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The growing demand and prices of fuel promote the development of technologies to improve the production process of biofuels. The energy integration in sugarcane biorefineries provides better use of utilities and cost reduction besides the possibility of increasing the amounts of ethanol or electricity produced. The latter is a result of the lower steam consumption in the plant, which allows diverting more bagasse to be processed into second-generation (2G) ethanol or electricity. This work assessed two case studies: case study 1 (CS1), which represents a biorefinery that produces first- and second-generation (1G/2G) ethanol and electricity, with disposal of the fraction of xylose, and case study 2 (CS2), where the pentose fraction is used to produce biogas. Differences in process operation conditions influence the design of a heat exchanger network (HEN). To handle this problem, concepts of synthesis of HEN with multiple operation periods were used. The multiperiod HEN synthesis problem is solved using a mixed integer nonlinear programming (MINLP) model. Each period has a different operating condition, and, for solving the MINLP problem, a hybrid meta-heuristic approach was used, which combines tabu search and particle swarm methods. For the cases studied in this work, energy integration can allow for surpluses of up to 8.8% of ethanol and 31.7% of electricity, as well as better use of environmental resources and energy security. The payback time of the HEN investment is a maximum of 5.2 years if the surplus bagasse is diverted to the 2G ethanol. [ABSTRACT FROM AUTHOR]

Second-generation technology (2G) is currently the industrial route that is being developed with the potential to meet the demand for biofuels and bioproducts. The technology studied in the present work is based on the non-food processing of sugarcane straw, which is unlike the bagasse processing route (a lignocellulosic residue) that is commonly used in boilers for steam and electricity generation. In the last years, cellulosic ethanol plants worldwide include the utilisation of corn stover, sugarcane bagasse, wood waste and plant residues. Therefore, a communication based on industrial aspects using sugarcane straw is important in order to expand the knowledge regarding this promising technology. The main objective of this work included listing the results obtained in a cellulosic-ethanol production industry using sugarcane straw, located in the Northeast region of Brazil and taking into account the efficiency of pre-treatment, enzymatic hydrolysis and fermentation processes and comparing these results with data found in the literature regarding studies with similar efficiency. It was possible to observe that the production of ethanol from sugarcane straw at an industrial scale achieved a productivity of 200 l of ethanol per tonne of biomass, exhibiting 90, 70 and 85% of pre-treatment, hydrolysis and fermentation efficiency, respectively. [ABSTRACT FROM AUTHOR]

Lignin is the main component of secondary cell walls and is essential for plant development and defense. However, lignin is recognized as a major recalcitrant factor for efficiency of industrial biomass processing. Genes involved in general phenylpropanoid and monolignol-specific metabolism in sugarcane have been previously analyzed at the transcriptomic level. Nevertheless, the number of genes identified in this species is still very low. The recently released sugarcane genome sequence has allowed the genome-wide characterization of the 11 gene families involved in the monolignol biosynthesis branch of the phenylpropanoid pathway. After an exhaustive analysis of sugarcane genomes, 438 haplotypes derived from 175 candidate genes from Saccharum spontaneum and 144 from Saccharum hybrid R570 were identified as associated with this biosynthetic route. The phylogenetic analyses, combined with the search for protein conserved residues involved in the catalytic activity of the encoded enzymes, were employed to identify the family members potentially involved in developmental lignification. Accordingly, 15 candidates were identified as bona fide lignin biosynthesis genes: PTAL1, PAL2, C4H4, 4CL1, HCT1, HCT2, C3'H1, C3'H2, CCoAOMT1, COMT1, F5H1, CCR1, CCR2, CAD2, and CAD7. For this core set of lignin biosynthetic genes, we searched for the chromosomal location, the gene expression pattern, the promoter cis-acting elements, and microRNA targets. Altogether, our results present a comprehensive characterization of sugarcane general phenylpropanoid and monolignol-specific genes, providing the basis for further functional studies focusing on lignin biosynthesis manipulation and biotechnological strategies to improve sugarcane biomass utilization. [ABSTRACT FROM AUTHOR]

In response to the new requirements of the sugar-energy sector, sugarcane breeding programs are addressing the selection of clones for different purposes, e.g., sucrose production, ethanol production for first-generation (1G) and second-generation (2G) biofuels. Consequently, agronomic variables such as fiber content, sucrose content and biomass yield, become more relevant in the selection process, for underlying the definition of conventional, high biomass and multipurpose ideotypes. The relation between fiber and sucrose contents and biomass quantity should be used to differentiate thee different clone types: conventional clones, with high sucrose content and high biomass; high biomass, with high fiber content and high biomass; or multipurpose, with high fiber and sucrose contents and high biomass. In view of the difficulty of selecting different ideotypes from the same population, the objective of this study was to develop a method of selecting sugarcane clones for the different purposes. A population with 220 clones derived from crosses involving parents of different Saccharum species were subjected to the new methodology of clone selection with a fuzzy controller programmed to classify experimental clones in three ideotypes. Apart from the selection involving real data, the fuzzy controller was tested on 26 simulated populations. The controller proved to be efficient in the classification and selection of clones from the three ideotypes with real and simulated data. [ABSTRACT FROM AUTHOR]

The employment of hemicellulose fractions from bagasse acid (HF-AC - rich in xylose) and hydrothermal (HF-HT - containing high amounts of xylooligosaccharides) pretreatments led to yields of 265 and 177 mL H2 /g carbohydrate after 18 and 45 h of fermentation, respectively. The anaerobic sludge used as inoculum was able to hydrolyze the xylooligosaccharides of HF-HT into simpler sugars, enabling microbial hydrogen production. The acid hydrolysis of xylooligosaccharides in HF-HT before fermentation improved the productivity by 30% and showed similar yield (231 mL H2 /g carbohydrate). The adaptive phase for HF-HT consumption was influenced by the hydrolytic step and by inhibitors, as the kinetics of hydrolyzed HF-HT was deeply affected in the first 18 h compared to HF-AC. Higher amounts of HF-AC in the media promoted fermentation inhibition, which could be related to the increased concentrations of acetic acid and carbohydrates, two factors that enhance the system osmolarity. Image 1 • C5 fractions from acid or hydrothermal pretreatment of sugarcane bagasse were used. • Oligosaccharides were hydrolyzed into simpler sugars by the anaerobic sludge. • Hydrolytic step and inhibitors influenced the hydrothermal C5 fraction consumption. • Total osmolarity of the fermentative media plays a role in H 2 production inhibition. [ABSTRACT FROM AUTHOR]

The development of lysigenous aerenchyma starts with cell expansion and degradation of pectin from the middle lamella, leading to cell wall modification, and culminating with cell separation. Here we report that nutritional starvation of sugarcane induced gene expression along sections of the first 5 cm of the root and between treatments. We selected two candidate genes: a RAV transcription factor, from the ethylene response factors superfamily, and an endopolygalacturonase (EPG), a glycosyl hydrolase related to homogalacturonan hydrolysis from the middle lamella. epg1 and rav1 transcriptional patterns suggest they are essential genes at the initial steps of pectin degradation during aerenchyma development in sugarcane. Due to the high complexity of the sugarcane genome, rav1 and epg1 were sequenced from 17 bacterial artificial chromosome clones containing hom(e)ologous genomic regions, and the sequences were compared with those of Sorghum bicolor. We used one hom(e)olog sequence from each gene for transactivation assays in tobacco. rav1 was shown to bind to the epg1 promoter, repressing β-glucuronidase activity. RAV repression upon epg1 transcription is the first reported link between ethylene regulation and pectin hydrolysis during aerenchyma formation. Our findings may help to elucidate cell wall degradation in sugarcane and therefore contribute to second-generation bioethanol production. [ABSTRACT FROM AUTHOR]

Abstract One of the major challenges involved in biofuel production from plant biomass is increasing the saccharification efficiency impaired by cell wall recalcitrance. The sugarcane transcription factor ShSHN1 was overexpressed in rice to evaluate its impacts on cell wall composition and potential for the development of refined lignocellulosic feedstocks for biofuel manufacturing. Plant phenotyping included biomass and cell wall component determination. Additionally, gene expression of biosynthetic cell wall polymers and wax/cutin-related genes were evaluated. ShSHN1 ectopic overexpression promoted an increase in biomass (91–340%), pectin (26–209%), cellulose content (10–22%) and saccharification efficiency (5–53%) in rice transgenic plants, as well as a reduction in the lignin content (17–35%) and an altered lignin composition. Such an increase in pectin is a new finding and opens up new research pathways for cell wall manipulation of energy crops. Furthermore, ShSHN1 overexpression led to changes in the expression patterns of all genes analyzed, suggesting a possible relation between ShSHN1 and the regulatory mechanisms involved in secondary plant cell wall formation. Saccharification improvement and biomass increase made the perfect combination for second generation ethanol production. This synergistic gain is discussed based on structural polysaccharides and lignin modification. Phenotypes and gene expression analysis provide insights into possible SHINE mechanisms of action and biological role in cell wall component biosynthesis. These results demonstrate the great potential of ShSHN1 to improve grass feedstocks as a source of energy. Highlights • Overexpression of ShSHN1 coordinates the biosynthesis of cell wall components in rice. • Rice ShSHN1 transgenic lines exhibited increase in pectin and decrease in lignin. • Genetic manipulation promoted biomass gain and improved saccharification efficiency. [ABSTRACT FROM AUTHOR]

Material balance and preliminary technical analyses of pilot scale sugarcane bagasse alkaline pretreatment, using sodium hydroxide with and without anthraquinone (AQ) addition were analyzed and compared to elucidate the carbohydrates and phenolic components flux in the streams. The lowest carbohydrates solubilization rates (9% wt for cellulose and 41% wt for hemicelluloses) were reached for the condition at 130 °C with AQ addition, however the highest lignin solubilization (87% wt) was accomplished for the condition using 170 °C with AQ addition. Preliminary technical analysis was carried out to evaluate the performance of the best pretreatment condition when integrated to a first and second generation ethanol plant, in a biorefinery concept, showing that 83.03 m 3 /h of ethanol can be produced by this process. Ethanol production (in L/ton biomass) for proposed process is 8.1% lower than the expected for short terms technologies concluding that upgrades on the process, as higher solids concentrations and lignin energy use or, principally, lignin valorization must be performed to allow viability of the process. [ABSTRACT FROM AUTHOR]

This work focuses a whole process assessment on post-harvesting sugarcane residues for 2G ethanol production by different saccharification-fermentation conditions at high solids loading, performed after steam explosion, alkaline and acidic pretreatments. Carbohydrate recoveries and enzymatic digestibility results showed that alkali and steam explosion pretreatments were effective for the biomass assayed. Due to a significant improvement (60%) of the glucose released by combining hemicellulases and cellulases only after the NaOH pretreatment, the most favorable process settled comprised an alkali-based pretreatment followed by a pre-saccharification and simultaneous saccharification and fermentation (PSSF). The produced ethanol reached 4.8% (w/w) as a result of an 80% conversion of the glucose from the pretreated biomass. Finally, an ethanol concentration of 3.2% (w/w) was obtained by means of a steam explosion followed by PSSF, representing a suitable start point to further develop a low environmental impact alternative for ethanol production. [ABSTRACT FROM AUTHOR]

• Technological advances in bagasse pretreatments should met sustainability criteria. • Water, energy and chemicals minimization is crucial for industrial sustainability. • Water reuse from evaporators could reduce water consumption in 2G ethanol production. • The use of green solvents for biomass pretreatment is an incipient, but important, area of research. • Lignin for energy is to be considered in a circular 1G + 2G ethanol production process. The sustainability of a biofuel is severely affected by the technological route of its production. Chemical pretreatment can be considered the traditional method of decomposition of the lignocellulose into its mono and oligomeric units, which can be further bioconverted to ethanol. The evaluation of the recent advances in chemical pretreatments of sugarcane bagasse, especially diluted acids, alkaline, organosolv and ionic liquids, identified the critical points for sustainability. In this context, chemicals recovery and reutilization or their substitution by green solvents, heat and electricity generation through bioenergy, reutilization of water from evaporators, vinasse concentration and the upgrading of lignin were discussed as strategic routes for developing sustainable chemical-based lignocellulose pretreatment. The advances in the technologies that allow greater fractionation of lignocellulosic biomass should be focused on the minimization of the use of natural resources, effluent generation and energy expenditure. [ABSTRACT FROM AUTHOR]