technologies. Additionally, inhibitory compounds and detoxification routes, fermentation downstream processes, life cycle and environmental impacts of recovered natural biopolymers, review green procurement policies in various countries, PHA strategies in line with the United Nations Sustainable Development Goals (SDGs) along with the fate of the spent polyhydroxybutyrate are outlined.

Modelling of fermentative bioethanol production from indigenous Ulva prolifera biomass by Saccharomyces cerevisiae NFCCI1248 using an integrated ANN-GA approach

Third generation biomass (marine macroalgae) has been projected as a promising alternative energy resource for bioethanol production due to its high carbon and no lignin composition. However, the major challenge in the technologies of production lies in the fermentative bioconversion process. Therefore, in the present study the predictive ability of an integrated artificial neural network with genetic algorithm (ANN-GA) in the modelling of bioethanol production was investigated for an indigenous marine macroalgal biomass (Ulva prolifera) by a novel yeast strain, Saccharomyces cerevisiae NFCCI1248 using six fermentative parameters, viz., substrate concentration, fermentation time, inoculum size, temperature, agitation speed and pH. The experimental model was developed using one-variable-at-a-time (OVAT) method to analyze the effects of the fermentative parameters on bioethanol production and the obtained regression equation was used as a fitness function for the ANN-GA modelling. The ANN-GA model predicted a maximum bioethanol production at 30 g/L substrate, 48 h fermentation time, 10% (v/v) inoculum, 30 °C temperature, 50 rpm agitation speed and pH 6. The maximum experimental bioethanol yield obtained after applying ANN-GA was 0.242 ± 0.002 g/g RS, which was in close proximity with the predicted value (0.239 g/g RS). Hence, the developed ANN-GA model can be applied as an efficient approach for predicting the fermentative bioethanol production from macroalgal biomass.

Insight into the recent advances of microwave pretreatment technologies for the conversion of lignocellulosic biomass into sustainable biofuel

The utilization of renewable lignocellulosic biomasses for bioenergy synthesis is believed to facilitate competitive commercialization and realize affordable clean energy sources in the future. Among the pathways for biomass pretreatment methods that enhance the efficiency of the whole biofuel production process, the combined microwave irradiation and physicochemical approach is found to provide many economic and environmental benefits. Several studies on microwave-based pretreatment technologies for biomass conversion have been conducted in recent years. Although some reviews are available, most did not comprehensively analyze microwave-physicochemical pretreatment techniques for biomass conversion. The study of these techniques is crucial for sustainable biofuel generation. Therefore, the biomass pretreatment process that combines the physicochemical method with microwave-assisted irradiation is reviewed in this paper. The effects of this pretreatment process on lignocellulosic structure and the ratio of achieved components were also discussed in detail. Pretreatment processes for biomass conversion were substantially affected by temperature, irradiation time, initial feedstock components, catalyst loading, and microwave power. Consequently, neoteric technologies utilizing high efficiency-based green and sustainable solutions should receive further focus. In addition, methodologies for quantifying and evaluating effects and relevant trade-offs should be develop to facilitate the take-off of the biofuel industry with clean and sustainable goals.

Synthesis, Characterization and Mechanical Properties of Novel Bio-Based Polyurethane Foams Using Cellulose-Derived Polyol for Chain Extension and Cellulose Citrate as a Thickener Additive

A novel series of bio-based polyurethane composite foams was prepared, employing a cellulose-derived polyol for chain extension and cellulose-citrate as a thickener additive. The utilized polyol was obtained from the reduction reaction of cellulose-derived bio-oil through the use of sodium borohydride and iodine. Primarily, we produced both rigid and flexible polyurethane foams through chain extension of the prepolymers. Secondly, we investigated the role of cellulose citrate as a polyurethane additive to improve the mechanical properties of the realized composite materials. The products were characterized by FT-IR spectroscopy and their morphologies were analysed by SEM. Mechanical tests were evaluated to open new perspectives towards different applications.

Chemical and Structural Changes of Ozonated Empty Fruit Bunch (EFB) in a Ribbon-Mixer Reactor

Agricultural wastes especially empty fruit bunch (EFB) are abundantly available to be utilized as a feedstock for biochemical synthesis or biofuel production. The components of the waste include lignin, hemicellulose and cellulose. Cellulose, the polymer of glucose, is the active component for producing bio-based chemicals. However, it is difficult to isolate cellulose since lignin, the most outer layer in the waste is recalcitrant. Therefore, the agricultural wastes need to be pre-treated prior to downstream processing. The aim of this study was to investigate the effect of ozone pretreatment on lignin degradation and total reducing sugar (TRS) yield. EFB was pre-treated using ozone gas in a ribbon-mixer reactor. The chemical and structural changes of ozonated EFB were analysed. The highest delignification obtained were 95.7 wt.% and TRS yield was enhanced to 84.9% at a moisture content of 40 wt.% with 60 g/m3 ozone concentration within one hour of reaction time. Both NMR and FTIR spectra conferred major peaks inferring higher lignin degradation could be achieved using ozonolysis. Copyright © 2021 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). 

Semidry acid hydrolysis of cellulose sustained by autoclaving for production of reducing sugars for bacterial biohydrogen generation from various cellulose feedstock

Cellulosic biowastes are one of the cheapest and most abundant renewable organic materials on earth that can be, subsequent to hydrolysis, utilized as an organic carbon source for several fermentation biotechnologies. This study was devoted to explore a semidry acid hydrolysis of cellulose for decreasing the cost and ionic strength of the hydrolysate. For semidry acid hydrolysis, cellulose was just wetted with HCl (0 to 7 M) and subjected to autoclaving. The optimum molar concentration of HCl and period of autoclaving for semidry acid hydrolysis of cellulose were 6 M and 50 min respectively. Subsequent to the semidry acid hydrolysis with a minimum volume of 6 M HCl sustained by autoclaving, the hydrolysate was diluted with distilled water and neutralized with NaOH (0.5 M). The reducing sugars produced from the semidry acid hydrolysis of cellulose was further used for dark fermentation biohydrogen production by Escherichia coli as a representative of most hydrogen producing eubacteria which cannot utilize non-hydrolyzed cellulose. An isolated E. coli TFYM was used where this bacterium was morphologically and biochemically characterized and further identified by phylogenetic 16S rRNA encoding gene sequence analysis. The reducing sugars produced by semidry acid hydrolysis could be efficiently utilized by E. coli producing 0.4 mol H₂ mol^-1 hexose with a maximum rate of hydrogen gas production of 23.3 ml H₂ h^-1 L^-1 and an estimated hydrogen yield of 20.5 (L H₂ kg^-1 dry biomass). The cheap cellulosic biowastes of wheat bran, sawdust and sugarcane bagasse could be hydrolyzed by semidry acid hydrolysis where the estimated hydrogen yield per kg of its dry biomass were 36, 18 and 32 (L H₂ kg^-1 dry biomass) respectively indicating a good feasibility of hydrogen production from reducing sugars prepared by semidry acid hydrolysis of these cellulosic biowastes. Semidry acid hydrolysis could also be effectively used for hydrolyzing non-cellulosic polysaccharides of dry cyanobacterial biomass. The described semidry acid hydrolysis of cellulosic biowastes in this study might be applicable not only for bacterial biohydrogen production but also for various hydrolyzed cellulose-based fermentation biotechnologies.

Impact of Thermal Treatment of Nb2O5 on Its Performance in Glucose Dehydration to 5-Hydroxymethylfurfural in Water

The cascade dehydration of glucose to 5-hydroxymethylfurfural (HMF) was carried out in water over a series of Nb₂O₅ catalysts, which were derived from the thermal treatment of niobic acid at 300 and 550 °C, under air or inert atmosphere. Amorphous niobic acid showed high surface area (366 m²/g) and large acidity (2.35 mmol/g). With increasing the temperature of the thermal treatment up to 550 °C, the amorphous Nb₂O₅ was gradually transformed into a pseudohexagonal phase, resulting in a decrease in surface area (27-39 m²/g) and total acidity (0.05-0.19 mmol/g). The catalysts' performance in cascade dehydration of glucose realized in pure water was strongly influenced by the total acidity of these materials. A remarkable yield of 37% HMF in one-pot reaction in water was achieved using mesoporous amorphous niobium oxide prepared by thermal treatment of niobic acid at 300 °C in air. The best-performing catalyst displayed a total acidity lower than niobic acid (1.69 mmol/g) which afforded a correct balance between a high glucose conversion and limited further conversion of the target product to numerous polymers and humins. On the other hand, the treatment of niobic acid at 550 °C, independently of the atmosphere used during the sample preparation (i.e., air or N₂), resulted in Nb₂O₅ catalysts with a high ratio of Lewis to Brønsted acid sites and poor total acidity. These materials excelled at catalyzing the isomerization step in the tandem process.

Influence of Coupling Agent in Mechanical, Physical and Thermal Properties of Polypropylene/Bamboo Fiber Composites: Under Natural Outdoor Aging

Researches on thermoplastic composites using natural fiber as reinforcement are increasing, but studies of durability over time are scarce. In this sense the objective of this study is to evaluate changes in the properties of polypropylene/bamboo fiber (PP/BF) composite and the influence of the use of coupling agent (CA) in these composites after natural ageing. The PP/BF (70/30 wt) composites and 3% wt CA (citric acid from natural origin and maleic anhydride grafted polypropylene from petrochemical origin) were prepared by using an internal mixer chamber and then injection-molded. The samples were exposed to natural weathering for a total period of 12 months and characterized before and after exposure. All exposed composites experienced a decrease in their properties, however, the use of CA promoted more stability; in mechanical properties, the composites with CA showed lower loss about 23% in Young's modulus, 18% in tensile stress at break, and 6% in impact strength. This behavior was similar in thermal and physical properties, the result for the CA of natural origin being similar to that of synthetic origin. These results indicate that the use of a CA may promote higher interaction between the fiber and the polymer. In addition, the CAs of organic origin and synthetic origin exhibited similar responses to natural ageing.

Ethanol production from residual lignocellulosic fibers generated through the steam treatment of whole sorghum biomass

Cellulosic ethanol could play a major role in the upcoming circular-economy once the process complexity, low carbohydrate extraction yields and high costs are resolved. To this purpose, different steam-treatment severity factors were employed on whole sweet sorghum biomass, followed by the delignification and hydrolysis of resulted lignocellulose fibers. A modified ASTM International (American Society for Testing and Material) standard cellulose hydrolysis approach as well as a newly developed SACH (Sulfuric Acid Cellulose Hydrolysis) process were used, recovering up to 24.3 wt% of cellulosic carbohydrates. This amounted to a total extractable and constitutive carbohydrate recovery of 51.7 wt% (dry basis) when a mild steam-treatment of whole sorghum biomass and the SACH cellulose hydrolysis were employed. An ethanol potential of 6378 L/ha/year was determined, comparable to values obtained from biomass such as sugarcane in warmer climates, supporting thus the opportunity of implementing this novel approach on a wider scale.

Eco-Friendly Ca-Montmorillonite Grafted by Non-Acidic Ionic Liquid Used as A Solid Acid Catalyst in Cellulose Hydrolysis to Reducing Sugars

An effective and friendly method was developed for the production of reducing sugars (RS) from the hydrolysis of cellulose over the solid catalyst of Ca-montmorillonite (Mt) grafted by non-acidic ionic liquid (Mt-IL) in water. The effect of mass ratio, water dosage, reaction temperature, and time were investigated in a batch reactor. Raw Mt showed only a 7.9% total reducing sugars (TRS) yield for the catalytic hydrolysis of cellulose in water. As the Mt was grafted by -SO₃H and IL, the TRS yield greatly increased under the same reaction conditions. The highest TRS yield of 35.7% was obtained on the catalyst of Mt grafted by non-acidic IL at 200 °C with the mass ratio of catalyst to cellulose of 0.2 for 120 min. The high TRS yield for Mt-IL should be attributed to the synergistic effect of the dissolution of cellulose by IL and the exposed metal ions on the layer with water. Although the yield of TRS on Mt-IL decreased gradually with recycling runs, the decrease after the first run was not very serious compared to the fresh catalyst. This work provides a promising strategy for efficient cellulose hydrolysis into fine chemicals by Mt with non-acidic IL.