3.1 | Aerobic and anaerobic environment
To evaluate the ability of the bioreactors to maintain aerobic and anaerobic conditions, two bioreactor modules were inoculated with a monoculture of the anaerobe Bifidobacterium longum subspeciesinfantis (B. infantis) and operated in the batch culture mode. This bacterium was able to grow and thrive as indicated by the increase in the OD600 of the culture after 24 h (Figure 2A). Analysis of the composition of the culture by qPCR confirmed that the increase in bacterial density over the 24 h of culture was due to the growth of B. infantis (Figure 2B). In a separate experiment, a set of bioreactor modules were inoculated with a mixed bacterial culture containing different species of bifidobacteria along with other bacterial species from two of the major phyla (Firmicutes and Actinobacteria) of the human gut microbiota (Kostic et al., 2013) to enable us to assess the growth dynamics of bifidobacteria within a mixed bacterial community. In this experiment, the MRS culture medium (Lee & Lee, 2008; Süle et al., 2014) was used and the bioreactor modules were operated in the continuous culture mode. As shown in Figure 2C, the mixed culture maintained under anaerobic condition showed higher growth rates compared to that maintained under aerobic condition. Moreover, the bacterial growth under anaerobic culture condition was attributable to the growth of Bifidobacterium spp . and Streptococcus spp. at the expense of the Lactobacillus spp. (Figure 2D). These results demonstrated the ability of the bioreactor modules to maintain anaerobic culture conditions and support the growth of anaerobic bacteria such as bifidobacteria.