Harvest acidity adjustments

In the manufacture of baker s yeast, the stock strain is inoculated into a medium that containing molasses and com steep liquor. The pH of the medium is adjusted to be slightly acidic at pH 4-5. The acidic pH may retard the bacterial growth. The inoculated medium is aerated during the incubation period. At the end, the cells are harvested by centrifuging out the fermentation broth, and they are recovered by filter press. A small amount of vegetable oil is added to act as plasticiser, and then the cell mass is moulded into blocks. The process is shown in Figure 1.2. 

Aconitic acid was the first organic acid properly established as a component of cane molasses.63 Louisiana molasses is a rich source and contains more than 6% of this acid in some cases.114 With a potential annual harvest of over 5,000,000 pounds of aconitic acid from Louisiana alone, it is nevertheless only recently that the commercial production of this acid from molasses has been initiated in Louisiana.116 Its isolation depends upon the insolubility and ready crystallizability of dicalcium magnesium (rans-aconitate hexahydrate.114118-118 Final, or an intermediate or B , molasses is diluted to 55% solids (55° Brix) with the appropriate wash water from the process (see below) and the pH is adjusted to 7 with lime. The solution is heated to 200°F. and calcium chloride is added. Heating is continued for forty-five minutes whereupon the precipitate is collected. It is resuspended at 195°F. in a volume of water sufficient to adjust the next lot of molasses to 55° Brix. The precipitate is again centrifuged it contains about 56% aconitic acid.116 Aconitic acid, either as such or after conversion to itaconic acid, is of present-day commercial interest.118"... 

With high-efficiency processes it may be beneficial or even necessary to control the process by a distinct, critical medium parameter, either for adjusting the optimum feeding rate or for defining a distinct state of the process (harvest time, switching point, etc.). The parameter may be sugar level, concentration of a distinct amino acid, free ammonia, etc. For the state of the art of measuring techniques, see Chapter 3, section 3.4. 

Fatty acid oxidation Inhibitor studies Each of the following solutions was used in place of 4L of distilled water during the isolation of volatiles by SDE from 1 kg tobacco (KY 14) stalk harvested 7 weeks after transplant 10 mM SnCl2 adjusted to pH... 

Isolation is simpler and yields are increased if the product is located entirely within the cells or culture fluid. It may be possible to manipulate the fermentation to transfer the product entirely to one phase, or this may be achievable by simple pH adjustment or other means, such as heat treatment, after harvest. For example, an acidic compound may appear to be intracellular at pH 4.0 because of reduced water solubility or adsorption on to cellular lipids, but at higher pH values the anionic form may be extracellular. 

The winemaker has all of the equipment required for controlling operations at his disposal. Before being transferred to the fermentor, the harvest is automatically sulfited by a dosing pump. Pre-fermentation adjustments such as modifying acidity and chaptalization can be performed. 

Culture and fermentation conditions. PHA production experiments were conducted in shake-flasks using cultures of Burkholderia cepacia, obtained from the American Type Culture Collection (ATCC No. 17759, Bethesda, MD). Cultures of B. cepacia were maintained at 25 C and transferred weekly on agar slants containing xylose (2.2 % w/v) and levulinic acid (0.3 % w/v) as carbon sources. Levulinic acid was added to cultures as a concentrated solution (pH adjusted to 7.2 via NaOH prior to sterilization). Inocula were prepared as 500-1000 ml cultures in 2,800 ml Fernbach flasks containing 2.2 % (w/v) xylose and 0.07 % (w/v) levulinic acid, incubated at 28 C and 150 rpm for 72 hours. For PHA production, shake-flasks were inoculated with a 5 % (v/v) aliquot of the above-described seed culture, incubated at 28 C and 150 rpm for 20 hours, and were then supplemented with a second dose (0-0.5 % w/v) of levulinic acid. Flasks were subsequently incubated for an additional 62-115 hours of growth in order to assess time-related differences in polymer production, and then harvested for biomass and PHA extraction, as previously described (20),... 

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