BIOGRAPHICAL MEMORANDA 



cultures showed that, except in the glucose solution, kojic acid was not 

 produced, thus supporting the contention that the positive results 

 obtained by others with growing cultures were due to substrate trans- 

 formations via glucose, and involving growth of the mould. It should, 

 however, be mentioned that this experiment does not provide con- 

 clusive evidence in favour of the proposed interpretation ; it is at least 

 possible that mycelia grown in the presence of other substrates might 

 have yielded different results. 



But the main point of this discussion is to illustrate the fundamental 

 difficulties inherent in the use of growing cultures for the study of 

 mould metabolism. It was therefore a distinct improvement when the 

 method of using pre-grown mycelium was introduced. This could first 

 be freed of the initial medium by washing, and then tested for its 

 effect on specific substrates under much better controlled conditions. 

 Nevertheless, even this technique had been found far from satisfactory; 

 this follows clearly from the fact that it is virtually impossible to du- 

 plicate the results of such experiments. 



It was the keen recognition of the complex situation encoun- 

 tered in cultures of filamentous fungi that led Kluyver and Perquin 

 [1933a] to develop a new methodology for the study of mould 

 metabolism; this was published in 1933 under the name of 'agi- 

 tated cultures'. The arguments for abandoning the stationary cul- 

 tures, even those with preformed mycelial mats, have been set forth 

 so clearly, and are so convincing that they are here quoted in some 

 detail. 



Having raised the question what factors are responsible for the 

 oftentimes incomplete oxidations performed by moulds, Kluyver and 

 Perquin concluded: 



'It is clear that a priori two different reasons could be held respon- 

 sible for this behaviour. Firstly, it is conceivable that the cells are 

 characterized by a specific low oxidative capacity. This is true, for 

 example, in the case of A. suboxydans, whose oxidative activity towards 

 certain substrates is restricted to a single dehydrogenation, even under 

 widely different external conditions. But secondly, it has long been 

 known that in many cases an incomplete oxidation is determined by 

 outside influences, so that cells fully capable of performing a complete 

 substrate oxidation may, under special circumstances, cause the ac- 

 cumulation of incomplete oxidation products. For such materials 



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