Growth inhibition of biomass adapted to the degradation of toluene and xylenes in mixture in a batch reactor with substrates supplied by pulses

P, S. CF, A. G. Exploring the styrene metabolism by aerobic bacterial isolates for the effective management of leachates in an aqueous system

In the present study, the styrene metabolic profile of three aerobic bacterial isolates explored in a batch mode study. The isolates found application in the management of elachates in the waste dump yard. These three bacterial species have different origins and were studied as a single and mixed consortia. The Lysinibacillus strain M01 (from marine sources), Lysinibacillus strain WD03 (from a waste dump yard), and Pseudomonas strain BG07 (from bovine gut) were used in the present study. The styrene concentration was fixed in the range between 0.5 and 1.5 mL L⁻¹. The metabolites obtained upon microbial degradation were assessed using high-performance liquid chromatography (HPLC), UV-visible spectroscopy, and FTIR spectroscopy (Fourier transform infrared spectroscopy). Furthermore, the genes (Sty A, B, C, D, and E) responsible for the degradation of styrene by the three abovementioned isolates were identified using PCR with respective designed primers. Instrumental analyses revealed the presence of phenylacetic acid (PAA) at significant levels in the growth medium after the scheduled experimental period and confirmed the metabolism of styrene by the chosen isolates. Compared to the case of individual cultures, the results of the mixed consortia support the metabolism of styrene at appreciable levels. The present study provides a suitable biological solution for the management of leachates containing styrene and a way to achieve industrially important chemicals (PAA) through a microbially mediated process.

Profile of the three potential aerobic bacterial isolates responsible for the metabolism of styrene.

Biofiltration of Air: A Review

In this paper we present a review of the existing air pollution control technologies (APCT), when used essentially for the elimination of volatile organic compounds (VOC). The biotechnologies referred to, bioscrubbers, biotrickling filters and biofilters, are also described. A more detailed review of biofiltration is proposed, presenting the most recent and latest developments achieved in the field of bioprocessing. In particular, the influence of the filter bed, the polluted air flowrates, the pollutants, the pressure drop, bed moisture content, temperature, nutrients, pH and the microorganisms are reviewed. Models of biofiltration are also presented.

Design of a large-scale surface-aerated bioreactor for biomass production using a VOC substrate

The design of a large-scale bioreactor for the production of bacterial biomass adapted to the biodegradation of volatile organic compounds was carried out. The bioreactor model used integrated the microbial kinetics and fluid dynamics described by the compartment model approach. The process conditions and kinetic parameters were adopted from the laboratory experimental study of (León, E., Seignez, C., Adler, N., Péringer, P., 1999. Growth inhibition of biomass adapted to the degradation of toluene and xylenes in mixture in a batch reactor with substrates supplied by pulses. Biodegradation 10, 245-250). The performance of the pulsed-batch stirred bioreactor under surface aeration conditions was simulated for different mixing configurations and conditions such as the impeller diameter, number of impellers, stirring speed, and oxygen pressure. The simulations were used for the cost analysis which resulted in the optimal design of the bioreactor.

Mass production of bacterial communities adapted to the degradation of volatile organic compounds (TEX)

This study focuses on the mass cultivation of bacteria adapted to the degradation of a mixture composed of toluene, ethylbenzene, o-, m- and p-xylenes (TEX). For the cultivation process Substrate Pulse Batch (SPB) technique was adapted under well-automated conditions. The key parameters to be monitored were handled by LabVIEW software including, temperature, pH, dissolved oxygen and turbidity. Other parameters, such as biomass, ammonium or residual substrate concentrations needed offline measurements. SPB technique has been successfully tested experimentally on TEX. The overall behavior of the mixed bacterial population was observed and discussed along the cultivation process. Carbon and nitrogen limitations were shown to affect the integrity of the bacterial cells as well as their production of exopolymeric substances (EPS). Average productivity and yield values successfully reached the industrial specifications, which were 0.45 kg(DW)m(-3) d(-1) and 0.59 g(DW)g (C) (-1) , respectively. Accuracy and reproducibility of the obtained results present the controlled SPB process as a feasible technique.

Biodegradation of C5+ hydrocarbons by a mixed bacterial consortium from a C(5+)-contaminated site

C5+, a mixture of benzene, toluene, xylene, styrene, dicyclopentadiene (DCPD), naphthalene and other compounds, is a byproduct of polyethylene production and has been introduced into the environment via accidental release. The degradation of C5+ was studied using a defined consortium of 11 distinct bacterial strains isolated from C(5+)-contaminated soil. Vigorous growth of individual strains on C5+ was no prediction of dominance in the consortium, when the latter was grown under the same conditions. The defined consortium was able to degrade benzene, toluene, styrene and naphthalene, and to codegrade m-xylene in the presence of toluene or naphthalene. It was unable to degrade DCPD, which was inhibitory when degradation of pairs of C5+ components was examined. The complete C5+ mixture appeared to be the best substrate for the consortium.

A mechanistic model for m-xylene treatment with a peat-bed biofilter

The painting of vehicles in the automobile industry generates large quantities of gaseous emissions which contain volatile organic compounds (VOC) like xylenes. This polluted air has a high moisture content and a temperature around 15-20 degrees C. It is thus possible to consider its treatment by a biological way. In this paper, laboratory tests are described which led to the choice of packing material to make a biofilter having good removal efficiency. Moreover this technique is known for its simplicity and low energy cost. The maximum treatment capacity was obtained with peat. A mathematical model which makes it possible to specify the different limiting steps of the process was carried out. This considered both physical parameters of the biofilter and properties of the biofilm. By choosing a lower Henry's constant than typical air:water system, we obtain a better simulation of the xylenes concentration according to the biofilter length and applied load.

A procedure for production of adapted bacteria to degrade chlorinated aromatics

Production of biomass adapted to the degradation of a mixture of chlorobenzene (CB) and 1,2-dichlorobenzene (DCB) was investigated in a batch culture with substrates supplied by pulses. CB and o-DCB concentrations which gave the best adapted biomass productivity were determined and found to be 150 and 30 microl l(-1), respectively. The biomass productivity was 51 mg l(-1) h(-1). The biomass yield was 0.38 g of biomass dry weight per gram of substrate. The pulses of 200 microl CB and 40 microl o-DCB, were inhibitory to the bacterial culture. Among the metabolites, muconic acid was found in large quantities in the medium and in the cells. At a time between two pulses of 60 min, adding 150 microl CB and 30 microl o-DCB per each pulse, 7.6g l(-1) of biomass was obtained. The produced biomass served as an inoculum for the biotrickling filter which treated industrial waste gases contaminated by CBs. The method of adapted biomass production was described using CBs, but the degradation of any other toxic volatile pollutant can be improved using this technique.