Isolation of lactic acid-forming bacteria from biogas plants

- Isolation of lactic acid-forming bacteria in biogas plants.
- Determination of the viable cell counts of lactic acid-forming bacteria.
- Development of a molecular qualitative detection system for the isolates.
- Features concerning the carbohydrate metabolism of the isolates are described.
- Design of specific qPCR primer sets for quantification of the isolates in biogas plants were designed.

Direct molecular approaches provide hints that lactic acid bacteria play an important role in the degradation process of organic material to methanogenetic substrates in biogas plants. However, their diversity in biogas fermenter samples has not been analyzed in detail yet. For that reason, five different biogas fermenters, which were fed mainly with maize silage and manure from cattle or pigs, were examined for the occurrence of lactic acid-forming bacteria. A total of 197 lactic acid-forming bacterial strains were isolated, which we assigned to 21 species, belonging to the genera Bacillus, Clostridium, Lactobacillus, Pediococcus, Streptococcus and Pseudoramibacter-related. A qualitative multiplex system and a real-time quantitative PCR could be developed for most isolates, realized by the selection of specific primers. Their role in biogas plants was discussed on the basis of the quantitative results and on physiological data of the isolates.