Three-factor response surface optimization of the production of dextran dextrinase by Gluconobacter oxydans.

Response surface methodology (RSM) and a five-level three-factor central composite rotatable design (CCRD) were used to evaluate the effect of glycerol and peptone concentration and initial pH on dextran dextrinase (DDase) production by Gluconobacter oxydans. Optimal fermentation conditions were 20.59 g/l of glycerol, 6.67 g/l of mycological peptone and an initial pH of 6.14. The predicted DDase yield of the optimised fermentation was 0.207 U/ml, whereas an actual experimental yield of 0.208 +/- 0.025 U/ml was obtained.

Fiber optic biosensor using Chlorella vulgaris for determination of toxic compounds.

A new biosensor is constructed for the detection of some herbicides based on kinetic measurements of chlorophyll-a fluorescence in Chlorella vulgaris cells. The microalgae are immobilized on removable membranes placed in front of the tip of an optical fiber bundle inside a homemade microcell. C. vulgaris was easily cultivated in laboratory and very sensitive to herbicides that effect the photosynthesis process. The response of the algal biosensor is studied in terms of detection limits, reversibility, and long-term activity. The effects of temperature and pH are also reported. The biosensor can be used to measure the concentration of a toxic chemical in the form of a single drop or dissolved in a continuous flow. The detection of 0.1 microg small middle dotL(-1) of a single herbicide as is required by European Community legislation for drinking water is possible with this algal biosensor especially for atrazine, simazine, and diuron.

[Hearing loss following lumbar puncture: case report and literature study]. / Gehoorsdaling na lumbaal punctie: gevalsbespreking met litteratuurstudie.

This report describes a patient with permanent hearing loss after spinal anesthesia. The literature is reviewed, particularly concerning incidence and possible causes. The incidence is surprisingly high and related to the size of the needle. The role of the cochlear aqueduct as a transmitter of a decreased fluid pressure in the subarachnoid space to the perilymph of the labyrinth is discussed.