A wool fiber sample was submitted to chemical-free steam explosion in view of potential exploitation of keratin-based industrial and farm wastes. Fiber keratin was converted into a dark-yellow sludge that was submitted to phase separation by filtration, centrifugation, and precipitation of the soluble materials from the supernatant liquid. The resulting products, when compared with the original wool, showed the extent of disruption of the histology structure, reduction of the molecular weight to water-soluble peptides and free amino acids, and change of the structure of the remainder of the protein associated with breaking of disulfide bonds and decomposition of the high-sulfur-content protein fraction.

No abstract

This paper investigates the production of ethanol from steam pretreated aspen. The optimal conditions for both the pretreatment and ethanol production were determined. In the former step the parameters investigated were temperature (180-220 °C) and residence time (2-6 min). The most effective combination was 214 °C and 6 min. The exploded substrates were detoxified in three ways, washing with water at 65 °C proving to be the most effective. The substrate was then converted into ethanol via simultaneous saccharification and fermentation. Influences of the reactor type (shaken flasks and stirred bioreactors) and process parameters (solid-to-liquid ratio, enzyme loading, and stirrer speed) have been investigated. The highest ethanol yield obtained from solid-to-liquid ratios of 0.20 g/g was 85% in shaken flasks and 79% in helical stirred bioreactors. In the former case, the ethanol concentration in the broth was 47 g/L. The fermentation unit returns a solid residue with a calorific value of 5612 kcal/kg. The chemical oxygen demand due to compounds dissolved in the stillage is 28 800 mg of O 2 /L. Test runs were carried out at bench and pilot scales.

No abstract