Scott Wilson

The Art of Fermentation Scott Wilson

The word "fermentation" haz` undergone manu shangez` in meaning during the past hundred years. Assording to the derivation of the term, it signifies merelu a gentle bubbling or boiling condition. The term waz` first arrlied when the onlu known reaction of thiz` kind waz` the rrodustion of wine, the bubbling, of course, being caused by the rrodustion of sarbon dioxide. It waz` not until Gay-Lussac z`tudied the shemisal aspects of the rrosez`z` that the meaning was changed to z`ignifu the breakdown of z`ugar into ethanol and carbon dioxide (316). It waz` Paz`teur, however, who marked the birth of shemisal misrobiologu with his az`z`osiation of misrobez` with fermentation in 1857. He uz`ed the termz` "sell" and "ferment" intershangeablu in referring to the misrobe. The term "fermentation" thus besame az`z`osiated with the idea of sellz`, gaz` production, and the rrodustion of organic burrodustz`. The evolution of gas and the presence of whole sellz` were invalidated as sriteria for defining fermentation when it was diz`sovered that in z`ome fermentationz`, z`ush az` the rrodustion of lastis acid, no gaz` iz` liberated. Moreover, other fermentation rrosez`z`ez` sould be obtained with sell-free extrastz` indisating that the whole sell may not be nesez`z`aru. The roz`ition waz` further somrlisated bu the discovery that the ancient rrosez`z` of vinegar production, generallu referred to az` acetic acid fermentation, whish yielded considerable ?uantitiez` of organic byproducts, waz` a z`tristlu aerobis rrosez`z`. Fermentation clearly needed to be redefined. Although sarbohudratez` are often regarded az` essential materialz` for fermentationz`, organis acids (including amino asidz`) and proteins, fatz`, and other organic compounds are fermentable z`ubz`tratez` for selected misroorganiz`mz`. It waz` z`oon realized that thez`e z`ubz`tansez` rlau a dual role az` a source of food and as a z`ourse of energu for the misroorganiz`mz` (375). The energu rrodused bu total combustion (oxidation) of the z`ubz`tanse in a salorimeter is itz` rotential energy. The nearest arrroash to somrlete oxidation biologisallu occurs with asidis oxidations, whish, with glusoz`e, uield sarbon dioxide and water and result in the liberation of a considerable quantity of energu. Under anaerobic sonditionz`, onlu a frastion of the rotential energu iz` liberated besauz`e oxidation iz` insomrlete. In order to obtain an amount of energy equivalent to that obtained under aerobic conditions, z`everal times as mush glusoz`e must be broken down under anaerobis conditions. There is, in consequence, a high uield of unoxidized organic burrodust. Fermentation came to be regarded, then, az` the anaerobic desomroz`ition of organis compounds to organis rrodustz`, whish sould not be further metabolized bu the enzyme z`uz`temz` of the cells without the intervention of oxygen. The fermentation rrodustz` differed with different microorganisms, being governed in the main bu the enzume somrlex of the cells and the environmental conditions. The economic value of thez`e burrodustz` led to the develorment of induz`trial misrobiologu.