The influence of light and of copper on fermentation. 361 
The influence of light and of copper on fermentation. By 
J. E. Purvis, M.A., St John’s College, and W. A. R. Wilks, B.A., 
Gonville and Caius College. 
\_Read 25 November 1907.] 
The action of light on various species of saccharomyces has 
been studied by different observers, and amongst these the re- 
searches of Kny and Lohmann are of some importance*. 
The former placed the yeast in culture solutions in flat dishes, 
and exposed a part to the light of five gas flames, whilst the other 
part was in the dark, the heat rays being removed by filtering 
the light through water. His conclusion was that the budding of 
S. Cerevisise took place in moderate light with the same activity 
as in dai’kness. 
Lohmann studied the action of both sunlight and the arc. He 
seeded cultures of S. Cerevisise on wort gelatine on glass slips, 
and exposed them to the action of a powerful arc lamp for 
eight hours. Above a temperature of 18° C. he found that the 
budding was retarded in the cultures subjected to the light. 
The same yeast was seeded on agar agar plates, and exposed to 
the action of sunlight, when the yeast was killed after several 
hours. He also noticed that even diffused daylight had a retarding 
influence on the budding of the cultures, but that this only occurred 
after prolonged exposure to the light. 
The influence of light and various spectral colours on the 
sporulation of saccharomyces has been studied by Purvis and 
Warwick*]*. They observed that the red rays accelerated the 
formation of spores more quickly than white light and more 
quickly than when the development took place in the dark : that 
the green rays retarded the development : that the blue and 
violet rays retarded the sporulation still more: and that the ultra- 
violet rays were still more effective, and that they influenced the 
vitality of the cells detrimentally when the latter were exposed to 
the influence for some time. 
It appeared to be of some interest to study the effect of light 
during a normal fermentation of hopped wort and other fermentable 
solutions, and the following notes describe the results of a com- 
parative study of the influence of light and of various spectral 
colours upon fermentation when conducted in (a) unsterilised 
copper vessels, (b) sterilised glass vessels, and (c) in unsterilised 
* Traits de Microbiologie, Duclaux, Vol. in. pp. 289 — 291 ; Kny, Ber. d. botan. 
Gesells. 1894, Heft 3; Lohmann, Inaug. Dissertation, Rostock, 1890. 
f Proc. Camb. Phil. Soc. Vol. xiv. Pt 1, pp. 30 — 40. 
