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The aim of this study was to analyse the basic mechanisms of the interaction of surfactants anionic rhamnolipids and non-ionic polysorbate-80 on a microbial consortium during the biodegradation of diesel oil under model conditions. The analysed surfactants significantly influenced the metapopulation changes of microorganisms and caused a decrease in metabolic activity; however, they did not decrease the biodiversity of the studied system. Polysorbate-80 was relatively resistant to biological decomposition, whereas rhamnolipids were subjected to biodegradation as well as microbial transformation, as confirmed by the activity of the RhlC gene. Determination of biodegradation kinetics confirmed the positive influence of polysorbate-80 on the degradation efficiency of diesel oil hydrocarbons. The addition of this surfactant in 2-fold and 4-fold critical micelle concentration revealed a positive influence on the total petroleum hydrocarbons biodegradation by 18% and 15% respectively. Rhamnolipids exhibited an inhibiting effect in all fractions, with the exception of n-alkanes. The biodegradation efficiency of total petroleum hydrocarbons was 47% and 40% lower in samples containing biosurfactants in 2-fold and 4-fold critical micelle concentration, compare to that of the control sample. The surfactant-enhanced bioremediation method is a promising alternative to traditional methods; however, the method's efficiency is associated with the proper selection of a surfactant and its concentration and consideration of the occurrence of toxic effects as well as changes in the local soil metapopulation. Image 1 • Surfactants robustly impact on shaping microbial community structure and activity. • Polysorbate-80 increases the biodegradation rate of aromatic hydrocarbons. • High concentrations of rhamnolipids decrease the biodegradation of hydrocarbons. • Exogenous rhamnolipids can be transformed by environmental consortia. • The transformation of rhamnolipids affects the development of microbial community. [ABSTRACT FROM AUTHOR]

Abstract: Due to high fat content the treatment of oiled bleaching earth is very challenging. The neutralization of such waste may be carried out by employing the composting process. In this study, the efficiency of the composting process conducted with 19% addition of commercial oiled bleaching earth to waste sludge was evaluated. Maize straw was used as a structural material. The activity of lipases and dehydrogenases was measured during the biodegradation process. As a result of composting, changes in C/N ratio occurred (from 31 to 15) and the efficiency of fatty acids biodegradation reached 95%. The composting process also resulted in the removal of the initial phytotoxicity of composts. The mature compost did not exhibit any form of phytotoxicity during assays with Phytotoxkit. The Ames test excluded mutagenicity of any components in the compost. These results suggest that the proposed composting method may potentially be employed for rapid and efficient remediation of industrial waste containing oiled bleaching earth and waste sludge. [Copyright &y& Elsevier]

Abstract: Composting of oiled bleaching earth with waste sludge and corn straw was carried out to investigate the ability of microorganisms to synthesize biosurfactants that might decrease the surface tension of composts. Analytical results and changes in the surface tension suggest that biodegradation of fatty by-products was the consequence of emulsifying properties of higher fatty acids. The surface tension for isolates from all composting phases was between 37 and 43mNm–1. No substances synthesized by microorganisms that might be able to decrease the surface tension were detected in composts. Tensammetric, TLC and HPLC-MS results and changes in surface tension suggest that biodegradation of fatty by-products results from the emulsifying properties of higher fatty acids. A decrease in fatty content from 144 to 6mgg–1 dry matter was obtained. [Copyright &y& Elsevier]

Abstract: This study aimed to determine nicotine biodegradation and the genotoxic potential of nicotine and its degradation products during the process of tobacco waste composting. Composting was carried out using two methods, i.e. the addition of 20% (bioreactor A) or 40% tobacco wastes to sewage sludge (bioreactor B) and control – sewage sludge (bioreactor C). Wheat straw was used as a structure-forming material. As a result of composting the contents of C and N in the bioreactors changed, the C:N ratio in bioreactor A changed from 22.8 to 13.00, and that in bioreactor B changed from 23.5 to 12.00. After composting, the biodegradation rate of nicotine was 78% in bioreactor A and 80% in bioreactor B, respectively. Using the Ames test it was shown that the composts produced did not exhibit mutagenicity. [Copyright &y& Elsevier]

Fresh, unpasteurized carrot juice is a popular element of the everyday diet of many consumers, and as such the matter of the juice's microbial safety remains an important one. Imaging flow cytometry (FCM) allows a fast enumeration and determination of cells, as well as their further differentiation. However, carrot juice is a difficult food product to analyze with the use of FCM due to interference from autofluorescence and the presence of plant debris. In this research, we aimed to obtain an effective and repeatable protocol for the preparation of carrot juice samples for FCM analysis. Through experimental and software-based means we successfully determined a reliable protocol for the preparation of fresh, unpasteurized carrot juice, which consisted of a sequence of filtering, centrifugation, enzyme treatment, and finally the implementation of the Machine Learning protocol for the best result. • Optimization of protocol for preparing carrot juice for the flow cytometry analysis. • The presence of pathogens raises the need for reliable methods of their analysis. • Filtering, centrifugation, and enzyme treatment enabled the analysis of juice. • Machine Learning allowed for differentiation between microbial cells and debris. [ABSTRACT FROM AUTHOR]

An attempt to incorporate a soil-isolated bacterial consortium capable of degrading hydrocarbons into the sweet flag rhizosphere was made in order to introduce the plant-bacteria combination into a wetland environment. The colonization of the rhizosphere occurred after a diesel oil degradation trial, where the plant was inoculated with the bacterial consortium. Both plant and bacterial growth were monitored. The 16S rRNA gene sequences method was used to verify the presence of the soil-isolates in the plants internal tissues and TTC-dehydrogenase measurements were employed to assess the microbial activity. The incorporation of bacterial cells into the sweet flag rhizosphere resulted in an increased diesel oil removal efficiency (by 50%) and enhanced bacterial and plant growth. Afterwards, the colonized sweet flag rhizomes were planted within a lake shoreline to evaluate the long-term prevalence of microorganisms in the natural environment. The bacterial DNA of the oil-degrading consortium species was detected in the harvested plants even after 8 months. [ABSTRACT FROM AUTHOR]

We studied long-term (64.5 weeks) biodegradation of diesel fuel, diesel/biodiesel blends (B10-B90) and biodiesel fuels in urban soil microcosms containing indigenous microorganisms, or indigenous microorganisms augmented with a hydrocarbon-degrading bacterial community. Mineralization extent (mmol of CO 2 per day) of B10-B30 blends was smaller compared with diesel fuel at both short- (28 days) and long-term (109 days), and increased with biodiesel content. Priming with hydrocarbon degraders accelerated mineralization in the short-term (by up to 140%), with highest influence using blends with lower biodiesel content, but did not significantly influence kinetics and mineralization extent in the long-term. Although the biodiesel fraction was degraded completely within 64.5 weeks, 3–12% of the total aromatic and aliphatic hydrocarbons remained in the microcosms. Barcoded 16S rRNA gene MiSeq sequencing analysis revealed a significant effect of blend type on the community structure, with a marked enrichment of Sphingobacteriia and Actinobacteria classes. However, no significant influence was determined in the long-term, suggesting that the inoculated bacterial community may not have survived. Our findings show that biodiesel is preferentially degraded in urban soil and suggest that the value of bioaugmentation for bioremediating biodiesel fuels with hydrocarbon-degrading bacteria is limited to short-term exposures to lower (B10-B30) blends. Unlabelled Image • Long-term (64.5 weeks) biodegradation of diesel/biodiesel in urban soil was studied. • 3–12% of the total aromatic and aliphatic hydrocarbons remained in the microcosms. • Effect of bioaugmentation was evaluated. • MiSeq sequencing analysis revealed a significant effect of blend type. • No significant influence of bioaugmentation was determined in the long-term. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the influence of Trichoderma viride on the metabolic activity and the community dynamics of soil bacteria during polyaromatic hydrocarbons (PAHs) biodegradation. Sixteen PAHs were introduced into soil microcosms mimicking natural conditions to achieve an initial concentration of 2000 mg kg −1 of soil. After 12 months of treatment, the efficiency of PAH removal was of 78% for the microcosms inoculated with a PAH-degrading bacterial consortium designated S3, 64% for those inoculated with the consortium S3 + T. viride , whereas an efficiency of only 47% was achieved in the microcosms inoculated with T. viride alone. Flow cytometry analysis of the bacterial metabolic activities, expressed as the oxidation-reduction potential, allowed differentiating single cells with regard to their metabolic activities. Prior to its introduction in soil microcosms, the consortium S3 consisted of 195 bacterial species which were identified by employing next generation sequencing (MiSeq, Illumina). It has been established that significant changes in the composition of the bacterial community occurred during the biodegradation process when it was carried out in the presence of T. viride . After such treatment only 73 bacterial species were identified from the metabiome, with the dominance of Stenotrophomonas retroflexus (47.46%), Ochrobactrum intermedium (25.83%) and Citrobacter freundii (19.87%). T. viride was able to degrade PAHs; however its presence mainly contributed to modify the bacterial metabiome via antagonistic interactions with the bacteria, which notably reduced the biodegradation efficiency and biodiversity in the microcosms. [ABSTRACT FROM AUTHOR]

Knowledge about biodegradability of ionic liquids (ILs) in terrestrial systems is limited. Here, using urban park soil microcosms spiked with either ammonium- or phosphonium-based ILs [didecyldimethylammonium 3-amino-1,2,4-triazolate, benzalkonium 3-amino-1,2,4-triazolate, trihexyl(tetradecyl)phosphonium chloride, or trihexyl(tetradecyl)phosphonium 1,2,4-triazolate], we studied their (i) 300-day primary biodegradation, and (ii) influence on CO 2 evolution from the microcosms. The primary biodegradation ranged from 21 to 33% of total compound in the dissolved phase. The evolution of CO 2 from spiked microcosms was either lower or within the range of background soil respiration, indicating no or small mineralization of the parent compounds and/or their metabolites, and their negligible or small toxicity to soil microorganisms. Our results suggest the potential for persistence of the four studied ILs in urban park soils. [ABSTRACT FROM AUTHOR]

Highlights: [•] The wastewater are characterized by a high concentration of nitrates. [•] The denitrification rate was at 44mgNg−1 dmd−1. [•] The microbial consortium were characterized by a diverse metabolic activity. [•] Shifts in the bacterial community dynamics of the consortium could be observed. [Copyright &y& Elsevier]

Abstract: Surfactant-mediated treatment increases hydrocarbon solubilization and potentially facilitates biodegradation, unless toxic co-contaminants inhibiting microbial activity are present in the hydrocarbon mixture. We assessed the effect of rhamnolipids on the performance of a bacterial consortium degrading diesel fuel employed as a model hydrocarbon-rich effluent, co-contaminated with toxic phenol, 4-chlorophenol (4-CP) or 2,4-dichlorophenol (2,4-DCP). This approach led to the unexpected finding that rhamnolipids reduced toxicity of 4-CP and 2,4-DCP to the hydrocarbon-degrading cells. The facts that rhamnolipids decreased diesel fuel – water partition coefficient (K FW) of 4-CP and 2,4-DCP and modified aggregate size distribution profiles of the dispersed diesel fuel – chlorinated phenols solutions, suggest the existence of specific interactions between rhamnolipids and the co-contaminants. Due to the polar nature of 4-CP and 2,4-DCP, possible explanations involve adsorption of 4-CP and 2,4-DCP on the surface of biosurfactant aggregates. This property of rhamnolipids is of interest to those using biosurfactants for microbial treatment of hydrocarbon-rich wastewaters co-contaminated with toxic compounds. [Copyright &y& Elsevier]