Arundo donax L.: a non-food crop for bioenergy and bio-compound production

Microanatomical Changes in the Leaves of Arundo donax (L.) Caused by Potentially Toxic Elements from Municipal Sewage Sediment

An open-field 3-year-long microplot experiment was set up with three micropropagated lines (SC Blossom, BFT Indiana, and STM Hajdúsági) of giant reed (Arundo donax L.). Plants were grown on a soil cover of a former sewage settling pond located in Debrecen Lovász-Zug, Hungary. Soil cover of the sewage sediment was moderately contaminated with various toxic elements (As, Ba, Cd, Cr, Cu, Mn, Ni, Pb, and Zn). The highest total concentration of examined toxic elements in leaves was found in the BFT Indiana line (∑326 mg/kg), while in the SC Blossom and STM Hajdúsági lines, ∑210 mg/kg and ∑182 mg/kg were measured, respectively. The highest Zn concentration (117 mg/kg) was found in the leaves of in BFT Indiana line and was 67% higher than that in SC Blossom and 95% more than in the STM Hajdúsági line. The BFT Indiana leaves showed typical signs of adaptation to heavy metal stress in the case of numerous micromorphometric characteristics. The extent of leaf mesophylls decreased, and the number of bulliform cells and phytoliths, as well as the sclerenchymatous stock, increased. The size of the vascular bundles was reduced. The size of the stomata decreased while the stomatal density increased. It can be concluded that the BFT Indiana line had the best adaptational response to heavy metal stress.

Role of KOH-activated biochar on promoting anaerobic digestion of biomass from Pennisetumgianteum

Pennisetum giganteum is a promising non-food crop feedstock for biogas production due to its high productivity and bio-methane potential. However, the accumulation of volatile fatty acids (VFA) usually restricts the conversion efficiency of P. giganteum biomass (PGB) during anaerobic digestion (AD). Here, the role of KOH-activated biochar (KB) in improving the AD efficiency of PGB and the related mechanisms were investigated in detail. The results revealed that KB exhibited excellent electrical conductivity, electron transfer capacity and specific capacitance, which might be related to the decrease in the electron transfer resistance after adding KB to the AD process. In addition, the KB addition not only reinforced metabolisms of energy and VFAs but also promoted the conversion of VFAs to methane, leading to a 52% increase in the methane production rate. Bioinformatics analysis showed that Smithella and Methanosaeta were key players in the KB-mediated AD process of PGB. The stimulatory effect of methanogenesis probably resulted from the establishment of direct interspecies electron transfer (DIET) between VFA-oxidizing acetogens (e.g., Smithella) and Methanosaeta. These findings provided a key step to improve the PGB-based AD process.

Comparative environmental and economic life cycle assessment of phytoremediation of dredged sediment using Arundo Donax, integrated with biomass to bioenergy valorization chain

The economic and environmental life cycle assessment (LCA) was integrated into a laboratory-based experiment to evaluate the feasibility and sustainability of phytoremediation of chloride-rich marine dredged sediment, using perennial reed Arundo Donax along with biomass valorization. As a prerequisite for life cycle assessments, a baseline mathematical model was developed to estimate the yields of biomass to bioenergy valorization chain including the estimation of biomass yield per m3 sediment, bioenergy yields from valorization schemes, expected green electricity yield, and the phytoremediation time frame. This mathematical model was applied to develop a parametric life cycle inventory for two scenarios of sediment phytoremediation separately or integrated with biomass valorization, for LCA and further sensitivity and uncertainty analysis. Comparative LCA unveiled that the cost and environmental impacts of annual phytoremediation of 1m3 sediment alone or integrated with biomass valorization are much inferior to the corresponding sediment landfill as the inevitable alternative approach for sediment management. With the chloride bioaccumulation capacity of 9940 mg per kg dry biomass of A. donax, the phytoremediation of sediment with chloride concentration higher than 1650 mg/kg may not be achievable in a realistic time frame. Due to the importance of considering sediment depth and the effectiveness of the plant rooting system in estimating the performance of phytoremediation and the time frame, the volume of sediment (1m3) is a more appropriate functional unit than the surface area (ha) for LCA studies of phytoremediation. In addition, considering the volume of sediment as a functional unit retains comparability to other valorization scenarios such as sediment incorporation in cementitious matrices and management scenarios such as landfill, which are generally expressed on a volume or mass basis. Integrating biomass-derived bioenergy production into phytoremediation could offer local and global benefits in terms of economy and environment mainly due to carbon sequestration and avoiding fossil-based fuels.

Potential of Artemisia dubia Wall Biomass for Natural Crop Protection

The Green Deal strategy has the very ambitious goal of transforming the European Union into the first climate-neutral continent by 2050. For the agricultural sector, one of the main challenges is to reduce the use of synthetic fertilizers and pesticides. Crop protection measures aim to maintain and ensure certain standards of yield and quality, which are generally achieved by the control of pests, diseases, and weeds. One of the possibilities to reduce the use of pesticides could be allelopathic plants, which are not only potential sources of allelochemicals but also renewable biomass sources. The aim of this study was to analyze the productivity of Artemisia dubia Wall and evaluate the allelopathic effects of biomass on crops and weeds. It was determined that the biomass productivity of A. dubia varied from 2 to 18 t ha-1, depending on how many times it is cut during the growing season and the fertilizer rate. A. dubia has allelopathic properties, which were verified using an aqueous extract and can completely suppress the germination of Taraxacum officinale seeds. Young plants harvested in the middle of summer were characterized by the highest number of phenolic compounds. This shows the strong allelopathic effect of A. dubia biomass on other plants.

Recent Developments of Gramine: Chemistry and Biological Activity

The natural alkaloid gramine has attracted significant attention in both academic and industrial circles because of its potential and diverse biological activities, including antiviral, antibacterial, antifungal, anti-inflammatory and antitumor activities; application in therapy for Alzheimer's disease; serotonin-receptor-related activity; insecticidal activity; and application as an algicide. In this review, we focus on the research advances that have been made for gramine-based molecules since their discovery, providing key information on their extraction and separation, chemical synthesis and diverse biological activities. Data regarding their mechanisms of action are also presented. This comprehensive and critical review will serve as a guide for developing more drug candidates based on gramine skeletons.

Advances in microbial pretreatment for biorefining of perennial grasses

Perennial grasses are potentially abundant sources of biomass for biorefineries, which can produce high yields with low input requirements, and many added environmental benefits. However, perennial grasses are highly recalcitrant to biodegradation and may require pretreatment before undergoing many biorefining pathways. Microbial pretreatment uses the ability of microorganisms or their enzymes to deconstruct plant biomass and enhance its biodegradability. This process can enhance the enzymatic digestibility of perennial grasses, enabling saccharification with cellulolytic enzymes to produce fermentable sugars and derived fermentation products. Similarly, microbial pretreatment can increase the methanation rate when the grasses are used to produce biogas through anaerobic digestion. Microorganisms can also increase the digestibility of the grasses to improve their quality as animal feed, enhance the properties of grass pellets, and improve biomass thermochemical conversion. Metabolites produced by fungi or bacteria during microbial pretreatment, such as ligninolytic and cellulolytic enzymes, can be further recovered as added-value products. Additionally, the action of the microorganisms can release chemicals with commercialization potential, such as hydroxycinnamic acids and oligosaccharides, from the grasses. This review explores the recent advances and remaining challenges in using microbial pretreatment for perennial grasses with the goal of obtaining added-value products through biorefining. It emphasizes recent trends in microbial pretreatment such as the use of microorganisms as part of microbial consortia or in unsterilized systems, the use and development of microorganisms and consortia capable of performing more than one biorefining step, and the use of cell-free systems based on microbial enzymes. KEY POINTS: • Microorganisms or enzymes can reduce the recalcitrance of grasses for biorefining • Microbial pretreatment effectiveness depends on the grass-microbe interaction • Microbial pretreatment can generate value added co-products to enhance feasibility.

Approaching Self-Bonded Medium Density Fiberboards Made by Mixing Steam Exploded Arundo donax L. and Wood Fibers: A Comparison with pMDI-Bonded Fiberboards on the Primary Properties of the Boards

This study presents an unexplored method to produce formaldehyde-free MDF. Steam exploded Arundo donax L. (STEX-AD) and untreated wood fibers (WF) were mixed at different mixing rates (0/100, 50/50, and 100/0, respectively) and two series of boards were manufactured, with 4 wt% of pMDI, based on dry fibers, and self-bonded. The mechanical and physical performance of the boards was analyzed as a function of the adhesive content and the density. The mechanical performance and dimensional stability were determined by following European standards. The material formulation and the density of the boards had a significant effect on both mechanical and physical properties. The boards made solely of STEX-AD were comparable to those made with pMDI, while the panels made of WF without adhesive were those that performed the worst. The STEX-AD showed the ability to reduce the TS for both pMDI-bonded and self-bonded boards, although leading to a high WA and a higher short-term absorption for the latter. The results presented show the feasibility of using STEX-AD in the manufacturing of self-bonded MDF and the improvement of dimensional stability. Nonetheless, further studies are needed especially to address the enhancement of the internal bond (IB).

Arundo donax L. growth potential under different abiotic stress

Arundo donax L. (giant reed) is a fast-growing, vegetatively multiplying, and rhizomatous perennial grass. It is considered a leading crop for biomass production on marginal and degraded lands under different adverse conditions such as drought, salinity, waterlogging, high and low temperatures, and heavy metal stress. The giant reed tolerance to those stresses is reviewed based on its effects on photosynthetic capacity and biomass production. Possible explanations for the giant reed tolerance against each particular stress were elucidated, as well as changes shown by the plant at a biochemical, physiological and morphological level, that may directly affect its biomass production. The use of giant reed in other areas of interest such as bioconstruction, phytoremediation, and bioremediation, is also reviewed. Arundo donax can be key for circular economy and global warming mitigation.

Arundo donax L Processing in Catalyzed Butanol-Water Media in the Scope of Lignocellulose Biorefineries

Arundo donax L samples, before or after aqueous extraction to remove extractives, were subjected to chemical fractionation in H₂SO₄-catalyzed mixtures of 1-butanol and water. The partial miscibility of 1-butanol and water at room temperature allowed the separation of the three major feedstock components in separate streams (lignin, accumulated in the 1-butanol-rich phase; hemicellulose-derived products, accumulated in the aqueous acidic phase; and cellulose, present in the solid phase). The effects of selected variables (temperature, catalyst concentration, reaction time and 1-butanol content of the reaction media) on variables measuring the solid recovery yield and the compositions of phases from fractionation were measured. Using water-extracted A. donax L as a substrate, the best operational conditions enabled 93.2% hemicellulose removal and 85.4% delignification with limited cellulose solubilization (15%). The experimental results provided key information to assess the proposed process in the scope of biorefineries.

Closing the Nutrient Loop-The New Approaches to Recovering Biomass Minerals during the Biorefinery Processes

The recovery of plant mineral nutrients from the bio-based value chains is essential for a sustainable, circular bioeconomy, wherein resources are (re)used sustainably. The widest used approach is to recover plant nutrients on the last stage of biomass utilization processes-e.g., from ash, wastewater, or anaerobic digestate. The best approach is to recover mineral nutrients from the initial stages of biomass biorefinery, especially during biomass pre-treatments. Our paper aims to evaluate the nutrient recovery solutions from a trans-sectorial perspective, including biomass processing and the agricultural use of recovered nutrients. Several solutions integrated with the biomass pre-treatment stage, such as leaching/bioleaching, recovery from pre-treatment neoteric solvents, ionic liquids (ILs), and deep eutectic solvents (DESs) or integrated with hydrothermal treatments are discussed. Reducing mineral contents on silicon, phosphorus, and nitrogen biomass before the core biorefinery processes improves processability and yield and reduces corrosion and fouling effects. The recovered minerals are used as bio-based fertilizers or as silica-based plant biostimulants, with economic and environmental benefits.

Extraction of high-quality grade cellulose and cellulose nanocrystals from different lignocellulosic agri-food wastes

Introduction

Prompted by the increasing need for an intensified valorization of agri-food waste, in this work a three-step chemical procedure was used to extract high-purity cellulose from garlic stalk, corncob, and giant cane cut-up by a sequential removal of hemicellulose, lignin, ash, and organic compounds. Cellulose nanocrystals of potential interest for nanocomposite applications were then obtained through acid hydrolysis.

Methods

The purity of the cellulose was determined employing Nuclear Magnetic Resonance and infrared spectroscopy, whereas dynamic light scattering, optical, atomic force microscopy, and transmission electron microscopy were used for morphological characterization. The high purity and crystallinity of cellulose was confirmed by comparison with the ultra-pure bacterial cellulose originating from K. sucrofermentans, irrespective of the waste used.

Results and discussion

At the end of the extraction procedure, cellulose yields of 35.73, 37.15, and 39.10%, for garlic stalk, corncob, and giant cane cut-up, respectively, were achieved. Dynamic light scattering and atomic force microscopy analyses showed that the length of the whisker-like nanocrystals depended on the raw material (from ~100 nm up to > 2μm), while the final yield was ~40–50% for all three wastes. The versatility and effectiveness of the method here proposed can be profitably used for a wide range of agro-waste feedstocks.

Assembling plant diversity mitigates greenhouse gas emissions and achieves high nitrogen removal when treating the low-C/N wastewater by constructed wetlands

The low carbon-to-nitrogen (C/N) ratio in wastewater will inhibit pollutant removal, and more seriously, it will cause an increment of nitrous oxide (N₂O) emissions of constructed wetlands (CWs). Raising the C/N ratio of wastewater is an effective way to solve this problem, while it may cause secondary pollution and is costly. Assembling plant diversity promotes N removal, while the effects of plant diversity and increasing C/N ratio on global warming potential (GWP) combined by N₂O and methane (CH₄) are lack of comparison. In this study, 108 CW microcosms were established to explore the effects of increasing the C/N ratio from 1 to 5 and assembling plant diversity on N removal and GHG emissions. Results showed that when the C/N ratio was 1, (1) increasing species richness reduced N₂O and CH₄ emissions then reduced the GWP by 70%; (2) the presence of Arundo donax in microcosms reduced GWP by 72%; (3) an A. donax × Tradescantia fluminensis × Reineckia carnea mixture resulted in a high N removal and decreased the GWP per g N removal by 92% with a cost increment of 0.05 USD per m³ wastewater treated; and (4) as the C/N ratio increasing to 5, the GWP per g N removal of monocultures was reduced by 96%, but the cost increased by at least 0.29 USD per m³ wastewater treated. In summary, configuring plant diversity in CWs is an efficient, clean, and cost-effective measure to treat wastewater with a low C/N ratio.

Statistical optimization of bioethanol production from giant reed hydrolysate by Candida tropicalis using Taguchi design

The economic production of bioethanol as a sustainable liquid fuel is particularly needed and attractive. Giant reed as a low-cost and renewable biomass can be utilized as a sustainable feedstock for bioethanol development. The current research focuses on optimizing the fermentation parameters to increase ethanol concentration while lowering production costs. In this work, the giant reed was hydrolyzed thermochemically using HCl; cellulose and hemicellulose fractions were maximally converted at optimized hydrolysis conditions (5% HCl, 30 min, and 120 °C), resulting in a high sugar concentration (≈ 55 g/L), which were fermented by Candida tropicalis Y-26 for bioethanol production (≈ 15 g/L). Taguchi design was used to optimize the fermentation parameters (temperatures, pH, incubation period, and nitrogen sources). Under optimum fermentation conditions (25 °C; 24 h.; pH 5.5; and ammonium nitrate as a nitrogen source), the ethanol concentration at flask level accomplished ≈ 21 g/L, while its scale-up to bioreactor level contributed ≈ 25 g/L (equivalent to 250 kg ethanol/ton biomass) with ≈ 67% increase than the fermentation under unoptimized conditions. Overall, these findings proved that optimizing the fermentation parameters by Taguchi design and scaling up at a bioreactor could improve bioethanol production from giant reed biomass.

1-Butyl-3-methylimidazolium acetate pretreatment of giant reed triggering yield improvement of biohydrogen production via photo-fermentation

Ionic liquids (ILs) have been considered as promising alternatives to traditional reagent for lignocellulosic biomass pretreatment because of their tunable physicochemical and "green" properties. In the study, the influence of 1-Butyl-3-methylimidazolium acetate ([Bmim]acetate) pretreatment of giant reed on H2 yield improvement via photo-fermentation (PF) was evaluated. Under the optimal pretreatment conditions (6 g/L [Bmim]acetate at 70 °C for 4 h), the delignification of giant reed was up to 26.7 %. In addition, the sugar yield (9.5 g/L) and hydrogen yield (72.3 mL/g TS) from giant reed were enhanced by 1.7-fold and 61.7 % over those of untreated giant reed, respectively. Moreover, ternary analysis showed that retention time had the strongest effect on delignification, sugar yield and hydrogen yield of giant reed compared to pretreatment temperature and [Bmim]acetate loading. These experimental results indicated that [Bmim]acetate pretreatment of giant reed is an effective approach to enhance the hydrogen yield via PF.

Leaf surfaces and neolithization - the case of Arundo donax L

Arundo donax L. (Arundinoideae subfamily, Poaceae family) is a sub-tropical and temperate climate reed that grows in arid and semi-arid environmental conditions, from eastern China to the Mediterranean basin, suggesting potential adaptations at the epicuticular level. A thorough physical-chemical examination of the adaxial and abaxial surfaces of A. donax leaf was performed herein in an attempt to track such chemophenetic adaptations. This sort of approach is of the utmost importance for the current debate about the hypothetical invasiveness of this species in the Mediterranean basin versus its natural colonization along the Plio-Pleistocene period. We concluded that the leaf surfaces contain, apart from stomata, prickles, and long, thin trichomes, and silicon-rich tetralobate phytolits. Chemically, the dominating elements in the leaf ashes are oxygen and potassium; minor amounts of calcium, silicon, magnesium, phosphorous, sulphur, and chlorine were also detected. In both surfaces the epicuticular waxes (whose density is higher in the adaxial surface than in the abaxial surface) form randomly orientated platelets, with irregular shape and variable size, and aggregated rodlets with variable diameter around the stomata. In the case of green mature leaves, the dominating organic compounds of the epicuticular waxes of both surfaces are triterpenoids. Both surfaces feature identical hydrophobic behaviour, and exhibit the same total transmittance, total reflectance, and absorption of incident light. The above findings suggest easy growth of the plant, remarkable epidermic robustness of the leaf, and control of water loss. These chemophenetic characteristics and human influence support a neolithization process of this species along the Mediterranean basin.

Switchgrass and Giant Reed Energy Potential when Cultivated in Heavy Metals Contaminated Soils

The cultivation of energy crops on degraded soils contributes to reduce the risks associated with land use change, and the biomass may represent an additional revenue as a feedstock for bioenergy. Switchgrass and giant reed were tested under 300 and 600 mg Cr kg−1, 110 and 220 mg Ni kg−1, and 4 and 8 mg Cd kg−1 contaminated soils, in a two year pot experiment. Switchgrass yields (average aerial 330 g.m−2 and below ground 430 g.m−2), after the second year harvest, were not affected by Cd contamination and 110 mg Ni kg−1, but 220 mg Ni kg−1 significantly affected the yields (55–60% reduction). A total plant loss was observed in Cr-contaminated pots. Giant reed aboveground yields (control: 410 g.m−2), in the second year harvest, were significantly affected by all metals and levels of contamination (30–70% reduction), except in 110 mg Ni kg−1 pots. The belowground biomass yields (average 1600 g.m−2) were not affected by the tested metals. Contamination did not affect the high heating value (HHV) of switchgrass (average 18.4 MJ.kg−1) and giant reed aerial fractions (average 18.9 MJ.kg−1, stems, and 18.1 MJ.kg−1, leaves), harvested in the second year, indicating that the biomass can be exploited for bioenergy.

Modulation of class III peroxidase pathways and phenylpropanoids in Arundo donax under salt and phosphorus stress

Arundo donax L. is an invasive species that has been recently employed for biomass production due to its well-known ability to colonize harsh environment. Based on previous observations, the present study investigated the potential role of phenylpropanoids and class III peroxidases to confer adaptation through biochemical and transcriptomic analysis in A. donax after Na⁺ and P excess supply, both in single stress and in combination, and after growth at low P level. The levels of hydrogen peroxide, flavonoids (i.e., quercetin, apigenin and kaempferol derivatives) and the activity of class III peroxidases, as well as the expression of several genes encoding for their enzymes involved in their biosynthesis, increased when Na⁺ was supplied in combination with P. These results suggest that those biomolecules are involved in the response of A. donax, to the presence of +Na and P in the soil. Moreover, even though at the sampling time no significant accumulation of lignin has been determined, the trend of accumulation of such metabolite and most of all the increase of several transcripts involved in its synthesis was found. This work for the first time indicates the need for further investigation devoted to elucidating whether the strengthening of cell walls via lignin synthesis is one of the mechanisms used by A. donax to adapt to harsh environments.

Low Indirect Land Use Change (ILUC) Energy Crops to Bioenergy and Biofuels—A Review

Energy crops are dedicated cultures directed for biofuels, electricity, and heat production. Due to their tolerance to contaminated lands, they can alleviate and remediate land pollution by the disposal of toxic elements and polymetallic agents. Moreover, these crops are suitable to be exploited in marginal soils (e.g., saline), and, therefore, the risk of land-use conflicts due to competition for food, feed, and fuel is reduced, contributing positively to economic growth, and bringing additional revenue to landowners. Therefore, further study and investment in R&D is required to link energy crops to the implementation of biorefineries. The main objective of this study is to present a review of the potential of selected energy crops for bioenergy and biofuels production, when cultivated in marginal/degraded/contaminated (MDC) soils (not competing with agriculture), contributing to avoiding Indirect Land Use Change (ILUC) burdens. The selected energy crops are Cynara cardunculus, Arundo donax, Cannabis sativa, Helianthus tuberosus, Linum usitatissimum, Miscanthus × giganteus, Sorghum bicolor, Panicum virgatum, Acacia dealbata, Pinus pinaster, Paulownia tomentosa, Populus alba, Populus nigra, Salix viminalis, and microalgae cultures. This article is useful for researchers or entrepreneurs who want to know what kind of crops can produce which biofuels in MDC soils.

Identification of Known and Novel Arundo donax L. MicroRNAs and Their Targets Using High-Throughput Sequencing and Degradome Analysis

MicroRNAs (miRNAs) are a class of non-coding molecules involved in the regulation of a variety of biological processes. They have been identified and characterized in several plant species, but only limited data are available for Arundo donax L., one of the most promising bioenergy crops. Here we identified, for the first time, A. donax conserved and novel miRNAs together with their targets, through a combined analysis of high-throughput sequencing of small RNAs, transcriptome and degradome data. A total of 134 conserved miRNAs, belonging to 45 families, and 27 novel miRNA candidates were identified, along with the corresponding primary and precursor miRNA sequences. A total of 96 targets, 69 for known miRNAs and 27 for novel miRNA candidates, were also identified by degradome analysis and selected slice sites were validated by 5′-RACE. The identified set of conserved and novel candidate miRNAs, together with their targets, extends our knowledge about miRNAs in monocots and pave the way to further investigations on miRNAs-mediated regulatory processes in A. donax, Poaceae and other bioenergy crops.

Leaf morpho-physiological comparison between native and non-native plant species in a Mediterranean island

Islands tend to be more prone to plant invasions than mainland regions, with the Mediterranean ones not being an exception. So far, a large number of studies on comparing leaf morphological and physiological traits between native and non-native plants in Mediterranean environments have been performed, although none of them on Mediterranean islands. To fill this gap, this study focuses on 14 plant species grown in a controlled growth chamber in the absence of stress. The goal was (1) to differentiate leaf morpho-physiological traits between native and non-native plants on a Mediterranean island and (2) to deepen in the underlying causes of the differential photosynthetic traits displayed by non-native species. Results showed that in Mediterranean islands, non-native plant species show on average larger values of net CO2 assimilation, stomatal conductance (gm), photosynthetic nitrogen-use efficiency, among others, and lower leaf mass per area (LMA) and leaf thickness, compared to the native species. Among the assessed traits, this study reports for the first time larger gm, and lower mesophyll conductance limitation in non-native species, which seems to be linked to their lower LMA. These novel traits need to be added to the ‘leaf physiological trait invasive syndrome’. It was also found that on a Mediterranean island, native and non-native species are placed on opposite sides of the leaf economics spectrum, with non-native species being placed on the ‘‘fast-return’’ end. In conclusion, this study demonstrates that non-native species inhabiting a Mediterranean island possess distinct leaf morphological and physiological traits compared to co-occurring native species, at least during the favorable growth season, which increases the chances of a successful invasion.

Substrate-to-inoculum ratio drives solid-state anaerobic digestion of unamended grape marc and cheese whey

Inoculation dose is a key operational parameter for the solid-state anaerobic digestion (SS-AD) of lignocellulosic biomass, maximum methane recovery, and stable digester performance. The novelty of this study was the co-digestion of unamended full-strength grape marc and cheese whey for peak methane extraction at variable inoculation levels. An acclimatised digestate from a preceding anaerobic treatment was used as a downstream inoculum. The impact of inoculum size (wet weight) was evaluated at 0/10, 5/5, 7/3 and 9/1 substrate-to-inoculum (S/I) ratios, corresponding to an initial concentration of 20-30% total solids (TS) in digesters over 58 days at 45°C. The optimal 7/3 S/I produced the highest cumulative methane yield, 6.45 L CH4 kg-1 VS, coinciding with the lowest initial salinity at 11%; the highest volumetric methane productivity rate of 0.289±0.044 L CH4 LWork-1 d-1; the highest average COD/N ratio of 9.88; the highest final pH of 9.13, and a maximum 15.07% elemental carbon removal; for a lag time of 9.4 days. This study identified an optimal inoculation dose and opens up an avenue for the direct co-digestion of grape marc and cheese whey without requirements for substrate pretreatment, thus improving the overall bioenergy profile of the winery and dairy joint resource recovery operations.

Towards high light conversion efficiency from photo-fermentative hydrogen production of Arundo donax L. By light-dark duration alternation strategy

Suitable illumination project would help in achieving high light conversion efficiency (LCE) for photo-fermentation. This study proposed an improvement strategy for LCE of photo-fermentative hydrogen production (PFHP) with a photosynthetic consortium by adopting light-dark duration alternation. For this purpose, 6 projects (continues light, 24 h light + 24 h dark, 24 h dark + 24 h light, 48 h light + 48 h light, 48 h dark + 48 h light, and continues dark) light disturbances were carried out to estimate the strategy. The fluctuation of cell growth (OD660) was corresponded to the light-dark alternation. 24 h dark + 24 h light alternation achieved the maximum hydrogen yield (HY) of 390.9 mL/g TS cell (6.7 % higher than continuous light) and maximum improvement of LCE of 114.7%. Moreover, heat map analysis revealed that the light period after inoculation had the closest relation (Pearson's r = 1) with the average hydrogen production rate (HPR) of photo-fermentation. Besides, decreased dark period after inoculation would increase the hydrogen yield of photo-fermentation.

Three-dimensional structure and properties of the giant reed (Arundo donax) lectin (ADL)

Arundo donax lectin (ADL) is a 170 amino acid protein that can be purified from the rhizomes of the giant reed or giant cane exploiting its selective binding to chitin followed by elution with N-acetyl-D-glucosamine. The lectin is listed in the UniProt server, the largest protein sequence database, as an uncharacterized protein with chitin-binding domains (A0A0A9P802). This paper reports the purification, three-dimensional structure and ligand-binding properties of ADL. The lectin is a homodimer in which the two protomers are linked by two disulphide bridges. Each polypeptide chain presents four carbohydrate-binding modules that belong to family 18 (CBM18). A high degree of sequence similarity is observed among the modules present in each protomer. We have determined the X-ray structure of the apo-protein to a resolution of 1.70 Å. The carbohydrate-binding modules, that span a sequence of approximately 40 amino acids, present four internal disulfide bridges a very short antiparallel central beta sheet and three short alpha helices, two on one side of the beta sheet and one on the other. The structures of the complexes of the lectin with N-acetylglucosamine, N-acetyllactosamine, N-acetylneuraminic acid and N-N'diacetylchitobiose reveal that ADL has two primary and two secondary carbohydrate-binding sites per dimer. They are located at the interface between the two protomers and each binding site involves residues of both chains. The lectin presents structural similarity to the wheat germ agglutinin (WGA) family, in particular to isoform 3.

Weed Management Practices to Improve Establishment of Selected Lignocellulosic Crops

Lignocellulosic biomass is one of the dominant renewable energy resources suited for the production of sustainable biofuels and other energy purposes. This study was focused on weed management strategies that can improve the establishment of six lignocellulosic crops. The studied crops included: giant miscanthus, switchgrass, giant reed, cardoon, sweet sorghum, and kenaf. Delayed planting, increased planting densities, and mulching techniques can suppress weeds in giant miscanthus. Weed competition is detrimental for switchgrass establishment. Seedbed preparation and cultivar selection can determine its ability to compete with weeds. Giant reed is unlikely to get outcompeted by weeds, and any weed control operation is required only for the first growing season. Competitive cultivars and increased seeding rates maximize the competitiveness of cardoon against weeds. Several cultural practices can be used for non-chemical weed management in sweet sorghum and kenaf. For all crops, pre-emergence herbicides can be applied. The available safe post-emergence herbicides are limited. Mechanical weed control during crucial growth stages can provide solutions for sweet sorghum, kenaf, and perennial grasses. Further research is required to develop effective weed management strategies, with emphasis on cultural practices, that can improve the establishment of these prominent lignocellulosic crops.

Arundo donax L. Biomass Production in a Polluted Area: Effects of Two Harvest Timings on Heavy Metals Uptake

Within the framework of energy biomass production, Arundo donax L. is very promising for its capability to grow on marginal lands with high yields. This potential can be realized in unused polluted areas where the energy production can be coupled with phytoremediation, and harvested biomass represents a resource and a means to remove contaminants from the soil. Two main processes are considered to evaluate A. donax L. biomass as an energy crop, determined by the timing of harvest: anaerobic digestion with fresh biomass before winter and combustion (e.g., pyrolysis and gasification) of dry canes in late winter. The aim of this work was to evaluate the use of A. donax L. in an area polluted by heavy metals for phytoextraction and energy production at two different harvest times (October and February). For that purpose, we established in polluted area in northern Italy (Caffaro area, Brescia) an experimental field of A. donax, and included switchgrass (Panicum virgatum L.) and mixed meadow species as controls. The results obtained by ICP-MS analysis performed on harvested biomasses highlighted a differential uptake of heavy metals depending on harvest time. In particular, considering the yield in the third year, A. donax was able to remove from the soil 3.87 kg ha−1 of Zn, 2.09 kg ha−1 of Cu and 0.007 kg ha−1 of Cd when harvested in October. Production of A. donax L. for anaerobic digestion or combustion in polluted areas represents a potential solution for both energy production and phytoextraction of heavy metals, in particular Cu, Zn and Cd.

Genetic Improvement of Arundo donax L.: Opportunities and Challenges

Arundo donax L., the giant reed-being a long-duration, low-cost, non-food energy crop able to grow in marginal lands-has emerged as a potential alternative to produce biomass for both energy production, with low carbon emissions, and industrial bioproducts. In recent years, pioneering efforts have been made to genetically improve this very promising energy crop. This review analyses the recent advances and challenges encountered in using clonal selection, mutagenesis/somaclonal variation and transgenesis/genome editing. Attempts to improve crop yield, in vitro propagation efficiency, salt and heavy metal tolerance by clonal selection were carried out, although limited by the species' low genetic diversity and availability of mutants. Mutagenesis and somaclonal variation have also been attempted on this species; however, since Arundo donax is polyploid, it is very difficult to induce and select promising mutations. In more recent years, genomics and transcriptomics data are becoming available in Arundo, closing the gap to make possible the genetic manipulation of this energy crop in the near future. The challenge will regard the functional characterization of the genes/sequences generated by genomic sequencing and transcriptomic analysis in a complex polyploid genome.

UAV-Based LiDAR for High-Throughput Determination of Plant Height and Above-Ground Biomass of the Bioenergy Grass Arundo donax

Replacing fossil fuels with cellulosic biofuels is a valuable component of reducing the drivers of climate change. This leads to a requirement to develop more productive bioenergy crops, such as Arundo donax with the aim of increasing above-ground biomass (AGB). However, direct measurement of AGB is time consuming, destructive, and labor-intensive. Phenotyping of plant height and biomass production is a bottleneck in genomics- and phenomics-assisted breeding. Here, an unmanned aerial vehicle (UAV) for remote sensing equipped with light detection and ranging (LiDAR) was tested for remote plant height and biomass determination in A. donax. Experiments were conducted on three A. donax ecotypes grown in well-watered and moderate drought stress conditions. A novel UAV-LiDAR data collection and processing workflow produced a dense three-dimensional (3D) point cloud for crop height estimation through a normalized digital surface model (DSM) that acts as a crop height model (CHM). Manual measurements of crop height and biomass were taken in parallel and compared to LiDAR CHM estimates. Stepwise multiple regression was used to estimate biomass. Analysis of variance (ANOVA) tests and pairwise comparisons were used to determine differences between ecotypes and drought stress treatments. We found a significant relationship between the sensor readings and manually measured crop height and biomass, with determination coefficients of 0.73 and 0.71 for height and biomass, respectively. Differences in crop heights were detected more precisely from LiDAR estimates than from manual measurement. Crop biomass differences were also more evident in LiDAR estimates, suggesting differences in ecotypes’ productivity and tolerance to drought. Based on these results, application of the presented UAV-LiDAR workflow will provide new opportunities in assessing bioenergy crop morpho-physiological traits and in delivering improved genotypes for biorefining.

Chemical and Bioenergetic Characterization of Biofuels from Plant Biomass: Perspectives for Southern Europe

The global demand for and, therefore, the production of primary energy is continuously increasing. Consequently, the need to intervene with appropriate measures has arisen in order to achieve sustainable economic, social, and environmental objectives. The reduction of fuel and electricity consumption, the containment of atmospheric emissions of greenhouse gases (like carbon dioxide, methane, other hydrocarbons, and nitrous oxide), and the improvement of environmental quality in urban centers can be considered to be among these objectives. The search for efficient measures for the overall improvement of the environment is directed towards the replacement of traditional fossil fuels with the production of bioenergy (also known as green energy) from different materials and biomasses obtained from specific agricultural activities and/or plant residues. These materials have physico-chemical and biological characteristics of interest regarding their use as sources of renewable energy. The purpose of this review was to provide an overview of the chemical and bioenergetic characteristics of biofuels, the main techniques and processes employed for their production, and the characteristics of the different feedstock materials, especially potential energy crops.

The Influence of Processing and Particle Size on Binderless Particleboards Made from Arundo donax L. Rhizome

The giant reed (Arundo donax L.) is considered one of the world's 100 worst invasive species. The main method by which this species propagates is by growth of scattered fragments of rhizome, spreading without control with very strong, deep roots. Agricultural waste consists of lignocellulosic materials that can substitute natural wood and offer a suitable alternative with which to manufacture boards for furniture, packaging and building purposes. The objectives of this work were to obtain binderless particleboards using giant reed rhizome as the raw material, to evaluate their mechanical and physical properties according to the applicable European standards and to assess the self-binding mechanism of the particles in the board. Six types of boards (12 classes) were manufactured with giant reed rhizome biomass. They were manufactured with a temperature of 110 °C, a pressure of 2.5 MPa and pressing times of 7 and 15 min, applying one or two pressing cycles. The results achieved for modulus of rupture (14.2 N/mm2), modulus of elasticity (2052.45 N/mm2) and internal bonding strength (1.12 N/mm2) show that the mechanical properties were improved by using a smaller rhizome particle size and two pressing cycles.

Arundo donax L. can substitute traditional energy crops for more efficient, environmentally-friendly production of biogas: A Life Cycle Assessment approach

Maize silage contributes to biogas production in Lombardy Region (400 anaerobic digestion plants) employing 47,000 Ha (Production Model - PM1). Reducing the area devoted to this energy crop is a goal to free soil for food production. Double cropping (PM2) and Arundo donax L. (PM3) have been proposed and tested to measure the impacts for the three Production Models by Life Cycle Assessment (LCA). The impact category related to Climate Change remained stable for PM2 while it decreased by 17% for Arundo donax L. (PM3) in comparison with PM1. Impact categories related to nutrient management (acidification, particulate matter eutrophication) showed an increase in the range of 3-5% for PM2 in comparison with PM1, while Arundo donax L. allowed the same impact categories to be reduced by 31%, 24%, 17% and 33%, respectively.

All-lignocellulosic Fiberboard from Steam Exploded Arundo Donax L

This paper explores the possibility of producing all-lignocellulosic fiberboards from Arundo donax L. as a source of lignocellulosic fibers with no synthetic binders. This raw material was steam exploded with a thermomechanical aqueous vapor process in a batch reactor. The Arundo donax raw material and its obtained pulp were characterized in terms of chemical composition and the results were compared to other lignocellulosic materials. The chemical composition of steam exploded Arundo fibers showed high cellulose and a moderate lignin content suggesting it was a good raw material for fiberboard production. The all-lignocellulosic fiberboards were produced on laboratory scale; using the steam exploded Arundo donax by means of a wet process. The effects of pressing pressure on physical and mechanical properties were evaluated and the conditions that optimize the responses were found. The analyzed properties were density (d); water absorption (WA); thickness swelling (TS); modulus of elasticity (MOE); modulus of rupture (MOR); and internal bond strength (IB). The tested levels of the pressing pressure range from 0.35 to 15 MPa. The optimum IB; MOE; MOR; WA and TS were 1.28 MPa, 7439 MPa, 40.4 MPa, 17.6% and 13.3%, respectively. The obtained fiberboards were of very good quality and more than satisfy the requirements of the relevant standard specifications.

Talaromyces borbonicus, sp. nov., a novel fungus from biodegraded Arundo donax with potential abilities in lignocellulose conversion

A novel fungal species able to synthesize enzymes with potential synergistic actions in lignocellulose conversion was isolated from the biomass of Arundo donax during biodegradation under natural conditions in the Gussone Park of the Royal Palace of Portici (Naples, Italy). In this work, this species was subjected to morphological and phylogenetic analyses. Sequencing of its genome was performed, resulting in 28 scaffolds that were assembled into 27.05 Mb containing 9744 predicted genes, among which 396 belong to carbohydrate-active enzyme (CAZyme)-encoding genes. Here we describe and illustrate this previously unknown species, which was named Talaromyces borbonicus, by a polyphasic approach combining phenotypic, physiological, and sequence data.

Duckweed systems for eutrophic water purification through converting wastewater nutrients to high-starch biomass: comparative evaluation of three different genera (Spirodela polyrhiza, Lemna minor and Landoltia punctata) in monoculture or polyculture

This study provides a new insight into the application of duckweed in eutrophic water advanced treatment and starch production.

Decomposition rate and enzymatic activity of composted municipal waste and poultry manure in the soil in a biofuel crops field

BACKGROUND

Biofuel crops are gaining importance because of the need to replace non-renewable sources. Also, due to the increasing amounts of wastes generated, there is the need to recycle them to the soil, both to fertilize crops and to improve soil physical properties through organic matter increase and microbiological changes in the rhizosphere. We therefore studied the influence of six biofuel crops (elephant grass, giant cane, sugarcane, blue gum, black cottonwood, willow) on the decomposition rate and enzymatic activity of composted municipal solid waste and poultry manure. Organic amendments were incubated in the field (litterbag method), buried near each plant or bare soil. Biomass decrease and dehydrogenase, urease and acid phosphatase level in amendments was monitored over a 180-day period. Soil under the litterbags was analysed for the same enzymatic activity and organic matter fractions (last sampling). After 365 days, a fractionation of organic matter was carried out in both amendments and soil under the litterbags.

RESULTS

For compost, willow and sugarcane generally led to the greatest enzymatic activity, at the end of the experiment. For manure, dehydrogenase activity decreased sharply with time, the smallest value near sugarcane, while phosphatase and urease generally presented the highest values, at the beginning or after 90 days' incubation. Clustering showed that plant species could be grouped based on biomass and enzymes measured over time.

CONCLUSIONS

Plant species influenced the decomposition rate and enzymatic activities of the organic amendments. Overall, mineralization of both amendments was associated with a greater urease activity in soils. Dehydrogenase activity in manure was closely associated with urease activity. © 2016 Society of Chemical Industry.

Energy and chemical conversion of five Australian lignocellulosic feedstocks into bio-crude through liquefaction

Thermal liquefaction of five potential feedstocks namely, banana bunch stems (BBS), pineapple tops (PT), Forage sorghum (FS), bagasse (Ba) and Arundo donax (AD) were examined from an energy perspective at a large laboratory scale.

De novo assembly, functional annotation, and analysis of the giant reed (Arundo donax L.) leaf transcriptome provide tools for the development of a biofuel feedstock

BACKGROUND

Arundo donax has attracted renewed interest as a potential candidate energy crop for use in biomass-to-liquid fuel conversion processes and biorefineries. This is due to its high productivity, adaptability to marginal land conditions, and suitability for biofuel and biomaterial production. Despite its importance, the genomic resources currently available for supporting the improvement of this species are still limited.

RESULTS

We used RNA sequencing (RNA-Seq) to de novo assemble and characterize the A. donax leaf transcriptome. The sequencing generated 1249 million clean reads that were assembled using single-k-mer and multi-k-mer approaches into 62,596 unique sequences (unitranscripts) with an N50 of 1134 bp. TransDecoder and Trinotate software suites were used to obtain putative coding sequences and annotate them by mapping to UniProtKB/Swiss-Prot and UniRef90 databases, searching for known transcripts, proteins, protein domains, and signal peptides. Furthermore, the unitranscripts were annotated by mapping them to the NCBI non-redundant, GO and KEGG pathway databases using Blast2GO. The transcriptome was also characterized by BLAST searches to investigate homologous transcripts of key genes involved in important metabolic pathways, such as lignin, cellulose, purine, and thiamine biosynthesis and carbon fixation. Moreover, a set of homologous transcripts of key genes involved in stomatal development and of genes coding for stress-associated proteins (SAPs) were identified. Additionally, 8364 simple sequence repeat (SSR) markers were identified and surveyed. SSRs appeared more abundant in non-coding regions (63.18%) than in coding regions (36.82%). This SSR dataset represents the first marker catalogue of A. donax. 53 SSRs (PolySSRs) were then predicted to be polymorphic between ecotype-specific assemblies, suggesting genetic variability in the studied ecotypes.

CONCLUSIONS

This study provides the first publicly available leaf transcriptome for the A. donax bioenergy crop. The functional annotation and characterization of the transcriptome will be highly useful for providing insight into the molecular mechanisms underlying its extreme adaptability. The identification of homologous transcripts involved in key metabolic pathways offers a platform for directing future efforts in genetic improvement of this species. Finally, the identified SSRs will facilitate the harnessing of untapped genetic diversity. This transcriptome should be of value to ongoing functional genomics and genetic studies in this crop of paramount economic importance.

Impact of torrefaction and low-temperature carbonization on the properties of biomass wastes from Arundo donax L. and Phoenix canariensis

The impact of torrefaction and low-temperature carbonization on the properties of biomass wastes from Arundo donax L. and Phoenix canariensis was studied. Thermal treatments were performed at temperatures from 200°C to 350°C during 15 to 90min and temperature was the parameter that more influenced mass and energy yields as well as biochar composition. Torrefaction reduced moisture, volatile matter, O/C and H/C ratios of the biomass, while increasing heating value, ash content and fixed carbon. For torrefaction at 250°C or higher temperatures grindability of the biochars was significantly improved. The low volatile matter contents and high ash contents of these biochars restricts their use as solid fuels but they can be valorized otherwise. Raw biomasses and the biochars torrefied at 200°C could remove methylene blue from an aqueous solution, in fast adsorption test with a contact time of only 3s, with efficiencies higher than 50%.

Ethanol production by Escherichia coli from Arundo donax biomass under SSF, SHF or CBP process configurations and in situ production of a multifunctional glucanase and xylanase

Diluted acid or liquid hot water (LHW) pretreated Arundo donax biomass was converted into ethanol under separated hydrolysis and fermentation (SHF) or simultaneous saccharification and fermentation (SSF) using Escherichia coli as the fermentative organism. Up to 0.26gL^-1h^-1 and 25.0gL^-1 of ethanol were obtained with diluted acid pretreated biomass under SSF compared to 0.17gL^-1h^-1 and 24gL^-1 under SHF. LHW pretreated biomass elicited 25% lower yields on average. Saccharification was carried out with Cellic CTec2 cocktail. Alternatively, under a consolidated bioprocess (CBP) where the ethanologenic bacteria was complemented with a novel multifunctional glucanase and xylanase, ethanol concentration was 7.6gL^-1 and 7.2gL^-1 after 96h for dilute acid or LHW pretreated biomass, respectively, without any prior saccharification step. According to these results, a bacterial fermentative host combined with in situ enzyme expression can improve ethanol production from A. donax biomass.

Lignocellulose-Adapted Endo-Cellulase Producing Streptomyces Strains for Bioconversion of Cellulose-Based Materials

Twenty-four Actinobacteria strains, isolated from Arundo donax, Eucalyptus camaldulensis and Populus nigra biomass during natural biodegradation and with potential enzymatic activities specific for the degradation of lignocellulosic materials, were identified by a polyphasic approach. All strains belonged to the genus Streptomyces (S.) and in particular, the most highly represented species was Streptomyces argenteolus representing 50% of strains, while 8 strains were identified as Streptomyces flavogriseus (synonym S. flavovirens) and Streptomyces fimicarius (synonyms Streptomyces acrimycini, Streptomyces baarnensis, Streptomyces caviscabies, and Streptomyces flavofuscus), and the other four strains belonged to the species Streptomyces drozdowiczii, Streptomyces rubrogriseus, Streptomyces albolongus, and Streptomyces ambofaciens. Moreover, all Streptomyces strains, tested for endo and exo-cellulase, cellobiase, xylanase, pectinase, ligninase, peroxidase, and laccase activities using qualitative and semi-quantitative methods on solid growth medium, exhibited multiple enzymatic activities (from three to six). The 24 strains were further screened for endo-cellulase activity in liquid growth medium and the four best endo-cellulase producers (S. argenteolus AE58P, S. argenteolus AE710A, S. argenteolus AE82P, and S. argenteolus AP51A) were subjected to partial characterization and their enzymatic crude extracts adopted to perform saccharification experiments on A. donax pretreated biomass. The degree of cellulose and xylan hydrolysis was evaluated by determining the kinetics of glucose and xylose release during 72 h incubation at 50°C from the pretreated biomass in the presence of cellulose degrading enzymes (cellulase and β-glucosidase) and xylan related activities (xylanase and β-xylosidase). The experiments were carried out utilizing the endo-cellulase activities from the selected S. argenteolus strains supplemented with commercial β-gucosidase and xylanase preparations from Genencore (Accellerase BG and Accellerase XY). Cellulose and xylan conversion, when conducted using commercial (hemi)cellulases, gave glucose and xylose yields of 30.17 and 68.9%, respectively. The replacement of the cellulolytic preparation from Genencor (Accellerase 1500), with the endo-cellulase from S. argenteolus AE58P resulted in almost 76% of the glucose yield obtained in the presence of the commercial counterpart. Due to the promising results obtained by using the enzymatic crude extracts from S. argenteolus AE58P in the pretreated A. donax saccharification experiments, the proteins putatively responsible for endo-cellulase activity in this strain were identified by proteomics. Several proteins were confidently identified in different Streptomyces spp., eight of which belong to the class of Carbohydrate active enzymes. Overall results highlighted the biotechnological potential of S. argenteolus AE58P being an interesting candidate biocatalyst-producing bacterium for lignocellulose conversion and production of biochemicals and bioenergy.

Giant cane (Arundo donax L.) can substitute traditional energy crops in producing energy by anaerobic digestion, reducing surface area and costs: A full-scale approach

Arundo donax L. (Giant cane) was used in a full-scale anaerobic digester (AD) plant (power of 380kWhEE) in partial substitution for corn to produce biogas and electricity. Corn substitution was made on a biomethane potential (BMP) basis so that A. donax L. after substitution accounted for 15.6% of the total mix-BMP (BMPmix) and corn for 66.6% BMPmix. Results obtained indicated that Giant cane was able to substitute for corn, reducing both biomass and electricity production costs, because of both higher biomass productivity (Mg total solid Ha(-1)) and lower biomass cost (€Ha(-1)). Total electricity biogas costs were reduced by 5.5%. The total biomass cost, the total surface area needed to produce the energy crop and the total cost of producing electricity can be reduced by 75.5%, 36.6% and 22%, by substituting corn completely with Giant cane in the mix fed to the full-scale plant.

Energy conversion of biomass crops and agroindustrial residues by combined biohydrogen/biomethane system and anaerobic digestion

Aim of this study was to evaluate the suitability of ensiled giant reed, ensiled maize, ensiled olive pomace, wheat bran for combined systems (CS: dark fermentation+anaerobic digestion (AD)) producing hydrogen-rich biogas (biohythane), tested in batch under basic operational conditions (mesophilic temperatures, no pH control). Substrates were also analyzed under a single stage AD batch test, in order to investigate the effects of DF on estimated energy recovery (ER) in combined systems. In CS, maize and wheat bran exhibited the highest hydrogen potential (13.8 and 18.9NLkgVS(-1)) and wheat bran the highest methane potential (243.5NLkgVS(-1)). In one-stage AD, giant reed, maize and wheat bran showed the highest methane production (239.5, 267.3 and 260.0NLkgVS(-1)). Butyrate/acetate ratio properly described the dark fermentation, correlating with hydrogen production (r=0.92). Wheat bran proved to be a promising residue for CS in terms of hydrogen/methane potential and ER.