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The objective of this study was to evaluate the ethanol production by Wickerhamomyces sp. using soybean straw and hull hydrolysates obtained by subcritical water hydrolysis and, afterward, the biogas production using the fermented hydrolysates. Ethanol was produced using the straw and hull hydrolysates diluted and supplement with glucose, reaching 5.57 ± 0.01 g/L and 6.11 ± 0.11 g/L, respectively. The fermentation in a bioreactor with changing the pH to 7.0 allowed achieving maximum ethanol production of 4.03 and 3.60 g/L for straw and hull hydrolysates at 24 h, respectively. The biogas productions obtained for the fermented hydrolysates of straw with and without changing the pH were 739 ± 37 and 652 ± 34 NmL/gVSad, respectively. The fermented hydrolysate of hull without changing the pH presented 620 ± 26 NmL/gVSad. The soybean residues produced biofuels, indicating these residues show potential as raw material for renewable energy production.

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Seawater (SW) and wastewater from shrimp production (WSP) were used as a solvent for the fermentation of papaya residues (Carica papaya) by Wickerhamomyces sp. UFFS-CE-3.1.2 and Saccharomyces cerevisiae CAT-1. For comparative purposes and evaluation of the effect of salinity, ultrapure water (UW) was used as control. Fermentative parameters were evaluated in Plackett-Burman planning to assess ethanol production's significant variables. Urea supplementation was the only variable not significant for the proposed process, suggesting that papaya residues contain all the nutrients needed for fermentation. The experiments conducted with the different water sources resulted in similar concentrations of ethanol. Maximum ethanol concentration was obtained after nine h of fermentation usingWickerhamomycessp. UFFS-CE-3.1.2 (27.31 ± 1.40 g L-1) and 12 h using S. cerevisiaeCAT-1 (24.53 ± 0.68 g L-1). This study demonstrated that SW and WSP could replace freshwater without affecting ethanol production. Papaya residues from the fruit and vegetable sectors can be considered a promising substrate source for ethanol production.

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Bioethanol production has been presented as an alternative for supplying energy demand and minimizing greenhouse gases effects. However, due to abrasively conditions employed on the biomass during pretreatment and hydrolysis processes, inhibitors for fermentation phase such as acetic acid and others can be generated. Based on this problem, the aim of this work was to evaluate the adsorption of acetic acid on microporous activated carbon and investigate the stripping of the same component with dried air. For adsorption process, three concentrations of acetic acid (5, 10, and 20%) were analyzed by adsorption kinetics and adsorption isotherms (Langmuir and Freundlich models). Pseudo-second order model showed to fit better when compared to Pseudo-first order model. The Intraparticle Diffusion model presented the first phase of the adsorption as the regulating step of the adsorption process. The Langmuir model showed the best fitting, and the maximum capacity of adsorption was found as 128.66 mg.g-1. For stripping procedure an apparatus was set in order to insert dried air by a diffusor within the solution in study. Increasing temperature showed to be determinant on augmenting acetic acid evaporation in 2.14 and 6.22 times for 40 and 60°C when comparing it to 20°C. The application of the pickling process for removal of fermentation inhibitors in sugarcane bagasse hydrolyzed allowed the production 8.3 g.L-1 of ethanol.

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This work aims to evaluate the production of second-generation ethanol from sugarcane bagasse hydrolysate without acetic acid (inhibitor) detoxification. Three isolated yeast strains from lignocellulosic materials were evaluated, and one strain (UFFS-CE-3.1.2), identified using large subunit rDNA sequences as Wickerhamomyces sp., showed satisfactory results in terms of ethanol production without acetic acid removal. A Plackett-Burman design was used to evaluate the influence of hydrolysate composition and nutrients supplementation in the fermentation medium for the second-generation ethanol production. Two fermentation kinetics were performed, with controlled pH at 5.5, or keeping the initial pH at 4.88. The fermentation conducted without pH adjustment and supplementation of nutrients reported the best result in terms of second-generation ethanol production. Wickerhamomyces sp., isolated as UFFS-CE-3.1.2, was considered promising in the production of second-generation ethanol by using crude (non-detoxified) sugarcane hydrolysate.

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