Biodegradation of used engine oil by novel strains of Ochrobactrum anthropi HM-1 and Citrobacter freundii HM-2 isolated from oil-contaminated soil

Isolation and characterization of mercury and multidrug-resistant Citrobacter freundii strains from tannery effluents in Kolkata, India

Mercury (Hg) is one of the most potent toxic heavy metals that distresses livestock, humans, and ecological health. Owing to uncontrolled exposure to untreated tannery industrial effluents, metals such as Hg are increasing in nature and are, therefore, becoming a global concern. As a result, understanding the thriving microflora in that severe condition and their characteristics becomes immensely important. During the course of this study, two Hg-resistant bacteria were isolated from tannery wastewater effluents from leather factories in Kolkata, India, which were able to tolerate 2.211 × 10- 3 M (600 µg/ml) Hg. 16 S rDNA analysis revealed strong sequence homology with Citrobacter freundii, were named as BNC22A and BNC22C for this study. In addition they showed high tolerance to nickel (Ni) and Chromium (Cr) at 6.31 × 10- 3 M (1500 µg/ml) and 6.792 × 10- 3 M (2000 µg/ml) respectively. However, both the isolates were sensitive to arsenic (As) and cadmium (Cd). Furthermore, their antibiotic sensitivity profiles reveal a concerning trend towards resistance to multiple drugs. Overuse and misuse of antibiotics in healthcare systems and agriculture has been identified as two of the main reasons for the decline in efficacy of antibiotics. Though their ability to produce lipase makes them industrially potent organisms, their competence to resist several antibiotics and metals that are toxic makes this study immensely relevant. In addition, their ability to negate heavy metal toxicity makes them potential candidates for bioremediation. Finally, the green mung bean seed germination test showed a significant favourable effect of BNC22A and BNC22C against Hg-stimulated toxicity.

Effect of ultra-violet light radiation on Scenedesmus vacuolatus growth kinetics, metabolic performance, and preliminary biodegradation study

This study presents the effect of ultra-violet (UV) light radiation on the process kinetics, metabolic performance, and biodegradation capability of Scenedesmus vacuolatus. The impact of the UV radiation on S. vacuolatus morphology, chlorophyll, carotenoid, carbohydrates, proteins, lipid accumulation, growth rate, substrate affinity and substrate versatility were evaluated. Thereafter, a preliminary biodegradative potential of UV-exposed S. vacuolatus on spent coolant waste (SCW) was carried out based on dehydrogenase activity (DHA) and total petroleum hydrocarbon degradation (TPH). Pronounced structural changes were observed in S. vacuolatus exposed to UV radiation for 24 h compared to the 2, 4, 6, 12 and 48 h UV exposure. Exposure of S. vacuolatus to UV radiation improved cellular chlorophyll (chla = 1.89-fold, chlb = 2.02-fold), carotenoid (1.24-fold), carbohydrates (4.62-fold), proteins (1.44-fold) and lipid accumulations (1.40-fold). In addition, the 24 h UV exposed S. vacuolatus showed a significant increase in substrate affinity (1/Ks) (0.959), specific growth rate (µ) (0.024 h-1) and biomass accumulation (0.513 g/L) by 1.50, 2 and 1.9-fold respectively. Moreover, enhanced DHA (55%) and TPH (100%) degradation efficiency were observed in UV-exposed S. vacuolatus. These findings provided major insights into the use of UV radiation to enhance S. vacuolatus biodegradative performance towards sustainable green environment negating the use of expensive chemicals and other unfriendly environmental practices.

Chemotactic response of p-nitrophenol degrading Pseudomonas asiatica strain PNPG3 through phenotypic and genome sequence-based in silico studies

The Pseudomonas asiatica strain PNPG3 was documented to possess chemotactic potential toward p-nitrophenol (PNP), and other nitroaromatic compounds. Initial screening with drop plate and swarm plate assays demonstrated significant movement of the strain toward the test compounds. A quantitative capillary assay revealed the highest chemotactic potential of the strain toward 4-Aminophenol (4AP), (CI: 12.33); followed by p-benzoquinone (PBQ), (CI: 6.8); and PNP, (CI: 5.33). Gene annotation revealed the presence of chemotactic genes (Che), (Methyl-accepting Proteins) MCPs, rotary motor proteins, and flagellar proteins within the genome of strain PNPG3. The chemotactic machinery of the strain PNPG3 comprised of thirteen Che genes, twenty-two MCPs, eight rotary motors, and thirty-four flagellar proteins that are involved in sensing chemoattractant. Two chemotactic gene clusters were recorded in the genome, of which the major cluster consisted of two copies of CheW, one copy of CheA, CheY, CheZ, one MotD gene, and several Fli genes. Various conserved regions and motifs were documented in them using a standard bioinformatics tool. Genes involved in the chemotaxis of strain PNPG3 were compared with three closely related strains and one distantly related strain belonging to Burkholderia sp. Considering these phenotypic and genotypic data, it can be speculated that it is metabolism-dependent chemotaxis; and that test compound activated the Che. This study indicated that strain PNPG3 could be used as a model organism for the study of the molecular mechanism of chemotaxis and bioremediation of PNP.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03809-3.

Production, characterization, and kinetic modeling of biosurfactant synthesis by Pseudomonas aeruginosa gi |KP 163922|: a mechanism perspective

Kinetic studies and modeling of production parameters are essential for developing economical biosurfactant production processes. This study will provide a perspective on mechanistic reaction pathways to metabolize Waste Engine Oil (WEO). The results will provide relevant information on (i) WEO concentration above which growth inhibition occurs, (ii) chemical changes in WEO during biodegradation, and (iii) understanding of growth kinetics for the strain utilizing complex substrates. Laboratory scale experiments were conducted to study the kinetics and biodegradation potential of the strain Pseudomonas aeruginosa gi |KP 163922| over a range (0.5-8% (v/v)) of initial WEO concentration for 168 h. The kinetic models, such as Monod, Powell, Edward, Luong, and Haldane, were evaluated by fitting the experimental results in respective model equations. An unprecedented characterization of the substrate before and after degradation is presented, along with biosurfactant characterization. The secretion of biosurfactant during the growth, validated by surface tension reduction (72.07 ± 1.14 to 29.32 ± 1.08 mN/m), facilitated the biodegradation of WEO to less harmful components. The strain showed an increase in maximum specific growth rate (µ_max) from 0.0185 to 0.1415 h^-1 upto 49.92 mg/L WEO concentration. Maximum WEO degradation was found to be ~ 94% gravimetrically. The Luong model (adj. R² = 0.97) adapted the experimental data using a non-linear regression method. Biochemical, ¹H NMR, and FTIR analysis of the produced biosurfactant revealed a mixture of mono- and di- rhamnolipid. The degradation compounds in WEO were identified using FTIR, ¹H NMR, and GC-MS analysis to deduce the mechanism.

Isolation and characterization of fungi and bacteria able to grow on media containing gasoline and diesel fuel

Petroleum products are significant environmental pollutants. This study aimed to isolate microorganisms able to grow on media containing gasoline and diesel fuel. Microorganisms were isolated from soils sampled near gasoline and diesel pumps. Bacterial isolates were characterized and tested on media containing concentrations ranging from 10 to 100 % gasoline and diesel fuel and combinations of both 50/50 % and 25/25/50 % (gasoline/ diesel/ Mueller Hinton broth). Results showed that microbial isolates belong to the genera Pseudomonas, Bacillus, Staphylococcus, Micrococcus, Flavobacterium, Actinobacteria, Penicillium, Hansfordia and Alternaria. Pseudomonas spp. and Bacillus spp. showed the ability to grow on both products up to the concentration of 80 %. However, no growth was noticed above that concentration and on both mixtures. Throughout this study, it has been shown that using a selective screening method for microorganisms able to grow on pollutants can present a significant advantage for bioremediation. Keywords: Pollution; gasoline; diesel; microorganisms.

Kerosene Biodegradation by Highly Efficient Indigenous Bacteria Isolated From Hydrocarbon-Contaminated Sites

Kerosene is widely used in Ethiopia as a household fuel (for lighting and heating), as a solvent in paint and grease, and as a lubricant in glass cutting. It causes environmental pollution and escorts to loss of ecological functioning and health problems. Therefore, this research was designed to isolate, identify, and characterize indigenous kerosene-degrading bacteria that are effective in cleaning ecological units that have been contaminated by kerosene. Soil samples were collected from hydrocarbon-contaminated sites (flower farms, garages, and old-aged asphalt roads) and spread-plated on mineral salt medium (Bushnell Hass Mineral Salts Agar Medium: BHMS), which consists of kerosene as the only carbon source. Seven kerosene-degrading bacterial species were isolated, 2 from flower farms, 3 from garage areas, and 2 from asphalt areas. Three genera from hydrocarbon-contaminated sites were identified, including Pseudomonas, Bacillus, and Acinetobacter using biochemical characterization and the Biolog database. Growth studies in the presence of various concentrations of kerosene (1% and 3% v/v) showed that the bacterial isolates could metabolize kerosene as energy and biomass. Thereby, a gravimetric study was performed on bacterial strains that proliferated well on a BHMS medium with kerosene. Remarkably, bacterial isolates were able to degrade 5% kerosene from 57.2% to 91% in 15 days. Moreover, 2 of the most potent isolates, AUG2 and AUG1, resulted in 85% and 91% kerosene degradation, respectively, when allowed to grow on a medium containing kerosene. In addition, 16S rRNA gene analysis indicated that strain AAUG1 belonged to Bacillus tequilensis, whereas isolate AAUG showed the highest similarity to Bacillus subtilis. Therefore, these indigenous bacterial isolates have the potential to be applied for kerosene removal from hydrocarbon-contaminated sites and the development of remediation approaches.

Biotreatment of oily sludge by a bacterial consortium: Effect of bioprocess conditions on biodegradation efficiency and bacterial community structure

We studied the biodegradation of oily sludge generated by a petroleum plant in Bahrain by a bacterial consortium (termed as AK6) under different bioprocess conditions. Biodegradation of petroleum hydrocarbons in oily sludge (C₁₁-C₂₉) increased from 24% after two days to 99% after 9 days of incubation in cultures containing 5% (w/v) of oily sludge at 40°C. When the nitrogen source was excluded from the batch cultures, hydrocarbon biodegradation dropped to 45% within 7 days. The hydrocarbon biodegradation decreased also by increasing the salinity to 3% and the temperature above 40°C. AK6 tolerated up to 50% (w/v) oily sludge and degraded 60% of the dichloromethane-extractable oil fraction. Illumina-MiSeq analyses revealed that the AK6 consortium was mainly composed of Gammaproteobacteria (ca. 98% of total sequences), with most sequences belonging to Klebsiella (77.6% of total sequences), Enterobacter (16.7%) and Salmonella (5%). Prominent shifts in the bacterial composition of the consortium were observed when the temperature and initial sludge concentration increased, and the nitrogen source was excluded, favoring sequences belonging to Pseudomonas and Stenotrophomonas. The AK6 consortium is endowed with a strong oily sludge tolerance and biodegradation capability under different bioprocess conditions, where Pseudomonas spp. appear to be crucial for hydrocarbon biodegradation.

Biodegradation of p-nitrophenol by a member of the genus Brachybacterium, isolated from the river Ganges

A p-nitrophenol (PNP) degrading halotolerant, Gram-variable bacterial strain designated as DNPG3, was isolated from a water sample collected from the river Ganges in Hooghly, West Bengal (WB), India, by enrichment culture technique. Based on 16S rRNA gene sequence analysis (carried out at EzTaxon server and Ribosomal data base project site), the strain DNPG3 was identified as Brachybacterium sp., with B. zhongshanense strain JBT (97.08% identity) as it is nearest phylogenetic relative. The strain could tolerate up to 3 mM of PNP, while the optimal growth for the strain was recorded as 0.25 mM. The strain could carry out biodegradation of PNP with concomitant release of nitrite and p-benzoquinone (PBQ) was detected as a hydrolysis product. Under the catabolic condition, it could carry out 36% biodegradation of PNP within 144 h, while, under co-metabolic condition (with glucose), 100% biodegradation was achieved within 48 h at 30 °C. Calcium alginate bead-based cell immobilization studies (of the strain DNPG3) indicated complete biodegradation of PNP (under catabolic condition) within 26 h. This is the first report of PNP biodegradation by any representative strain of the genus Brachybacterium. The study definitely indicated that Brachybacterium sp. strain DNPG3 has biotechnological potential and the strain may be a suitable candidate for developing clean, green, eco-friendly, cost-effective bioremediation processes towards effective removal of PNP from the contaminated sites.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-022-03263-7.

Dendrobium officinale Endophytes May Colonize the Intestinal Tract and Regulate Gut Microbiota in Mice

Dendrobium officinale is a traditional Chinese medicine for treating gastrointestinal diseases by nourishing “Yin” and thickening the stomach lining. To study whether D. officinale endophytes can colonize the intestinal tract and regulate gut microbiota in mice, we used autoclave steam sterilizing and 60Co-γ radiation to eliminate D. officinale endophytes from its juice. Then, high-throughput ITS1-ITS2 rDNA and 16S rRNA gene amplicons were sequenced to analyze the microbial community of D. officinale endophytes and fecal samples of mice after administration of fresh D. officinale juice. Sterilization of D. officinale juice by autoclaving for 40 min (ASDO40) could more effectively eliminate the D. officinale endophytes and decrease their interference on the gut microbiota. D. officinale juice could increase beneficial gut microbiota and metabolites including short-chain fatty acids. D. officinale endophytes Pseudomonas mosselii, Trichocladium asperum, Titata maxilliformis, Clonostachys epichloe, and Rhodotorula babjevae could colonize the intestinal tract of mice and modulate gut microbiota after oral administration of the juice for 28 days. Thus, the regulatory effect of D. officinale juice on gut microbiota was observed, which provides a basis for inferring that D. officinale endophytes might colonize the intestinal tract and participate in regulating gut microbiota to treat diseases. Thus, this study further provides a new approach for the treatment of diseases by colonizing plant endophytes in the intestinal tract and regulating gut microbiota.

Bacterias aisladas de biosólidos de la PTAR San Fernando en Medellín-Colombia con capacidad para reducir cromo hexavalente

En las últimas décadas se ha trabajado activamente para reducir el impacto ambiental generado por las actividades antrópicas que constantemente liberan componentes tóxicos al ambiente generando inestabilidad y daños en la salud de las comunidades biológicas. Entre los diferentes contaminantes, los metales pesados revisten importancia en virtud de sus propiedades, que dificultan su degradación o transformación en otros compuestos menos tóxicos. El cromo es uno de los metales de mayor interés a nivel global por su uso en múltiples industrias. Los métodos convencionales que utilizan materiales cromados en sus procesos, no sólo arrojan cantidades considerables de residuos al ambiente, sino que dan poca cuenta de la fracción de Cr6+ presente en determinados ecosistemas. La biorremediación se ha propuesto como una alternativa económicamente viable y ambientalmente sostenible. El propósito del presente trabajo fue evaluar la capacidad de reducción de cromo por bacterias, aisladas de una matriz de biosólidos de la Planta de tratamiento de aguas residuales (PTAR) San Fernando en la ciudad de Medellín-Colombia. Muestras de biosólidos se cultivaron en Agar Nutritivo enriquecido con diferentes concentraciones de Cr6+. Las cepas que presentaron mayor tolerancia al cromo fueron aisladas para realizar ensayos de reducción por triplicado, monitoreando la concentración del metal en el tiempo. Se obtuvieron siete especies bacterianas diferentes dentro de las cuales se destacaron Staphylococcus saprophyticus, Ochrobactrum anthropi y Bacillus cereus por la capacidad de reducir Cr6+ a 96 h con eficiencias de 29.0%, 61.1% y 100%,  respectivamente.

Characterization of Dietzia maris AURCCBT01 from oil-contaminated soil for biodegradation of crude oil

A bacterial strain was isolated from an oil-contaminated site and on its' further characterization, exhibited the potential of synthesising metabolites and the ability to degrade crude oil. Its' morphological, biochemical and 16S rRNA analysis suggested that the bacterium belongs to Dietzia maris AURCCBT01. This strain rapidly grew in the medium supplemented with n-alkanes C14, C18, C20, C28 and C32 utilizing them as a sole carbon source and produced a maximum canthaxanthin pigment of 971.37 µg/L in the n-C14 supplemented medium and produced the lowest pigment yield of 389.48 µg/L in the n-C-32 supplemented medium. Moreover, the strain effectively degraded 91.87% of crude oil in 7 days. The emulsification activity of the strain was 25% with the highest cell surface hydrophobicity (70.26%) and it showed a decrease in surface tension, indicating that the biosurfactant production lowers the surface tension. This is the first report on the characterization of the strain, Dietzia maris AURCCBT01 and its' novelty of alkane degradation and simultaneous production of canthaxanthin pigment.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-021-02807-7.

Enhanced surface properties, hydrophobicity, and sorption behavior of ZnO nanoparticle-impregnated biomass support for oil spill treatment

Metallic nanoparticles (NPs) have gained significant attention in recent years due to their efficiency in the adsorption of water pollutants. Except for magnetic NPs, metallic NPs are rarely used in oil sorption studies, due to the difficulty in recovering the NPs from the treated water. This study reports for the first time the application of ZnONPs for oil spill treatment. The ZnONPs were impregnated onto Musa acuminata peel (MP) support to form a novel material (ZnOMP), which was utilized for the sorption of oil from synthetic oil spills. The as-prepared sorbents were characterized by the SEM, EDS, BET, FTIR, FE-SEM, TGA, and XRD techniques. The presence of 31.32-nm average-sized ZnONPs enhanced the oil uptake characteristics, with clear affinity for the oil phase in comparison to the pristine MP. A maximum sorption capacity of 4.146 g/g and 5.236 g/g was obtained for biosorbents MP and ZnOMP, respectively, which was higher than most reported sorbents. The Freundlich model presented the best fit for the isotherm data, while the pseudo-second-order model was most suited for the kinetics. The presence of competing heavy metal ions in solution did not have any significant effect on the oil sorption capacity onto ZnOMP. The sorption mechanism was attributed to absorption and hydrophobic interactions. ZnONPs impregnated onto the biomass enhanced the spontaneity of oil uptake at higher temperatures. Over 82% desorption of the oil contaminant from the biosorbents was achieved during recovery, using petroleum ether and n-pentane as eluents. Concisely, ZnONPs enhanced the uptake and hydrophobic characteristic of MP biomass and showed good recovery and reusability. Thus, the application of ZnONPs impregnated onto biosorbents in oil spill treatment is highly recommended.

Microbial glycoconjugates in organic pollutant bioremediation: recent advances and applications

The large-scale application of organic pollutants (OPs) has contaminated the air, soil, and water. Persistent OPs enter the food supply chain and create several hazardous effects on living systems. Thus, there is a need to manage the environmental levels of these toxicants. Microbial glycoconjugates pave the way for the enhanced degradation of these toxic pollutants from the environment. Microbial glycoconjugates increase the bioavailability of these OPs by reducing surface tension and creating a solvent interface. To date, very little emphasis has been given to the scope of glycoconjugates in the biodegradation of OPs. Glycoconjugates create a bridge between microbes and OPs, which helps to accelerate degradation through microbial metabolism. This review provides an in-depth overview of glycoconjugates, their role in biofilm formation, and their applications in the bioremediation of OP-contaminated environments.

Enhanced Bioavailability and Microbial Biodegradation of Polystyrene in an Enrichment Derived from the Gut Microbiome of Tenebrio molitor (Mealworm Larvae)

As the global threat of plastic pollution has grown in scale and urgency, so have efforts to find sustainable and efficient solutions. Research conducted over the past few years has identified gut environments within insect larvae, including Tenebrio molitor (yellow mealworms), as microenvironments uniquely suited to rapid plastic biodegradation. However, there is currently limited understanding of how the insect host and its gut microbiome collaborate to create an environment conducive to plastic biodegradation. In this work, we provide evidence that T. molitor secretes one or more emulsifying factor(s) (30-100 kDa) that mediate plastic bioavailability. We also demonstrate that the insect gut microbiome secretes factor(s) (<30 kDa) that enhance respiration on polystyrene (PS). We apply these insights to culture PS-fed gut microbiome enrichments, with elevated rates of respiration and degradation compared to the unenriched gut microbiome. Within the enrichment, we identified eight unique gut microorganisms associated with PS biodegradation including Citrobacter freundii, Serratia marcescens, and Klebsiella aerogenes. Our results demonstrate that both the mealworm itself and its gut microbiome contribute to accelerated plastic biodegradation. This work provides new insights into insect-mediated mechanisms of plastic degradation and potential strategies for cultivation of plastic-degrading microorganisms in future investigations and scale-up.

Decolourization of textile effluent using native microbial consortium enriched from textile industry effluent

A robust and efficient treatment process is required to address the problem of residual colour and avoid expensive post-treatment steps while dealing with textile effluents. In the present work, a novel microbial consortium enriched from textile effluent was used to optimize the process of decolourization under extreme conditions with minimum inputs. With PreTreatment Range (PTR) effluent as a carbon source and only 0.5 g/L yeast extract as external input, the process enabled 70-73% colour reduction (from 1910-1930 to 516-555 hazen) in dyeing unit wastewater. Unhindered performance at higher temperatures (30 °C-50 °C) and wide pH range (7-12) makes this process highly suitable for the treatment of warm and extremely alkaline textile effluents. No significant difference was observed in the decolourization efficiency for effluents from different batches (Colour: 1647-4307 hazen; pH-11.5-12.0) despite wide variation in nature and concentration of dyes employed. Long term (60 days) continuous mode performance monitoring at hydraulic retention time of 48 h in lab-scale bioreactor showed consistent colour (from 1734-1980 to 545-723 hazen) and chemical oxygen demand (1720-2170 to 669-844 mg/L) removal and consistently neutral pH of the treated water. Present study thus makes a significant contribution by uncovering the ability of native microbial consortium to reliably treat dye laden textile wastewater without any dilution or pre-treatment and with minimum external inputs. The results ensure easy applicability of this indigenously developed process at the industrial scale.

Characterization and application of rhamnolipid from Pseudomonas plecoglossicida BP03

The production of rhamnolipid (glycolipid) biosurfactant was achieved under optimized conditions from newly isolated bacteria (Pseudomonas plecoglossicida BP03) from rice mill effluent. The isolated biosurfactant was structurally characterized using FTIR and NMR spectroscopic studies. The obtained biosurfactant (1·39 g l^-1 ) showed a variety of applications including larvicidal and pupicidal activity against malarial vector (Anopheles sunadicus). It also exhibited antimicrobial activity against human pathogens, and possessed potent anti-biofilm activity against Staphylococcus aureus, Bacillus subtilis and Aeromonas hydrophila. The obtained biosurfactant showed a dose-dependent inhibition of exopolymeric substance (EPS) and growth curve in S. aureus. Furthermore, the cytotoxicity assays revealed that the biosurfactant exhibit a cytotoxic potency against the human fibroblastic sarcoma cells Ht-1080. An in silco analysis was also performed using Schrodinger maestro 9.3 against surface protein (SasG) of S. aureus, and the resultant analysis revealed an interactive docking score of -3·4 kcal mol^-1 . The obtained result indicates that the synthesized economically viable biosurfactant ensures excellent applications towards various fields.

Coal-Degrading Bacteria Display Characteristics Typical of Plant Growth Promoting Rhizobacteria

Coal mining produces large quantities of discard that is stockpiled in large dumps. This stockpiled material, termed coal discard, poses an environmental threat emphasising the need for appropriate bioremediation. Here, metagenomic analysis of the 16S rRNA from ten coal-degrading strains previously isolated from coal slurry from discard dumps and from the rhizosphere of diesel-contaminated sites was used to establish genetic relatedness to known plant growth-promoting (PGP) bacteria in the NCBI database. Measurement of indole and ammonium production and solubilisation of P and K were used to screen bacteria for PGP characteristics. BLAST analysis revealed ≥ 99% homology of six isolates with reference PGP strains of Bacillus, Escherichia, Citrobacter, Serratia, Exiguobacterium and Microbacterium, while two strains showed 94% and 91% homology with Proteus. The most competent PGP strains were Proteus strain ECCN 20b, Proteus strain ECCN 23b and Serratia strain ECCN 24b isolated from diesel-contaminated soil. In response to L-trp supplementation, the concentration of indolic compounds (measured as indole-3-acetic acid) increased. Production of ammonium and solubilisation of insoluble P by these strains was also apparent. Only Serratia strain ECCN 24b was capable of solubilising insoluble K. Production of indoles increased following exposure to increasing aliquots of coal discard, suggesting no negative effect of this material on indole production by these coal-degrading bacterial isolates and that these bacteria may indeed possess PGP characteristics.

Isolation and characterization of a novel bacterial strain from a Tris-Acetate-Phosphate agar medium plate of the green micro-alga Chlamydomonas reinhardtii that can utilize common environmental pollutants as a carbon source

Background:Chlamydomonas reinhardtii, a green micro-alga can be grown at the lab heterotrophically or photo-heterotrophically in Tris-Phosphate-Acetate (TAP) medium which contains acetate as the sole carbon source. When grown in TAP medium, Chlamydomonas can utilize the exogenous acetate in the medium for gluconeogenesis using the glyoxylate cycle, which is also present in many bacteria and higher plants. A novel bacterial strain, LMJ, was isolated from a contaminated TAP medium plate of Chlamydomonas. We present our work on the isolation and physiological and biochemical characterizations of LMJ.

Methods: Several microbiological tests were conducted to characterize LMJ, including its sensitivity to four antibiotics. We amplified and sequenced partially the 16S rRNA gene of LMJ. We tested if LMJ can utilize cyclic alkanes, aromatic hydrocarbons, poly-hydroxyalkanoates, and fresh and combusted car motor oil as the sole carbon source on Tris-Phosphate (TP) agar medium plates for growth.

Results: LMJ is a gram-negative rod, oxidase-positive, mesophilic, non-enteric, pigmented, salt-sensitive bacterium. LMJ can ferment glucose, is starch hydrolysis-negative, and is very sensitive to penicillin and chloramphenicol. Preliminary spectrophotometric analyses indicate LMJ produces pyomelanin. NCBI-BLAST analyses of the partial 16S rRNA gene sequence of LMJ showed that it matched to that of an uncultured bacterium clone LIB091_C05_1243. The nearest genus relative of LMJ is an Acidovorax sp. strain. LMJ was able to use alkane hydrocarbons, fresh and combusted car motor oil, poly-hydroxybutyrate, phenanthrene, naphthalene, benzoic acid and phenyl acetate as the sole carbon source for growth on TP-agar medium plates.

Conclusions: LMJ has 99.14% sequence identity with the Acidovorax sp. strain A16OP12 whose genome has not been sequenced yet. LMJ’s ability to use chemicals that are common environmental pollutants makes it a promising candidate for further investigation for its use in bioremediation and, provides us with an incentive to sequence its genome.

Biodegradation of low viscosity spindle oil causing environmental pollution

Three hydrocarbon degrading microorganisms were isolated from the soil samples collected from the storage sites of low viscosity spindle oil containers and identified on the basis of morphological and biochemical characteristics as Aeromonas hydrophila, Bacillus subtilis and Staphylococcus aureus. The study has revealed high ability of these microorganisms for oil biodegradation. The results have indicated that all isolates had the potential to breakdown the hydrocarbon. The most efficient bacteria among these examined was Aeromonas hydrophila which biodegraded almost all tested hydrocarbon giving a treatment percentage of 98% within 30 days which was considered as the perfect period for degradation. Also, a small scale was designed to treat the spindle oil with the using of oxidation process and all the tested organic materials were biodegraded in a treatment percentage of 100% within retention time of 20 days.

A novel fatty alkene from marine bacteria: A thermo stable biosurfactant and its applications

In this study, a novel thermo stable biosurfactants, 1-Pentanonacontene (C₉₅H₁₉₀) a fatty alkene and 3-Hydroxy-16-methylheptadecanoic acid (C₁₈H₃₆O₃) were isolated from a marine isolate SGD-AC-13. Biosurfactants were produced using 1% yeast extract in tap water as production medium at 24 h in flask and 12 h in bioreactor. Using 16S rRNA gene sequence (1515 bp) and BCL card (bioMérieux VITEK^®), strain was identified as Bacillus sp. Crude biosurfactant reduced the surface tension of distilled water to 31.32 ± 0.93 mN/m with CMC value of 0.3 mg/ml. Cell free supernatant showed excellent emulsification and oil displacement activity with stability up to 160 °C, pH 6-12 and 50 g/L NaCl conc. Biosurfactants were characterized using FTIR, TLC, HPLC LC-MS and NMR spectroscopy. Cell free supernatant reduced the contact angle of distilled water droplet from 117° to 52.28° and of 2% pesticide from 78.77° to 73.42° while 750 μg/ml of crude biosurfactant reduced from 66.06° to 56.33° for 2% pesticide and recovered 35% ULO and 12% HWCO from the contaminated sand. To our best of knowledge, this is the first report of thermo stable fatty alkene as a biosurfactant and is structurally different from previously reported, with having potential application in agriculture, oil recovery and bioremediation.

Aluminium removal and recovery from wastewater and soil using isolated indigenous bacteria

This paper elucidates the capability of isolated indigenous bacteria to remove aluminium from wastewater and soil. Two indigenous species of Brochothrix thermosphacta and Vibrio alginolyticus were isolated from an aluminium-contaminated site. These two species were used to treat aluminium-containing wastewater and contaminated soil using the bioaugmentation method. B. thermosphacta showed the highest aluminium removal of 57.87 ± 0.45% while V. alginolyticus can remove aluminium up to 59.72 ± 0.33% from wastewater. For aluminium-contaminated soil, B. thermosphacta and V. alginolyticus, showed a highest removal of only 4.58 ± 0.44% and 5.48 ± 0.58%, respectively. The bioaugmentation method is more suitable to be used to treat aluminium in wastewater compared to contaminated soil. The produced biomass separation after wastewater treatment was so much easier and applicable, compared to the produced biomass handling from contaminated soil treatment. A 48.55 ± 2.45% and 40.12 ± 4.55% of aluminium can be recovered from B. thermosphacta and V. alginolyticus biomass, respectively, with 100 mg/L initial aluminium concentration in wastewater.

One-step reductive synthesis of Ti3+ self-doped elongated anatase TiO2 nanowires combined with reduced graphene oxide for adsorbing and degrading waste engine oil

A sustainable photocatalyst of Ti³⁺ self-doped elongated anatase nanowires combined with reduced graphene oxide (TiO₂ NWs@rGO) was prepared via a facile one-step reductive synthesis process using NaBH₄ as reductant for the first time. The obtained optimal TiO₂ NWs@rGO composite has a large surface area,182 m²  g^-1, which demonstrates strong adsorption capacity due to the multilayered structure built by highly crystallized nanowires of TiO₂ and ultrathin rGO layers. When the photocatalyst was applied in removing waste engine oil (100 mL, 50 mg L^-1), it exhibited outstanding performance with up to COD 98.6% removal extent (from 145 initial to 2 mg L^-1 final COD) after 5 h, which is 34.1% higher than that of TiO₂ NWs (64.5% COD removal extent). Gas chromatography-mass spectrometry analyses of residual waste engine oil after photocatalysis shows significant reductions of C₆-C₁₉ chemicals as well as total disappear of C₁₅,C₁₆, C₁₇, C₁₈ chemicals. The outstanding photocatalytic activity of TiO₂ NWs@rGO benefits from sensitive response to visible light, improved surface reactivity and high electron flux enabled by rGO and Ti³⁺ in TiO₂. In addition, this composite catalyst can be self-cleaned, and recycled for reuse, which suggests promising potential for waste engine oil treatment.

Development of a bacterial consortium comprising oil-degraders and diazotrophic bacteria for elimination of exogenous nitrogen requirement in bioremediation of diesel-contaminated soil

The purpose of this study was to develop an effective bacterial consortium and determine their ability to overcome nitrogen limitation for the enhanced remediation of diesel-contaminated soils. Towards this, various bacterial consortia were constructed using oil-degrading and nitrogen-fixing microbes. The diesel removal efficiency of various developed consortia was evaluated by delivering the bacterial consortia to the diesel-contaminated soils. The consortium Acinetobacter sp. K-6 + Rhodococcus sp. Y2-2 + NH₄NO₃ resulted in the highest removal (85.3%) of diesel from the contaminated soil. The consortium containing two different oil-degrading microbes (K-6 + Y2-2) and one nitrogen-fixing microbe Azotobacter vinelandii KCTC 2426 removed 83.1% of the diesel from the soil after 40 days of treatment. The total nitrogen content analysis revealed higher amounts of nitrogen in soil treated with the nitrogen-fixing microbe when compared with that of the soil supplemented with exogenous inorganic nitrogen. The findings in this present study reveal that the consortium containing the nitrogen-fixing microbe degraded similar amounts of diesel to that degraded by the consortium supplemented with exogenous inorganic nitrogen. This suggests that the developed consortium K-6 + Y2-2 + KCTC 2426 compensated for the nitrogen limitation and eliminated the need for exogenous nitrogen in bioremediation of diesel-contaminated soils.

Kinetics of aluminium removal by locally isolated Brochothrix thermosphacta and Vibrio alginolyticus

The emergence of the aluminium recycling industry has led to an increase in aluminium-containing wastewater discharge to the environment. Biological treatment of metal is one of the solutions that can be provided as green technology. Screening tests showed that Brochothrix thermosphacta and Vibrio alginolyticus have the potential to remove aluminium from wastewater. Brochothrix thermosphacta removed up to 49.60%, while Vibrio alginolyticus was capable of removing up to 59.72% of 100 mg/L aluminium in acidic conditions. The removal of aluminium by V. alginolyticus was well fitted with pseudo-first-order kinetics (k₁ = 0.01796/min), while B. thermosphacta showed pseudo-second-order kinetics (k₂ = 0.125612 mg substrate/g adsorbent. hr) in the process of aluminium removal. V. alginolyticus had a higher rate constant under acidic conditions, while B. thermosphacta had a higher rate constant under neutral pH conditions.

Isolation, identification, and characterization of diesel-oil-degrading bacterial strains indigenous to Changqing oil field, China

In the present study, 12 indigenous diesel-oil-degrading bacteria were isolated from the petroleum-contaminated soils of the Changqing oil field (Xi'an, China). Measurement of the diesel-oil degradation rates of these strains by the gravimetric method revealed that they ranged from 42% to 66% within 2 weeks. The highest degradation rates were observed from strains CQ8-1 (66%), CQ8-2 (62.6%), and CQ11 (59%), which were identified as Bacillus thuringiensis, Ochrobactrum anthropi, and Bordetella bronchialis, respectively, based on their 16S rDNA sequences. Moreover, the physiological and biochemical properties of these three strains were analyzed by Gram staining, catalase, oxidase, and Voges-Proskauer tests. Transmission electron microscopy showed that all three strains were rod shaped with flagella. Gas chromatography and mass spectrometric analyses indicated that medium- and long-chain n-alkanes in diesel oil (C11-C29) were degraded to different degrees by B. thuringiensis, O. anthropi, and B. bronchialis, and the degradation rates gradually decreased as the carbon numbers increased. Overall, the results of this study indicate strains CQ8-1, CQ8-2, and CQ11 might be useful for environmentally friendly and cost-effective bioremediation of oil-contaminated soils.

Enhanced degradation of indeno(1,2,3-cd)pyrene using Candida tropicalis NN4 in presence of iron nanoparticles and produced biosurfactant: a statistical approach

Seven yeast isolates were screened for the remediation of indeno(1,2,3-cd)pyrene (InP) using biosynthesized iron nanoparticles and produced biosurfactant in growth medium. Four yeast isolates showed positive response to produce biosurfactant which was confirmed by drop collapse test, emulsification index, methylene blue agar plate method, oil displacement test and lipase activity. The yeast strain showing maximum potential for InP degradation and biosurfactant production was identified as Candida tropicalis NN4. The produced biosurfactant was characterized as sophorolipid type through TLC and FTIR analysis. Iron nanoparticles were biosynthesized using mint leaf extract and characterized by various instrumental analysis. Response surface methodology (RSM), three-level five-variable Box-Behnken design (BBD) was employed to optimize the factors, viz., pH (7), temperature (30 °C), salt concentration (1.5 g L-1), incubation time (15 days) and iron nanoparticles concentration (0.02 g L-1) for maximum InP degradation (90.68 ± 0.7%) using C. tropicalis NN4. It was well in close agreement with the predicted value which was obtained by RSM model (90.68 ± 0.4%) indicating the validity of the model. InP degradation was confirmed through FTIR and GC-MS analysis. A kinetic study demonstrated that InP degradation fitted first-order kinetic model. This is the first report on yeast-mediated nanobioremediation of InP and optimization of the whole process using RSM.

Biosurfactant and enzyme mediated crude oil degradation by Pseudomonas stutzeri NA3 and Acinetobacter baumannii MN3

The present study focuses on the optimization of biosurfactant (BS) production using two potential biosurfactant producer Pseudomonas stutzeri NA3 and Acinetobacter baumannii MN3 and role of enzymes in the biodegradation of crude oil. The optimal conditions for P. stutzeri NA3 and A. baumannii MN3 for biodegradation were pH of 8 and 7; temperature of 30 and 40 °C, respectively. P. stutzeri NA3 and A. baumannii MN3 produced 3.81 and 4.68 g/L of BS, respectively. Gas chromatography mass spectrometry confirmed that BS was mainly composed of fatty acids. Furthermore, the role of the degradative enzymes, alkane hydroxylase, alcohol dehydrogenase and laccase on biodegradation of crude oil are explained. Maximum biodegradation efficiency (BE) was recorded for mixed consortia (86%) followed by strain P. stutzeri NA3 (84%). Both bacterial strains were found to be vigorous biodegraders of crude oil than other biosurfactant-producing bacteria due to their enzyme production capabilities and our results suggests that the bacterial isolates can be used for effective degradation of crude oil within short time periods.