RESUMO A produção aquícola mundial tem demandado estudos que buscam soluções para os problemas produtivos e sanitários apresentados na piscicultura. Nesse contexto, o uso de produtos probióticos demonstra ser uma abordagem promissora. Dessa forma, o presente trabalho teve como objetivo avaliar a viabilidade de um pool de cepas de Lactobacillus incorporados à ração de truta-arco-íris. Para tanto, as respectivas cepas foram previamente cultivadas em caldo MRS e submetidas à criocentrifugação. As células obtidas foram ressuspensas em soro fisiológico acrescentado de 2% de óleo de soja, sendo posteriormente incorporadas à ração por meio de misturador circular. Essa ração foi devidamente armazenada sob refrigeração a 4°C, por 120 dias, sendo retiradas aleatoriamente três amostras, a cada 15 dias, para avaliação da viabilidade das bactérias, por meio da contagem em placas. Os resultados demonstraram que houve uma redução não significativa (P>0,05) na população de células viáveis, correspondente a 2%, após 30 dias de armazenamento. Verificou-se também, após esse período, uma população aproximada equivalente a 3,00 x 108 UFC/g. Dessa forma, demonstrou-se a possibilidade de desenvolvimento de formulações probióticas por meio da incorporação de cepas específicas em rações de trutas, o que poderá contribuir para o desenvolvimento de tecnologias alternativas para produção de peixes.

ABSTRACT Among the exotic species of fish produced in Brazil, the rainbow trout (Oncorhynchus mykiss) has been highlighted during the past few years. The expansion of this sector has been intensifying the need for further studies in order to decrease production and health problems presented in aquaculture, as well as to develop alternative technics to controversial antimicrobial treatments. In this context, the use of probiotics has been shown to be a promising approach to the improvement in trout husbandry. Thus, the present study aimed to contribute to the development of an alternative technology in the rainbow trout husbandry by evaluating the effect of probiotic preparations on the performance of the animals subjected to conventional husbandry conditions or chronic stress. Therefore, in this paper we report the results regarding the evaluation of the viability of a pool of 4 Lactobacillus probiotic strains incorporated into rainbow trout ration using soybean oil as vehicle. The results have demonstrated a high efficacy of cell incorporation into the ration with high viability rate after storage for 120 days at 4°C.

The influence of oxygen supply rate on the growth and the production of both ethanol and acetaldehyde by the aerotolerant fermentative bacterium Z. mobilis is discussed in this work. The results showed similar values of cell mass yield (0.043 g/g) for the five different levels of initial volumetric oxygen transfer coefficient (K La) studied. The maximum specific growth rate (µx,m.) under anaerobic conditions was higher than those found in aerated runs. Anaerobic cultivation resulted in the best ethanol yield (0.38 g/g). For initial K La values of 62, 94, and 118 h-1, ethanol yields were 0.10, 0.12, and 0.09 g/g, respectively, whereas for K La of 30 h-1, an intermediate value (0.24 g/g) was achieved. Under anaerobiosis, no acetaldehyde was produced. With initial K La values of 62, 94, and 118 h-1, acetaldehyde yields were similar (0.12 to 0.17 g/g), and for K La of 30 h-1 only 0.07 gram of acetaldehyde was formed per gram of glucose. Although increasing values for the maximal specific acetaldehyde formation rate were calculated as K La was increased, our results showed that the presence of an excess of dissolved oxygen throughout fermentation is enough to provide appropriate conditions for the production of acetaldehyde by Z. mobilis.

Acid sugarcane bagasse hydrolyzate was submitted to pH shifts in order to remove toxic compounds from the medium. The hydrolyzate was treated with bases containing mono-, di- or tri-valent cations and H2SO4, and its performance as a fermentation medium was evaluated by the production of xylitol by Candida guilliermondii FTI 20037. The use of bases containing mono-valent cations was not an efficient method of detoxification, and the use of a tri-valent cation did not show any detectable improvement in detoxification. The treated hydrolyzate recovery (in volume) is greatly affected by the utilized base. Treatment using Al(OH)3 and NaOH showed the best hydrolyzate recovery (87.5%), while the others presented a recovery of about 45% of the original hydrolyzate volume. Considering the whole process, best results were achieved by treatment using Al(OH)3 and NaOH which allowed 0.55 g of xylitol produced from each gram of xylose in the raw hydrolyzate.

Hydrolysis of the hemicellulosic fraction of sugarcane bagasse by sulphuric acid was performed in laboratory (25 mL) and semi-pilot (25 L) reactors under different conditions of temperature, time and acid concentration. On the laboratory scale, the three highest recovery yields were obtained at: 140ºC for 10 min with 100 mg acid/g dm (yield=73.4%); 140ºC for 20 min with 100 mg acid/g dm (yield=73.9%) and 150ºC for 20 min with 70 mg acid/g dm (yield=71.8%). These conditions were also used for hydrolysis in a semi-pilot reactor, and the highest xylose recovery yield (83.3%) was obtained at 140ºC for 20 min with 100 mg acid/g dm