Batch fermentor

Commercial-scale operations are conducted in batch, fed-batch, or continuous culture systems. Fermentation vessels include the conventional baffled aerated tank, with or without impeller agitation, and the ak-lift tower fermentors in which ak is sparged into an annular space between the... 

S. cerevisiae is produced by fed-batch processes in which molasses supplemented with sources of nitrogen and phosphoms, such as ammonia, ammonium sulfate, ammonium phosphate, and phosphoric acid, are fed incrementally to meet nutritional requirements of the yeast during growth. Large (150 to 300 m ) total volume aerated fermentors provided with internal coils for cooling water are employed in these processes (5). Substrates and nutrients ate sterilized in a heat exchanger and then fed to a cleaned—sanitized fermentor to minimize contamination problems. 

C. uti/is yeast is produced by either fed-batch or continuous processes. Aerated-agitated fermentors range up to 300 m total capacity and ate operated in the same manner as described for S. cerevisiae (2,5). C. utilis is capable of metabolizing both hexose and pentose sugars. Consequendy, papermiU wastes such as sulfite waste Hquot that contain these sugars often ate used as substrates. 

The batch and fed-batch procedures are used for most commercial antibiotic fermentations. A typical batch fermentor may hold over 150,000 Hters. When a maximum yield of antibiotic is obtained, the fermentation broth is processed by purification procedures tailored for the specific antibiotic being produced. Nonpolar antibiotics are usually purified by solvent extraction procedures water-soluble compounds are commonly purified by ion-exchange methods. Chromatography procedures can readily provide high quaHty material, but for economic reasons chromatography steps are avoided if possible. 

Bakers Yeast Production. Bakers yeast is grown aerobicaHy in fed-batch fermentors under conditions of carbohydrate limitation. This maximizes the yield of yeast biomass and minimizes the production of ethanol. Yeasts grown under these conditions have exceUent dough leavening capabHity and perform much better in the bakery than yeast grown under anaerobic conditions. 

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). 

The dried malted barley is ground and mashed in a tub, after which the Hquid portion is drained off, cooled, and placed in the fermentor. After fermentation, a batch distillation system is usually used to separate the whisky from the fermented wort. The stiU consists of a copper ketde with a spiral tube or "worm" leading from the top. The dimensions and shape of the stills have a critical effect on the character of the whisky. The product taken off in the first part of the distillation is called foreshots (heads). The middle portion is the high wines and the last portion is the feints (tails). The middle portion is redistilled at the 140—160° proof (70—80%) range and matured in used oak cooperage. 

The alternative to batch mode operation is continuous operation. In the continuous mode there is a continuous flow of medium into the fermentor and of product stream out of the fermentor. Continuous bioprocesses often use homogenously mixed whole cell suspensions. However, immobilised cell or enzyme processes generally operate in continuous plug flow reactors, without mixing (see Figure 2.1, packed-bed reactors). 

True. Batch cultures give lower overall outputs than continuous cultures, as they suffer from non-productive down-time (the time taken to empty, clean, re-sterilise and re-fill the fermentor). After inoculation, considerable time can be taken for biomass to build up to a level where substrates are effectively utilised. Continuous cultures do not suffer such drawbacks once they are in operation. 

Fig. 5. Growth curve and PHAs production during batch fermentation of sweet sorghum by Bacillus arybhattai in 3 L fermentor (Tanamool et al., 2011)...

Fed-batch fermentation process is a production technique between batch and continuous fermentation. A proper medium feed rate is required to add sequentially into the fermentor during the process and the product is harvested at the end of fermentation just like a batch type. 

Fig. 6 shows a fed batch fermentation of sweet sorghum juice (SSJ) by Bacillus aryabhattai in 3 L fermentor under cultivating condition with agitation rate at 200 rpm, air rate of 1.5 1/min, at 30° C and feeding time at 18 and 24 hr during log phase of the culture. It was found that the cell could continuously produce both biomass and PHAs. Maximum cells were obtained at about 14.20 g/1 at 54 hr when PHAs content reached 4.84 g/1 after 66 hr (Tanamool et al., 2011). In addition, in Table 2, fed batch fermentation by A, latus was used for the production of PHAs (Yamane et al, 1996 Wang Lee, 1997). It could yield high productivity with the use of cheap carbon sources. 

However, it should be noted that there is a small percentage of the total time in which productivity rate is near its maximum. It is sometimes possible to maintain very high rates of products for a long time with continuous fermentation. Although it can get much more productivity from the fermentor, enhancement over batch fermentation in terms of the total volume of fermentor is not high because equipment needs to be sterilized to support the continuous tank. 

Bakshi and Stephanopoulos (1994b) have applied the above procedure to a fed-batch fermentation process. The problem involved 41 sets of batch records on 24 measured variables. Of these variables only very few were found by the decision tree to be relevant, and yield rules such as the following for guiding the diagnosis or control of a fermentor. 

For the detailed discussion on the inductive learning of diagnostic and control rules around the fed-batch fermentor system, the reader should refer to the work of Bakshi and Stephanopoulos (1994b). 

Probably most investigations have been carried out in conventional batch cultures, but attention should be drawn to an attractive and flexible procedure using a cyclone fermentor (Liu et al. 1981). 

Tragardh, Ch., A Hydrodynamic Model for the Simulation of an Aerated Agitated Fed-Batch Fermentor . Proceedings of the 2nd International Conference on Bioreactor Fluid Dynamics, Cambridge, UK 117-134 (1988). 

Reaction times of fermentation range from a few hours to several days. Batch processes are common, but continuous stirred tanks also are used either singly or in stages. A continuous stirred tank reactor (CSTR) also is called a chemostat. Figure 8.4 is a schematic of a fermentor with representative dimensions from the literature. 

Luus, R. Optimization of Fed-batch Fermentors by Iterative Dynamic Programming. Biotechnol Bioeng 41 599-602 (1992). 

Some very nice engineering and experimental work was performed by Pollard et al. in measuring a fungal fermentation in real time.21 The work was performed on a 75-1 fermentor and showed detection limits for fructose, glutamate, and proline in production matrices of 0.1,0.5, and 0.5 g/1, respectively. Glucose and phosphate were measured in a 280-1 pilot scale batch with detection limits for both of 0.1 g/1. 

Large-scale fermentor used for culture of D. gigas, with tube of hydrogenase extracted from a 3001 batch... 

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