Dynamics of abundance of C. acetobutylicum TSH1 and B.
cereus TSH2 in the symbiotic system
Under microaerobic condition, B. cereus TSH2 provided
anaerobic environment for C. acetobutylicum TSH1.
However, the mutual mechanism of these two strains was
not clear yet. In order to illustrate the interspecies relationship
between C. acetobutylicum TSH1 and B. cereus
TSH2, dynamic relative abundance during fermentation
process under microaerobic static conditions were quantified
by real-time PCR. The initial inoculation ratio of C.
acetobutylicum TSH1/B. cereus TSH2 (C/B) was 10:1(5 %
C. acetobutylicum TSH1: 0.5 % B. cereus TSH2), 1:1(2.5 %
C. acetobutylicum TSH1: 2.5 % B. cereus TSH2) and
1:10 (5 % C. acetobutylicum TSH1: 0.5 B. cereus TSH2),
respectively.
When C/B ratio was 10:1, C. acetobutylicum TSH1
accounted for 94.5 % of the whole population at the
beginning, whereas B. cereus TSH2 was only 5.5 %
(Fig. 4a). However, the ratio of B. cereus TSH2 increased
fast and reached 59.2 % at 4 h, while ratio C. acetobutylicum
TSH1 declined to 40.2 %. Correspondingly, dissolved
oxygen was totally exhausted in this period (Fig. 2). The
abundance of B. cereus TSH2 started to decline sharply
from 4 to 12 h, and maintained at a very low level of
0.15 % after 24 h. At the same time, abundance of C.
Table 3 Butanol concentration, yield and productivity with different C. acetobutylicum TSH1 inoculum volume