Anaerobic fungi are prime candidates for the conversion of agricultural waste products to biofuels. Despite the increasing interest in these organisms, their growth requirements and metabolism remain largely unknown. The isolation of five strains of anaerobic fungi and their identification as Neocallimastix cameroonii, Caecomyces spec., Orpinomyces joyonii, Pecoramyces ruminantium, and Khoyollomyces ramosus, is described. The phylogeny supports the reassignment of Neocallimastix californiae and Neocallimastix lanati to Neocallimastix cameroonii and points towards the redesignation of Cyllamyces as a species of Caecomyces. All isolated strains including strain A252, which was described previously as Aestipascuomyces dubliciliberans, were further grown on different carbon sources and the produced metabolites were analyzed; hydrogen, acetate, formate, lactate, and succinate were the main products. Orpinomyces joyonii was lacking succinate production and Khoyollomyces ramosus was not able to produce lactate under the studied conditions. The results further suggested a sequential production of metabolites with a preference for hydrogen, acetate, and formate. By comparing fungal growth on monosaccharides or on the straw, a higher hydrogen production was noticed on the latter. Possible reactions to elevated sugar concentrations by anaerobic fungi are discussed.
Keywords: Neocallimastigomycota; lignocellulose; metabolites.