Degradation of wheat straw and maize stem by a monocentric and a polycentric rumen fungi, alone or in association with rumen cellulolytic bacteria

Abstract Two rumen anaerobic fungi, Neocallimastix frontalis MCH3 and Orpinomyces (Neocallimastix) joyonii TP 90-9 were cultured on wheat straw or maize stem alone or in association with one of two rumen cellulolytic bacteria, Ruminococcus flavefaciens 007 and Fibrobacter succinogenes S85. Observations by scanning electron microscopy showed that the behaviour of the different microorganisms was qualitatively similar. The phloem and inner parenchyma of the wheat straw and maize stem were completely degraded after 48 h in both the monocultures and cocultures. Quantitatively, the two fungal species degraded comparable amounts of wheat straw and maize stem as the two cellulolytic bacteria. In the coculture of N. frontalis or O. joyonii with F. succinogenes , wheat straw or maize stem were digested to the same extent as in the fungal monocultures. The associations of N. frontalis with R. flavefaciens on the two substrates and of O. joyonii with R. flavefaciens on wheat straw were less efficient than the fungal monocultures. R. flavefaciens exerted an inhibitory effect on the cellulolytic activity of N. frontalis and O. joyonii while F. succinogenes did not interact with the two fungal species.