In situ downstream strategies for cost-effective bio/surfactant recovery.

Since 60-80% of total costs of production are usually associated with downstream collection, separation, and purification processes, it has become advantageous to investigate how to replace traditional methods with efficient and cost-effective alternative techniques for recovery and purification of biosurfactants. In the traditional techniques, large volumes of organic solvents are usually used for increasing production cost and the overall environmental burden. In addition, traditional production and separation methods typically carried out in batch cultures reduce biosurfactant yields due to product inhibition and lower biosurfactants activity as a result of interaction with the organic solvents used. However, some in situ recovery methods that allow continuous separation of bioproducts from culture broth leading to an improvement in yield production and fermentation efficiency. For biosurfactants commercialization, enhancement of product capacity of the separation methods and the rate of product removal is critical. Recently, interest in the integration of separation methods with a production step as rapid and efficient techniques has been increasing. This review focuses on the technology gains and potentials for the most common methods used in in situ product removal: foam fractionation and ultrafiltration, especially used to recover and purify two well-known biosurfactants: glycolipids (rhamnolipids) and lipopeptides (surfactins).

Bioelectrochemical BTEX removal at different voltages: assessment of the degradation and characterization of the microbial communities.

BTEX compounds (Benzene, Toluene, Ethylbenzene and Xylenes) are toxic hydrocarbons that can be found in groundwater due to accidental spills. Bioelectrochemical systems (BES) are an innovative technology to stimulate the anaerobic degradation of hydrocarbons. In this work, single chamber BESs were used to assess the degradation of a BTEX mixture at different applied voltages (0.8V, 1.0V, 1.2V) between the electrodes. Hydrocarbon degradation was linked to current production and to sulfate reduction, at all the tested potentials. The highest current densities (about 200mA/m2 with a maximum peak at 480mA/m2) were observed when 0.8V were applied. The application of an external voltage increased the removal of toluene, m-xylene and p-xylene. The highest removal rate constants at 0.8V were: 0.4±0.1days-1, 0.34±0.09days-1 and 0.16±0.02days-1, respectively. At the end of the experiment, the microbial communities were characterized by high throughput sequencing of the 16S rRNA gene. Microorganisms belonging to the families Desulfobulbaceae, Desulfuromonadaceae and Geobacteraceae were enriched on the anodes suggesting that both direct electron transfer and sulfur cycling occurred. The cathodic communities were dominated by the family Desulfomicrobiaceae that may be involved in hydrogen production.

37Cl-compound specific isotope analysis and assessment of functional genes for monitoring monochlorobenzene (MCB) biodegradation under aerobic conditions.

A laboratory approach was adopted in this study to explore the potential of 37Cl-CSIA in combination with 13C-CSIA and Biological Molecular Tools (BMTs) to estimate the occurrence of monochloroenzene (MCB) aerobic biodegradation. A new analytical method for 37Cl-CSIA of MCB was developed in this study. This methodology using a GC-IRMS allowed to determine δ37Cl values within an internal error of ±0.3‰. Samples from a heavily MCB contaminated site were collected and MCB aerobic biodegradation microcosms with indigenous cultures in natural and enhanced conditions were set up. The microcosms data show a negligible fractionation for 13C associated to MCB mass decrease of >95% over the incubation time. Conversely, an enrichment factor of -0.6±0.1‰ was estimated for 37Cl, which is a reflection of a secondary isotope effect. Moreover, the dual isotope approach showed a pattern for aerobic degradation which differ from the theoretical trend for reductive dehalogenation. Quantitative Polymerase Chain Reaction (qPCR) results showed a significant increase in todC gene copy number with respect to its initial levels for both natural attenuation and biostimulated microcosms, suggesting its involvement in the MCB aerobic degradation, whereas phe gene copy number increased only in the biostimulated ones. Indeed, 37Cl fractionation in combination with the dual carbon­chlorine isotope approach and the todC gene copy number represent valuable indicators for a qualitative assessment of MCB aerobic biodegradation in the field.

Effect of preservation method on the assessment of bacterial community structure in soil and water samples.

The methods used in sample preservation may affect the description of the microbial community structure by DNA-based techniques. This study aims at evaluating the effect of different storage conditions, including freezing, adding two liquid-based preservatives or simply storing samples with no preservative, on the structure of the microbial communities in aliquots of organic-rich soil and water samples as revealed by a terminal restriction fragment length polymorphisms. The results showed that the number of terminal restriction fragments (TRFs) detected in soil aliquots stored with LifeGuard(™) solution was significantly lower than that of samples analyzed immediately after sampling. Moreover, cluster and PCA analyses showed that soil aliquots stored using LifeGuard(™) clustered separately from those stored with the other methods. Conversely, soil and water aliquots stored with DMSO-EDTA-salt solution did not show either significant reduction in the number of TRFs or any change in the structure of the microbial community. Finally, the number of TRFs and the structure of microbial communities from soil aliquots stored with no preservative did not differ from those of aliquots analyzed immediately after sampling. Preservation methods should therefore be accurately evaluated before collecting samples that have to be stored for long time before DNA extraction.