Sarita Cândida Rabelo

Effects of the pretreatment method on high solids enzymatic hydrolysis and ethanol fermentation of the cellulosic fraction of sugarcane bagasse.

This work evaluated ethanol production from sugarcane bagasse at high solids loadings in the pretreatment (20-40% w/v) and hydrolysis (10-20% w/v) stages. The best conditions for diluted sulfuric acid, AHP and Ox-B pretreatments were determined and mass balances including pretreatment, hydrolysis and fermentation were calculated. From a technical point of view, the best pretreatment was AHP, which enabled the production of glucose concentrations near 8% with high productivity (3.27 g/Lh), as well as ethanol production from 100.9 to 135.4 kg ethanol/ton raw bagasse. However, reagent consumption for acid pretreatment was much lower. Furthermore, for processes that use pentoses and hexoses separately, this pretreatment produces the most desirable pentoses liquor, with higher xylose concentration in the monomeric form.

Adsorption characteristics of cellulase and β-glucosidase on Avicel, pretreated sugarcane bagasse, and lignin

Although adsorption is an essential step in the enzymatic hydrolysis of lignocellulosic materials, literature reports controversial results in relation to the adsorption of the cellulolitic enzymes on different biomasses/pretreatments, which makes difficult the description of this phenomenon in hydrolysis mathematical models. In this work, the adsorption of these enzymes on Avicel and sugarcane bagasse pretreated by the hydrothermal bagasse (HB) and organosolv bagasse (OB) methods was evaluated. The results have shown no significant adsorption of β‐glucosidase on Avicel or HB. Increasing solids concentration from 5% (w/v) to 10% (w/v) had no impact on the adsorption of cellulase on the different biomasses if stirring rates were high enough (>100 rpm for Avicel and >150 rpm for HB and OB). Adsorption equilibrium time was low for Avicel (10 Min) when compared with the lignocellulosic materials (120 Min). Adsorption isotherms determined at 4 and 50 °C have shown that for Avicel there was a decrease in the maximum adsorption capacity (Emax) with the temperature increase, whereas for HB increasing temperature increased Emax. Also, Emax increased with the content of lignin in the material. Adsorption studies of cellulase on lignin left after enzymatic digestion of HB show lower but significant adsorption capacity (Emax = 11.92 ± 0.76 mg/g).

Detoxification of sugarcane-derived hemicellulosic hydrolysate using a lactic acid producing strain

Furfural and HMF are known for a negative impact in different bioprocesses, including lactic acid fermentation. There are already some methods described to remove these inhibitory compounds from the hydrolysates. However, these methods also reduce the yield of sugars from the hydrolysis and increase the process costs. In this work, the detoxification of sugarcane-derived hemicellulosic hydrolysate was performed by Lactobacillus plantarum during the fermentation time. At the end of the fermentation, a decrease of 98% of furfural and 86% of HMF and was observed, with a final lactic acid titer of 34.5 g/L. The simultaneous fermentation and bio-detoxification simplify the process and reduce operational costs, leading to economic competitiveness of second-generation feedstock for lactic acid production.

Industrial Waste Recovery

The Brazilian sugar–alcohol sector is known for generating large amounts of residues of sugarcane processing due to its size. Therefore, the utilization of these residues by the industry becomes necessary not only from the environmentalal point of view, but also as a way of avoiding wasting materials which may add value to the sugarcane productive chain. The search for sustainable processes and increases in gains make products that were once considered a problem in the sugar–alcohol sector to be viewed as considerable sources of income for the sugarcane plants. In this chapter the use and application of the main byproducts in the sugar–alcohol industry will be approached, as well as the use of sugarcane bagasse and straw to produce biofuels, chemical products and animal food; the use of yeasts in human and animal feeding; as well as the use of molasses, filter cake, vinasse, and carbon dioxide.

Second-generation ethanol ( GII ). The contribution of CTBE

The Brazilian Bioethanol Science and Technology Laboratory (CTBE) one of the laboratories of the Brazilian Center of Research in Energy and Materials (CNPEM) has as one of its main goals contribute to the development of the process of obtaining second generation ethanol ( GII ) mainly from lignin cellulosic fractions of cane sugar. To achieve this goal leads its own line of research, develop partnerships with other public and private institutions or acting as national laboratory offers its facilities of laboratories and process development pilot plant to researchers involved in projects to produce ethanol, energy and chemicals from lignocelluloses materials. The activities of CTBE are based on research and development line that integrates the current process of obtaining first-generation ethanol ( GI ) of the sugars extracted from cane sugar coupled with the second generation process of deconstruction of lignocelluloses fractions (bagasse and straw), enzymatic hydrolysis of cellulose and fermentation of pentose and hexoses. The production of ethanol GII although technically demonstrated, at the present time not achieved results that enable production at competitive costs. The critical barriers to overcome to achieve this goal are: • Pretreatment: efficient fractionation of lignocelluloses material for better recovery and hydrolysis of pentose and cellulignin. • Hydrolases: Obtaining a more efficient and productive hydrolases complex; • Enzymatic hydrolysis: optimization of hydrolysis of cellulose; • Ethanol from pentose: development of pentose fermentation to ethanol. The negative impact of these barriers on the process of obtaining second-generation ethanol will be discussed. The research lines proposed for overcome it and improve the performance of this process integrated with first generation ethanol will be presented.