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Note for Chemical Engineering Thermodynamics - CET by Prashasti Dwivedi

  • Chemical Engineering Thermodynamics - CET
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  • Jaypee University Of Information Technology - JUIT
  • Computer Science Engineering
  • B.Tech
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Prashasti Dwivedi
Prashasti Dwivedi
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Preface Recent developments in genetic and molecular biology have excited world-wide interest in biotechnology. The ability to manipulate DNA has already changed our perceptions of medicine, agriculture and environmental management. Scientific breakthroughs in gene expression, protein engineering and cell fusion are being translated by a strengthening biotechnology industry into revolutionary new products and services. Many a student has been enticed by the promise ofbiotechnology and the excitement of being near the cutting edge of scientific advancement. However, the value of biotechnology is more likely to be assessed by business, government and consumers alike in terms of commercial applications, impact on the marketplace and financial success. Graduates trained in molecular biology and cell manipulation soon realise that these techniques are only part of the complete picture; bringing about the full benefits of biotechnology requires substantial manufacturing capability involving large-scale processing of biological material. For the most part, chemical engineers have assumed the responsibility for bioprocess development. However, increasingly, biotechnologists are being employed by companies to work in co-operation with biochemical engineers to achieve pragmatic commercial goals. Yet, while aspects of biochemistry, microbiology and molecular genetics have for many years been included in chemical-engineering curricula, there has been relatively little attempt to teach biotechnologists even those qualitative aspects of engineering applicable to process design. The primary aim of this book is to present the principles of bioprocess engineering in a way that is accessible to biological scientists. It does not seek to make biologists into bioprocess engineers, but to expose them to engineering concepts and ways of thinking. The material included in the book has been used to teach graduate students with diverse backgrounds in biology, chemistry and medical science. While several excellent texts on bioprocess engineering are currently available, these generally assume the reader already has engineering training. On the other hand, standard chemical-engineering texts do not often consider examples from bioprocessing and are written almost exclusively with the petroleum and chemical industries in mind. There was a need for a textbook which explains the engineering approach to process analysis while providing worked examples and problems about biological systems. In this book, more than 170 problems and calculations encompass a wide range of bioprocess applications involving recombinant cells, plant- and animal-cell cultures and immobilised biocatalysts as well as traditional fermentation systems. It is assumed that the reader has an adequate background in biology. One of the biggest challenges in preparing the text was determining the appropriate level of mathematics. In general, biologists do not often encounter detailed mathematical analysis. However, as a great deal of engineering involves formulation and solution of mathematical models, and many important conclusions about process behaviour are best explained using mathematical relationships, it is neither easy nor desirable to eliminate all mathematics from a textbook such as this. Mathematical treatment is necessary to show how design equations depend on crucial assumptions; in other cases the equations are so simple and their application so useful that non-engineering scientists should be familiar with them. Derivation of most mathematical models is fully explained in an attempt to counter the tendency of many students to memorise rather than understand the meaning of equations. Nevertheless, in fitting with its principal aim, much more of this book is descriptive compared with standard chemicalengineering texts. The chapters are organised around broad engineering subdisciplines such as mass and energy balances, fluid dynamics, transport phenomena and reaction theory, rather than around particular applications ofbioprocessing. That the same fundamental engineering principle can be readily applied to a variety of bioprocess industries is illustrated in the worked examples and problems. Although this textbook is written primarily for senior students and graduates ofbiotechnology, it should also be useful in food-, environmental- and civil-engineering

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Preface xiY , courses. Because the qualitative treatment of selected topics is at a relatively advanced level, the book is appropriate for chemical-engineering graduates, undergraduates and industrial practitioners. I would like to acknowledge several colleagues whose advice I sought at various stages of manuscript preparation. Jay Bailey, Russell Cail, David DiBiasio, Noel Dunn and Peter Rogers each reviewed sections of the text. Sections 3.3 and 11.2 on analysis of experimental data owe much to Robert J. Hall who provided lecture notes on this topic. Thanks are also due to Jacqui Quennell whose computer drawing skills are evident in most of the book's illustrations. Pauline M. Doran University ofNew South Wales Sydney, Australia January 1994

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I Bioprocess Development: An Interdisciplinary Challenge Bioprocessing is an essentialpart of many food, chemical andpharmaceutical industries. Bioprocess operations make use of microbial, animal andplant cells and components of cells such as enzymes to manufacture newproducts and destroy harmful wastes. Use of microorganisms to transform biological materials forproduction offermented foods has its origins in antiquity. Since then, bioprocesseshave been developedfor an enormous range of commercialproducts, from relatively cheap materials such as industrial alcohol and organic solvents, to expensive specialty chemicals such as antibiotics, therapeuticproteins and vaccines. Industrially-useful enzymes and living cells such as bakers'and brewers'yeast are also commercialproducts of bioprocessing. Table 1.1 gives examples of bioprocesses employing whole cells. Typical organisms used and the approximate market size for the products are also listed. The table is by no means exhaustive; not included are processes for wastewater treatment, bioremediation, microbial mineral recovery and manufacture of traditional foods and beverages such as yoghurt, bread, vinegar, soy sauce, beer and wine. Industrial processes employing enzymes are also not listed in Table 1.1; these include brewing, baking, confectionery manufacture, fruit-juice clarification and antibiotic transformation. Large quantities of enzymes are used commercially to convert starch into fermentable sugars which serve as starting materials for other bioprocesses. Our ability to harness the capabilities of cells and enzymes has been closely related to advancements in microbiology, biochemistry and cell physiology. Knowledge in these areas is expanding rapidly; tools of modern biotechnology such as recombinant DNA, gene probes, cell fusion and tissue culture offer new opportunities to develop novel products or improve bioprocessing methods. Visions of sophisticated medicines, cultured human tissues and organs, biochips for new-age computers, environmentally-compatible pesticides and powerful pollution-degrading microbes herald a revolution in the role of biology in industry. Although new products and processes can be conceived and partially developed in the laboratory, bringing modern biotechnology to industrial fruition requires engineering skills and know-how. Biological systems can be complex and difficult to control; nevertheless, they obey the laws of chemistry and physics and are therefore amenable to engineering analysis. Substantial engineering input is essential in many aspects of bioprocessing, including design and operation of bioreactors, sterilisers and product-recovery equipment, development of systems for process automation and control, and efficient and safe layout of fermentation factories. The subject of this book, bioprocessengineering, is the study of engineering principles applied to processes involving cell or enzyme catalysts. I.I Steps in Bioprocess Development: A Typical New Product From Recombinant DNA The interdisciplinary nature of bioprocessing is evident if we look at the stages of development required for a complete industrial process. As an example, consider manufacture of a new recombinant-DNA-derived product such as insulin, growth hormone or interferon. As shown in Figure 1.1, several steps are required to convert the idea of the product into commercial reality; these stages involve different types of scientific expertise. The first stages ofbioprocess development (Steps 1-11) are concerned with genetic manipulation of the host organism; in this case, a gene from animal DNA is cloned into Escherichia coil Genetic engineering is done in laboratories on a small scale by scientists trained in molecular biology and biochemistry. Tools of the trade include Petri dishes, micropipettes, microcentrifuges, nano-or microgram quantities of restriction enzymes, and electrophoresis gels for DNA and protein fractionation. In terms of bioprocess development, parameters of major importance are stability of the constructed strains and level of expression of the desired product. After cloning, the growth and production characteristics of

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I Bioprocess Development: An Interdisciplinary Challenge Table 1.1 4 Major products of biological processing (Adaptedj~om M.L. Shuler, 1987, Bioprocess engineering. In: Encyclopedia of Physical Science and Technology, vol 2, R.A. Meyers, Ed., Academic Press, Orlando) Fermentation product Typical organism used Approximate worm market size (kg yr- 1) Saccharomyces cerevisiae Clostridi u m acetobu tylicu m 2 x 1010 2 x 106 (butanol) Lactic acid bacteria or bakers' yeast 5x 108 Pseudomonas methylotrophus or Candida utilis 0.5-1 • 108 Aspergillus niger Aspergillus niger Lactobacillus delbrueckii Aspergillus itaconicus 2-3 x 108 5xlO 7 2 x 10 7 Corynebacterium glutamicum Brevibacterium flavum Corynebacterium glutamicum Brevibacterium flavum Corynebacterium spp. 3 x 108 3 x 107 2 x 106 2 x 106 lxlO 6 Rh izop us a rrhizus A cetobacter su boxyda ns 4 x 10 7 Bulk organics Ethanol (non-beverage) Acetone/butanol Biomass Starter cultures and yeasts for food and agriculture Single-cell protein Organic acids Citric acid Gluconic acid Lactic acid I taconic acid Amino acids l,-glutamic acid L-lysine l.-phenylalanine L-arginine Others Microbial transformations Steroids D-sorbitol to L-sorbose (in vitamin C production) Antibiotics Penicillins Cephalosporins Tetracyclines (e.g. 7-chlortetracycline) Macrolide antibiotics (e.g. erythromycin) Polypeptide antibiotics (e.g. gramicidin) Aminoglycoside antibiotics (e.g. streptomycin) Aromatic antibiotics (e.g. griseofulvin) Extracellular polysaccharides Xanthan gum Dextran Penicillium chrysogenum Cephalosporium acremonium Streptomyces aureofaciens Strep to myces erythreus Bacillus brevis Strep to myces griseus Penicillium griseofulvum 3 - 4 x 10 7 lxlO 7 lx10 7 2 x 106 l • 106 Xanthomonas campestris Leuco nostoc mesenteroides 5• 106 small

Lecture Notes