Biochemical Engineering

An Introductory Textbook

Debabrata Das, Debayan Das, Debabrata Das, Debayan Das

• Éditeur: Jenny Stanford Publishing
• Année: 2019
• ISBN:
  9780429632044
• Édition: 1
• Sujet: Ciencias biológicas
• Sous-sujet: Bioquímica

All engineering disciplines have been developed from the basic sciences. Science gives us the information on the reasoning behind new product development, whereas engineering is the application of science to manufacture the product at the commercial level. Biological processes involve various biomolecules, which come from living sources. It is now possible to manipulate DNA to get the desired changes in biochemical processes.

This book provides students the knowledge that will enable them to contribute in various professional fields, including bioprocess development, modeling and simulation, and environmental engineering. It includes the analysis of different upstream and downstream processes. The chapters are organized in broad engineering subdisciplines, such as mass and energy balances, reaction theory using both chemical and enzymatic reactions, microbial cell growth kinetics, transport phenomena, different control systems used in the fermentation industry, and case studies of some industrial fermentation processes. Each chapter begins with a fundamental explanation for general readers and ends with in-depth scientific details suitable for expert readers. The book also includes the solutions to about 100 problems.

Chapter 1

Introduction

All engineering disciplines have been developed from the basic sciences. Biological processes involve different biomolecules that come from living sources. Chemical processes deal with the reactions of different reactants to get the desired products. The major bottlenecks of these processes are high temperature and pressure and use of different raw materials for different products. On the other hand, biochemical processes are mostly operated at the ambient temperature and atmospheric pressure and can produce different products from the substrate like sucrose using different microorganisms. Biochemical reactions are mostly chain and reversible reactions in nature. However, biochemical processes are complicated as compared to chemical processes. Biochemical engineering involves not only mathematical modeling but also scaling up of the process for commercial application. The purpose of this book is to initially distinguish the differences between conventional chemical reaction engineering and biochemical reaction engineering. Students will be gradually conversant with the rate laws and their applications in understanding the reaction engineering behavior. With this expertise, they will be able to apply the acquired knowledge in designing bioreactors. They will also learn the stoichiometry of the bioprocesses for material and energy analyses. The transport phenomena of bioprocesses are also very important for their operation. This textbook will provide students with the ability to contribute their knowledge in various professional fields such as bioprocess development, modeling and simulation, environmental engineering, etc.

1.1 Biological Sciences

Biological science or biology is the study of living organisms such as plants, animals, and other living organisms. The word biology comes from the Greek words bios meaning “life” and logos meaning “the study of” (knowledge). The subject of biology is divided into many separate fields such as behavior, human anatomy, botany, physiology, zoology, ecology, and genetics. Biology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, evolution, distribution, identification, and taxonomy. Living organisms are characterized by their ability to grow, reproduce, metabolize, acclimatize, generate waste products, and display sensitivity to the surrounding environment. All living things are composed of one or more cells, which are the basic structural and functional units of life. Cells are considered to be the building blocks of life. There are two distinct types of cells: prokaryotic and eukaryotic cells. The difference lies in their structure, nature of nucleus, organelles, metabolism, and so on. Table 1.1 shows the major differences between prokaryotic and eukaryotic cells.

About two million different kinds of organisms live on earth. It is impossible to study every living organism individually; therefore, they are classified into various groups based on their similarities. The science dealing with the description, identification, naming, and classification of organisms is known as taxonomy. It was first developed by Carl Linnaeus. He is known as the father of taxonomy. For the naming of organisms, he introduced a binomial nomenclature comprising a genus name and a species name. Microorganisms can be classified based on their cell type, phenotypic, genotypic, and analytical. The most widely accepted classification based on cell type is the three-domain system introduced by Carl Woese et al. in 1977. It divides cellular life forms into archaea, bacteria, and eukarya domains (Table 1.2). For each domain, the final scientific hierarchy for classification is as follows: Domain > Kingdom > Phylum > Class > Order > Family > Genus > Species.

Table 1.1 Comparison of prokaryotic and eukaryotic cells

Feature	Prokaryote	Eukaryote
Cell size (diameter)	Average 0.5–5 μm	> 10 μm
Organization	Unicellular or filamentous	Unicellular or filamentous or multicellular
Cell wall	Rigid, containing polysaccharide plus protein. Murein is the main strengthening compound.	Rigid in plants (cellulose) and fungi (chitin), absent in animal cells
Cell membrane	Present	Present
Nucleus	No nuclear envelope, no nucleolus	Nucleus bound by nuclear envelope, nucleolus present
Chromosome	Single circular, containing only DNA	Multiple, containing DNA and protein
Ribosome	70S, 50S+30S subunits	80S, 60S+40S subunits
Mitochondrion	Absent	Present
Cell division	Asexual (binary fission)	Sexual (mitosis and meiosis)
Flagellum	Simple, lacking microtubule (not enclosed by cell surface membrane)	Complex, with 9+2 microtubules, (surrounded by cell surface membrane)

Table 1.2 Classification of living organisms based on the three-domain system

Group	Cell type	Typical organisms
Archaea (Archaebacteria)	Prokaryote	Methanogens, acidophiles, halophiles, extreme thermophiles
Bacteria (Eubacteria)	Prokaryote	Enteric bacteria, cyanobacteria
Eukarya	Eukaryote	Algae, fungi, protozoa, plants, and animals

The study of living things has undergone tremendous expansion in the recent years, and topics such as cell biology, neuroscience, evolutionary biology, and ecology are advancing rapidly. This rapid expansion has been accompanied by a blurring of the distinctions between disciplines: A biologist with an interest in tropical plants may well use many of the tools and techniques that are indispensable to a molecular geneticist.

1.2 Microbiology

Microorganisms can be viewed only with the aid of a microscope. Microbes are found in a variety of shapes, and their sizes range from 0.01 μm to 20 μm. The first microbe was discovered by Antonie van Leeuwenhoek using a compound microscope. He is known as the father of microbiology. Microbes are diversified in nature and can be grouped into six classes, which include eubacteria, archaebacteria, viruses, fungi, algae, and protozoa. The specific characteristic features of each of these classes can be found in standard microbiology textbooks. Microorganisms are ubiquitous in nature. They are tenacious and can thrive in extreme environments. The growth conditions (such as nutrition, temperature, pH, etc.) of each of these organisms vary distinctly. Based on nutrition, they can either be autotrophic (can utilize sunlight and inorganic carbon as their energy and carbon source) or heterotrophic (dependent on organic carbon for energy and carbon source) in nature.

Some microorganisms can grow at −20°C (psychrophiles), while others can grow at 20–40°C (mesophiles) and 50–120°C (thermophiles). Similarly, microbes that prefer pH values below 6 are known as acidophiles, while others that grow well above 9 are termed alkaliphiles. The organisms that grow in high salt regions are known as halophiles. Depending on the availability of oxygen in the surrounding environment, microbes have developed different metabolic regimes. The microbes that cannot survive without oxygen are known as aerobes, while others that are inhibited by the slightest presence of oxygen are obligate anaerobes. However, a few organisms that can switch their metabolic pathways to thrive in both conditions are called facultative microbes.

Microorganisms play a crucial role in day-to-day life. The concept of using microbes for the production of industrially relevant products is not new. From several decades, microbes were used for the production of wine, beer, vinegar, etc. without the acknowledgement of their presence. In addition, dairy industries widely rely on thermophilic bacteria for acquiring yoghurt from milk. The discovery of microbes has helped in the development of modern microbiology and its contribution to industrial biotechnology. Over the years, different microbial metabolites such as ethanol, butanol, acetic acid, lactic acid, riboflavin, and enzymes such as protease, amylase, invertase, etc. have been produced for commercial usage. Figure 1.1 shows the different microbial products that have been explored till date. The first antibiotic produced on a large scale was penicillin (a fungal product) during World War II. After that, other antibiotics have been discovered using microbial exploitation. By using genetic engineering approaches, many useful non-microbial products such as insulin, human growth hormone, vaccines, interferons, and other pharmaceutical products have been successfully commercialized since the 1980s. This great diversity provides a nexus of o...