A novel airlift photobioreactor with baffles for improved light utilization through the flashing light effect.

A newly developed flat panel airlift photobioreactor with a defined circulation path was tested for microalgal culture. The bioreactor exposed the cells to intermittent light to improve the efficiency of light utilization through the flashing-light effect. During batch cultures in the new photobioreactor, the biomass productivity of Chlorella vulgaris was 1.7 times greater than in a randomly mixed bubble column of identical dimension. A reduction in light path from 30 to 15 mm increased the biomass productivity by 2.5-fold. A maximum dry biomass productivity of 0.11 g l(-1) h(-1) was obtained at an artificial illumination of 980 mu E m(-2) s(-1).

Treatment of urban wastewater in a membrane bioreactor at high organic loading rates.

Membrane bioreactors can replace the activated sludge process and the final clarification step in municipal wastewater treatment. The combination of bioreactor and crossflow microfiltration allows for a high chemical oxygen demand (COD) reduction of synthetic wastewater. From biomass, grown at high production rates in the aerobic bioreactor, energy rich biogas can be obtained in a subsequent anaerobic bioreactor. In this paper, experimental data from a laboratory scale membrane bioreactor are presented. The degradation of synthetic wastewater at short hydraulic retention times down to 1.5 h has been studied. The organic loading rate (OLR) has been varied in the range of 6-13 kg m(-3) per day. At steady state a high quality filtrate could be obtained at different operating conditions. At biomass concentrations of 10-22 g l(-1), COD reduction was above 95%.

Effects of oxygen supply on the production of nikkomycin with immobilized cells of Streptomyces tendae.

For continuous production of the antibiotic nikkomycin immobilized cells have been used in a fluidized bed bioreactor. Cells of Streptomyces tendae were immobilized on sintered glass particles. Different biomass concentrations on the particles correspond to different thicknesses of mycelial layers because growth occurs only on the outer surface of the particles. The antibiotic productivity decreased with increasing layer thickness. In fermentations with higher concentrations of both biomass on the particles and dissolved oxygen levels of about 70% the productivity was also limited because of limited oxygen diffusion in the layers.

A study of N- and P-dependence of nikkomycin production in continuous culture with immobilized cells.

The influence of nitrogen and phosphate on the biosynthesis of nikkomycin was studied in chemically defined medium. Cells of Streptomyces tendae were immobilized on porous glass particles in a fluidized-bed reactor for continuous production of nikkomycin. Phosphate had no significant influence on the biosynthesis of nikkomycin. However, even a very low concentration of phosphate in the production medium (0.0125 mmol/l) resulted in microbial growth on the particles. The concentration of nitrogen was highly effective in the regulation of the biosynthesis of nikkomycin. A high level of antibiotic production (maximum 3.05 mg/g dry cell weight per hour) was maintained for a period of about 200 h in a medium that contained nitrogen at a concentration of 0.2 g NH4NO3/l.

Instrumentation and specimen preparation for electron beam X-ray microanalysis of frozen hydrated bulk specimens.

A cooling chain for the handling of frozen hydrated bulk specimens is described. Use of this method permits the specimen to be kept fully hydrated. After quench freezing, the specimen is transferred to a freeze etch apparatus, freeze fractured, carbon coated and transferred onto the precooled cold stage of the SEM by means of an airlock. The specimen is examined in the secondary electron mode and analysed using an energy dispersive X-ray analyser. The midgut of Chironomus thummi larvae and frog skin epithelium were used to test the performance.