Mass transport in a partially filled horizontal drum: Modelling and experiments

Improving enzyme production by solid-state cultivation in packed-bed bioreactors by changing bed porosity and airflow distribution

Enzymes production by solid-state cultivation in packed-bed bioreactor needs to be improved by mathematical modeling and also by experimentation. In this work, a mixture of sugarcane bagasse and wheat bran was used for the growth of the fungus Myceliophthora thermophila I-1D3b, able to secrete endoglucanase and xylanase, enzymes of interest in the second-generation ethanol production. Bench and pilot-scale bioreactors were used for the experiments, while critical parameters as bed porosity and airflow distribution were evaluated. Results showed enzymes with higher activities for the most porous medium, even though the less substrate amount to be cultivated. For the pilot-scale bioreactor, only the most porous medium was evaluated using different airflow distribution techniques. Using an inner tube for air supply resulted in more homogeneous enzyme production, with higher activities. The results here presented will be helpful for the scale-up of this class of bioreactor into industrial apparatuses.

Analysis of the use of a non-conventional rotary drum for dehydration of microalga Spirulina platensis

The high content of bioactive compounds in the microalga Spirulina platensis has recently attracted attention from food and pharmaceutical industries. However, for its application an effective preservation technique must be developed. In this paper, we investigated the use of a non-conventional rotary dryer (with an inert bed) for drying the microalga Spirulina biomass and the effects of the operational conditions (air temperature, intermittent feeding interval, filling degree of inert particles, and rotation speed) on its bioactive compounds. The results indicated that this non-conventional drying system offers an effective alternative for expanding the use of this biomass in an adequate form. We identified the conditions in which the dried material had maintained satisfactory contents of phenolics (air temperature of 70 °C and intermittent feeding interval of 10 min), flavonoids (intermittent feeding interval of 17.4 min), and phycocyanin compounds (air temperature of 40 °C), which were near to those present in fresh microalga.