The microbes identified in MC3F are broadly similar to that
reported previously from rice straw compost [6], suggesting that
the lignocellulose degrading mechanisms are similar among lignocellulolytic
consortia obtained from different substrates and
conditions. Based on the previously proposed mechanism in analogous
consortium [11,12], the facultative anaerobic Rhodocyclaceae
bacterium is probably the key oxygen utilizing microbe in MC3F.
Rhodocyclaceae is a family of Betaproteobacteria. Most of them
are aerobic or denitrifying bacteria found in aquatic habitats and
have versatile metabolic capabilities. Based on previous reports
[11,12], this bacterial strain together with other facultative anaerobes
would consume available oxygen in the upper liquid region in
the early phase, triggering oxygen depletion in the system. The fact
that some Rhodocyclaceae bacteria can utilize fermentation products
e.g. acetate under microaerophilic or anaerobic conditions [37]
also suggested the role of this bacterium in anaerobic phase of the
batch cycle. In oxygen-limiting conditions, oxygen-tolerant strains
of anaerobic Clostridium and Thermoanaerobacterium can grow in
the lower liquid region. Clostridium is an important cellulolytic
bacterial group in degradation of lignocellulosic plant biomass