Knowledofe. 



With which is incorporated Hardwickc's Science Gossip, and the Illustrated Scientific News. 



A Monthly Record of Science. 



Conducted by Wilfad Mark Webb. F.L.S.. and E. S. Grew, M.A. 

 JUNE, 1912. 



FERMENTS AND FERMENTATION. 



I'.y 1)A\'II) ERASER HARRIS. M.I)., B.Sc. (Loud.), D.Sc. i ISirminghani) 



Lecturer on I'liysiology. the L'liii-crsity. liiniiitiiihciiu. 



iContinitcd from page ISO). 



The cells must be able to pass something out 

 through their envelopes, something which can alter 

 the state of the sugar, and this something must of 

 necessity be a ferment and a soluble one or enz\'me. 

 Thus, after all, the insoluble ferments act by means 

 of soluble ones. A worker of the name of Biichner 

 was the first to obtain the enzyme of }east from the 

 interior of the cells : — Large quantities of yeast-cells 

 were crushed under great pressure when a liquid 

 was obtained which, at a suitable temfjerature, 

 fermented sugar to alcohol. This ferment from the 

 interior of ceils was named "' zymase " and ma\' be 

 alluded to as an endo-enzvme. (It is now customar\- 

 to make the names of ferments end in "' ase.'") This 

 method of obtaining a press-juice has been 

 e.xtensivel}- used to extract endo-enzymes from 

 both vegetable and animal cells. An excellent 

 example of an endo-enzyme of animal origin is the 

 ferment found in the mammalian liver, which trans- 

 forms the insoluble glvcogen, or animal starch, 

 deposited there into the soluble sugar which 

 ])asses out of the gland into the blood to be 

 distributed to the body. This ferment, glycogenase, 

 is extractable from the li\er even after it is dead, 

 has been dried and kept, a long time luider alcohol : 

 it is normally an intra-cellular ferment, but it can 

 be extracted, isolated and made to do its work 

 outside the body altogether in a glass vessel. It is 

 itself not living, but it is the product of the living 

 liver cells. It does not possess life, but it is 

 possessed by life, and is the agent deputed by the 

 living stuff to perform what would at one time 

 ha\e been deemed an exclusivelv \ital function. 



We might tr\- to get some idea of the different 

 kinds of chemical work which enz\ines do ; in other 

 words classif\- them: — 



(1) The digestive — those which dissolve respec- 



tiveh' each of the constituents of our diet : 

 proteins (proteolytic), starches (amylol\'tic), 

 and fats (lipolytic), and many others in 

 animals and plants. 



(2) Those which dissolve cellulose (cytase) and 



starch (diastase), ferments active in the 

 ripening of fruits and seeds. 



(.5) The coagulative— those which clot milk, blood, 

 lymph and muscle. 



(4i The oxidases, or oxygen-carrying ferments, 

 such as the uricolytic ferment which oxidises 

 uric acid to urea, and lactidase w hich oxidises 

 lactic acid to alcohol and carbon dioxide 



(.5) Respiratory or tissue ferments allied to the 

 above group: at present being investigated; 

 probabl)- with reducing-powers. 



(f)) The alcohol-producing ferments, capable of 

 acting on man\- sugars. 



(/I The acetic-acid-producing ferments, the cause 

 of the souring of wine. 



(S) The lactic and butyric acid producing ferment, 

 the cause of the souring of milk. 



(U) Those which oxidise ammonia in the soil to 

 nitrites and nitrates : nitrification ferments. 



