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Reference materials are important tools for maintaining high-quality assurance standards, including for biological materials. A significant number of environmental international standards, including biodegradability and toxicity, involve utilization of activated sludge (AS) inocula. The absence of inoculum standardization in these tests is a potential source of error influencing the results. In this study three defined microbial consortia, two commercial inocula and a designed bacterial inoculum, were evaluated as an AS alternative seed for the Zahn-Wellens test, using diethylene glycol as the reference chemical. The results showed that to achieve diethylene glycol biodegradation with these inocula, a number of 10(5) colony-forming units per milliliter of effective degrader microorganisms had to be present. Moreover, the addition of AS supernatant to the test mixtures improved inocula performance (the biodegradability curves), bringing them closer to those obtained with AS inocula. Among the three defined consortia, the designed inoculum replicates bested the AS behavior in the range of concentrations tested, with degradation completed in 12-14 days. Comparisons of the community substrate utilization profiles corroborated these results, showing that the designed inoculum profile was the most similar to the AS profile. The biodegradability and metabolism results provided support for the assertion that the designed inoculum can be used in the Zahn-Wellens test and as a base to develop reference inocula for other biodegradability and toxicity tests.

During the last years there has been an increasing interest in using ethanol as a substitute for fossil fuels. The bioethanol used today is mainly produced from sugar cane and cereals, but reducing the production costs of ethanol is still crucial for a viable economic process. Cellulose from vegetable biomass will be the next cheap raw material for second generation fuel ethanol production and agricultural by-products with a low commercial value, as corn stover, corn fiber and cane bagasses would become an attractive feedstock for bioethanol production.In this study, different strains of Saccharomyces cerevisiae have been screened for the ability of bioethanol production. Yeasts were grown in a synthetic liquid medium containing sucrose in batch regime and the growth rates, ethanol and biomass productions were determined as well as their growth ability in cane molasses.The results indicate that a flocculent yeast, isolated in our lab and designated by strain F, was the most promising yeast strain among those tested for continuous ethanol production. This strain was isolated from corn hydrolysates, obtained from a Portuguese distillery facility (DVT, Torres Novas, Portugal) showing highest growth rate (0.49h-1), highest ethanol yield (0.35g/g) and high flocculation capacity.The study on ethanol production in continuous reactor process with the selected yeast strain (strain F) was made on sucrose and cane molasses at different dilution rates (0.05-0.42 h-1). A steady flocculating yeast fluidized bed reactor system was established allowing the functioning of the reactor for 1000 h. Data shows that when the dilution rate rose to 0.42h-1, the highest productivity (20g/Lh) was obtained attaining an ethanol concentration in the reactor of 47g/L for sucrose and molasses media.

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