Biomedical Engineering Reference
In-Depth Information
industry. Except for tartaric acid, which is a by-product of wine fermentation from
grapes, most of the other organic acids are produced by fermentation. Although
lactic acid and malic acid have a large ratio of chemical synthesis production, the
final product is a racemic type that the body cannot absorb. So, the production of L-
type organic acids in the food and pharmaceutical industries is the inevitable trend
of future development.
The common view is that the metabolic pathways for the fermentation production
of organic acids enter the citric acid cycle by the Embden-Meyerhof Parnas (EMP)
pathway. Most of the industrial versatile use organic acids mentioned can find
the corresponding location on the metabolic pathways. So, we can achieve the
accumulation of organic acid by metabolic regulation. In addition, the original
precursors of organic acids by microbial fermentation are glucose and sucrose.
Then, the hydrolysis of sucrose or glucose is likely to become raw materials for
production of these organic acids. In fact, the traditional fermentation industry did
use such substances as the fermentation raw materials, such as raw sugar, refined
sugar, or glucose solution; some starch-containing material, such as corn, potato,
and rice; and beet molasses or cane molasses, the by-products of the sugar industry
rich in sucrose.
With the deepening of research on cellulose, cellulose hydrolysates as raw
materials for organic acid fermentation have received increasing attention.
7.3.1
Lactic Acid and Polylactic Acid
Lactic acid is an important organic acid. The amount of lactic acid worldwide
already exceeded 1.2
10
5
t in 1994 and is increasing yearly at the rate of 14 %.
Early lactic acid was produced by a chemical synthesis method. In 1863, Wilcenus
invented the method to produce lactic acid by hydrolysis of lactonitrile made from
acetonitrile and hydrogen cyanide. Later, there were some companies using this
method for the commercial production of lactic acid. As the technology advanced
in recent years, lactic acid is produced mainly by fermentation. The raw materials
are carbohydrates, such as starch, cellulose, and so on. Industrial production can
even use some of the waste, such as molasses from the sugar industry, whey from
the dairy industry, and sulfite pulp waste from the paper industry.
Lactic acid is an important organic acid. It is widely used in the food, chemical,
and pharmaceutical sectors. In recent years, lactic acid has been used as a raw
material to manufacture new biodegradable packaging materials. This material
not only has the same barrier property as polyester, but also has the same gloss,
transparency, and processing ability as polystyrene. Using it instead of the current
widely used plastic packaging materials can be a fundamental solution to the
problem of plaguesome white pollution, a kind of pollution that made by the
undegradability of waste plastic and toxicity of additives. This provides a huge
market for the development of the lactic acid industry.
