Biorefinery Setting Research Articles

Environment-friendly epoxidation of limonene using tungsten-based polyoxometalate catalyst

Terpene epoxides play a vital role as chemical intermediates in industries such as flavourings, fragrances, paints, and polymers manufacturing. However, current methods for limonene epoxidation suffer from low selectivity and environmental concerns. To address these limitations, we aimed to develop a highly selective and environmentally benign process for limonene epoxidation. Our approach involved employing hydrogen peroxide (H2O2) as an oxidant in the presence of tungsten-based polyoxometalates as catalysts. A novel catalyst was synthesized using sodium tungstate dihydrate (Na2WO4·2H2O), phosphoric acid (H3PO4), sulfuric acid (H2SO4), and sodium sulfate (Na2SO4) as an inorganic salt. We investigated the influence of various process variables, including the limonene:H2O2 molar ratio, reaction time, temperature, and solvent type, to optimize the epoxidation process. Through systematic screening, we achieved remarkable results, attaining 96% limonene conversion, 80% selectivity to limonene-1,2-epoxide, and 19% selectivity to limonene bis-epoxide within a short reaction time of 15 min. Notably, this high performance was accomplished by introducing H2O2 in a single step. To mitigate the hydrolysis of the epoxide, we employed sodium sulphate (Na2SO4) to saturate the reaction mixture. Furthermore, we proposed a comprehensive mechanism for the limonene epoxidation process using tungsten-based polyoxometalates as catalysts. Our kinetic study revealed a first-order reaction with respect to both limonene and the catalyst. Importantly, the decomposition of H2O2 was negligible under the investigated operating conditions, confirming the stability and efficiency of our approach. Our findings present eco-friendly, scalable, and catalytic epoxidation methods as valuable synthetic tools for converting inexpensive bio-renewable terpene feedstocks into essential chemical building blocks. The implications of our work extend to the synthesis of useful chemical products in a biorefinery setting, promoting a more sustainable and efficient utilization of terpenes.

Valorization of Hemp-Based Packaging Waste with One-Pot Ionic Liquid Technology.

The range of applications for industrial hemp has consistently increased in various sectors over the years. For example, hemp hurd can be used as a resource to produce biodegradable packaging materials when incorporated into a fungal mycelium composite, a process that has been commercialized. Although these packaging materials can be composted after usage, they may present an opportunity for valorization in a biorefinery setting. Here, we demonstrate the potential of using this type of discarded packaging composite as a feedstock for biofuel production. A one-pot ionic liquid-based biomass deconstruction and conversion process was implemented, and the results from the packaging material were compared with those obtained from untreated hemp hurd. At a 120 °C reaction temperature, 7.5% ionic liquid loading, and 2 h reaction time, the packaging materials showed a higher lignocellulosic sugar yield and sugar concentrations than hemp hurd. Hydrolysates prepared from packaging materials also promoted production of higher titers (1400 mg/L) of the jet-fuel precursor bisabolene when used to cultivate an engineered strain of the yeast Rhodosporidium toruloides. Box-Behnken experiments revealed that pretreatment parameters affected the hemp hurd and packaging materials differently, evidencing different degrees of recalcitrance. This study demonstrated that a hemp hurd-based packaging material can be valorized a second time once it reaches the end of its primary use by supplying it as a feedstock to produce biofuels.

Life cycle assessment of a seaweed-based biorefinery concept for production of food, materials, and energy

Blue Economy is seen as an essential contributor to a sustainable development, and it is an important part of the EU Green Deal. Seaweed plays a key role in the Blue Economy as a source of food, feed, and feedstock for biorefineries. Today, the largest part of global seaweed production is based in Asia, but there is also a growing interest in seaweed production in Europe. However, more knowledge on the environmental impacts is needed to ensure sustainable growth of the sector. Seaweed can be used in biorefineries to produce a variety of products for food and non-food applications. The aim of this paper was to perform a life cycle assessment (LCA) of a seaweed value-chain, including seaweed cultivation and production into sodium alginate, biodegradable materials, biogas, and fertilizer in a biorefinery setting. The LCA included 19 environmental impact categories but focused on climate change. The seaweed Saccharina latissima was cultivated and processed in Ireland. Sodium alginate was then extracted by means of ultrasound-assisted extraction, a novel extraction technology. Cellulosic residues produced after the extraction were used for the production of films used as a packaging material. Residues that remain after the production of the films were sent to anaerobic digestion to achieve a no-waste concept. For seaweed cultivation, fuel use and drying of seaweed biomass were the main environmental hot spots; and for the alginate extraction process, the yield and purification after extraction were the main hot spots. Overall, the results of this paper showed that the seaweed-based biorefinery has the potential to be sustainable, but several improvements are necessary before it is competitive with land-based systems.

A decision-support framework for techno-economic-sustainability assessment of resource recovery alternatives

The careful consideration of technology readiness, economics and sustainability holds the key to identifying and then transitioning a resource recovery opportunity into actual implemented solution. Currently this decision-making process is carried out based on in-house experience of stake-holders as there is no established framework that can be followed. This work presents a systematic computer-aided decision-support framework to tackle challenges faced when attempting to identify and develop resource recovery projects. The framework is hierarchical and combines key evaluation aspects in one integrated approach. The framework will enable industries transition towards more sustainable production, providing users with the opportunity to evaluate and support decisions on not only a financial basis, but also from a comprehensive techno-economic and sustainability angle. To this end, the framework collects relevant aspects within the sustainability field and addresses concepts such as circular economy, resource recovery, and waste management. This research also aims to add additional relevant inputs for increasing the possibilities to reach the scope of cleaner production. The proposed methodology is generic and can be applied to a wide variety of potential resource recovery projects. The application of the framework is highlighted through an industrial case study of the monosaccharide recovery from wheat straw liquor in bio-refinery setting.

Towards the Production of mcl-PHA with Enriched Dominant Monomer Content: Process Development for the Sugarcane Biorefinery Context

The production of short-chain-length polyhydroxyalkanoates (scl-PHAs) in a sugarcane biorefinery setting has been demonstrated to be an effective strategy to reduce production costs. Medium-chain-length PHA (mcl-PHA) have elastomeric properties and are more suitable for high value-added applications, but its industrial production is not yet established. Mcl-PHA synthesis occurs via different metabolic routes and thus requires distinct microorganisms and substrates compared to scl-PHA. In the present study, sucrose-derived carbohydrates were evaluated as co-substrates for the production of mcl-PHA from decanoic acid (DA). Fermentation strategies were investigated to produce mcl-PHA with enriched dominant monomer content, which is desirable for commercial applications. The mcl-PHA production was investigated in carbon-limited, fed-batch fermentations with wild-type and β-oxidation knockout mutant strains of Pseudomonas putida KT2440. The experimental results demonstrated that a mixture of glucose and fructose was a suitable co-feed with DA for mcl-PHA production, yielding equivalent results to those obtained with starch-derived glucose, a more traditional feedstock for PHA production. The use of a β-oxidation-impaired strain was essential to attain high dominant monomer content. A near-homopolymeric mcl-PHA was produced under exponential feeding, containing 99 mol% of 3-hydroxydecanoate. This work demonstrates the potential for near-homopolymeric mcl-PHA production in a sugarcane biorefinery, using hydrolyzed sucrose and DA.

Breeding for dual-purpose wheat varieties using marker-trait associations for biomass yield and quality traits.

This study demonstrates that an active breeding nursery with rotation can be used to identify marker-trait associations for biomass yield and quality parameters that are important for biorefinery purposes. Wheat straw is a valuable feedstock for bioethanol production, but due to the recalcitrant nature of lignocellulose, its efficient use in biorefineries is limited by its low digestibility and difficult conversion of structural carbohydrates into free sugars. A genome-wide association study (GWAS) was conducted to search for significant SNP markers that could be used in a breeding programme to improve the value of wheat straw in a biorefinery setting. As part of a 3-year breeding programme (2013-2016), 190 winter wheat lines were phenotyped for traits that affect the yield and quality of the harvested biomass. These traits included straw yield, plant height, lodging at three growth stages and Septoria tritici blotch (STB) susceptibility. Release of glucose, xylose and arabinose was determined after hydrothermal pretreatment and enzymatic hydrolysis of the straw. The lines were genotyped using 15K SNP markers and 5552 SNP markers could be used after filtering. Heritability for all traits ranged from 0.02 to 0.74. GWASs were conducted using CMLM, SUPER and FarmCPU algorithms, to analyse which algorithm could detect the highest number of marker-trait associations (MTAs). Comparable tendencies were obtained from CMLM and FarmCPU, but FarmCPU produced the most significant results. MTAs were obtained for lodging, harvest index, plant height, STB, glucose, xylose and arabinose at a significance level of p < 9.01 × 10-6. MTAs in chromosome 6A were observed for glucose, xylose and arabinose, and could be of importance for increasing sugar release for bioethanol production.

Mono- and poly-unsaturated triacylglycerol fractionation from Chlorella sp. using supercritical carbon dioxide

Extraction of unsaturated triacylglycerols from microalgae is important towards the viability of a sustainable biorefinery. Supercritical carbon dioxide was used to extract and enrich the mono- and poly-unsaturated triacylglycerols using a step-wise extraction scheme where the supercritical carbon dioxide density was increased from 450 to 550 to 750 mg/ml over a total of 170 min. At the lowest density of 450 mg/ml, saturated fatty acid triacylglycerols comprised 88% (mol) of the extract while mono- and poly-unsaturated triacylglycerols were over 60% and 80% (mol) at 550 and 750 mg/ml supercritical carbon dioxide respectively. This extraction scheme was informed by solubility and intermolecular interactions of mixed triacylglycerols. Chrastil's solubility parameters suggested that saturated fatty acid triacylglycerols were susceptible to intermolecular interactions while mono- and poly-unsaturated triacylglycerols are less susceptible to these interactions. Combined with the low solubility of mono- and poly-unsaturated triacylglycerols and high solubility of saturated fatty acid triacylglycerols at low densities, these phenomena were combined to demonstrate how supercritical carbon dioxide can be tuned to fractionate mono- and poly-unsaturated triacylglycerols from saturated fatty acids from microalgae. This is significant as supercritical carbon dioxide extraction technology is scalable and suitable as a first unit process for separations in a biorefinery setting.

Enhancement of cellulase production in Trichoderma reesei RUT-C30 by comparative genomic screening

BackgroundCellulolytic enzymes produced by the filamentous fungus Trichoderma reesei are commonly used in biomass conversion. The high cost of cellulase is still a significant challenge to commercial biofuel production. Improving cellulase production in T. reesei for application in the cellulosic biorefinery setting is an urgent priority.ResultsTrichoderma reesei hyper-cellulolytic mutant SS-II derived from the T. reesei NG14 strain exhibited faster growth rate and more efficient lignocellulosic biomass degradation than those of RUT-C30, another hyper-cellulolytic strain derived from NG14. To identify any genetic changes that occurred in SS-II, we sequenced its genome using Illumina MiSeq. In total, 184 single nucleotide polymorphisms and 40 insertions and deletions were identified. SS-II sequencing revealed 107 novel mutations and a full-length wild-type carbon catabolite repressor 1 gene (cre1). To combine the mutations of RUT-C30 and SS-II, the sequence of one confirmed beneficial mutation in RUT-C30, cre196, was introduced in SS-II to replace full-length cre1, forming the mutant SS-II-cre196. The total cellulase production of SS-II-cre196 was decreased owing to the limited growth of SS-II-cre196. In contrast, 57 genes mutated only in SS-II were selected and knocked out in RUT-C30. Of these, 31 were involved in T. reesei growth or cellulase production. Cellulase activity was significantly increased in five deletion strains compared with that in two starter strains, RUT-C30 and SS-II. Cellulase production of T. reesei Δ108642 and Δ56839 was significantly increased by 83.7% and 70.1%, respectively, compared with that of RUT-C30. The amount of glucose released from pretreated corn stover hydrolyzed by the crude enzyme from Δ108642 increased by 11.9%.ConclusionsThe positive attribute confirmed in one cellulase hyper-producing strain does not always work efficiently in another cellulase hyper-producing strain, owing to the differences in genetic background. Genome re-sequencing revealed novel mutations that might affect cellulase production and other pathways indirectly related to cellulase formation. Our strategy of combining the mutations of two strains successfully identified a number of interesting phenotypes associated with cellulase production. These findings will contribute to the creation of a gene library that can be used to investigate the involvement of various genes in the regulation of cellulase production.

Engineering Non-cellulosic Polysaccharides of Wood for the Biorefinery.

Non-cellulosic polysaccharides constitute approximately one third of usable woody biomass for human exploitation. In contrast to cellulose, these substances are composed of several different types of unit monosaccharides and their backbones are substituted by various groups. Their structural diversity and recent examples of their modification in transgenic plants and mutants suggest they can be targeted for improving wood-processing properties, thereby facilitating conversion of wood in a biorefinery setting. Critical knowledge on their structure-function relationship is slowly emerging, although our understanding of molecular interactions responsible for observed phenomena is still incomplete. This review: (1) provides an overview of structural features of major non-cellulosic polysaccharides of wood, (2) describes the fate of non-cellulosic polysaccharides during biorefinery processing, (3) shows how the non-cellulosic polysaccharides impact lignocellulose processing focused on yields of either sugars or polymers, and (4) discusses outlooks for the improvement of tree species for biorefinery by modifying the structure of non-cellulosic polysaccharides.

Pretreatment of trace element-enriched biomasses grown on phytomanaged soils for bioethanol production

Phytotechnologies are a set of sustainable, ecological options notably for alleviating pollutant linkages induced by contaminated soils. However, concerns exist regarding the processing of trace elements (TE)-enriched biomass and the fate of TEs in the end-products. The fractionation of phytoremediation TE-enriched non-woody lignocellulosic (tobacco) and woody (birch, willow) phytoremediation-borne biomasses was studied using ethanol organosolv, soda and dilute acid pretreatments. TE distribution in the process fractions (pulp, liquid effluents and lignin) was further examined. In dilute acid conditions, a wood pretreatment performed at 170°C in the presence of 2% w/w of sulfuric acid allowed an efficient extraction of the metals in the water effluent (≈90% for Mn and Zn) producing a clean pulp. A soda pretreatment resulted in a low metal extractability, especially at high temperature. At 170°C or above with 15% w/w of NaOH, metals were mostly recovered in the cellulosic pulp (70%- 98%). Using organosolv pulping, the TE contents were in the decreasing order: pulp≫water stream>lignin. The TE organosolv extraction in the liquid phase varied depending on the TE metal and on the species but was generally low. Metal extractability increased with the water content in the solvent of the organosolv pulping but decreased with temperature. Enzymatic hydrolyses of TE-enriched and metal-free pulps were investigated and it was concluded that the TE concentrations had little or no effect on polysaccharide enzymatic hydrolysability by cellulases. The final destination of the various fractions for valorization in a biorefinery setting is discussed, regarding their TE content.

Green Solvents in Biomass Processing

As new applications expand in the field of biomass refining and valorization, appropriate solvent development and usage will aid in viable implementation. This work presents an overview of green solvent applications within biomass production. Particular solvent needs for biomass fractions to produce fuels and value-added products are presented. Green solvent metrics with respect to functionality and environmental, safety, and health impacts from a process and life cycle view are also addressed and applied to conventional and neoteric solvents. Current and potential applications of various solvents for extractions and conversions are provided for consideration in a biorefinery setting with discussion of future needs.

Microalgae-based unsaponifiable matter as source of natural antioxidants and metal chelators to enhance the value of wet Tetraselmis chuii biomass

AbstractThe present work aimed to determine the antioxidant, metal chelating and neuroprotective potential of the unsaponifiable matter (UM) of Tetraselmis chuii to be applied to a biorefinery setting. The UM obtained via saponification from crude lipids extracted from microalgal wet biomass showed a radical scavenging activity (RSA) towards the DPPH radical of 90.7±1.3% and 57.1±1.2% at a concentration of 10 and 5 mg/mL, respectively. The UM fraction also displayed metal chelating capacity at a concentration of 5 mg/mL: 58.5±1.4% and 50.9±4.0% for copper and iron, respectively. The chemical characterization of the UM revealed significant levels of total phenolics (TPC, 13.61 mg GAE/g) and carotenoids (2.45 mg/g of β-carotene, lutein and violaxanthin). Overall, the separation of the UM containing high value metabolites might significantly upgrade the total wet biomass value in a biorefinery, allowing the exploitation of a stream with relevant antioxidant and metal chelating activities.

Conversion of levulinic acid into γ-valerolactone using Fe3(CO)12: mimicking a biorefinery setting by exploiting crude liquors from biomass acid hydrolysis.

The conversion of biomass-derived levulinic acid (LA) into gamma-valerolactone (GVL) using formic acid (FA) and Fe3(CO)12 as the catalyst precursor was achieved in 92% yield. To mimic a biorefinery setting, crude liquor (containing 20% LA) from the acid hydrolysis of sugarcane biomass in a pilot plant facility was directly converted into GVL in good yield (50%), without the need for isolating LA.

Monitoring switchgrass composition to optimize harvesting periods for bioenergy and value-added products

Switchgrass (Panicum virgatum) is a perennial grass that has emerged as an ideal candidate for production of biofuel and value-added co-products. One of the primary requirements for the successful manufacturing of these switchgrass-derived bioproducts is to produce a consistent feedstock with reliable and adequate amounts of the substrate constituent needed. For example, the biofuels industry requires a fast-growing energy crop with higher cellulose content and lower inhibitors found in secondary constituents. Other industries would profit from higher lignin content for products such as carbon fibers, or higher water and ethanol-soluble extracts containing compounds of interest. Two switchgrass field plots in eastern Tennessee were monitored over a period of six months, including before and after traditional harvesting times for the biorefinery. Characterization of the biomass and its constituents, such as water and ethanol extracts, cellulose, hemicelluloses, lignin, and ash, was performed to examine chemical changes in switchgrass that occurred prior to, during, and after traditional harvesting times used in a biorefinery setting. Total carbohydrate (65.6–66.7 wt%) and lignin (21.7–23.2 wt%) content was found to peak in January. Extractives content was at a maximum in early harvests at 15.9–16.6 wt% and decreased to 5.5–5.8 wt% in February. An inverse relationship exists between the extractives and lignin content (R2 = 0.94). Nonstructural soluble sugars peaked in early October with 5.1 wt% of the switchgrass composition. Remobilization efficiencies of K, Mg, P, and Fe increased with time, indicating conservation of soil nutrients if harvests were completed in late winter.

Expression and functional studies of genes involved in transport and metabolism of glycerol in Pachysolen tannophilus

BackgroundPachysolen tannophilus is a non-conventional yeast, which can metabolize many of the carbon sources found in low cost feedstocks including glycerol and xylose. The xylose utilisation pathways have been extensively studied in this organism. However, the mechanism behind glycerol metabolism is poorly understood. Using the recently published genome sequence of P. tannophilus CBS4044, we searched for genes with functions in glycerol transport and metabolism by performing a BLAST search using the sequences of the relevant genes from Saccharomyces cerevisiae as queries.ResultsQuantitative real-time PCR was performed to unveil the expression patterns of these genes during growth of P. tannophilus on glycerol and glucose as sole carbon sources. The genes predicted to be involved in glycerol transport in P. tannophilus were expressed in S. cerevisiae to validate their function. The S. cerevisiae strains transformed with heterologous genes showed improved growth and glycerol consumption rates with glycerol as the sole carbon source.ConclusionsP. tannophilus has characteristics relevant for a microbial cell factory to be applied in a biorefinery setting, i.e. its ability to utilise the carbon sources such as xylose and glycerol. However, the strain is not currently amenable to genetic modification and transformation. Heterologous expression of the glycerol transporters from P. tannophilus, which has a relatively high growth rate on glycerol, could be used as an approach for improving the efficiency of glycerol assimilation in other well characterized and applied cell factories such as S. cerevisiae.

Production and characterization of Escherichia coli glycerol dehydrogenase as a tool for glycerol recycling

NAD+-dependent glycerol (Gro) dehydrogenase (GroDHase) catalyzes the conversion of Gro into dihydroxyacetone (DHA), the first step for fermentative Gro metabolism in Escherichia coli. In this work, we cloned the gldA gene that codes for the E. coli GroDHase and homologously expressed, purified, and kinetically characterized the recombinant protein. To achieve this, the enzyme was over-produced using Gro supplemented growth medium and lactose as the inducer. The enzyme was highly purified using either pseudo-affinity chromatography or a simple heat-shock treatment, which is potentially valuable for industrial production of GroDHase. We detected efficient oxidation of Gro derived from biodiesel production to DHA by gas chromatography. The results presented in this work support recombinant GroDHase production in a biorefinery setting as a relevant tool for converting Gro into DHA for future biotechnological applications.

Ethanol in biorefining and dehydration of agricultural materials: energy, capital cost, and product quality implications

AbstractThe production of aqueous ethanol from fermentation‐based biorefining operations suggests the availability and possibility for its use within the refinery to aid in separations prior to and after fermentation. A variety of uses that have been considered are described here. In general, these rely on biomass constituent solubility enhanced by ethanol concentration and temperature so that lipids, proteins, and lignin may be dissolved and recovered. Additionally, ethanol may be applied to remove water from solids, such as wet starch, wet gluten, and distillers' wet grains. This technology has been described in the past as ‘extractive’ or ‘displacement’ drying and replaces conventional solids dehydration (a unit operation) with solvent drying plus solvent regeneration (a system of unit operations). Materials as diverse as wood, peat, coal, and starch have been dried experimentally in this way. General criteria using best‐case assumptions for this replacement are developed here. Applied to ethanol, these suggest significant potential energy savings for a system that combines low‐load solvent drying with distillation. Distillation energy for regenerating ethanol solvent to 90%v or less and producing water is equivalent to a 3 to 4 effect evaporation of water when compared on a separation‐energy per unit‐of‐water‐removed basis. Material properties of the dehydrated substance may be enhanced since the solvent drying is at a lower temperature and leaves the matrix without structural collapse. The parameters for capital cost comparison are delineated with important considerations and economies identified that result from the use of low‐cost solvent and compatible technologies in the biorefinery setting. Published in 2010 by John Wiley &amp; Sons, LtdThis article is a US Government work and is in the public domain in the USA