CAROTENOIDS 



when transferred to a medium containing glucose but no nitrogen, the 

 concentration of carotene in myceha growing on a N-free medium 

 being greater than that in myceha on a medium containing nitrogen. 



Ejfect of Light. Deventer (quoted by Zechmeister) ^ ' found that 

 hght was necessary for carotene formation by Neurospora sitophilla. 

 Haxo, 2 ' on the other hand, found that Hght was not essential for 

 carotenoid synthesis in A^^. crassa but that it did stimulate synthesis 

 considerably, the spectral region between 520 and 580 Tn\i. being the 

 most effective. Schopfer^* stated that blue light was necessary for 

 carotene synthesis by Phycomyces blakesleeanus, for none was produced 

 in the dark or in red light. Garton et al. i ». 2 o could not reproduce 

 Schopfer's original observations, and the results of many experiments 

 indicated that Phycomyces cultured in the dark always produced about 

 one half as much carotene as did cultures grown in the light. Further, 

 the wavelength of the light used appeared to be of little importance ; 

 as long as some light was falling on the cultures full carotene produc- 

 tion occurred. Recently Schopfer has informed us that his original 

 analytical methods were such that small amounts of carotene in his 

 dark cultures may have gone unobserved. ^ ® Furthermore, as he points 

 out there is always the possibility that the Phycomyces of 1951 does not 

 behave in the same way as the strain of 1934. 



Although stimulating the production of coloured carotenoids, light 

 did not effect the synthesis of phytofluene in Neurospora crassa ; ^ ' in 

 Phycomyces on the other hand, synthesis of all the carotenoid com- 

 ponents appears to be equally affected by light. ^ ^ 



It has been reported that the pigments of Microcerca coccophila 

 (Hypocreacea), which is very probably a carotenoid, is produced in the 

 conidia in light and darkness, but in the mycelia only in the light. ' • 



Effect of Temperature^ Oxygen Tension^ pH, and other Factors, 

 According to Fromageot and Tschang*^ pigmentation in R. sanniei 

 remains qualitatively the same within the temperature limits 14-28° 

 and the pH limits 5-2-7 -6. Luteraan and Dieng*® claim that pigment 

 (? carotenoid, see below) formation in Saccharomyces cerevisiae depends 

 on the O2 tension of the enviroment and Mery^^ noticed a similar 

 effect in R. gracilis. 



It has been stated by Luteraan and Dieng " ^ that exposure of Rhodo- 

 torula spp. to the vapours of camphor, terpineol or menthol results 

 in the decolouration of the yeast within 24-48 hours. If these cultures 

 are then washed free from the terpenes and transferred to a new 

 medium, rapid and abnormal pigmentation and growth take place. 

 Saccharomyces cerevisiae, which normally does not produce carotenoids 

 takes on a red tinge when treated in this way ; it has been assumed 



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