Shaking speed

As seen from Fig. 4.12, the yield of Gal-jS-CD increases with the increase of shaking speed and levels when the shaking speed is higher than 75 r/min [35]. 

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The automated extraction procedure was optimized for maximum extraction efficiency. The extraction parameters investigated were shaking time, shaking speed and solvent/ sample ratio. Three different shaking times (30 min, 60 min, and f20 min), two different shaking speeds (iOO and 190) and two different solvent/sample ratios (0.25 and 0.1667) were examined. These parameters resulted in 12 possible sets of experimental conditions. Twelve spiked water samples were analysed in dupficate, in random order (selected using software), under these experimental conditions. The total volumes and the analyte concentrations were kept constant. 

Again, there are several choices of extractant, and the preferred one depends mainly on the type of soil under test. One of the most widely used procedures is the Olsen method (Olsen ef al., 1954), which was developed in the USA to correlate crop response to fertilizer on calcareous soils. The amount of P extracted will vary with temperature (increases by 0.43 mg P kg- per degree rise between 20°C and 30°C) and shaking speed, so conditions should be standardized. The extractant is 0.5 M sodium bicarbonate adjusted to pH 8.5. The bicarbonate competes with phosphate on the adsorption sites extracts, and removes most, but not all of it, together with some soluble calcium phosphate. Addition of phosphate-free activated carbon before shaking is necessary if coloured soil extracts are obtained, and then they will require filtration. 

The Olsen method is extremely sensitive to changes in operating conditions, and unless care is taken, reproducible results will not be obtained. It is therefore imperative that all the extractions are done at the same temperature, at the same shaking speeds, and on the same shaker each time if results are to be compared between soils. For example, it is important even to adopt a standard method of filtration. The one we use is to swirl the flask briskly, add soil extract to the filter paper, and then replace the flask on the bench. Proceed in exactly the same way with the next soil replicate. If a top up is required, all flasks should be topped up in the same way. Analyze the same day if possible, although extracts may be frozen. 

Hou et al. (1991) reported the discovery of a new compound, 7,10-dihydroxy-8( )-octadecenoic acid (DOD), which was produced from oleic acid at a greater than 60% yield by PR3. Maximum DOD production was achieved after 48 hour incubation under pH 7.0,30°C, and 150rpm shaking speed. The yield of DOD production by strain PR3 was improved to over 80% through modifying the culture medium and reaction parameters (Kuo et al., 1998).The production of a similar compound by Pseudomonas sp. 42A2 was reported and studied (De Andres et al., 1994 Mercade et al., 1988). 

No reaction at all took place at 25°C in the absence of carbon so that the measured rates could be completely ascribed to the action of the catalyst, Decolorizing Charcoal Cl77. The concentrations of both cobalt complexes were spectrophotometrically monitored with time and it was noted that the sums of the concentrations of the two species were always 2-3% short of the initial concentrations. Since the intercepts of the first-order rate plots at zero time also gave concentrations 2-3% lower than the initial values, these apparent discrepancies clearly pointed to a small amount of fast adsorption. The rates were independent of the shaking speed which marked the catalysis as surface-controlled. The kinetics of this surface reaction were, however, extremely complicated. Mureinik systematically varied the concentrations of the relevant species he found that the plot of the effective first-order rate... 

Gas-liquid mass transport limitation can be a problem with reactions run in the larger reactor bottles using the standard shaking speed for agitation. This can... 

The sediment/soil should be in complete suspension during the extraction. If this is not the case, adjust the shaking speed to ensure that the suspension is maintained. 

Dry a separate 1 g sample of the sediment in a layer of about 1 mm depth in an oven at 105 °C for 2 h and weigh. From this a correction to dry mass is obtained and applied to all analytical values reported (quantity per g dry sediment). Perform the extractions by shaking in a mechanical shaker at 20 2 °C. Measure the temperature of the room at the start and at the end of the extraction procedure. The sediment should be continually in suspension during the extraction. If this is not verified, the shaking speed should be adapted in order to ensure a continuous suspension of the mixture. 

McDaniel LE, Bailey EG (1969) Effect of shaking speed and type of closure on shake flask cultures. Appl Microbiol 17 286-290... 

Fig. 4.11. Effect of temperature on the yield of Gal-/3-CD. Reaction conditions /3-CD 0.2mol/L, melibiose 0.2mol/L, a-Gal SOnkat, 2mL acetate buffer (50mmol/L, pH 6), reaction time 36 h, the shaking speed 100 r/mtn [35].

Take 100 mg of the product powder, dissolve it in 2 mL of 50 mmol/L acetic acid buffers (pH 6), and add sufficient quantities of a-Gal (50 nkat) and stir to dissolve. The reaction temperature is 30°C, reaction time is 36 h and the shaking speed is 100 r/min. After the enzymatic reaction, put the container into boiling water bath for 10 min and the a-Gal can be fiiUy inactivated. Add a certain amount of ultra-pure water to the inactivated mixture, and transfer into the centrifuge tube and centrifuge at 5,000 r/min for 5 min. Take the supernatant for HPLC analysis. The results are shown in Fig. 4.17. 

In our laboratory, saturation shake-flask solubility is routinely performed at pH 6.8 and pH 1.0 (for acids only) 0.5 mL of buffer is added to about 2 mg of sample in a small borosilicate vial (2 mL) and sonicated for 3 minutes using a sonicating bath. The suspension is then incubated at 25.0°C for 20 hours in a thermostated water bath at a shaking speed of200 cycles/min.The phases are separated by decantation/centrifugation.The supernatant is carefully collected and the solute quantified using the analytical method defined previously. Before each injection, a blank is performed to avoid phantom peaks due to carryover or impurities present in the system. After the centrifugation it is advisable to re-check the pH of the medium. 

Agitate the Miniblock reactor at shaking speed of 600-700 rpm on a shaker for 24 h. 

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