Characteristics of mixed microbial culture at different sludge ages: Effect on variable kinetics for substrate utilization

The study focused on variable kinetics for substrate utilization, primarily addressing the following issue: Is variable process kinetics observed under different operating conditions and culture history (sludge ages), the result of changes inflicted on the metabolic machinery of the same microbial culture? Or, is this the result of a different microbial population selected under different operating conditions? For this purpose, the study mainly emphasized to assess the microbial population composition sustained at different sludge ages. It explored the relationship between observed process kinetics and microbial population structure using respirometric modeling and high-throughput sequencing of 16S rRNA gene. Experimental results indicated a significant change in the composition of the microbial community fed with the same organic substrate, when the culture history was changed, lower sludge age selecting a different and faster growing microbial community.

► Microbial population structure was assessed using sequencing of 16S rRNA gene.
► Different microbial community was observed when the culture history was changed.
► Model evaluation indicated variable process kinetics as a function of culture history.
► Change in the microbial community was a major factor for variable process kinetics.