Open fermentation

Fermenters can be located outdoors in most countries ofthe world. The working platforms usually are enclosed and heated in temperate zones, and only shaded in more tropical zones. In more populated areas, open fermenter buildings make too much noise for local residents. The environmental awareness, or the tolerance of the public, could preclude open fermenter buildings in the friture. Odor is also offensive to the public. The environmental authorities are demanding that equipment be installed to eliminate the offensive odor ofthe off-gases. (Noise levels inside a fermenter building will be greater than 90 dBA if no preventive measures are taken.)... 

For conventional rectangular open fermenters, the distance between opposite cooling walls should not exceed about 5 m (16 ft), assuming that the depth is not greater than 2 75 m (9 ft). Any increase in these measurements requires additional cooling surfaces - as a vertical panel or series of tubes just below the wort surface [22]. It has been suggested that similar requirements may apply to very tall vessels. Thus with a cylindroconical vessel of 4-2 m (13 8 ft) diameter of 1640 hi (1000 brl), it was noted that the beer was warmer at the central axis than nearer the walls, despite vigorous convection currents [23]. 

Enclosed vessels have several desirable features. Less cooling is needed because the heating of the beer by air is minimized. It has been calculated that refrigeration of enclosed vessels is about 15 % of that needed for open fermenters [22]. 

The carbon dioxide can of course be recovered readily from the enclosed vessels. For one unit weight of sugar, about half this weight is theoretically recoverable as carbon dioxide and, considering the cost of the gas and the great use for it in the post-fermentation period of beer treatment, the escape from open fermenters appears to be an expensive waste. In practice, the percentage of carbon dioxide recovered is rarely above 50% of the theoretical (see Chapter 20). There is, however, considerable debate on the economics... 

Hopping. Hops (dried flowers of the hop vine) are added to the wort in the brew kettle to impart to beer its traditional odor and bitter taste. The mixture is then boiled to extract the aromatic components of the hops, and to sterilize and concentrate the wort prior to fermentation. After boiling, the hops are removed by passing the mixture through a strainer. The hopped wort is held in a tank where the excess protein settles out. Tannins from the hops react with the protein so that it comes out of solution. Otherwise, it might cause clouding of the beer. The spent hops are saved for use as a livestock feed ingredient. After the protein has been removed, the wort is piped to a cooler, then to an open fermentation tank. 

Fermentation. This process is started by the addition of yeast to the hopped wort in the open fermentation tank. 

Table 12.4. Influence of pumping-over on color and tannin dissolution in open fermenters (Sudraud, 1963)...

Ma K, Maeda T, You H, Shirai Y (2014) Open fermentative production of L-LA with high optical purity by thermophilic Bacillus coagulans using excess sludge as nutrient. Bioresour Technol 151 28-35. doi 10.1016/j.biortech.2013.10.022... 

The other bottleneck for lactic acid production is the operating cost. For example, sterilization is necessary for fermentative production. Hence, microorganisms have an optimal fermentation temperature between 30 2°C (John et al., 2007). Therefore it is difficult to avoid contamination if the medium is not sterilized. Qin et al. (2009) have reported the use of a newly isolated thermophilic strain. Bacillus sp. strain 2 to 6, for the unsterilized fermentative production of L-lactic acid. A high yield (97.3%), productivity (4.37g/L/h), and optical purity of L-lactic acid (99.4%) were obtained in batch and fed-batch open fermentations (Qin et al., 2009). This will help to reduce energy consumption and lower labor costs. Moreover, because of the inhibitory effects of a low pH on cell growth and lactic acid production, CaCOs must be added to maintain a constant pH as a consequence, the regeneration of precipitated calcium lactate is observed (Datta and Henry, 2006). To solve this problem, a sodium lactate-tolerant strain. Bacillus sp. Na-2, was obtained by ion-beam implantation and applied during an L-lactic acid production process (Qin et al., 2010). On the other hand, new processes can be applied to prevent the production of calcium lactate, for example, reverse osmosis, ultrafiltration, electrodialysis, and solvent extraction (Datta and Henry, 2006). 

Zhao, B., Wang, L., Ma, C., et al., 2010. Repeated open fermentative production of optically pure L-lactic acid using a thermophilic Bacillus sp. strain. Bioresource Technology 101,6494-6498. 

AH cephalosporins found in nature (Tables 1 and 2) have the D-a-aminoadipic acid 7-acyl side chain (21). AH of these compounds can be classified as having rather low specific activity. A substantial amount of the early work in the cephalosporin area was unsuccessfiiHy directed toward replacing the aminoadipic acid side chain or modifying it appropriately by fermentation or enzymatic processes (6,22). A milestone ia the development of cephalosporins occurred in 1960 with the discovery of a practical chemical process to remove the side chain to afford 7-ACA (1) (1). Several related processes were subsequendy developed (22,23). The ready avaHabHity of 7-ACA opened the way to thousands of new semisynthetic cephalosporins. The cephalosporin stmcture offers more opportunities for chemical modification than does that of penicillins There are two side chains that especiaHy lend themselves to chemical manipulation the 7-acylamino and 3-acetoxymethyl substituents. 

In the early 1970s open fermentors and the continuous fermenting systems were found to be obsolete. The batch process was going to survive, and many new fermentor constmctions appeared. The cylindroconical fermentor seemed to be the preferred solution for both a single- and a combi-vessel fermentation system, ie, fermentation and 1 agering in the same vessel (Fig. 11). 

O. P. Ward, ed.. Fermentation Biotechnology Principles, Processes, Products, Vol. 1, Open University Press, Milton Keynes, 1989. 

Activities associated with bioreactors include gas/hquid contacting, on-hne sensing of concentrations, mixing, heat transfer, foam control, and feed of nutrients or reagents such as those for pH control. The workhorse of the fermentation industry is the conventional batch fermenter shown in Fig. 24-3. Not shown are ladder rungs inside the vessel, antifoam probe, antifoam system, and sensors (pH, dissolved oxygen, temperature, and the like). Note that coils may lie between baffles and the tank wall or connect to the top to minimize openings... 

Aofstossen, v.i. ferment anew become acid (wine) chance (upon). — v.t. push up, push open. 

We can also see from Figure 8.5 that glucose is consumed rapidly during growth (open squares) and that almost all glucose is consumed by the end of die fermentation. 

Deoxy-4-fluoro-D-fructose (552) was prepared (59%) by fermentation of 3-deoxy-3-fluoro-D-mannitol with Gluconobacter oxydans. The structure of 552 (fi-T) form) was confirmed by the n.m.r. spectrum, which resembles that of 4-deoxy-4-fluoro-Q -D-sorbopyranose (553) 552 was identical with one of the products obtained from the oxirane-ring opening of 3,4-anhy-dro-l,2-0-isopropylidene- -D-tagatopyranose with KHFj. 

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