Pyrolysis kinetics of potassium-impregnated rubberwood analyzed by evolutionary computation

To explore the catalytic effect of potassium on pyrolysis characteristics of biomass, the rubberwood is pyrolyzed by a thermogravimetric analyzer. The samples are impregnated by three concentrations of potassium carbonate (0.004 M, 0.008 M, and 0.012 M). The pyrolysis kinetics is analyzed by an independent parallel reaction (IPR) model to describe the catalytic effect on the four-pseudo components model in the rubberwood. The particle swarm optimization (PSO) is adopted to optimize the fit quality between the established kinetic models and experimental data. It is found that the pyrolysis of rubberwood impregnated with 0.012 M concentration of K₂CO₃ can reduce the activation energy of cellulose from 223.86 to 204.14 kJ mol^-1, whereas there is no obvious effect on the activation energies of hemicelluloses and lignin. The starting temperature and ending temperature of cellulose thermodegradation also move toward lower temperatures, indicating that the addition of potassium enhances the degradation of cellulose.

Comprehensive analysis of important parameters of choline chloride-based deep eutectic solvent pretreatment of lignocellulosic biomass

Choline chloride based deep eutectic solvents have showed great potential in lignocellulosic biomass pretreatment. In this study, for DES pretreatment with different hydrogen bond donners of different raw materials under different reaction conditions, multivariate analysis methods including principal component analysis and partial least squares analysis were used for reveal the pretreatment mechanism by evaluating the inner relationships among 42 key process factors. Furthermore, based on molecular simulation, the detailed relationships between key variables were further analyzed. Meanwhile, four-dimensional color graphs were used to intuitively reveal the synergistic influence of multivariate conditions variables on pretreatment effect to obtain better economic benefits and energy consumption indicators for DES pretreatment. The results showed that HBD hydrophilic ability, HBD polarity, HBD acidity, HBD ability to form hydrogen bonds, molar ratio of HBD to choline chloride and pretreatment severity had great influence on the Choline chloride based deep eutectic solvents pretreatment effect.

Hydrothermal liquefaction of Prosopis juliflora biomass for the production of ferulic acid and bio-oil

The objective of this work was to study the hydrothermal liquefaction (HTL) of Prosopis juliflora biomass for the production of ferulic acid and bio-oil. Biomass was processed with various solvents (NaOH, KOH, HCl and H₂SO₄) to produce ferulic acid (FA). FA oxidation was carried out using the Nano ZnO catalyst to produce an optimum vanillin yield of 0.3 g at 70 °C with 0.4% catalyst loading for a time of 60 min. The spent solid residue was then processed using HTL at 5 MPa pressure and a temperature range of 240-340 °C. Various biomass loading (2.5 g to 12.5 g) was taken for a fixed water content of 200 mL. Bio-oil optimum yield was 22.5 wt% for 10 g/200 mL of biomass loading ratio. The optimum temperature was 300 °C for a processing time of 1 h. The catalyst showed the reusable capability of two three consecutive cycles.

A review on selective production of value-added chemicals via catalytic pyrolysis of lignocellulosic biomass

Increasing fossil fuel consumption and global warming has been driving the worldwide revolution towards renewable energy. Biomass is abundant and low-cost resource whereas it requires environmentally friendly and cost-effective conversion technique. Pyrolysis of biomass into valuable bio-oil has attracted much attention in the past decades due to its feasibility and huge commercial outlook. However, the complex chemical compositions and high water content in bio-oil greatly hinder the large-scale application and commercialization. Therefore, catalytic pyrolysis of biomass for selective production of specific chemicals will stand out as a unique pathway. This review aims to improve the understanding for the process by illustrating the chemistry of non-catalytic and catalytic pyrolysis of biomass at the temperatures ranging from 400 to 650 °C. The focus is to introduce recent progress about producing value-added hydrocarbons, phenols, anhydrosugars, and nitrogen-containing compounds from catalytic pyrolysis of biomass over zeolites, metal oxides, etc. via different reaction pathways including cracking, Diels-Alder/aromatization, ketonization/aldol condensation, and ammoniation. The potential challenges and future directions for this technique are discussed in deep.

Integration of Pleurotus tuoliensis cultivation and biogas production for utilization of lignocellulosic biomass as well as its benefit evaluation

The present study was to assess the economic benefit of integrated P. tuoliensis cultivation and biogas production based on the utilization of lignocellulosic biomass. Among the five evaluated cultivation substrates, that consisting of 55% cottonseed hull, 25% corncob, 10% wheat bran, 5% corn flour, 4% lime, and 1% gypsum was demonstrated to be optimal for the simultaneous production of P. tuoliensis mushrooms and biogas fuel. Preliminary estimation shows that, for the consumption of dry substrate per unit mass (calculated in per kg), a total of 561 g fresh mushroom product was harvested and 189.88 L biogas was generated. Accordingly, the production costs were abolished and an economic benefit of approximately $0.592 was obtained, with the high-value mushroom product being the main contributor to profit. Moreover, this integrated process also exhibited positive ecological and social benefits and as such, is worthy of promotion and further application.

Construction of the R17L mutant of MtC1LPMO for improved lignocellulosic biomass conversion by rational point mutation and investigation of the mechanism by molecular dynamics simulations

To enhance the biomass conversion efficiency, the R17L mutant of the lytic polysaccharide monooxygenase (LPMO) MtC1LPMO with improved catalytic efficiency was constructed via rational point mutation based on the HotSpot Wizard 3.0 and dezyme web servers. Compared with the wild-type (WT) MtC1LPMO, R17L exhibited a 1.8-fold increase of specific activity and 1.92-fold increase of catalytic efficiency (k_cat/K_m). The degree of increase of the reducing sugar yield from microcrystalline cellulose and three plant biomass materials during synergistic hydrolysis using cellulase in combination with R17L was about 2 times higher than with the WT. Molecular dynamics simulations revealed that the R17L mutation reduced the stability of the region R18-I36, which then weakened the direct interactions between region N24-V31 and the substrate cellohexaose. Consequently, the deflection time of the cellohexaose conformation in R17L was prolonged compared to the WT, which enhanced its catalytic efficiency.

Enzymatic hydrolysis of several pretreated lignocellulosic biomasses: Fractal kinetic modelling

Enzymatic hydrolysis of three pre-treated lignocellulosic biomasses -LCB- (wheat straw-WS-, corn stover-CSV- and cardoon stems -CS-) is studied. These biomasses were pre-treated by two methods: diluted sulfuric acid and acid ethanol-water extraction at six severity levels (H values). Pretreated solid fractions were hydrolyzed with commercial enzyme cocktails at standard conditions. A first-order kinetic fractal model was fitted to the experimental results. This model accurately describes the hydrolysis of all biomasses at all pre-treatment conditions studied. The results show that the formal first-order kinetic constant k depends on the biomass nature. The hydrolysis rate increases as the pre-treatment severity does, while the fractal exponent value h decreases. With these pre-treatments, and in terms of k and h, WS is highly reactive and, at medium H with EW pretreatment, highly accessible; CSV has a low reactivity and high accessibility and CS has the lowest reactivity and an increasing accessibility as severity rises.

Characterization of an AA9 LPMO from Thielavia australiensis, TausLPMO9B, under industrially relevant lignocellulose saccharification conditions

BACKGROUND

The discovery of lytic polysaccharide monooxygenases (LPMO) has changed our perspective on enzymatic degradation of plant biomass. Through an oxidative mechanism, these enzymes are able to cleave and depolymerize various polysaccharides, acting not only on crystalline substrates such as chitin and cellulose, but also on other polysaccharides, such as xyloglucan, glucomannan and starch. Despite their widespread use, uncertainties related to substrate specificity and stereospecificity, the nature of the co-substrate, in-process stability, and the nature of the optimal reductant challenge their exploitation in biomass processing applications.

RESULTS

In this work, we studied the properties of a novel fungal LPMO from the thermophilic fungus Thielavia australiensis, TausLPMO9B. Heterologous expression of TausLPMO9B in Aspergillus niger yielded a glycosylated protein with a methylated N-terminal histidine showing LPMO activity. High sequence identity of the AA9 domain to that of MtLPMO9B (MYCTH_80312) from Myceliophthora thermophila (84%) indicated strictly C1-oxidizing activity on cellulose, which was confirmed experimentally by the analysis of products released from cellulose using HPAEC. The enzyme was stable and active at a pH ranging from 4 to 6, thus matching the conditions commonly used in industrial biomass processing, where a low pH (between 4 and 5) is used due to the pH-optima of commercial cellulases and a desire to limit microbial contamination.

CONCLUSION

While the oxidative cleavage of phosphoric acid swollen cellulose (PASC) by TausLPMO9B was boosted by the addition of H2O2 as a co-substrate, this effect was not observed during the saccharification of acid pretreated corn stover. This illustrates key differences between the lab-scale tests with artificial, lignin-free substrates and industrial settings with lignocellulosic biomass as substrate.

Towards a Miniaturized Culture Screening for Cellulolytic Fungi and Their Agricultural Lignocellulosic Degradation

The substantial use of fungal enzymes to degrade lignocellulosic plant biomass has widely been attributed to the extensive requirement of powerful enzyme-producing fungal strains. In this study, a two-step screening procedure for finding cellulolytic fungi, involving a miniaturized culture method with shake-flask fermentation, was proposed and demonstrated. We isolated 297 fungal strains from several cellulose-containing samples found in two different locations in Thailand. By using this screening strategy, we then selected 9 fungal strains based on their potential for cellulase production. Through sequence-based identification of these fungal isolates, 4 species in 4 genera were identified: Aspergillus terreus (3 strains: AG466, AG438 and AG499), Penicillium oxalicum (4 strains: AG452, AG496, AG498 and AG559), Talaromyces siamensis (1 strain: AG548) and Trichoderma afroharzianum (1 strain: AG500). After examining their lignocellulose degradation capacity, our data showed that P. oxalicum AG452 exhibited the highest glucose yield after saccharification of pretreated sugarcane trash, cassava pulp and coffee silverskin. In addition, Ta. siamensis AG548 produced the highest glucose yield after hydrolysis of pretreated sugarcane bagasse. Our study demonstrated that the proposed two-step screening strategy can be further applied for discovering potential cellulolytic fungi isolated from various environmental samples. Meanwhile, the fungal strains isolated in this study will prove useful in the bioconversion of agricultural lignocellulosic residues into valuable biotechnological products.

A comprehensive review on the framework to valorise lignocellulosic biomass as biorefinery feedstocks

An effective pretreatment is the first step to enhance the digestibility of lignocellulosic biomass - a source of renewable, eco-friendly and energy-dense materials - for biofuel and biochemical productions. This review aims to provide a comprehensive assessment on the advantages and disadvantages of lignocellulosic pretreatment techniques, which have been studied at the lab-, pilot- and full-scale levels. Biological pretreatment is environmentally friendly but time consuming (i.e. 15-40 days). Chemical pretreatment is effective in breaking down lignocellulose and increasing sugar yield (e.g. 4 to 10-fold improvement) but entails chemical cost and expensive reactors. Whereas the combination of physical and chemical (i.e. physicochemical) pretreatment is energy intensive (e.g. energy production can only compensate 80% of the input energy) despite offering good process efficiency (i.e. > 100% increase in product yield). Demonstrations of pretreatment techniques (e.g. acid, alkaline, and hydrothermal) in pilot-scale have reported 50-80% hemicellulose solubilisation and enhanced sugar yields. The feasibility of these pilot and full-scale plants has been supported by government subsidies to encourage biofuel consumption (e.g. tax credits and mandates). Due to the variability in their mechanisms and characteristics, no superior pretreatment has been identified. The main challenge lies in the capability to achieve a positive energy balance and great economic viability with minimal environmental impacts i.e. the energy or product output significantly surpasses the energy and monetary input. Enhancement of the current pretreatment techno-economic efficiency (e.g. higher product yield, chemical recycling, and by-products conversion to increase environmental sustainability) and the integration of pretreatment methods to effectively treat a range of biomass will be the steppingstone for commercial lignocellulosic biorefineries.

In situ measurements of viscoelastic properties of biomass during hydrothermal treatment to assess the kinetics of chemical alterations

This work aimed to use continuous measurements of viscoelastic properties to evaluate the effect of hydrothermal treatment on poplar samples. Different conditions (temperature and pre-soaking liquid: acidic, neutral and alkaline) were tested on wood in both tangential and radial directions. Two viscoelastic properties were determined: the modulus of elasticity and the stress relaxation. The applicability of these properties as indicators of the kinetics of biomass deconstruction was also evaluated, thanks to the chemical analyses performed on the treated solid and the recovered liquid phase. The ultimate goal is to build a macroscopic indicator capable of establishing rules to optimize the hydrothermal treatment before the explosion stage. The joint use of the two parameters succeeded in revealing the effects of chemical degradation, including the coexistence of cleavage and re-condensation and the impact of process conditions (temperature, residence time, and pre-soaking liquid). The monotonous behavior of stress relaxation is a major asset as a possible macroscopic indicator of biomass deconstruction.

Process design and economic assessment of butanol production from lignocellulosic biomass via chemical looping gasification

Biomass chemical looping gasification (BCLG) is a promising gasification technology to convert biomass into synthesis gas with no need for molecular oxygen. In this study, a novel process for butanol production from lignocellulosic biomass based on BCLG is proposed. The proposed process is simulated using Aspen Plus and composed of main sub-processes such as BCLG, acid gas removal, synthesis and separation of alcohol. An economic assessment is conducted according to results of Aspen Plus model. The equipment cost for the proposed process is evaluated as 4.65 × 10⁸ CNY and the minimum butanol selling price is estimated as 9.35 CNY/kg. Sensitivity analysis of the process indicates that pine sawdust price has the largest effect on the minimum butanol selling price followed by total equipment cost and plant lifetime. Finally, impacts of CO conversion and carbon tax on the minimum butanol selling price are explored.

Molecular engineering to improve lignocellulosic biomass based applications using filamentous fungi

Lignocellulosic biomass is an abundant and renewable resource, and its utilization has become the focus of research and biotechnology applications as a very promising raw material for the production of value-added compounds. Filamentous fungi play an important role in the production of various lignocellulolytic enzymes, while some of them have also been used for the production of important metabolites. However, wild type strains have limited efficiency in enzyme production or metabolic conversion, and therefore many efforts have been made to engineer improved strains. Examples of this are the manipulation of transcriptional regulators and/or promoters of enzyme-encoding genes to increase gene expression, and protein engineering to improve the biochemical characteristics of specific enzymes. This review provides and overview of the applications of filamentous fungi in lignocellulosic biomass based processes and the development and current status of various molecular engineering strategies to improve these processes.

Biotransformation of lignocellulosic biomass into industrially relevant products with the aid of fungi-derived lignocellulolytic enzymes

Lignocellulosic material has drawn significant attention among the scientific community due to its year-round availability as a renewable resource for industrial consumption. Being an economic substrate alternative, various industries are reevaluating processes to incorporate derived compounds from these materials. Varieties of fungi and bacteria have the ability to depolymerize lignocellulosic biomass by synthesizing degrading enzymes. Owing to catalytic activity stability and high yields of conversion, lignocellulolytic enzymes derived from fungi currently have a high spectrum of industrial applications. Moreover, these materials are cost effective, eco-friendly and nontoxic while having a low energy input. Techno-economic analysis for current enzyme production technologies indicates that synthetic production is not commercially viable. Instead, the economic projection of the use of naturally-produced ligninolytic enzymes is promising. This approach may improve the economic feasibility of the process by lowering substrate expenses and increasing lignocellulosic by-product's added value. The present review will discuss the classification and enzymatic degradation pathways of lignocellulolytic biomass as well as the potential and current industrial applications of the involved fungal enzymes.

Propionic acid production by Propionibacterium freudenreichii using sweet sorghum bagasse hydrolysate

Propionic acid, a widely used food preservative and intermediate in the manufacture of various chemicals, is currently produced from petroleum-based chemicals, raising concerns about its long-term sustainability. A key way to make propionic acid more sustainable is through fermentation of low-cost renewable and inedible sugar sources, such as lignocellulosic biomass. To this end, we utilized the cellulosic hydrolysate of sweet sorghum bagasse (SSB), a residue from a promising biomass source that can be cultivated around the world, for fermentative propionic acid production using Propionibacterium freudenreichii. In serum bottles, SSB hydrolysate supported a higher propionic acid yield than glucose (0.51 vs. 0.44 g/g, respectively), which can be attributed to the presence of additional nutrients in the hydrolysate enhancing propionic acid biosynthesis and the pH buffering capacity of the hydrolysate. Additionally, SSB hydrolysate supported better cell growth kinetics and higher tolerance to product inhibition by P. freudenreichii. The yield was further improved by co-fermenting glycerol, a renewable byproduct of the biodiesel industry, reaching up to 0.59 g/g, whereas volumetric productivity was enhanced by running the fermentation with high cell density inoculum. In the bioreactor, although the yield was slightly lower than in serum bottles (0.45 g/g), higher final concentration and overall productivity of propionic acid were achieved. Compared to glucose (this study) and hydrolysates from other biomass species (literature), use of SSB hydrolysate as a renewable glucose source resulted in comparable or even higher propionic acid yields. KEY POINTS: • Propionic acid yield and cell growth were higher in SSB hydrolysate than glucose. • The yield was enhanced by co-fermenting SSB hydrolysate and glycerol. • The productivity was enhanced under high cell density fermentation conditions. • SSB hydrolysate is equivalent or superior to other reported hydrolysates.

Sophorolipid Production Using Lignocellulosic Biomass by Co-culture of Several Recombinant Strains of Starmerella bombicola with Different Heterologous Cellulase Genes from Penicillum oxalicum

One of the reasons hindering large-scale application of sophorolipids (SLs) is high production cost. In this study, six recombinant strains of Starmerella bombicola, sbEG1, sbEG2, sbCBH1, sbCBH1-2, sbBGL1, and sbCBH2 expressing cellulase genes eg1, eg2, cbh, cbh1-2, bgl1, and cbh2 from Penicillium oxalicum were respectively constructed. Four strains showed cellulase activities and were co-cultivated in fermentation media containing 2% glucose, 1% Regenerated Amorphous Cellulose (RAC), 2% glucose, and 1% RAC, respectively. After 7 days' cultivation, concentration of SLs in medium with 1% RAC (g/L) reached 1.879 g/L. When 2% glucose and 1% of RAC were both contained, the titer of SLs increased by 39.5% than that of control strain and increased by 68.8% than that in the medium with only 2% glucose. Results demonstrated that cellulase genes from filamentous fungi in S. bombicola can function to degrade lignocellulosic cellulose to produce SLs.

Weak-base pretreatment to increase biomethane production from wheat straw

Weak-base pretreatment of wheat straw was investigated for its ability to improve biomethane production. Anaerobic digestion (AD) was performed on wheat straw pretreated with 3%, 5%, or 7% Na₂CO₃ as a weak base. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR) spectra demonstrated disruption of lignocellulosic structures by pretreatment. In the 5% Na₂CO₃ treatment group, cellulose and hemicellulose were retained effectively, with efficient removal of lignin. The removal rates of cellulose, hemicellulose, and lignin were 27.9%, 20.4%, and 31.0%, respectively, after 5% Na₂CO₃ pretreatment. The methane content (53.3-77.3%) was improved in the 5% Na₂CO₃ treatment group, with maximum methane production (307.9 L/kg VS) that was 41.6% higher than that of the untreated sample. Cellulose and hemicelluloses were degraded 59.3% and 56.3% after AD. It took 20 days to reach 80% of the maximum cumulative methane production for the 5% Na₂CO₃ pretreatment group, which was 4 days faster than the untreated group. These results indicate that 5% Na₂CO₃ pretreatment improve the lignocellulose structure of wheat straw, allowing better biodegradability of wheat straw in AD for increased biogas production, enhanced methane content, and decreased digestion time.

Comprehensive assessment of 2G bioethanol production

The advancements in second-generation bioethanol produced from lignocellulosic biomass, such as crops residues, woody crops or energy grasses are gaining momentum. Though, they are still representing less than 3% of total bioethanol production, the GHG reduction potential is higher than for 1G-bioethanol. The environmental impacts of bioethanol production are totally dependent on feedstock availability and conversion technology. The biochemical conversion route must overcome several technological and economical challenges such as pre-treatment, fermentation, hydrolysis process and separation. A completely mature technology is still to be developed and must adapted to the nature of the feedstock. Nevertheless, using process simulation software, Life Cycle Assessment and integrating the different steps of bioresource harvesting and treatment processes, including the energy balances and the water requirements, it is shown that 2G bioethanol production will reduce environmental impacts provided the evaluation addresses a long-time perspective, including all conversion steps and the regeneration of the bioresource.

Saccharification of water hyacinth biomass by a combination of steam explosion with enzymatic technologies for bioethanol production

In the present work, bioethanol was produced by sugar fermentation obtained from water hyacinth using a novelty hybrid method composed of steam explosion and enzymatic hydrolysis, using hydrolytic enzymes produced by solid-state fermentation and water hyacinth as substrate. The highest activity, 42 U for xylanase and 2 U for cellulase per gram of dry matter, respectively, was obtained. Steam explosion pretreatment was performed at 190 ℃ for 1, 5, and 10 min, using water hyacinth sampled from the Maria Lizamba Lagoon, the Arroyo Hondo and the Amapa River. The highest amounts of reducing sugars of water hyacinth were obtained form the samples from the lagoon (5.4 g/50 g of dry matter) after 10 min of treatment. Steamed biomass was hydrolysed using the enzymes obtained by solid-state fermentation, obtained reducing sugars (maximum 15.5 g/L); the efficiency of enzymatic hydrolysis was 0.51 g of reducing sugars per gram of water hyacinth. Finally, reducing sugars were fermented using Saccharomyces cerevisiae for conversion to ethanol, with the highest ethanol concentration (7.13 g/L) and an ethanol yield of 0.23 g/g of dry matter.

Impact of hydrothermal pretreatment on anaerobic digestion efficiency for lignocellulosic biomass: Influence of pretreatment temperature on the formation of biomass-degrading byproducts

Anaerobic digestion (AD) of lignocellulosic biomass is appealing because of the abundance and ease of obtaining the biomass locally. However, the recalcitrance of lignocellulosic biomass presents an obstacle in the hydrolysis step of AD and lowers the process efficiency. In this study, sunflower, which is a model lignocellulosic biomass, was pretreated by thermal (hydrothermal pretreatment, HTP) and non-thermal (milling) methods; the methane yield and biodegradability of the pretreated biomass were determined using a series of batch tests. The thermal pretreatment method showed a significantly higher methane yield (213.87-289.47 mL g^-1 VS) and biodegradability (43-63%) than those of the non-thermally pretreated biomass, and the optimum pretreatment effect was observed at an HTP temperature of 180 °C. However, at an HTP temperature exceeding 200 °C, the induced formation of 5-hydroxymethylfurfural and furfural significantly lowered the methane yield and biodegradability. This study revealed that the HTP temperature is closely related to the formation of lignocellulosic biomass-degrading byproducts, which potentially hinder the methanogenesis step in AD; severe HTP conditions may have the opposite effect on the AD performance of lignocellulosic biomass.

YMR152W from Saccharomyces cerevisiae encoding a novel aldehyde reductase for detoxification of aldehydes derived from lignocellulosic biomass

Aldehydes are the main inhibitors generated during the pretreatment of lignocellulosic biomass, which can inhibit cell growth and disturb subsequent fermentation. Saccharomyces cerevisiae has the intrinsic ability to in situ detoxify aldehydes to their less toxic or nontoxic alcohols by numerous aldehyde dehydrogenases/reductases during the lag phase. Herein, we report that an uncharacterized open reading frame YMR152W from S. cerevisiae encodes a novel aldehyde reductase with catalytic functions for reduction of at least six aldehydes, including two furan aldehydes (furfural and 5-hydroxymethylfurfural), three aliphatic aldehydes (acetaldehyde, glycolaldehyde, and 3-methylbutanal), and an aromatic aldehyde (benzaldehyde) with NADH or NADPH as the co-factor. Particularly, Ymr152wp displayed the highest specific activity (190.86 U/mg), and the best catalytic rate constant (K_cat), catalytic efficiency (K_cat/K_m), and affinity (K_m) when acetaldehyde was used as the substrate with NADH as the co-factor. The optimum pH of Ymr152wp is acidic (pH 5.0-6.0), but this enzyme is more stable in alkaline conditions (pH 8.0). Metal ions, chemical protective additives, salts, and substrates could stimulate or inhibit enzyme activities of Ymr152wp in varying degrees. Ymr152wp was classified into the quinone oxidoreductase (QOR) subfamily of the medium-chain dehydrogenase/reductase (MDR) family based on the results of amino acid sequence analysis and phylogenetic analysis. Although Ymr152wp was grouped into the QOR family, no quinone reductase activity was observed using typical quinones (9,10-phenanthrenequinone, 1,2-naphthoquinone, and p-benzoquinone) as the substrates. This study provides guidelines for exploring more uncharacterized aldehyde reductases in S. cerevisiae for in situ detoxification of aldehyde inhibitors derived from lignocellulosic hydrolysis.

Fed-batch polyhydroxybutyrate production by Paraburkholderia sacchari from a ternary mixture of glucose, xylose and arabinose

Polyhydroxybutyrate (PHB) is a biodegradable bioplastic that is comparable with many petroleum-based plastics in terms of mechanical properties and is highly biocompatible. Lignocellulosic biomass conversion into PHB can increase profit and add sustainability. Glucose, xylose and arabinose are the main monomer sugars derived from upstream lignocellulosic biomass processing. The sugar mixture ratios may vary greatly depending on the pretreatment and enzymatic hydrolysis conditions. Paraburkholderia sacchari DSM 17165 is a bacterium strain that can convert all three sugars into PHB. In this study, fed-batch mode was applied to produce PHB on three sugar mixtures (glucose:xylose:arabinose = 4:2:1, 2:2:1, 1:2:1). The highest PHB concentration produced was 67 g/L for 4:2:1 mixture at 41 h corresponding to an accumulation of 77% of cell dry weight as PHB. Corresponding sugar conversion efficiency and productivity were 0.33 g PHB/g sugar consumed and 1.6 g/L/h, respectively. The results provide references for process control to maximize PHB production from real sugar streams derived from corn fibre.

Pretreatment of Mango (Mangifera indica L. Anacardiaceae) Seed Husk for Bioethanol Production by Dilute Acid Treatment and Enzymatic Hydrolysis

One of the targets of the Sustainable Development Goals is clean and affordable energy. This is also the aim of the Biofuels Act of 2007 in the Philippines. However, this law is confronted with challenges such as the limitation of lignocellulosic feedstock, specifically available for bioethanol production. The present study sought to address the issue by exploring the potential of mango seed husk (MSH), a by-product of the mango industry, in bioethanol production. MSH is considered a waste material and its utilization also permit value-addition as this can serve as an alternative and affordable source of feedstock in energy production. Two pretreatment strategies are employed to exploit the cellulose and hemicellulose content of MSH, namely, dilute acid treatment and enzymatic hydrolysis. Results show that the %H₂SO₄ resulting in the highest glucose concentration and yield is 4% v/v at 95 °C hydrolysis temperature, 1:10 (w/v) solid-to-solvent ratio, and 60-min hydrolysis time. For enzymatic hydrolysis using a commercial enzyme preparation, the reaction time up to 72 h did not affect glucose concentration and yield at the following conditions: 50 °C hydrolysis temperature, 150 rpm, pH 5.0, 10% solids loading, and 4% enzyme loading. This could be attributed to the lignin and non-structural compounds present in MSHs. However, a combined process strategy of dilute acid pretreatment followed by enzymatic hydrolysis in the pretreatment of MSH contributes to an increased concentration and yield of sugars in the hydrolysates, which is advantageous for bioethanol production. Graphical Abstract.

A critical review of the production and advanced utilization of biochar via selective pyrolysis of lignocellulosic biomass

Biochar is a carbon-rich product obtained from the thermo-chemical conversion of biomass. Studying the evolution properties of biochar by in-situ modification or post-modification is of great significance for improving the utilisation value of lignocellulosic biomass. In this paper, the production methods of biochar are reviewed. The effects of the biomass feedstock characteristics, production processes, reaction conditions (temperature, heating rate, etc.) as well as in-situ activation, heteroatomic doping, and functional group modification on the physical and chemical properties of biochar are compared. Based on its unique physicochemical properties, recent research advances with respect to the use of biochar in pollutant adsorbents, catalysts, and energy storage are reviewed. The relationship between biochar structure and its application are also revealed. It is suggested that a more effective control of biochar structure and its corresponding properties should be further investigated to develop a variety of biochar for targeted applications.

Derivation of volatile fatty acid from crop residues digestion using a rumen membrane bioreactor: A feasibility study

This study evaluates the feasibility of a novel rumen membrane bioreactor (rumen MBR) to produce volatile fatty acids (VFA) from crop residues (i.e. lignocellulosic biomass). Rumen MBR can provide a sustainable route for VFA production by mimicking the digestive system of ruminant animals. Rumen fluid was inoculated in a reactor coupled with ultrafiltration (UF) membrane and fed with maize silage and concentrate feed at 60:40% (w/w). Continuous VFA production was achieved at an average daily yield of 438 mg VFA/g substrate. The most abundant VFA were acetic (40-80%) and propionic (10-40%) acids. The majority (73 ± 15%) of produced VFA was transferred through the UF membrane. Shifts in dominant rumen microbes were observed upon the transition from in vivo to in vitro environment and during reactor operation, however, stable VFA yield was maintained for 35 days, providing the first proof-of-concept of a viable rumen MBR.