Analysis of microbial components of two-liquid phase bioreactors for improved volatile organic compund biofiltration

Abstract

The dynamics of the microbial communities in a two-liquid phase partitioning bioreactors (TPPBs) for treatment of volatile organic compounds (VOCs) was investigated. The TPPBs were set up in 0.5 L stirred reactors using silicone oil (at 10% v/v) as the non-aqueous liquid (NAL) phase and hexane as

Development and analysis of two bioaugmentation approaches: a volatile organic compound bioaugmentation case and a pentachlorophenol bioaugmentation case

“…The strains that would be used to develop the bioaugmentative consortia in this study originated from a highly aerated two-phase partitioning bioreactor (TPPB) designed for hexane removal. It had been seeded from a microbial community isolated from oil-contaminated soil and acclimatized by hexane, and then allowed to run for more than a year with a stable feed of hexane (Ng, 2014). The hexane biodegradation was carried out through catabolic pathways involving alkane monooxygenase and/or cytochrome c in the first step, which require molecular oxygen.…”

“…The source microbial community used to initiate the project was sampled from a patch of petroleum-contaminated soil in a car park in Singapore (Ng, 2014). Since petroleum and machine oils associated with cars are expected to carry some of the other target VOCs for our current application, we considered this community to be an appropriate source to formulate the bioaugmentative co-cultures necessary for the air-purification device.…”

“…The TPPB was operated with a daily feed of hexane for over a year, and it was found that hexane removal efficiency increased gradually up to week 24 and thereafter maintained a steady high level, up to and beyond the full one year. The community within the TPPB was analyzed with a combination of culture-dependent (isolation on solid media) and culture-independent (DGGE and 16S rDNA clone library) methods (Ng, 2014).…”

“…A total of 23 genera identified are listed in the phylogenetic tree where 9 genera (boxed in magenta) had multiple species isolated and 6 genera (boxed in yellow) had only one species identified in culture. The remaining 8 genera found (boxed in green) had no culturable isolates sampled from the TPPB (Ng, 2014).…”

“…As described in the earlier Introduction section, the hexane biofiltration TPPBs which our laboratory had previously maintained for more than a year was able to sustain a high rate of hexane removal from week 24 onwards. From the analysis of community structure of week 32-40 (Figure 2.1), out of the 23 genera identified by molecular means, 15 genera were found to be culturable (Ng, 2014). For the remaining 8 genera, no culturable isolates were sampled from the TPPB during the course of the previous study.…”