INSTITUTE, PUSA, FOR 1916-17 109 



rely upon the production of acidity by bacterial action in 

 the steeping vat or possibly in the khazana, mineral acids 

 being too high in price at present for economic use. It has 

 been found by the Indigo Research Chemist that extrac- 

 tion and acidity bear a close proportional relationship, and 

 endeavour will be made either to isolate bacteria capable 

 of combining acid production with indican hydrolyzing 

 powers, or to use different species for these two purposes 

 either concurrently or in succession. 



Hydrolysis. Numerous species of indican hydrolyzing 

 bacteria were isolated by means of indican agar ; these were 

 tested for hydrolyzing power and arranged in a relative 

 order taking into account not only this physiological func- 

 tion, but also the opposite destructive action which many 

 of them possessed. There can be no doubt that the very 

 large differences between yields of various factories are due 

 mainly to differences in the composition of the bacterial 

 flora in the steeping vats ; how far this may be due to bac- 

 teria carried by the plant or to those existing in the khazana 

 water is not at present known, but examination of a large 

 number of samples of the latter has demonstrated a very 

 close connection between the actual yield of the factory and 

 the number of hydrolyzing bacteria present in the water 

 supply. Actual cases of increased yield as a consequence 

 of inoculation of the vats of one factory with the steeped 

 liquor from another of higher yield substantiate this view. 



In order to make use of the inoculation method it will 

 be necessary not only to obtain efficient species of bacteria 

 but to ascertain the conditions under which it will be pos- 

 sible to introduce them into the steeping vat in sufficient 

 numbers and in a sufficiently high state of activity to 

 influence the style of fermentation therein. This will prob- 

 ably be difficult in view, firstly, of the very large volume of 

 water involved (some seven or eight thousand gallons in 

 each vat, and as many as six to twelve vats in use at one 

 time) and, secondly, of the large number of other bacteria 

 necessarily present already on the plant and in the water. 

 As before pointed out it may be found necessary to remove 



the possibly deleterious influence of these latter, by use of 



" h2 



