The biorefining opportunities in Wales: Understanding the scope for building a sustainable, biorenewable economy using plant biomass

Bioenergy Potential and Greenhouse Gas Emissions from Intensifying European Temporary Grasslands

Agricultural intensification is considered essential for meeting growing demand for food and biomass for energy purposes. Intensifying grasslands is under-represented, although it is a promising option given their large land area and relatively low management levels. This study quantifies the bioenergy potential from intensifying temporary grasslands in Europe and the integral greenhouse gas emission effects in 2030. We first conducted a literature review of intensification options for European grasslands and then applied the environmental impact assessment model MITERRA-Europe to implement the key intensification option of using multi-species grass mixtures. The results showed that 853 kha (or 8%) of temporary grassland could be made sustainably available for additional biomass production. This can be translated into a bioethanol potential of 23 PJ yr−1 and an emission mitigation potential of 5.8 Mt CO2-eq yr−1 (if conventional grass mixture from surplus temporary grassland is used for energy) or 72 PJ yr−1 and 4.0 Mt CO2-eq yr−1 (if surplus temporary grassland is used for grassy energy crops). Although the bioenergy potential is limited, the key advantage of intensification measure is that it results in a better environmental performance of temporary grasslands. This makes it a key option for sustainably producing bioenergy in areas with high shares of temporary grasslands.

Co-production of 11α-hydroxyprogesterone and ethanol using recombinant yeast expressing fungal steroid hydroxylases

BACKGROUND

Bioethanol production from sustainable sources of biomass that limit effect on food production are needed and in a biorefinery approach co-products are desirable, obtained from both the plant material and from the microbial biomass. Fungal biotransformation of steroids was among the first industrial biotransformations allowing corticosteroid production. In this work, the potential of yeast to produce intermediates needed in corticosteroid production is demonstrated at laboratory scale following bioethanol production from perennial ryegrass juice.

RESULTS

Genes encoding the 11α-steroid hydroxylase enzymes from Aspergillus ochraceus (11α-SH^Aoch) and Rhizopus oryzae (CYP509C12) transformed into Saccharomyces cerevisiae for heterologous constitutive expression in p425TEF. Both recombinant yeasts (AH22:p11α-SH^Aoch and AH22:p509C12) exhibited efficient progesterone bioconversion (on glucose minimal medial containing 300 µM progesterone) producing either 11α-hydroxyprogesterone as the sole metabolite (AH22:p11α-SH^Aoch) or a 7:1 mixture of 11α-hydroxyprogesterone and 6β-hydroxyprogesterone (AH22:p509C12). Ethanol yields for AH22:p11α-SH^Aoch and AH22:p509C12 were comparable resulting in ≥75% conversion of glucose to alcohol. Co-production of bioethanol together with efficient production of the 11-OH intermediate for corticosteroid manufacture was then demonstrated using perennial ryegrass juice. Integration of the 11α-SH^Aoch gene into the yeast genome (AH22:11α-SHAoch+K) resulted in a 36% reduction in yield of 11α-hydroxyprogesterone to 174 µmol/L using 300 µM progesterone. However, increasing progesterone concentration to 955 µM and optimizing growth conditions increased 11α-hydroxyprogesterone production to 592 µmol/L product formed.

CONCLUSIONS

The progesterone 11α-steroid hydroxylases from A. ochraceus and R. oryzae, both monooxygenase enzymes of the cytochrome P450 superfamily, have been functionally expressed in S. cerevisiae. It appears that these activities in fungi are not associated with a conserved family of cytochromes P450. The activity of the A. ochraceous enzyme was important as the specificity of the biotransformation yielded just the 11-OH product needed for corticosteroid production. The data presented demonstrate how recombinant yeast could find application in rural biorefinery processes where co-production of value-added products (11α-hydroxyprogesterone and ethanol) from novel feedstocks is an emergent and attractive possibility.

Optimisation of slow-pyrolysis process conditions to maximise char yield and heavy metal adsorption of biochar produced from different feedstocks

The objective of this work was to identify biomass feedstocks and optimum pyrolysis process conditions to produce a biochar capable of adsorbing metals from polluted groundwater. Taguchi experimental design was used to determine the effects of slow-pyrolysis process conditions on char yield and zinc adsorption. Treatments were repeated using six candidate feedstocks (Lolium perenne, Lolium perenne fibre, Miscanthus x giganteus, Salix viminalis, Fraxinus excelsior and Picea sitchensis) and the resultant chars were tested for metal adsorption performance. Chars produced from L. perenne and its extracted fibre displayed the greatest zinc adsorption performance and removed 83.27-92.96% respectively. Optimum process conditions in terms of both char yield and zinc adsorption performance were achieved from slow-pyrolysis at 300°C for 2h using a feedstock with a particle size of less than 1mm.

Analysis of the lignocellulosic components of biomass residues for biorefinery opportunities

The present study aims to identify the renewable resources available in Brazil such as açai seed, coconut husks, coffee husks, rice husks, eucalyptus sawdust, grass, soy peel, bamboo, banana stems and banana stalks. To identify such renewable energy sources, samples were examined for their physical and chemical characteristics using X-ray diffraction (XRD), proximate and ultimate analyses, thermogravimetric analysis (TGA), calorific value determination, near-infrared (NIR) spectroscopy, UV spectroscopy, high-pH anion-exchange chromatography (HPAEC-PAD) and accelerated solvent extraction (ASE). Among the biomasses, açai and coffee exhibited higher total sugar content, 67.70% and 62.55%, respectively. Sawdust exhibited low ash, along with the highest calorific value and lignin content. The highest glucose contents were observed in bamboo (44.65%) and sawdust (38.80%). The maximum yield for the bioproducts levulinic acid (LA), formic acid (FA) and furfural were estimated; açai exhibited the highest yield of LA and FA, while coffee exhibited the best furfural yield. All of these properties indicate that the residues are potential candidates for bioenergy production.

Economically viable components from Jerusalem artichoke (Helianthus tuberosus L.) in a biorefinery concept

Biorefinery applications are receiving growing interest due to climatic and waste disposal issues and lack of petroleum resources. Jerusalem artichoke (Helianthus tuberosus L.) is suitable for biorefinery applications due to high biomass production and limited cultivation requirements. This paper focuses on the potential of Jerusalem artichoke as a biorefinery crop and the most viable products in such a case. The carbohydrates in the tubers were found to have potential for production of platform chemicals, e.g., succinic acid. However, economic analysis showed that production of platform chemicals as a single product was too expensive to be competitive with petrochemically produced sugars. Therefore, production of several products from the same crop is a must. Additional products are protein based ones from tubers and leaves and biogas from residues, although both are of low value and amount. High bioactive activity was found in the young leaves of the crop, and the sesquiterpene lactones are of specific interest, as other compounds from this group have shown inhibitory effects on several human diseases. Thus, future focus should be on understanding the usefulness of small molecules, to develop methods for their extraction and purification and to further develop sustainable and viable methods for the production of platform chemicals.

Increased delignification by white rot fungi after pressure refining Miscanthus

Pressure refining, a pulp making process to separate fibres of lignocellulosic materials, deposits lignin granules on the surface of the fibres that could enable increased access to lignin degrading enzymes. Three different white rot fungi were grown on pressure refined (at 6 bar and 8 bar) and milled Miscanthus. Growth after 28 days showed highest biomass losses on milled Miscanthus compared to pressure refined Miscanthus. Ceriporiopsis subvermispora caused a significantly higher proportion of lignin removal when grown on 6 bar pressure refined Miscanthus compared to growth on 8 bar pressure refined Miscanthus and milled Miscanthus. RM22b followed a similar trend but Phlebiopsis gigantea SPLog6 did not. Conversely, C. subvermispora growing on pressure refined Miscanthus revealed that the proportion of cellulose increased. These results show that two of the three white rot fungi used in this study showed higher delignification on pressure refined Miscanthus than milled Miscanthus.

Co-production of bioethanol and probiotic yeast biomass from agricultural feedstock: application of the rural biorefinery concept

Microbial biotechnology and biotransformations promise to diversify the scope of the biorefinery approach for the production of high-value products and biofuels from industrial, rural and municipal waste feedstocks. In addition to bio-based chemicals and metabolites, microbial biomass itself constitutes an obvious but overlooked by-product of existing biofermentation systems which warrants fuller attention. The probiotic yeast Saccharomyces boulardii is used to treat gastrointestinal disorders and marketed as a human health supplement. Despite its relatedness to S. cerevisiae that is employed widely in biotechnology, food and biofuel industries, the alternative applications of S. boulardii are not well studied. Using a biorefinery approach, we compared the bioethanol and biomass yields attainable from agriculturally-sourced grass juice using probiotic S. boulardii (strain MYA-769) and a commercial S. cerevisiae brewing strain (Turbo yeast). Maximum product yields for MYA-769 (39.18 [±2.42] mg ethanol mL⁻¹ and 4.96 [±0.15] g dry weight L⁻¹) compared closely to those of Turbo (37.43 [±1.99] mg mL⁻¹ and 4.78 [±0.10] g L⁻¹, respectively). Co-production, marketing and/or on-site utilisation of probiotic yeast biomass as a direct-fed microbial to improve livestock health represents a novel and viable prospect for rural biorefineries. Given emergent evidence to suggest that dietary yeast supplementations might also mitigate ruminant enteric methane emissions, the administration of probiotic yeast biomass could also offer an economically feasible way of reducing atmospheric CH₄.

Energy Supply Chain Optimization of Hybrid Feedstock Processes: A Review

The economic, environmental, and social performances of energy systems depend on their geographical locations and the surrounding market infrastructure for feedstocks and energy products. Strategic decisions to locate energy conversion facilities must take all upstream and downstream operations into account, prompting the development of supply chain modeling and optimization methods. This article reviews the contributions of energy supply chain studies that include heat, power, and liquid fuels production. Studies are categorized based on specific features of the mathematical model, highlighting those that address energy supply chain models with and without considerations of multiperiod decisions. Studies that incorporate uncertainties are discussed, and opportunities for future research developments are outlined.

Co-production of ethanol and squalene using a Saccharomyces cerevisiae ERG1 (squalene epoxidase) mutant and agro-industrial feedstock

BACKGROUND

Genetically customised Saccharomyces cerevisiae that can produce ethanol and additional bio-based chemicals from sustainable agro-industrial feedstocks (for example, residual plant biomass) are of major interest to the biofuel industry. We investigated the microbial biorefinery concept of ethanol and squalene co-production using S. cerevisiae (strain YUG37-ERG1) wherein ERG1 (squalene epoxidase) transcription is under the control of a doxycycline-repressible tet0 7 -CYC1 promoter. The production of ethanol and squalene by YUG37-ERG1 grown using agriculturally sourced grass juice supplemented with doxycycline was assessed.

RESULTS

Use of the tet0 7 -CYC1 promoter permitted regulation of ERG1 expression and squalene accumulation in YUG37-ERG1, allowing us to circumvent the lethal growth phenotype seen when ERG1 is disrupted completely. In experiments using grass juice feedstock supplemented with 0 to 50 μg doxycycline mL(-1), YUG37-ERG1 fermented ethanol (22.5 [±0.5] mg mL(-1)) and accumulated the highest squalene content (7.89 ± 0.25 mg g(-1) dry biomass) and yield (18.0 ± 4.18 mg squalene L(-1)) with supplements of 5.0 and 0.025 μg doxycycline mL(-1), respectively. Grass juice was found to be rich in water-soluble carbohydrates (61.1 [±3.6] mg sugars mL(-1)) and provided excellent feedstock for growth and fermentation studies using YUG37-ERG1.

CONCLUSION

Residual plant biomass components from crop production and rotation systems represent possible substrates for microbial fermentation of biofuels and bio-based compounds. This study is the first to utilise S. cerevisiae for the co-production of ethanol and squalene from grass juice. Our findings underscore the value of the biorefinery approach and demonstrate the potential to integrate microbial bioprocess engineering with existing agriculture.

Latitudinal variation in ambient UV-B radiation is an important determinant of Lolium perenne forage production, quality, and digestibility

Few studies to date have considered the responses of agriculturally important forage grasses to UV-B radiation. Yet grasses such as Lolium perenne have a wide current distribution, representing exposure to a significant variation in ambient UV-B. The current study investigated the responses of L. perenne (cv. AberDart) to a simulated latitudinal gradient of UV-B exposure, representing biologically effective UV-B doses at simulated 70, 60, 50, 40, and 30° N latitudes. Aspects of growth, soluble compounds, and digestibility were assessed, and results are discussed in relation to UV-B effects on forage properties and the implications for livestock and bio-ethanol production. Aboveground biomass production was reduced by approximately 12.67% with every 1 kJ m(-2) day(-1) increase in biologically weighted UV-B. As a result, plants grown in the highest UV-B treatment had a total biomass of just 13.7% of controls. Total flavonoids were increased by approximately 76% by all UV-B treatments, while hydroxycinnamic acids increased in proportion to the UV-B dose. Conversely, the digestibility of the aboveground biomass and concentrations of soluble fructans were reduced by UV-B exposure, although soluble sucrose, glucose, and fructose concentrations were unaffected. These results highlight the capacity for UV-B to directly affect forage productivity and chemistry, with negative consequences for digestibility and bioethanol production. Results emphasize the need for future development and distribution of L. perenne varieties to take UV-B irradiance into consideration.