Downstream processing, influencing

Before the details of a particular reactor are specified, the biochemical engineer must develop a process strategy that suits the biokinetic requirements of the particular organisms in use and that integrates the bioreactor into the entire process. Reactor costs, raw material costs, downstream processing requirements, and the need for auxiliary equipment will all influence the final process design. A complete discussion of this topic is beyond the scope of this chapter, but a few comments on reactor choice for particular bioprocesses is appropriate. 

As the ligand-protein interaction takes place at the internal surface of porous adsorbents, kinetics and equilibrium of the interaction should be independent of the interstitial voidage within an adsorbent bed. Therefore the equilibrium capacity of an adsorbent will not be influenced by different experimental configurations e.g. batch stirred tank, batch fluidized bed, frontal application to packed or fluidized beds. The major difference arises from the medium from which the protein is isolated. As fluidized beds are used for whole broth adsorption, the properties of the broth have to be considered regarding the possible influence of components which are removed in conventional primary recovery steps and therefore are not present during the initial chromatography operations in a standard downstream process. These are on one hand nucleic... 

The selectivity of the used membranes is of large influence as well. A selectivity larger than 500 would significantly reduce the amount of impurities in the permeate stream and thereby downstream processing of the synthesis gas. 

Basically all process parameters, some of which are fixed and some of which are variable, influence the quality of the final product of the precipitation. Usually precipitates with specific properties are desired. These properties could be the nature of the phase formed, chemical composition, purity, particle size, surface area, pore sizes, pore volumes, separability from the mother liquor, and many more, including the demands which arc imposed by the requirements of downstream processes, like drying, pelletizing, or calcination. It is therefore necessary to optimize the parameters in order... 

The crude oil feedstock heavily influences the product slate for the refinery and the downstream processing required to meet the refinery s product goals. Fuels are blended to meet product specifications of volatility, sulfur content, and octane number. Most important, refiners constantly seek to optimize their blending programs to meet product goals without giving up product. 

Nevertheless, as noted by Douglas (1988), the reactor system is often the heart of the chemical process, as it dictates the downstream processes (e.g., separation and waste treatment) and strongly influences both the recycle and separation structures as well as the energy network. Despite this, the general approach is to design the reactor system in isolation and then to design the... 

Feeding-rate control, for smooth operation. Setting control influences mainly product size and quality, while feed control determines capacity. Flow must also be synchronized with the feed requirements of downstream processes such as ball mills, and improved crusher efficiency can reduce the load on the more costly downstream grinding. 

Besides the production of L-lactic acid, the fermentation process can simultaneously produce various other metabolites such as acetic acid, f umaric acid, ethanol, malic acid, etc. However, the amount of these metabolites can have a significant influence on the downstream process and the quality of the L(+)-lactic acid produced (Wang et al., 2005). Fumaric acid is the main by-product and its accumulation is affected by many factors,... 

The primary parameters that influence the performance of the HKR reaction include the catalyst loading, the amount of water, the reaction temperature, and the rate and mode of water addition. The yield, the time for completion and the amounts of side-products are directly connected to these parameters, as well as to the downstream processing conditions. 

The fermentation process and downstream processing are usually unlinked. The fermentation broth is harvested and stored, and the recovery is carried out later. In rare cases, when the product is not stable, purification is carried out immediately after fermentation. The construct of the expression plasmid also influences the purification strategy. It is important to take this fact into account when an efficient and sustainable process must be designed. The expression plasmid determines whether a protein is secreted into the culture medium, into the periplasm, or stays in the cytoplasm. It also plays a pivotal role in the half-life of a protein. Although it may sound odd, the N-terminal amino acid is responsible for the half-life of a protein in the cell [26,27]. The most important features determining the functionality of an expression system are listed in Table 2. The expression system, together with the mode of operation, produces a characteristic product concentration profile with time (Fig. 3). 

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