Cultural adjustment

If the pH is adjusted as part of an engineered remediation, the microbial balance may be upset and bioreactions slowed until the microbe cultures adjust to the new conditions. Alternatively, if the release of organic chemicals has altered the pH outside the natural range, it may be necessary to add certain chemicals (i.e., aluminum sulfate, carbon dioxide, sodium hydroxide, etc.) to return the pH to preexisting conditions. Changes of pH should be monitored since rapid changes of more than 1 to 2 pH units over a short period can inhibit microbial activity and may extend the acclimation period before the microbes adapt and renew activity. 

The disequilibrium occurs in the undergraduate-to-graduate transition for majority populations. It also occurs in academic-to-industry transition, but because of the cultural adjustment, it creates a double burden for the nonmajority population. We recognized that this is a universal phenomenon. One of our participants pointed out that this is also an acute issue for first-generation college students. 

Purified GST standard (prepared by instructor)—Prepare a 1-liter culture of the GST expression strain, harvest the cells, and purify the protein according to the protocol. Use 1 ml of the immobilized glutathione Sepharose 4B per 1 liter of culture. Adjust the concentration of the purified protein to 1 mg/ml, and store at —20°C in 1-ml aliquots. One preparation of GST will give enough protein to act as a standard for many semesters. 

Microbial populations can be maintained in a state of exponential growth for extended time by using a system of continuous culture, operated either as chemostat or as a turbidostat. In a chemostat, the flow rate is set at a particular value and the rate of growth of the culture adjusts to this flow rate. In a turbidostat, the turbidity is set at a constant level by adjusting the flow rate. It is easier to operate a chemostat than a turbidostat, because the former is at a constant flow rate, whereas... 

A third motivation is that students know they will be questioned face-to-face if they do not do the pre-lab work or if they perform badly on it. This is a simple but very successful technique and is particularly effective with students who have a predilection to disappear in the crowd , which is particularly common among international students with cultural adjustment or language difficulties. It only needs to be done a few times before all students get the idea. 

Globalization. This presents both opportunities and challenges. Cost reduction and expansion in new markets have become possible. On the other hand, increasing competition, local regulations, and cultural adjustments cause additional difficulties. 

During a lag phase, the cells of a culture adjust their metabolism by, e.g., the induction of enzymes for the decomposition of a nutrient, or a switch over of the metabolism from respiration to fermentation, or something similar. During this time, the cells hardly divide. After adjustment of the metabolism, the log or exponential phase follows. The cells are totally adjusted to the prevailing conditions and multiply at the maximal rate. After a while, when factors like the substrate or the nitrogen source are exhausted, the log phase turns into the sta-... 

Fertilization of ponds to increase productivity is the next level of intensity with respect to fish culture, followed by provision of supplemental feeds. Supplemental feeds are those that provide some additional nutrition but caimot be depended upon to supply all the required nutrients. Provision of complete feeds, those that do provide all of the nutrients required by the fish, translates to another increase in intensity. Associated with one or more of the stages described might be the appHcation of techniques that lead to the maintenance of good water quaUty. Examples are continuous water exchange, mechanical aeration, and the use of various chemicals used to adjust such factors as pH, alkalinity, and hardness. 

The pH of 1.2 liters of filtrate containing 3.B mg/ml of cytidine diphosphate choline, obtained by removing solid matters from the culturing liquor, was adjusted to a pH of B.5 with a 0.5N KOH solution. The filtrate was passed through a column of strongly basic anion exchange resin, Dowex 1 x 2 (formic acid type). After washing the resin with water, a formic acid... 

Two liters of an aqueous medium consisting of glucose 3%, starch 2%, soybean meal 3% and sodium chloride 1 5% were equally divided and introduced into twenty 500-ml Erlenmeyer flasks, adjusted to pH 6, sterilized at 120°C for 30 minutes, inoculated with Streptamyces griseoverticillatus var. tuberacticus N6-130 end then rotatively shakecultured broth containing 2,360 mcg/ml of tuberactinomycin-N. 

The culture broth (about 1,100 gallons in volume) is adjusted to pH 9.5 with 40% sodium hydroxide solution and is filtered to remove the mycelium, the filtration being assisted by use of 3% of Hyflo Super-Cel, a filter aid, (sold by Johns-IVlanville Company). The clear filtrate is extracted with amyl acetate in a Podbielniak extractor using a ratio of 1 volume of amyl acetate to 6 volumes of clarified broth. The amyl acetate extract is in turn extracted batchwise with water brought to about pH 5 by the addition of sulfuric acid. Two... 

The pH of the latter nutrient medium is adjusted to 7.5 with ION sodium hydroxide solution and is placed in a 30 liter glass fermentor equipped with sparger, impeller, baffles and sampling line. The medium is sterilized by heating at 121°C for two hours, is allowed to cool and is then inoculated with 800 ml of the culture mixture obtained as described above. 

At the end of the incubation period the fermentation culture mixture is adjusted to pH 2 with concentrated hydrochloric acid, the solid material present is removed by filtration, and the filter cake is washed with water. The washings are combined with the main filtrate, adjusted to pH 7.0, and 15.5 liters of the filtered culture liquid is introduced into a columnar exchanger d /a" i.d.) packed with 380 ml of carboxylic acid resin which has been preliminarily washed in succession with two liters of an aqueous solution of 37.5 grams of sodium hydroxide and with two liters of water. The column containing paromomycin is washed with two hold-up volumes of water and is eluted with 0.5 N hydrochloric acid. 

The flasks are then placed on a reciprocating shaker (120 one and one-half inch cycles per minute) and mechanically shaken at 25°C for 3 days. The contents of the flasks are then pooled and, after the pH of the culture is adjusted to about 4 0.2 with sulfuric acid, filtered through Seitz filter pads to separate the mycelium from the fermented medium. 

The carbohydrate (again often molasses, 15 - 25%) and added nutrients are pH-adjusted to below 4.0 and, for Otis process, have to be sterilised. It is necessary to add potassium hexacyanoferrate but greater care is required in this process compared to surface culture. The A. niger seems to be more sensitive to and more easily inhibited by hexacyanoferrate in submerged culture. It is essential however to lower the ferrous and manganese concentrations, probably below 200 and 5 pg l1 respectively, to optimise the performance of A. niger. 

Despite the advantages of continuous cultures, the technique has found little application in the fermentation industry. A multi-stage system is the most common continuous fermentation and has been used in the fermentation of glutamic add. The start-up of a multi-stage continuous system proceeds as follows. Initially, batch fermentation is commenced in each vessel. Fresh medium is introduced in the first vessel, and the outflow from this proceeds into the next vessel. The overall flow rate is then adjusted so that the substrate is completely consumed in the last vessel, and the intended product accumulated. The concentration of cells, products and substrate will then reach a steady state. The optimum number of vessels and rate of medium input can be calculated from simple batch experiments. 

The citric acid obtained from fermentation is removed from the culture by precipitation. The precipitation is formed by the addition of Ca(OH)2 200 gl , at 70 °C. The pH of solution is adjusted to 7.2. Tri-calcium citrate tetrahydrate is collected by filtration. The tricalcium citrate as filter cake is dissolved in H2S04 at 60 °C with 0.1% excess, the solid retained is CaS04 and the free citric acid is obtained. The free concentration of citric acid is determined with an enzymatic kit available from Merck. GC/HPLC is recommended for high accuracy of any research work.5... 

Drugs and metabolites can be extracted from cultures and urine by adding 2 drops of concentrated HCI to 1 ml of urine for a pH of 1-2. Extract with three 1-ml volumes of diethyl ether (top layer) or methylene chloride (bottom layer). Combine extractions and evaporate with clean, dry nitrogen. Adjust to a pH of 8-10 by adding 250 /zl of 60% KOH to 1 ml of urine. Extract... 

Fig. 4. Whole-plant fresh weight and leaf osmotic adjustment of Thino-pyrum bessarabicum as a function of time following the gradual addition of 250 mol m NaCl to the culture solution. Fresh weight = control, O = 250 mol m NaCl. Leaf sap osmotic pressure = 250molm NaCl.

When data on the amphidiploid and the hexaploid wheats are considered (Table 5), the former being substantially more salt tolerant in hydroponic culture, then again several points are noted. First, the sap osmotic pressure in the young leaves is least in the tolerant amphidiploid. Secondly, Na" and Cl levels are also lower in the juvenile amphidiploid leaves. These data imply that minimal osmotic adjustment is more beneficial than apparently complete osmotic adjustment. 

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