h i g h l i g h t s Sequential Alk-H 2 O 2 /NaOH pretreatment was developed. FTIR, SEM, X-ray and crystallinity indexes have evidenced modifications in solids. Delignified MCF was more susceptible the enzymatic action. SSSF strategy allowed to obtain higher ethanol production than SSF. Step of presaccharification had a positive effect on the overall ethanol yield.

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In search to increase the offer of liquid, clean, renewable and sustainable energy in the world energy matrix, the use of lignocellulosic materials (LCMs) for bioethanol production arises as a valuable alternative. The objective of this work was to analyze and compare the performance of Saccharomyces cerevisiae, Pichia stipitis and Zymomonas mobilis in the production of bioethanol from coconut fibre mature (CFM) using different strategies: simultaneous saccharification and fermentation (SSF) and semisimultaneous saccharification and fermentation (SSSF). The CFM was pretreated by hydrothermal pretreatment catalyzed with sodium hydroxide (HPCSH). The pretreated CFM was characterized by X-ray diffractometry and SEM, and the lignin recovered in the liquid phase by FTIR and TGA. After the HPCSH pretreatment (2.5% (v/v) sodium hydroxide at 180 C for 30 min), the cellulose content was 56.44%, while the hemicellulose and lignin were reduced 69.04% and 89.13%, respectively. Following pretreatment, the obtained cellulosic fraction was submitted to SSF and SSSF. Pichia stipitis allowed for the highest ethanol yield e 90.18% e in SSSF, 91.17% and 91.03% were obtained with Saccharomyces cerevisiae and Zymomonas mobilis, respectively. It may be concluded that the selection of the most efficient microorganism for the obtention of high bioethanol production yields from cellulose pretreated by HPCSH depends on the operational strategy used and this pretreatment is an interesting alternative for add value of coconut fibre mature compounds (lignin, phenolics) being in accordance with the biorefinery concept.

The use of coconut fiber mature, green coconut shell, mature coconut shell and cactus is an important alternative as substrates for bioethanol production, since these lignocellulosic materials (LCMs) are abundant in Brazil, mainly in the Northeast Region. The first objective of this work was to evaluate the autohydrolysis pretreatment (AP) on these LCMs and the susceptibility of the treated materials to enzymatic hydrolysis (EH). The second part of the work deals with the application of semi-simultaneous saccharification and fermentation (SSSF) and simultaneous saccharification and fermentation (SSF) using Zymomonas mobilis, Pichia stipitis, Saccharomyces cerevisiae and as substrate the green coconut shell (selected according to the results obtained in the first part of the work). The LCMs after AP using the highest severity factor (4.64) showed changes in the chemical composition in comparison to the untreated LCMs: between the LCMs the cellulose increase was 48.55%, the hemicellulose decrease was 76.77% and an increase of 62.26% was observed for lignin. The green coconut shell was characterized by SEM, X-ray and FTIR after AP and its EH conversion into glucose was 92.52%. The best results on ethanol yield (90.09%) and ethanol productivity (0.21 g/(L h)) from green coconut shell were obtained by S. cerevisiae using SSSF. Overall, an efficient process for the bioethanol production from green coconut shell was developed.

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Today's search for alternative sources of energy to reduce the use of fossil fuels is motivated by environmental, socioeconomic and political reasons. The use of agro-industrial and municipal wastes of plant origin for ethanol production appears to be the best option to solve the dilemma of using food sources to produce biofuels, since it adds value to these wastes in eco-efficient processes. This paper highlights the potential of agro-industrial and municipal wastes for cellulosic ethanol production.

The search for new sources of lignocellulosic raw materials for the generation of energy and new compounds encourages the search for locations not well known and with a high potential for biomass availability as is the case of the Northeast Region of Brazil. Thus, the cactus (CAC), green coconut shell (GCS), mature coconut fibre and mature coconut shell were pretreated by NaClO 2-C 2 H 4 O 2 and sequential NaClO 2-C 2 H 4 O 2 /autohydrolysis aiming at the obtention of high added-value compounds in the liquid fraction and solid phase. The yield of the solid phase was between 61.42 and 90.97% and the reduction up to 91.63% of lignin in the materials pretreated by NaClO 2-C 2 H 4 O 2. After NaClO 2-C 2 H 4 O 2 /autohydrolysis pretreatment the obtained solids yield was between 43.57 and 52.08%, with a solubilization of the hemicellulose content up to 81.42%. For both pretreatments the cellulosic content remained almost unchanged. The pretreated solids were characterized by SEM, X-ray and crystallinity indexes showing significant modifications when submitted to pretreatments. These results were further confirmed by the enzymatic conversion yields of 81.68-90.03 and 86.97-90.36% of the LCMs pretreated by NaClO 2-C 2 H 4 O 2 and pretreated by NaClO 2-C 2 H 4 O 2 /autohydrolysis, respectively. The resulting liquors had a total phenolic compounds content between 0.20 and 3.05 g/L, lignin recovered up to 7.40 g/L (absence of sulphur) and xylooligosaccharides between 16.13 and 20.37 g/L. Thus, these pretreatments showed an efficient fractionation of LCMs, especially in the GCS, being an important requirement for the generation of products and byproducts in the context of the biorefinery.

Production of cellulosic ethanol and holocellulosic ethanol from vegetable or microbial biomass starts with a hydrolysate containing compounds which may produce negative effects in the enzymatic hydrolysis and fermentation stages due to the need of pretreatment of the materials. In this way, the simultaneous presence of hydroxymethylfurfural (HMF), furfural, acetic acid, levulinic acid, and formic acid in different concentrations was tested in the fermentation using Saccharomyces cerevisiae, Pichia stipitis, and Zymomonas mobilis. The substitution of freshwater by seawater in the culture medium was also analyzed. Thus, inhibitory effects were stronger in the fermentation using P. stipitis, followed by Z. mobilis and S. cerevisiae. Formic acid and acetic acid presented more significant effects among the inhibitory compounds, followed by HMF, furfural and levulinic acid. Fermentation performed in culture medium with seawater showed promising results, especially in the ethanol yield using S. cerevisiae (0.50 g ethanol/g glucose) and Z. mobilis (0.49 g ethanol/g glucose). Whereas the production of cellulosic ethanol and holocellulosic ethanol are in early stages of development on an industrial scale, and that the availability and use of freshwater may cause socio-environmental problems for expansion of ethanol production, the use of seawater appears as an alternative to mitigate this problem.