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In this work, the effect of initial sugar concentration and temperature on the production of ethanol by Saccharomyces cerevisiae CCA008, a flocculent yeast, using cashew apple juice in a 1L-bioreactor was studied. The experimental results were used to develop a kinetic model relating biomass, ethanol production and total reducing sugar consumption. Monod, Andrews, Levenspiel and Ghose and Tyagi models were investigated to represent the specific growth rate without inhibition, with inhibition by substrate and with inhibition by product, respectively. Model validation was performed using a new set of experimental data obtained at 34 °C and using 100 g L of initial substrate concentration. The model proposed by Ghose and Tyagi was able to accurately describe the dynamics of ethanol production by S. cerevisiae CCA008 growing on cashew apple juice, containing an initial reducing sugar concentration ranging from 70 to 170 g L and temperature, from 26 to 42 °C. The model optimization was also accomplished based on the following parameters: percentage volume of ethanol per volume of solution (%V /V), efficiency and reaction productivity. The optimal operational conditions were determined using response surface graphs constructed with simulated data, reaching an efficiency and a productivity of 93.5% and 5.45 g L h, respectively.

Ethanol production from acidic-alkaline pretreated cashew apple bagasse (CAB-OH) was investigated using separated hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) processes. First, a screening of Kluyveromyces strains was conducted by SHF and a maximum ethanol concentration of 24.1 g L(-1) was obtained using Kluyveromyces marxianus ATCC36907, which presented similar profiles when compared to results obtained by a Saccharomyces strain. The effect of temperature on ethanol production conducted by SHF using K. marxianus ATCC36907 was investigated, and the maximum ethanol yield (YE/G) was obtained at 40 °C (0.46 g g(-1)) using a synthetic medium. In the SHF using CAB-OH hydrolysate, the maximum ethanol concentration obtained was 24.9 g L(-1), 5.92 g L(-1) h(-1) of productivity, and ethanol yield of 0.43 g g(-1) at 40 °C. Afterwards, K. marxianus ATCC36907 was used in the bioconversion of CAB-OH by SSF, and an ethanol concentration of 41.41 ± 0.2 g L(-1) was obtained using 10 % CAB-OH at 40 °C, 150 rpm and 24 h, resulting in a Y'E/G of 0.50 gE gG (-1) and an efficiency of 98.4 %, in the process conducted with cellobiase supplementation. SHF and SSF processes using CAB-OH and K. marxianus ATCC36907 can be used to ethanol production, but the SSF process required only one step to achieve the same production.

RESUMOCom base no consumo hídrico excessivo na produção agrícola e da expansão do cultivo da cana-de-açúcar impulsionada pela crescente demanda de etanol, tem-se questionado em relação a um uso mais racional da água de irrigação e ao reúso de água na produção agrícola. Desta forma objetivou-se, com o presente trabalho, avaliar os efeitos do reúso de efluente de esgoto doméstico tratado na irrigação da cana-deaçúcar. O estudo foi conduzido no Centro de Pesquisa sobre Tratamento e Reúso de Águas Residuárias, em Aquiraz, CE. O delineamento experimental adotado foi o de blocos ao acaso, no esquema de parcelas subdivididas, com quatro repetições. Nas parcelas avaliaram-se os efeitos de dois tipos de água (água potável e esgoto doméstico tratado); e nas subparcelas se alocaram cinco lâminas de irrigação baseadas em percentuais da evaporação medida em um tanque do tipo classe A (ECA). Concluiu-se que a água residuária proporcionou o maior potencial produtivo de colmos (272,1 Mg ha -1 ) e a maior densidade de plantas (126.000 plantas ha -1 ). O aumento das lâminas de irrigação proporcionou incrementos no potencial produtivo e na densidade de plantas, independente do tipo de água.Palavras-chave: reúso de água, gotejamento, Saccharum officinarum L.Reuse of treated domestic sewage effluent as an alternative water source for the production of sugarcane ABSTRACT With the excessive consumption of water in agricultural production, and the expansion of the cultivation of sugarcane due to growing demand for ethanol, in this context, a rational use of water for irrigation and use of wastewater in agricultural production has been raised. Therefore, the objective of this study was to evaluate the effects of reuse of treated domestic sewage effluent for irrigation of sugarcane. The study was conducted at the Research Center on Treatment and Reuse of Wastewater, in Aquiraz, CE. The experimental design was randomized blocks in split plots with four replications. In the plots were evaluated the effects of two types of water (well water and treated domestic sewage); in the subplots five irrigation water depths were allocated, based on percentage of evaporation in a Class "A" tank. It can be concluded that wastewater provided the highest potential yield of stem (272.1 Mg ha -1 ) and higher plant density (126,000 plants ha -1 ). The increase in irrigation water depths provided increase in potential yield and plant density, regardless of the type of water.

The aim of this study was to isolate and identify an indigenous yeast from cashew apple juice (CAJ) and then use it in the production of first- and second-generation ethanol, using CAJ and the enzymatic hydrolysate of cashew apple bagasse (MCAB-OH), respectively. The isolated yeast was identified as belonging to the genus Hanseniaspora. Afterward, the effect of the medium initial pH on the production of ethanol from CAJ was evaluated in the range of 3.0 to 5.5, with its maximum ethanol production of 42 g L(-1) and Y P/S of 0.44 g g(-1) and 96 % efficiency. The effect of temperature (28-38 °C) on ethanol production was evaluated in a synthetic medium, and no difference in ethanol production in the temperature range evaluated (28-36 °C) was observed. At 32 °C, the yield, concentration, efficiency, and productivity of ethanol when using the CAJ medium were higher when compared to the results achieved for the synthetic medium. Regarding second-generation ethanol, the results showed that the yeast produced 24.37 g L(-1) of ethanol with an efficiency of 80.23 % and a productivity of 4.87 g L(-1) h(-1) at 5 h. Therefore, Hanseniaspora sp., isolated from CAJ, is a promising microorganism for the production of first- and second-generation ethanol.

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Biofuels have been gaining more space in the global energy sector, with special attention to ethanol, which has shown growing demand. Ethanol is a potential and promising alternative fuel due to the use of abundant renewable sources and its combustion characteristics. From this scenario, this research aimed to optimize ethanol production by a flocculant Saccharomyces cerevisiae CCA008 using cashew apple juice (CAJ) as feedstock. The alcoholic fermentation of CAJ was influenced for all evaluated variables (inoculum and substrate concentration, temperature, and agitation) and statistical models were successfully applied to describe the interaction between these variables and to optimize the operating conditions. The optimum conditions were initial substrate concentration (S 0) of 102 g L −1 , inoculum concentration (X 0) of 5 g L −1 , temperature (T) and agitation (Agit) settings at 34 °C and 140 rpm, respectively. Last, but not least, the scale-up of ethanol production was carried out using the predicted optimum operating conditions, the fluid dynamics characteristics and applying the best scaleup criterion (power per unit of volume). The efficiencies of the processes (on bench and pilot-scale) were not significantly different and high efficiencies (96.6-98.2%) were achieved, demonstrating satisfactory results. Moreover, maximum ethanol concentration (P max), Y P/S and productivity (Q P) did not vary significatively when the process was scaled-up. On the pilotscale, P max , Y P/S and Q P were 49.2 ± 2.2 g L −1 , 0.493 ± 0.00 g g −1 and 5.0 ± 0.2 g L −1 h −1 , respectively. Therefore, ethanol could be efficiently produced by the fermentation of CAJ using the flocculent yeast S. cerevisiae CCA008 and the process could be easily scaled up.