Eucalyptus urograndis is a hybrid eucalyptus of major economic importance to the Brazilian pulp and paper industry. Although widely used in forest nurseries around the country, little is known about the biochemical changes imposed by environmental stress in this species. In this study, we evaluated the changes in the stem proteome after short-term stimulation by exposure to low temperature. Using two-dimensional gel electrophoresis coupled to high-resolution mass spectrometry-based protein identification, 12 proteins were found to be differentially regulated and successfully identified after stringent database searches against a protein database from a closely related species Eucalyptus grandis. The identification of these proteins indicated that the E.
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Metrics details. Cellulosic ethanol is one of the most important biotechnological products to mitigate the consumption of fossil fuels and to increase the use of renewable resources for fuels and chemicals. By performing this process at high total solids TS and low enzyme loadings EL , one can achieve significant improvements in the overall cellulosic ethanol production process. Also, the fermentability of their corresponding hydrolysates was tested using an industrial strain of Saccharomyces cerevisiae Thermosacc Dry from Lallemand.
Enzymatic hydrolysis of steam-treated E. On the other hand, E. Cellulosic ethanol was produced from steam-exploded substrates that were derived from Eucalyptus urograndis chips and sugarcane bagasse using high total solids and low enzyme loadings. Cellulosic ethanol is currently produced by fermentation of carbohydrates that are released from plant polysaccharides by enzymatic hydrolysis.
Such production process depends on five sequential steps involving: 1 collection and preparation of plant biomass; 2 pretreatment for increasing the susceptibility of plant polysaccharides to bioconversion at high process yields; 3 enzymatic hydrolysis for converting plant polysaccharides into fermentable sugars; 4 microbial fermentation for cellulosic ethanol production; and, finally, 5 the recovery of ethanol by distillation [ 1 — 3 ].
Several agro-industrial and forestry residues are of great interest as feedstocks for cellulosic ethanol production, such as in the case of sugarcane bagasse and short rotation clones of Eucalyptus sp.
Most of this bagasse is currently used for energy purposes but there is a surplus that still represents a great opportunity for the development of sustainable biorefineries. In addition, other species of Eucalyptus sp. Hence, the availability and favorable properties of these lignocellulosic materials has motivated a great interest in their use for the production of cellulosic ethanol and other important building blocks for the chemical industry, as well as composites and structural materials in both nano and fiber scales [ 11 — 13 ].
Besides, biomass upgrading to fuels, chemicals and materials offers no immediate risks to food security issues. Steam explosion is one of the most widely used pretreatment method for cellulosic ethanol production [ 14 — 16 ]. This method increases the accessibility of cellulose by deconstructing the associative structure of the plant cell wall, causing an increase in the substrate surface area and pore volume. Changes are also introduced into the biomass chemistry, particularly by acid hydrolysis and partial dissolution of hemicelluloses and lignin [ 17 , 18 ].
However, pretreatment conditions must be optimized to avoid undesirable side reactions such as carbohydrate dehydration and lignin condensation. Enzymatic hydrolysis is accomplished by different classes of enzymes which are intended to convert all of the available plant polysaccharides into fermentable sugars. According to Wingren et al. Hence, by performing this step at high TS and low enzyme loadings EL , it is possible to achieve significant improvements in the economics of the overall cellulosic ethanol production process.
These improvements involve a better integration of process streams, energy savings and reductions in capital cost for hydrolysis and distillation, particularly coming from the fact that high sugar concentrations are produced for fermentation [ 2 , 20 — 22 ].
Different process configurations have been developed so far for cellulosic ethanol production. If fermentation is carried out after enzymatic hydrolysis using substrate hydrolysates that were filtered to remove suspended solids, the process configuration is referred to as separate hydrolysis and fermentation SHF.
The advantages of SHF are that both steps can be carried out at their optimal conditions and yeast recycling is perfectly feasible, but the capital cost is higher and enzymatic hydrolysis is limited by end-product inhibition.
Ethanol can also be produced by simultaneous saccharification and fermentation SSF and, in this case, the capital cost is lower, the total processing time is reduced and end-product inhibition is alleviated because sugars are fermented as they are produced by the concerted action of the enzymes.
However, SSF does not allow yeast recycling and hydrolysis is usually carried out below its optimal temperature. In both configurations mentioned above, ethanol yields can be increased if the fermenting organism is able to convert pentoses and hexoses simultaneously [ 23 , 24 ]. Wood chips of E. As expected, differences were observed in the chemical composition of both native sugarcane bagasse and E.
In general, sugarcane bagasse presented lower glucan and lignin contents while its total extractives, pentosan and ash contents were much higher than those of E.
Both eucalypt and sugarcane bagasse hemicelluloses were partially quantified as xylans because the High Performance Liquid Chromatography HPLC method used for analysis was not able to quantify uronic acids and to resolve xylose, galactose and mannose in biomass acid hydrolysates.
The extractives content was generally higher for sugarcane bagasse due to the presence of larger quantities of waxes, cinnamic acid derivatives, terpenes, lipids and other extractable materials [ 25 , 27 ]. On the other hand, the high ash content of sugarcane bagasse may be partially due to unavoidable contaminations with soil, which are due to the current mechanical harvesting techniques. Biogenic ashes usually contain variable amounts of alkaline and alkaline earth oxides that are easily leached out by a mild acid treatment.
Hence, the buffering capacity of this acid leaching may partially compromise the efficiency of pretreatment methods that rely on acid hydrolysis. The ash content of STB-WI was higher than that of sugarcane bagasse and this was probably a result of its abrasiveness when processed at high total solids.
STB-WI had a higher acid-insoluble lignin content compared to STE-WI as well as a higher amount of dehydrated pentoses, which were attributed to the presence of arabinoxylans in sugarcane bagasse. Also, the amount of dehydrated pentoses in steam-treated substrates was much lower than that of native materials, with hydroxymethylfurfural becoming the main sugar dehydration by-product. This observation was not only associated to the lower hemicellulose content of steam-treated substrates but also to the higher chemical accessibility of their steam-treated glucans.
Aguiar et al. The chemical composition of the resulting material showed On the other hand, Martin-Sampedro et al. For instance, substrates containing However, differences in pretreatment procedure as well as in the chemical composition of both eucalypt species may have been highly influential as well. The Fig. Despite their similar enzymatic hydrolysis profile, conversion of cellulose to soluble sugars was higher for eucalypt compared to bagasse.
Ramos et al. Despite the use of an exogenous acid catalyst at different pretreatment conditions, This better hydrolysis performance can be explained by differences in substrate accessibility but also by differences in the hydrolysis procedure, since the later glucose release was obtained under stepwise substrate addition fed-batch feeding and a more efficient mechanical agitation.
Martins et al. At the end of this process, The corresponding ethanol productivities were 1. However, this study involved pretreated substrates that were derived from sugarcane bagasse by alkaline hydrogen peroxide pretreatment. This way, pretreated substrates were produced and whole pretreatment slurries were submitted to SSF for cellulosic ethanol production.
Since pSSF usually gives better ethanol productivities than SSF [ 23 , 33 ], this unexpected result was probably due to the presence of inhibitors in the fermentation media. By contrast, Neves et al. However, these results were obtained in the absence of fermentation inhibitors using low enzyme loadings of Cellic CTec2 and the S. Therefore, the corresponding ethanol productivities were much lower at 0. However, these values cannot be compared to those described above because the strategy used for fermentation was completely different.
These projections were calculated by considering the recovery yield of water-washed steam-treated fractions STB-WI and STE-WI , the amount of glucose that was obtained after enzymatic hydrolysis and the corresponding fermentation efficiency for ethanol production.
On the basis of these, These numbers are considerably high if compared to the theoretical amount of ethanol that can be produced from both sugarcane bagasse and eucalypt steam-exploded substrates, whose maximum fermentation efficiency produces Nevertheless, it is important to mention that 7.
By contrast, the complete eucalypt harvest cycle usually takes seven years [ 35 ]. One effective way to achieve a more realistic comparison between these two biomass types is to consider their average annual productivities, which are projected to be around Hence, eucalypt plantations are able to achieve cellulosic ethanol productivities of Gonzalez et al.
In fact, both prices varied a lot throughout the year but sugarcane bagasse was always more expensive due to its increased demand for bioenergy applications such as cogeneration. Hence, both biomass types showed good potential for cellulosic ethanol production but E. Pretreatment of sugarcane bagasse and eucalypt chips by steam explosion resulted in high yields of enzymatic hydrolysis at high total solids and a relatively low enzyme loading.
With regard to fermentation, both hydrolysates were readily fermented in good yields by an industrial yeast strain of S. The quantification was performed by external calibration 0. Pretreatment by steam explosion was carried out in a 10 L stainless steel reactor that was provided with sensors to control reaction parameters such as the pretreatment pressure, temperature and time. The steam explosion experiments were performed under pre-optimized conditions to recover most of the three main biomass components and to increase the susceptibility of the resulting substrate to enzymatic hydrolysis and fermentation.
Pretreatment mass yields were calculated by difference before and after pretreatment, always in relation to the dry mass of the corresponding materials. Cellic CTec3 was used at an EL of EL was expressed in relation to the wet mass of the enzyme preparation and its total cellulase activity was determined according to Ghose [ 51 ].
Aliquots of 0. Hydrolysis yields were expressed in relation to the glucan content of the pretreated substrates. Renew Sust Energ Rev — Bioresour Technol — Biofuels Bioprod Biorefin — Sustain Chem Process Ind Crops Prod — Biotechnol Biofuels Google Scholar. Tree Genet Genomes — Int J For Res.
Green Chem — Annu Rev Chem Biomol Eng — Maity SK Opportunities, recent trends and challenges of integrated biorefinery: part I. Enzyme Microb Technol 46 2 — Ramos LP The chemistry involved in the pretreatment of lignocellulosic materials.
Ind Crops Prod 35 1 — Biotechnol Progress 19 4 — Biomass Bioenergy — Biotechnol Bioeng 2 — Bioresour Technol 7 —
Autohydrolysis and kraft pulping were sequentially applied to Eucalyptus urograndis wood to obtain added-value products from hydrolysis liquor. A biorefinery approach was used to bleach the resulting solid phase containing the cellulose pulp with an optimized O—D— EP —D bleaching sequence, where O denotes delignification with the sequence D bleaching with chlorine dioxide and EP alkaline extraction with soda and hydrogen peroxide. The pulp was then beaten to obtain paper sheets. The two-stage process yielded pulp with a small Kappa number relative to conventional delignification 4. Additionally, the Kappa number and brightness obtained after bleaching with an O-D-EP-D sequence were suitable for preparing dissolving grade pulp. The brightness of the pulp obtained was identical with that of the reference pulp Beating the pulp for PFI revolutions produced paper sheets with slightly better tensile strength and tear index than those for sheets from the reference pulp viz.
Scientific Name: Eucalyptus urograndis Eucalyptus grandis x E. Distribution: Grown on plantations in Brazil. Tree Size: ft m tall, ft Janka Hardness: 1, lb f 6, N.
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