The main objective is development and optimization of a production process for butyric acid from crude glycerol based on Mixed Microbial Culture (MMC) biotechnology. This includes analyses of the composition and development of microbial populations of the MMC during fermentations. The current delivery characterizes the microbial composition of the MMC in general and the butyric acid bacteria in particular. The microbial composition were monitored by Next Generation Sequencing.
Next Generation Sequencing was used as a tool to monitor changes in the microbial composition during fermentations. Changes in the microbial communities at different stages of the fermentations (different transfers) have been monitored by next Generation Sequencing techniques based on DNA sequencing technologies primarily targeting the 16S rDNA region.
For the activated sludge samples, the dominating bacteria in all samples belonged to the phylum Firmicutes in particular the classes Clostridia and Bacilli as well as Gammaproteobacteria. Among the most dominating genera were known glycerol consumers like Clostridium, Klebsiella and Escherichia.
For the anaerobic sludge the dominating genera in the batch test (enriched hexane pretreated crude glycerol) were Clostridium and Klebsiella together with unclassified genera belonging to Proteobacteria while enriched untreated glycerol in fed-batch was dominated by the genus Blautia followed by Clostridia and unclassified genera belonging to Firmicutes.
Both the genera Clostridium and Blautia includes species typical associated with butyric acid production. Species like C. tyrobutyricum, C. butyricum and B. coccoides (reclassified from C. coccoides) are identified in samples from MMC fermentations.
The sulfate reducing bacteria in the inoculum from the anaerobic sludge was diverse, however all genera appeared at very low frequencies all below the cut-off of 1 %. The kinetic control seemed to control the SRBs while the absence of kinetic control allowed for the growth of SRBs leading to the problems relating to the production of H2S.