Bacterial Communities in Various Conditions of the Composting Reactor Revealed by 16S rDNA Clone Analysis and DGGE - Sustainable Biotechnology: Sources of Renewable Energy - page 166

Bacterial Communities in Various Conditions
of the Composting Reactor Revealed by 16S
rDNA Clone Analysis and DGGE

Keiko Watanabe, Norio Nagao, Tatsuki Toda, and Norio Kurosawa

Abstract Composting is an efficient and cost-effective process for organic waste
treatment. In order to expand our knowledge regarding microorganisms in the com-
posting reactor, bacterial community structures in a variety of composting processes
were examined by 16S rRNA gene (rDNA) clone analysis including denaturing
gradient gel electrophoresis (DGGE), as a case study. As previously reported, the
dominant bacteria consist of members of the order Bacillales in a typical compost-
ing condition with woodchips as the bulking agent. However, these aerobic bacteria
decreased to 14%, and anaerobes or facultative anaerobes arose when the decom-
position rate of organic compounds dropped following aggregation of the contents.
In the composting reactor operated with plastic bottle flakes as bulking agent, the
order Lactobacillales co-dominated with the Bacillales , regardless of reactor size,
accounting for about 70% of the detected organisms during first week of the opera-
tion, gradually decreasing to about 30% with maturation of the composting process.
Most species detected by clone analysis have not been cultivated, and may be
VBNC (viable but non-culturable) species, implying symbiotic interactions among
the microorganisms. In addition, the 16S rDNA-clone and DGGE methods are also
introduced in this chapter.

Keywords Aggregate · Bacterial community · Bulking agent · Clone

analysis · Compost · Denaturing gradient gel electrophoresis (DGGE) · Large-scale

fed-batch composting reactor · Plastic bottle · Polyethylene terephthalate · 16S

rRNA gene (16S rDNA)