Introduction - Bioprocess Engineering: Kinetics, Biosystems, Sustainability and Reactor Design - page 3

On a somewhat different scale, we can now manipulate life at its most basic level: the
genetic. For thousands of years, people have practiced genetic engineering at the level of
selection and breeding or directed evolution. But now it can be done in a purposeful, prede-
termined manner with the molecular-level manipulation of DNA, at a quantum leap level (as
compared with directed evolution) or by design. We now have tools to probe the mysteries of
life in a way unimaginable prior to the 1970s. With this intellectual revolution emerges new
visions and new hopes: new medicines, semisynthetic organs, abundant and nutritious
foods, computers based on biological molecules rather than silicon chips, organisms to
degrade pollutants and clean up decades of unintentional damage to the environment,
zero harmful chemical leakage to the environment while producing a wide array of
consumer products, and revolutionized industrial processes. Our aim of comfortable living
standards is ever higher.
Without hard work, these dreams will remain merely dreams. Engineers will play an
essential role in converting these visions into reality. Biosystems are very complex and beau-
tifully constructed, but they must obey the rules of chemistry and physics and they are
susceptible to engineering analysis. Living cells are predictable, and processes to use them
can be methodically constructed on commercial scales. There lies a great task: analysis,
design, and control of biosystems to the greater benefit of a sustainable humanity. This is
the job of the bioprocess engineer.
This text is organized such that you can learn bioprocess engineering without requiring
a profound background in reaction engineering and biotechnology. To limit the scope of
the text, we have left out the product purification technologies, while focusing on the produc-
tion generation. We attempt to bridge molecular-level understandings to industrial applica-
tions. It is our hope that this will help you to strengthen your desire and ability to participate
in the intellectual revolution and to make an important contribution to the human society.
1.2. GREEN CHEMISTRY
Green chemistry, also called sustainable chemistry, is a philosophy of chemical research
and engineering that encourages the design of products and processes that minimize the
use and generation of hazardous substances while maximizing the efficiency of the desired
product generation. Whereas environmental chemistry is the chemistry of the natural envi-
ronment, and of pollutant chemicals in nature, green chemistry seeks to reduce and prevent
pollution at its source. In 1990, the Pollution Prevention Act was passed in the United States.
This act helped create a modus operandi for dealing with pollution in an original and innova-
tive way. It aims to avoid problems before they happen.
Examples of green chemistry starts with the choice of solvent for a process: water, carbon
dioxide, dry media, and nonvolatile (ionic) liquids, which are some of the excellent choices.
These solvents are not harmful to the environment as either emission can easily be avoided or
they are ubiquitous in nature.
Paul Anastas, then of the United States Environmental Protection Agency, and John C.
Warner developed 12 principles of green chemistry, which help to explain what the definition
means in practice. The principles cover such concepts as: a) the design of processes to maxi-
mize the amount of (all) raw material that ends up in the product; b) the use of safe,