Bacterial Communities in Various Conditions of the Composting Reactor Revealed by 16S rDNA Clone Analysis and DGGE - Sustainable Biotechnology: Sources of Renewable Energy - page 175

( Lactococcus sp. and Lactobacillus sp.). They were dominant in the first 14
days, and these results showed a possibility that the dominant order of the
Lactobacillales and decreasing pH may be correlated (data not shown), and
this may cause rancidity depending on operating conditions [31]. After which
order of the Lactobacillales decreased and other species, e.g. Bacillus coagulans ,
Corynebacterium sp., appeared. B . coagulans was often detected from various
composting reactors [5, 10, 28, 29], even in different systems or wastes. Ishii
et al. indicated how the acidic environment early in this phase is suitable for
B . coagulans , which requires a slightly low pH value (6.0) for the initiation of
growth [29]. The samples derived from day 0, 7, 16 and 21 were also analyzed
by 16S rDNA clone analysis, which showed a bacterial community succession
from the order Lactobacillales to the order Bacillales and Actinomycetales (Fig. 4).
The large-scale reactor was batch operated. Therefore, this community succession,
similar to field heaping compost, might be occurred.
In conclusion, 16S rDNA analysis showed that microbial community structures
depended on the type or condition of the reactors, and some species can be used
for indicators of reactor conditions. However, the family Bacillaceae is generally
dominant or detected even though each composting reactor has independent micro-
bial community structures. As we expected, unidentified genus were detected from
each reactor. For example, 65% of the total clones might be derived from VBNC
microorganisms in the reactor A (Fig. 2). It will be necessary to reveal the function
of these VBNC microorganisms for totally understanding of biological reactions in
the reactor.
5 Expert Commentary and 5 Year View
In recent years, microbial analysis by using molecular biological methods have been
applied and developed to reveal its community or succession, to detect and deter-
mine quantity of them, Clone analysis and DGGE analysis, which were introduced
in this manuscript, are able to apply ecological analysis in various environments
including the artificial reactor. For example, to reveal the microbial community
or succession in the soil, various aquatic environments, artificial reactor or pro-
cesses such as anaerobic methane fermentation reactor, composting reactor, sewage
disposal system, food and beverage industrial reactor (i.e. beer, juice) or ethanol
fermentation reactor, and so on.
Clone analysis and DGGE analysis are useful to detect the contamination of
microorganisms. Bacterial contamination is frequently a problemwith yeast fermen-
tations for the production of ethanol or food industrial reactors because of spoilage
bacterium or fungus contamination. However, these methods are not able to give
absolute quantity of microorganisms. Therefore, it is important to combine use of
these methods and cell counting by using SYBR Gold (described in this manuscript)
or Fluorescence in situ hybridization (FISH). FISH can detect not only absolute
quantity but also biomass ratio, and it can detect microbial presence in which part
of the samples.