Fermentation theory

thumb|[[Louis Pasteur, Archives Photographiques]]

In biochemistry, fermentation theory refers to the historical study of models of natural fermentation processes, especially alcoholic and lactic acid fermentation. Notable contributors to the theory include Justus Von Liebig and Louis Pasteur, the latter of whom developed a purely microbial basis for the fermentation process based on his experiments. Pasteur's work on fermentation later led to his development of the germ theory of disease, which put the concept of spontaneous generation to rest. Although the fermentation process had been used extensively throughout history prior to the origin of Pasteur's prevailing theories, the underlying biological and chemical processes were not fully understood. In the contemporary, fermentation is used in the production of various alcoholic beverages, foodstuffs, and medications.

Overview of fermentation

thumb|Process of [[Fermentation]]

Fermentation is the anaerobic metabolic process that converts sugar into acids, gases, or alcohols in oxygen starved environments. Yeast and many other microbes commonly use fermentation to carry out anaerobic respiration necessary for survival. Even the human body carries out fermentation processes from time to time, such as during long-distance running; lactic acid will build up in muscles over the course of long-term exertion. Within the human body, lactic acid is the by-product of ATP-producing fermentation, which produces energy so the body can continue to exercise in situations where oxygen intake cannot be processed fast enough. Although fermentation yields less ATP than aerobic respiration, it can occur at a much higher rate. Fermentation has been used by humans consciously since around 5000 BCE, evidenced by jars recovered in the Iran Zagros Mountains area containing remnants of microbes similar to those present in the wine-making process.

History

Prior to Pasteur's research on fermentation, there existed some preliminary competing notions of it. One scientist who had a substantial degree of influence on the theory of fermentation was Justus von Liebig. Liebig believed that fermentation was largely a process of decomposition as a consequence of the exposure of yeast to air and water. This theory was corroborated by Liebig's observation that other decomposing matter, such as rotten plant and animal parts, interacted with sugar in a similar manner as yeast. That is, the decomposition of albuminous matter (i.e. water-soluble proteins) caused sugar to transform to alcohol. Liebig held this view until his death in 1873. Pasteur had previously been attempting to derive connections between substances' chemical structures and external shape, and the optically active amyl alcohol did not follow his expectations according to the proposed 'law'. These observations provided Pasteur with a working hypothesis for future experiments. Pasteur then cultivated the microorganisms in a culture with his laboratory. He was then able to accelerate the lactic acid fermentation process in fresh milk by administering the cultivated sample to it. Later on, Felix Pouchet argued for the existence of 'plastic forces' within plant and animal debris capable of spontaneously generating eggs, and new organisms were born from these eggs. Just as it is commonly known, alcohol of all types and brands are also produced by way of fermentation and distillation. Moonshine is a classic example of how this is carried out. Finally, foods such as yogurt are made by fermentation processes as well. Yogurt is a fermented milk product that contains the characteristic bacterial cultures Lactobacillus bulgaricus and Streptococcus thermopiles.

Fermentation theory

Overview of fermentation

History

See also

References