Characterization and performance evaluation of a two-phase partitioning bioreactor for volatiles organic compounds treatment in off-gas

[Abstract] The treatment of the industrials off-gas strongly evolves with change of the environmental legislation on a worldwide scale. Biotechnics existing for their treatment sometimes present limits for some volatile organic compounds (VOC) such as BTEX because of their poor water solubility. The use of two phase-partitioning bioreactors (TPPB) is an interesting alternative in this case. In this work, a laboratory scale TPPB (water / silicone oil) was monitored at high level of Isopropropylbenzene (IPB) air pollution (7g/Nm3) and a flow of 1 VVM. We focused ourselves on the inoculation with the strain Rhodococcus erythropolis T 902.1. We showed that the increase of the inoculums size to 5 g DM/l. induces a better initial abatement of the pollutant, however performances of the TPPB decrease quickly because of cellular mortality. The use of a smaller inoculum (0,2g DM /l) seems to be a good compromise to observe progressive improvement of the IPB abatement with adaptation of biomass. The TPPB was followed during 38 days in order to confirm its potentialities and characterise its evolution. We showed that the performances of the TPPB are maintained with an elimination rate near to 63 % for IPB polluted air (7 g/Nm3) and punctually reach 92 %. The biomass grows gradually and stabilizes itself around 10 g/l. With fluorescent double stain Rhodamine/ propidium iode, we also shown that cellular viability strongly evolve: cellular viability was low (30 %) in the first operating hours but is quickly increased after adaptation to IPB (80%); we also suggested an endorespiration phenomenon in the bioreactor. In this work, we could confirm the previously estimated elimination performances of the two- phase partitioning bioreactor with silicone-oil as second phase. Elimination rate of a monoaromatic compound at high concentration (7 g / Nm3) can be maintained between 240 g /m3.h and 360 g /m3.h. in the TPPB

Action of Patulin on Yeast

The action of patulin on Saccharomyces cerevisiae was studied. At weak doses, the drug inhibited growth, but inhibition was transient. After 10 min, syntheses of rRNA, tRNA, and probably mRNA were blocked; this was shown by radioactive precursor incorporation assays and gel electrophoresis of RNAs. After recovery of growth, patulin disappeared from the medium. It seemed that this degradation resulted from the activity of an inducible enzymatic system. Induced cells resisted very high patulin concentrations

E.coli prpoS::gfp strain as biosensor of glucose heterogeneity inside industrial bioreactors

• OBJECTIVE: Escherichia coli is a microorganism widely used in the industry for the production of recombinant proteins. The performances obtained at the laboratory level are not reproducible at a large scale. Actually, the mixing operation is not efficient enough: gradients of glucose and oxygen appear when operating in fed-batch mode (addition of glucose during the culture). These gradients cause adverse impacts on the production of biomass and recombinant protein. The aim of this work is to use the microbial population as biocaptor of the encoutered stress inside heterogeneous industrial bioreactors to better scale-up and regulate these reactors. • MATERIALS AND METHODS: A plasmid carrying a stress promoter followed by the coding sequence of the Green Fluorescent Protein (GFP) is introduced in the bacterial host (in our case, the strain E. coli K12 will be considered as a model organism). When the cell is submitted to given stress condition, GFP synthesis is induced and accumulated into the cytoplasm, leading to the increase of the cell's fluorescence. Flow cytometry detection is used in order to quantify the fluorescence at the single cell level. Obtained results are frequency histograms of fluorescenceintensity in the microbial population • RESULTS: The rpoS gene is a gene of the general stress response, mainly induced at the entrance to stationary phase (during a lack of glucose). The tracking of the GFP fluorescence linked to the activation / repression of the rpoS promoter gives good results. Indeed, there is appearance of a segregation at the level of the GFP content among the microbial population. The intensity of the segregation, as well as its time of appearance during the culture can be related to the bioreactor mixing efficiency. • CONCLUSION: prpoS::gfp strains can be used as biosensors of the heterogeneity of glucose encountered inside industrial reactors. • POTENTIAL APPLICATIONS & KEY BENEFITS: These strains could be used to validate a fed-batch regulation (addition of glucose) at the industrial level

Microsale interactions between earthworms and microorganisms, a review

Peer reviewe

Comparison of explant responses treated with leachate and leonardite sources of humic substances during in vitro rooting of woody plants.

As heterogeneous mixtures of compounds resulting from the physical, chemical and microbiological transformations of organic residues, humic substances (HS) are mostly recognized for their biostimulation of plant growth that firstly involve the root development and architecture before further putative improvement of nutrients uptakes. To avoid the interferences currently reported from external origins, the successive steps of rooting have been carried out using shoots and isolated leaves of birch and alder vitro-plants. Extracts issued from landfill leachate (LHS) has been compared to a stable formulation from leonardite ("Humifirst" 12% humic acid 3% and fulvic acid) commercialized by TRADECORP company's (HHS). Chemical analysis showed that LHS source typically contain much higher N (mainly as ammonium (93%) and chloride concentration than HHS. Used at low concentration (10 ppm) during root induction/initiation phase, both HS sources may be slightly unfavorable to the root formation (21% of reduction in primary root number) of alder but not of birch. While, in root elongation phase, there is an increase in the primary root length and lateral root number. The direct effects of HS on in vitro root development vary from one species to another depending on the root treatment stage. Results showed that both explants type response are equivalent in the development of a complete rooting system

Accelerated storage testing of freeze-dried Pseudomonas fluorescens BTP1, BB2 and PI9 strains

Freeze-dried cultures of Pseudomonas fluorescens are used in agriculture and microbiological industry. However, P. fluorescens is very susceptible to damage during freeze-drying and subsequent storage and it would be useful to increase culture viability during storage. The viability of freeze-dried P. fluorescens strains (BTP1, PI9 and BB2) was evaluated by using the Arrhenius model. This model was described by measuring the reaction rate constants (D or k) and temperature sensitivity of rate constant (z or Ea). The freeze-dried P. fluorescens strains were stored in glass tubes at 60, 37 and 4°C for 8 h, 28 days and two months, respectively. D value decreased or k increased with an increase of the storage temperature. By comparing their decimal reduction time (D), we observed that BB2 strain was more resistant than BTP1 and PI9 at 37 and 60°C. The activation energy of all P. fluorescens strains were not significantly different and thermal inactivation may occur by the same mechanism. Thus, it was possible to compare rate constants of survival for the freeze-dried P. fluorescens strains. These results will be useful to the development of improved reference materials and samples held in culture collections.Key words: Arrhenius model, accelerated storage testing (AST), freeze-drying, storage stability

Influence of electrical properties on the evaluation of the surface hydrophobicity of Bacillus subtilis

The surface hydrophobicity of nine Bacillus subtilis strains in different states (spores, vegetative cells, and dead cells) was assessed by water contact angle measurements, hydrophobic interaction chromatography (HIC) and bacterial adhesion to hydrocarbon (BATH). Electrokinetic properties of B, subtilis strains were characterized by zeta potential measurements and found to differ appreciably according to the strain, Correlations between HIC data, BATH data and zeta potential showed that HIC and RATH are influenced by electrostatic interactions. Water contact angle measurements thus provide a better estimate of cell surface hydrophobicity. The water contact angle of B. subtilis varied according to the strain and the state, the spores tending to be more hydrophobic than vegetative cells. (C) 2001 Elsevier Science B.V. All rights reserved

Bioreactor mixing efficiency modulates the activity of a prpoS::GFP reporter gene in E. coli

<p>Abstract</p> <p>Background</p> <p>Extensive studies have shown that up-scaling of bioprocesses has a significant impact on the physiology of the microorganisms. Among the factors associated with the fluid dynamics of the bioreactor, concentration gradients induced by loss of the global mixing efficiency associated with the increasing scale is the main phenomena leading to strong physiological modifications at the level of the microbial population. These changes are not fully understood since they involve complex physiological mechanisms. In this work, we intend to investigate, at the single cell level, the expression of the rpoS gene associated with the stress response of <it>E. coli</it>. The cultures of the reporter strain have been performed in a small scale reactor as well as in a series of scaled-down bioreactors able to induce extracellular perturbations with increasing level of magnitude.</p> <p>Results</p> <p>The rpoS level has been monitored by the aim of a transcriptional reporter gene based on the synthesis of the green fluorescent protein (GFP). It has been observed that the level of GFP increases during the transition from batch to fed-batch phase. After this initial increase, the GFP content of the cell drops, primarily due to the dilution by cell division. However, a significant drop of the GFP content has been observed if using a partitioned bioreactor, for which the mixing conditions are very bad, leading to the exposure of the cells to cyclic and stochastic extracellular fluctuations. If considering the flow cytometric profile of the cell to cell GFP content, this drop has to be attributed to the appearance of segregation at the level of the GFP content among the microbial population.</p> <p>Conclusion</p> <p>The generation of extracellular perturbations (in the present case, at the level of the sugar concentration and the dissolved oxygen level) has led to a drop at the level of the rpoS expression level. This drop has to be attributed to a segregation phenomenon in microbial population, with a major sub-population exhibiting a low expression level and a minor sub-population keeping its initial elevated expression level. The intensity of the segregation, as well as its time of appearance during the culture can be related to the bioreactor mixing efficiency.</p