Wastewater valorization by pure bacterial cultures to Extracellular Polymeric Substances (EPS) with high emulsifying potential and flocculation activities

Nowadays much effort has been devoted for the development of cost-effective and environmentally friendly processes to obtain extracellular polymeric substances (EPS) with high emulsifying and flocculation activities. The aim of this study was to evaluate the capacity of bacterial strains previously isolated from oil-contaminated areas to produce EPS with high emulsification and bioflocculant properties during cultivation in domestic and bilge wastewater and in industrial crude glycerol. A total of seven bacterial strains were screened for EPS production, from which two strains, Pseudomonas aeruginosa LVD-10 and Enterobacter sp. SW, were selected as potential EPS producers. EPS with high emulsifying capacity in olive oil (a maximum of 96.6 and 89.8% for strain SW and LVD-10, respectively) was produced using bilge wastewater as substrate. EPS with a slightly lower emulsifying capacity was obtained using crude glycerol. In addition, the flocculation activity of the EPS extracted from strains LVD-10 and SW grown on crude glycerol was considerably higher (81.6 and 73.3%, respectively) than that obtained with other substrates. This is the first study that points out that EPS with emulsifying and flocculation potential activity can be produced from bilge wastewater and crude glycerol. The production of biopolymers with broad biotechnological applications using low-cost substrates can be a means to valorise waste streams.info:eu-repo/semantics/publishedVersio

Assessment of Bilge Water Degradation by Isolated Citrobacter sp. and Two Indigenous Strains and Identification of Organic Content by GC-MS

Bilge water is oily saline wastewater accumulated on the hull at the bottom of a vessel, generated from leakage from pipes and engines and wash-down freshwater containing cleaning solvents. The present study focused on isolating microorganisms from oil-contaminated sites and indigenous species from raw bilge water and assessment of their ability to biodegrade bilge water. Using phenanthrene as a carbon source Citrobacter species was isolated from oil-contaminated sites and its optimum growth condition was found. The results indicated significant tolerance of the bacterium which presented great biodegradation ability for the tested carbon source. At high salinity (33 g L−1 of NaCl), sufficient phenathrene removal was achieved (81%), whereas variation of pH from 5 to 10 did not affected the survival of the microorganism. Regarding the effect of temperature and nutrients, Citrobacter sp. was better adapted at 30◦ C, while lack of nutrients presented a negative impact on its growth. Halomonas and Exiguobacterium sp. were isolated from real bilge water using phenanthrene and phenol as a carbon source. The isolated strains independently exposed to high and low range bilge water pointed out around 83% and 53% chemical oxygen demand (COD) removal, respectively. Analysis of untreated bilge water by gas chromatography-mass spectrometry (GC-MS) was carried out, and the results confirmed the presence of organic compounds having a high similarity with Heptane, N-hexadecanoic acid, Methyl isobutyl Ketone and 1-butoxy-2-propanol. Chromatographic analysis of treated bilge water after exposure to isolated strains indicated the existence of new compounds. These metabolites presented high similarity with N-hexadecanoic, methyl ester, N-hexadecanoic and Octadecanoic acid methyl ester

Insights into the metabolic basis of the halotolerant Pseudomonas aeruginosa strain LVD-10 during toluene biodegradation

In this work a Pseudomonas aeruginosa strain (LVD-10) has been isolated from activated sludge, based on its capability to biodegrade toluene under extreme conditions. In 0, 20 and 40gL-1 NaCl the percentage of toluene removal reached 86%, 98% and 89% within 24h, respectively. Interestingly, the removal of toluene occurred significantly faster compared to biomass growth, while the strain achieved 79.1% and 91.7% of 1mLL-1 diesel removal after 7 days at 0 and 30gL-1 NaCl, respectively. The pathways used by LVD-10 were determined through PCR amplification of genes that encode key enzymes involved in aromatics degradation and genes of the Quorum Sensing (QS) system. The genes XylE1, 1,2-CTD, 2,3-CTD, rhlR1 and rhlR2 were detected in LVD-10 whereas tbmD, TodC1 and Rmo were not found. The transcription level of genes measured by Q-PCR did not show any significant variation in gene expression of cells stimulated with salinity conditions of 30gL-1 NaCl. However, when NaCl was increased to 50gL-1 the genes were significantly down-regulated 48h after toluene induction, while the expression of genes was restored to normal levels at 120h. Furthermore, the expression of genes RhlI and RhlR2, which have been proposed to be involved in the Quorum Sensing (QS) system of P. aeruginosa, indicates that the strain has great ability to tolerate toxic environments as well as to perform efficient degradation of aromatic hydrocarbons

Biodegradation of bilge water: Batch test under anaerobic and aerobic conditions and performance of three pilot aerobic Moving Bed Biofilm Reactors (MBBRs) at different filling fractions

The bilge water that is stored at the bottom of the ships is saline and greasy wastewater with a high Chemical Oxygen Demand (COD) fluctuations (2–12 g COD L−1). The aim of this study was to examine at a laboratory scale the biodegradation of bilge water using first anaerobic granular sludge followed by aerobic microbial consortium (consisted of 5 strains) and vice versa and then based on this to implement a pilot scale study. Batch results showed that granular sludge and aerobic consortium can remove up to 28% of COD in 13 days and 65% of COD removal in 4 days, respectively. The post treatment of anaerobic and aerobic effluent with aerobic consortium and granular sludge resulted in further 35% and 5% COD removal, respectively. The addition of glycine betaine or nitrates to the aerobic consortium did not enhance significantly its ability to remove COD from bilge water. The aerobic microbial consortium was inoculated in 3 pilot (200 L) Moving Bed Biofilm Reactors (MBBRs) under filling fractions of 10%, 20% and 40% and treated real bilge water for 165 days under 36 h HRT. The MBBR with a filling fraction of 40% resulted in the highest COD decrease (60%) compared to the operation of the MBBRs with a filling fraction of 10% and 20%. GC-MS analysis on 165 day pointed out the main organic compounds presence in the influent and in the MBBR (10% filling fraction) effluent

Insights into the metabolic basis of the halotolerant Pseudomonas aeruginosa strain LVD-10 during toluene biodegradation

In this work a Pseudomonas aeruginosa strain (LVD-10) has been isolated from activated sludge, based on its capability to biodegrade toluene under extreme conditions. In 0, 20 and 40gL-1 NaCl the percentage of toluene removal reached 86%, 98% and 89% within 24h, respectively. Interestingly, the removal of toluene occurred significantly faster compared to biomass growth, while the strain achieved 79.1% and 91.7% of 1mLL-1 diesel removal after 7 days at 0 and 30gL-1 NaCl, respectively. The pathways used by LVD-10 were determined through PCR amplification of genes that encode key enzymes involved in aromatics degradation and genes of the Quorum Sensing (QS) system. The genes XylE1, 1,2-CTD, 2,3-CTD, rhlR1 and rhlR2 were detected in LVD-10 whereas tbmD, TodC1 and Rmo were not found. The transcription level of genes measured by Q-PCR did not show any significant variation in gene expression of cells stimulated with salinity conditions of 30gL-1 NaCl. However, when NaCl was increased to 50gL-1 the genes were significantly down-regulated 48h after toluene induction, while the expression of genes was restored to normal levels at 120h. Furthermore, the expression of genes RhlI and RhlR2, which have been proposed to be involved in the Quorum Sensing (QS) system of P. aeruginosa, indicates that the strain has great ability to tolerate toxic environments as well as to perform efficient degradation of aromatic hydrocarbons