OTHF.R CARRON SOURCES 83 



/. OTHER CARBON SOURCES 



Pure Compounds. The lower monohydric aliphatic alcohols — meth- 

 anol, ethanol, etc. — are not generally utilized, although Aspergillus 

 niger makes a limited growth with both methanol (6) and ethanol 

 (201). The most extensive study of the alcohols is that of Stahl and 

 Pessen (192), who found that Aspergillus versicolor grows poorly with 

 ethanol and not at all with the other primary alcohols from methyl 

 through undecyl (C x through C n ). Alcohols with 12 to 18 carbon 

 atoms support some growth of A. versicolor, and there appears to be 

 an optimum chain length of 13 to 15. 



Amino acids, of course, provide carbon as well as nitrogen and 

 many can serve as sole sources of carbon (139, 203). In general, if 

 enough amino acid carbon is supplied for growth the accumulation of 

 ammonia raises the pH to an unfavorably high level, so that the 

 amino acids alone cannot compare with the carbohydrates in the 

 amount of growth supported. 



Enrichment culture methods have been used successfully in the 

 isolation of an actinomycete able to use urethane as sole source of 

 carbon (176). Proactinomyces spp. make visible growth with several 

 aromatic compounds, e.g., phenol, aniline, and nitrobenzene, as sole 

 sources of carbon (133). 



Natural Products. Lignin is a complex amorphous polymer of high 

 molecular weight, the units of which are aromatic in nature, but neither 

 the chemical nor the physical structure is known precisely. It is a 

 plant product and is particularly abundant in wood. 



There is good evidence, based on the analysis of plant materials 

 before and after decomposition by pure cultures, that some fungi are 

 able to decompose lignin in situ, i.e., in association with other sub- 

 stances of the plant. Evidence on the fungi is limited, however, to the 

 litter-decomposing and the wood-destroying basidiomycetes. The 

 lignin of litter is decomposed actively by species of Marasmius, Col- 

 lybia, Mycena, Clavaria, and other soil-inhabiting Hymenomycetes 

 (118). Most of the species studied use both the lignin and the cellulose 

 of litter, but a few appear to utilize only the lignin (75, 118). 



The wood-rotting basidiomycetes have long been differentiated into 

 two groups (63, 64): the brown rot fungi, e.g., Merulius domesticus, 

 attacking primarily the cellulose of wood, and the white rot fungi, e.g., 

 Polyporus annosus, which attack the lignin more rapidly. Bavendamm 

 (11) differentiated these two groups by their reaction on a tannic acid 



