Bioprocessing, integrated

In terms of the process, very little has been achieved. The mass transfer limitations still exist although emulsification has solved the problem partially, but not without creating another problem downstream in separation of the product from the rest of the stream and the issue still needs further work. The IP portfolio contains very few real process concepts. The patented material refers to a BDS process several times, but the process referred to, is no more than a simple description of the pH, temperature, etc., and the particular use of a given biocatalyst in an application. Some protected subject matter concerns the integration of a bioprocess into the flow sheet of the refinery, but again those are no more than theoretical scheme proposed for implementation, with no actual evidence with real feedstocks. 

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. 

Decolorization of azo dyes by WRF technology improvements will require integration of all major areas of industrial biotechnology novel enzymes and microorganisms, functional genomics, protein engineering, biomaterial development, bioprocess design and applications. 

Due to the complexity of bioprocesses, and the lack of direct in-process measurements of critical process variables, much work is being done on development of soft sensors and model predictive control of such systems. Soft sensors have long been used to estimate biomass concentration in fed-batch cultivations. The soft sensors can be integrated into automated control structures to control the biomass growth in the fermentation. 

Bioreactions. The use of supercritical fluids, and in particular C02, as a reaction media for enzymatic catalysis is growing. High diffusivities, low surface tensions, solubility control, low toxicity, and minimal problems with solvent residues all make SCFs attractive. In addition, other advantages for using enzymes in SCFs instead of water include reactions where water is a product, which can be driven to completion increased solubilities of hydrophobic materials increased biomolecular thermostability and the potential to integrate both the reaction and separation bioprocesses into one step (98). There have been a number of biocatalysis reactions in SCFs reported (99—101). The use of lipases shows perhaps the most commercial promise, but there are a number of issues remaining unresolved, such as solvent—enzyme interactions and the influence of the reaction environment. A potential area for increased research is the synthesis of monodisperse biopolymers in supercritical fluids (102). 

There are two frequently used algorithms to determine the control action in a feedback control system for bioprocess control, an on-off (two-positioned) control, and a PID (proportional-integral-derivative) control. 

Gerigk, M.R., Maass, D., Kreutzer, A., Sprenger, G., Bongaerts, J., Wubbolts, M. and Takors, R. (2002) Enhanced pilot-scale fed-batch L-phenylalanine production with recombinant escherichia coli by fully integrated reactive extraction. Bioprocess and Biosystems Engineering, 25, 43. 

Since such pioneering times, the need for integrated sensor systems has increased in science and research for monitoring purposes in medicine. In addition, sensor systems are now also used in analytical science, environmental control and bioprocessing. 

The integration of two unit operations lies at the heart of process engineering. More often in bioprocesses it is the integration of product formation with the following recovery steps that is critical.5 In the specific case of biocatalytic processes the product recovery is also critical, but in this chapter the focus will be on the integration of the surrounding chemical steps with the biocatalysis. 

---