Shake-flask experiment monitoring

All experiments in the bioreactor were conq ared to conventional shake flask experiments. Whereas the bacterial growth in the shake flask can be easily monitored by the optical density which is directly depended on the number of cells per volume unit, the monitoring of the cell density in the bioreactor was not possible, due to the cluster-like growth pattern, see Figure 2. Other analysis techniques had to be explored to reliably monitor Ihe cell growth in the... 

In an effort to differentiate between the influence of simulated microgravity and differences in the oxygen supply to the cells, the oxygen profile in the bioreactor was adapted to match that of the shake flask as closely as possible. The established oxygen supply profile is given in Table 2. Since the initial phase of the bacterial gro is the one that exhibited significant differences compared to conventional shake flask experiments, the first 6 hours of the fermentation were monitored closely. 

Measurement of Xylose Isomerization Kinetics and Equilibrium All experiments were carried out at 34 °C in a volume of 25 ml in 50-ml shake flasks agitated at 130 rpm in an incubated shaker. Each experiment was conducted in duplicate. All experiments used 60 g/ 1 xylose, and unless otherwise noted, 5.2 g/1 of enzyme pellets (0.13 g) was used for each experiment. Buffered solutions used in making the isomerization media were 0.01 M Tris buffer (pHed to 7.5 using 0.01 M NaOH) and 0.05 M sodium citrate buffer (pHed to 4.5 using citric acid). The pH was measured at the beginning of the experiments but was not monitored throughout. We have observed a small drift in pH of less than 1 unit over the course of 48 hrs. Even with this drift, the pH of the bulk solution stayed within the range suitable for fermentation and well-below the pH optimum of XI (pH 7.5). In experiments with co-inunobilized pellets, urea concentration was 0,0.01, or 0.1 M. 

Fluorescence spectra of phenanthrene in LMWOA solution Control experiments showed that malic acid, citric acid and butylic acid had little effect on the spectral characteristics of phenanthrene or its fluorimetric determination. Measurement of phenanthrene biodegradation by fluorescence method. 50.0 mL MSM were added to each incubation flask the final concentration of phenanthrene was 1000 u g/L. After sterilization at 121 C for 15 min, the bacterial strain was inoculated into individual incubation flasks and incubated on a rotary shaking incubator at 25 °C and 150 rpm in the dark. The biodegradation rate of phenanthrene was monitored directly by the fluorescence method without solvent extraction. 

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