Bioremediation offers a viable alternative for the reduction of contaminants from the environment, particularly petroleum and its recalcitrant derivatives. In this study, the ability of a strain of ...Pseudomonas BUN14 to degrade crude oil, pristane and dioxin compounds, and to produce biosurfactants, was investigated. BUN14 is a halotolerant strain isolated from polluted sediment recovered from the refinery harbor on the Bizerte coast, north Tunisia and capable of producing surfactants. The strain BUN14 was assembled into 22 contigs of 4,898,053 bp with a mean GC content of 62.4%. Whole genome phylogeny and comparative genome analyses showed that strain BUN14 could be affiliated with two validly described Pseudomonas Type Strains, P. kunmingensis DSM 25974
and P. chloritidismutans AW-1
. The current study, however, revealed that the two Type Strains are probably conspecific and, given the priority of the latter, we proposed that P. kunmingensis DSM 25974 is a heteronym of P. chloritidismutans AW-1
. Using GC-FID analysis, we determined that BUN14 was able to use a range of hydrocarbons (crude oil, pristane, dibenzofuran, dibenzothiophene, naphthalene) as a sole carbon source. Genome analysis of BUN14 revealed the presence of a large repertoire of proteins (154) related to xenobiotic biodegradation and metabolism. Thus, 44 proteins were linked to the pathways for complete degradation of benzoate and naphthalene. The annotation of conserved functional domains led to the detection of putative genes encoding enzymes of the rhamnolipid biosynthesis pathway. Overall, the polyvalent hydrocarbon degradation capacity of BUN14 makes it a promising candidate for application in the bioremediation of polluted saline environments.
A number of
strains function as inoculants for biocontrol, biofertilization, and phytostimulation, avoiding the use of pesticides and chemical fertilizers. Here, we present a new metabolically ...versatile plant growth-promoting rhizobacterium,
S211, isolated from a pesticide contaminated artichoke field that shows biofertilization, biocontrol and bioremediation potentialities. The S211 genome was sequenced, annotated and key genomic elements related to plant growth promotion and biosurfactant (BS) synthesis were elucidated. S211 genome comprises 5,948,515 bp with 60.4% G+C content, 5306 coding genes and 215 RNA genes. The genome sequence analysis confirmed the presence of genes involved in plant-growth promoting and remediation activities such as the synthesis of ACC deaminase, putative dioxygenases, auxin, pyroverdin, exopolysaccharide levan and rhamnolipid BS. BS production by
S211 grown on olive mill wastewater based media was effectively optimized using a central-composite experimental design and response surface methodology (RSM). The optimum conditions for maximum BS production yield (720.80 ± 55.90 mg/L) were: 0.5% (v/v) inoculum size, 15% (v/v) olive oil mill wastewater (OMWW) and 40°C incubation temperature at pH 6.0 for 8 days incubation period. Biochemical and structural characterization of S211 BS by chromatography and spectroscopy studies suggested the glycolipid nature of the BS.
rhamnolipid was stable over a wide range of temperature (40-90°C), pH (6-10), and salt concentration (up to 300 mM NaCl). Due to its low-cost production, emulsification activities and high performance in solubilization enhancement of chemical pesticides, the indigenous BS-producing PGPR S211 could be used as a promising agent for environmental bioremediation of pesticide-contaminated agricultural soils.
Microbial electrochemistry and microbial electrochemical technology (MET) is an interdisciplinary research area that has been intensively growing in the past decades. However, in some regions like ...Latin America & Caribbean (LA & C) and Africa, capacity building within this realm is scarce. Hence, the advancement of research and development in this field is slower and less established than in Europe, Asia Pacific, or North America. This is of special concerns as MET may be important components of a biobased circular economy. Here, we highlight the specific challenges researchers in LA & C and Africa have to face and put these into perspective to their general research and education environment. Subsequently, we discuss possible solutions to these challenges and showcase examples on how to overcome these. We hope that thereby awareness can be created and how each researcher in the field around the globe can individually contribute to decrease the gap in capacity building in LA & C and Africa compared to other regions.
Bioelectrochemical systems (BESs), rather than physicochemical processes, are used for wastewater remediation, electricity production, and zero carbon dioxide emission. Textile effluents contain ...organic and inorganic compounds that can fuel BESs. The main goal of this study was to understand the interplay between the anode material, its surface area, the potential applied to the working electrode (WE), and the concentration of the co-substrate, and how these factors lead to the formation of highly efficient thermohalophilic bioanodes (THB) retrieved from Chott El Djerid (SCD) hypersaline sediment for the treatment of synthetic textile wastewater. To this end, twenty-seven bioanode formation experiments were designed using a Box-Behnken matrix and response surface methodology to understand concomitant interactions. All experiments were conducted in electrochemical reactors of final volume 750 mL inoculated with 80% of enrichment medium containing three azo dyes at a concentration of 300 ppm and 20% of biocatalyst microbial SCD source, at 45 °C. The optimal levels were predicted using NemrodW software as carbon felt (CF) anode material, 6 cm2 anode surface, 7 g/L glucose concentration, and −0.1 V applied potential. These theoretical results were experimentally validated, using maximum current output of 5.23 ± 0.30 A/m2, decolorization rate of 100%, and a chemical oxygen demand (COD) removal rate of 96 ± 1%. Illumina Miseq results revealed that bacterial community harbored the bioanode was dominated at phylum level by Firmicutes (67.1%). At the species level, the biofilm was mainly colonized by Orenia metallireducens species (59.5%). Obtained findings show a promising application of THB in the degradation of recalcitrant molecules as well as for the energy recovery.
The present study examines the use of waste cooking oil (WCO) as a substrate for medium-chain-length polyhydroxyalkanoates (mcl-PHA) production by
Pseudomonas rhizophila
S211. The genome analysis ...revealed that the S211 strain has a mcl-PHA cluster (
phaC1ZC2DFI
) encoding two class II PHA synthases (PhaC1 and PhaC2) separated by a PHA depolymerase (PhaZ), a transcriptional activator (PhaD) and two phasin-like proteins (PhaFI). Genomic annotation also identified a gene encoding family I.3 lipase that was able to hydrolyze plant oils and generate fatty acids as favorable carbon sources for cell growth and PHA synthesis via β-oxidation pathway. Using a three-variable Doehlert experimental design, the optimum conditions for mcl-PHA accumulation were achieved in 10% of WCO-based medium with an inoculum size of 10% and an incubation period of 48 h at 30 °C. The experimental yield of PHA from WCO was 1.8 g/L close to the predicted yield of 1.68 ± 0.14 g/L. Moreover,
1
H nuclear magnetic resonance spectroscopy analysis confirmed the extracted mcl-PHA. Overall, this study describes
P. rhizophila
as a cell factory for biosynthesis of biodegradable plastics and proposes green and efficient approach to cooking oil waste management by decreasing the cost of mcl-PHA production, which can help reduce the dependence on petroleum-based plastics.
The aim of this study was to characterize novel cellulase-producing bacteria isolated from desertic environments in Tunisia, and then applied for cellulosic ethanol production. In the first instance, ...27 alkali-thermo-halotolerant bacterial strains, belonging to Bacillaceae family, were screened on agar plates containing carboxymethyl cellulose as the sole carbon source. The selected high cellulase producing bacteria were identified as
Bacillus mojavensis
AG21,
Bacillus vallismortis
J77,
Bacillus sonorensis
7.26 and
Bacillus safiensis
AJ49. Production of cellulolytic enzymes by selected bacteria was further tested in submerged cultures with
Posidonia oceanica
leaves,
Peganum Harmala
biomass,
Stevia rebaudiana
leaves (SRL), Olive cake, Spent coffee ground and peanut hulls as low-cost cellulosic substrates. Response surface methodology was applied to evaluate the effect of SRL concentration, NaCl concentration, cultivation pH and temperature on carboxymethyl cellulase production and to optimize enzyme yields by selected bacteria. Maximum cellulase production yields of about 1890, 1642, 1516 and 1455 IU/L were recorded for
B. mojavensis
AG21,
B.vallismortis
J77,
B. sonorensis
7.26 and
B. safiensis
AJ49, respectively. Production of reducing sugars by hydrolysis of
Stevia rebaudiana
leaves with bacterial cellulases and commercially fungal cellulases was investigated and compared. The overall reducing sugar yields of
B. mojavensis, B.vallismortis, B. sonorensis, B. safiensis, Aspergillus niger
and
Trichoderma reesei
treated- SSR biomasses reached 3620 ± 181, 3040 ± 164, 3656 ± 164, 2654 ± 106, 2646 ± 145 and 2253 ± 123 mg/L respectively. The unique property of cellulase-producing extremotolerant bacteria, proves the potential candidature for current mainstream agricultural cellulosic biomass conversion into fuel ethanol.
The treatment of textile wastewater (TWW) loaded with recalcitrant azo dyes in bioelectrochemical systems (BES) rather than in physicochemical processes is a low-cost and environmentally friendly ...process. The main objective of this study is to investigate the potential of different saline sediments collected from extreme Tunisian environments for the formation of bioanodes capable ofsimultaneous azo dyes degradation and electric current generation in synthetic (STWW) and real textile wastewaters (RTWW) characterized by a varied composition of azo dyes and a high salinity. The obtained bioanodes and anolytes were studied comparatively by electrochemical, microscopic, analytical, and molecular tools.Based on the UV–visible spectra analysis, the breakdown of the azo bond was confirmed. With RTWW, the BES achieved a chemical oxygen demand (COD) abatement rate of 85%with a current density of 2.5 A/m2. Microbial community analysis indicated that a diverse community of bacteria was active for effluent treatment coupled with energy production. At the phylum level, the electrodes were primarily colonized by proteobacteria and firmicutes, which are the two phyla most involved in bioremediation. The analysis of the microbial community also showed the abundance of Marinobacter hydrocarbonoclasticus and Marinobacter sp. species characterized by their high metabolic capacity, tolerance to extremophilic conditions, and role in hydrocarbon degradation.
In this work, a native exopolysaccharide (nEPS) produced by Halomonas desertis G11 isolated from a Tunisian extreme environment was modified by gamma irradiation. Characterization as well as the ...antioxidant and antitumor activities of nEPS and its gamma-irradiated derivatives (iEPSs) were comparatively evaluated. In vitro and in vivo antioxidant potentials were determined by using different methods and through different antioxidant enzymes. The antitumor activity was checked against a human colon cancer cell line. Analyses of the complete genome sequence were carried out to identify genes implicated in the production of nEPS. Thus, the genomic biosynthesis pathway and the export mechanism of nEPS were proposed. Analyses of irradiation data showed that iEPSs acquired new functional groups, lower molecular weights, and gained significantly (p < 0.05) higher antioxidant and antitumor abilities compared with nEPS. These findings provide a basis for using iEPSs as novel pharmaceutical agents for human therapies.
The plant cell wall degradation by extremophilic bacteria is an interesting biological process that is highly relevant for biofuel generation from agrowastes. The halotolerant actinobacterium
...Microbacterium metallidurans
TL13, previously isolated from a tannery wastewater, was studied for its capacity to degrade cellulose and hemicellulose based on genomic and experimental enzymatic analyses. Genome annotation of TL13 strain in dbCAN 2 meta server revealed a total of 158 genes encoding CAZymes including 83 glycosidic hydrolases (GH), 6 carbohydrate esterases, and 25 carbohydrate-binding proteins. Cooperative hydrolytic enzymes required for cellulose degradation such as GH1 and GH3 β-glucosidases and GH6 endo-β-1,4-glucanase were found in TL13 genome. For hemicellulases involved in xylan backbone degradation, the related genes were annotated as endo-1,4-β-xylanase, β-xylosidase, α-arabinofuranosidase, acetyl xylan esterase, and α-galactosidase. In TL13 strain, osmoprotectants are taken up by the ProU (ProVWX) transport systems. The synthesis of the powerful compatible solute glycine betaine, which protects the actinobacterium against the high-osmolarity stress, proceeds by the action of three enzymes consisting of choline high‐affinity transport system (BetT), choline dehydrogenase (BetA), and betaine aldehyde dehydrogenase (BetB). The presence of genes encoding enzymes involved in osmoadaptation and cellulose/hemicellulose degradation in the TL13 genome is well synchronized with the enzymatic assays, in which CMCase, β-glucosidase, and xylanase activities were slightly higher under saline conditions compared to controls. Furthermore, the polysaccharide-degrading enzymes of TL13 strain revealed an efficient hydrolysis of untreated
Posidonia oceanica
waste into fermentable sugars compared to commercial enzymes. The bioethanol production reached 33.35% of the theoretical maximum yield. These genomic and experimental findings make
Microbacterium
biocatalysts promising green tools for seagrass-based biorefinery.
The textile and clothing industry is the first manufacture sector in Tunisia in terms of employment and number of enterprises. It generates large volumes of textile dyeing wastewater (TDWW) ...containing high concentrations of saline, alkaline, and recalcitrant pollutants that could fuel tenacious and resilient electrochemically active microorganisms in bioanodes of bioelectrochemical systems. In this study, a designed hybrid bacterial halothermotolerant bioanode incorporating indigenous and exogenous bacteria from both hypersaline sediment of Chott El Djerid (HSCE) and TDWW is proposed for simultaneous treatment of real TDWW and anodic current generation under high salinity. For the proposed halothermotolerant bioanodes, electrical current production, chemical oxygen demand (COD) removal efficiency, and bacterial community dynamics were monitored. All the experiments of halothermotolerant bioanode formation have been conducted on 6 cm
carbon felt electrodes polarized at -0.1 V/SCE and inoculated with 80% of TDWW and 20% of HSCE for 17 days at 45°C. A reproducible current production of about 12.5 ± 0.2 A/m
and a total of 91 ± 3% of COD removal efficiency were experimentally validated. Metagenomic analysis demonstrated significant differences in bacterial diversity mainly at species level between anodic biofilms incorporating allochthonous and autochthonous bacteria and anodic biofilm containing only autochthonous bacteria as a control. Therefore, we concluded that these results provide for the first time a new noteworthy alternative for achieving treatment and recover energy, in the form of a high electric current, from real saline TDWW.
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