Simultaneous heavy metal removal and anthracene biodegradation by the oleaginous bacteria Rhodococcus opacus

Rhodococcus erythropolis ATCC 4277 behavior against different metals and its potential use in waste biomining

Rhodococcus erythropolis bacterium is known for its remarkable resistance characteristics that can be useful in several biotechnological processes, such as bioremediation. However, there is scarce knowledge concerning the behavior of this strain against different metals. This study sought to investigate the behavior of R. erythropolis ATCC 4277 against the residue of chalcopyrite and e-waste to verify both resistive capacities to the metals present in these residues and their potential use for biomining processes. These tests were carried out in a stirred tank bioreactor for 48 h, at 24ºC, pH 7.0, using a total volume of 2.0 L containing 2.5% (v/v) of a bacterial pre-culture. The pulp density of chalcopyrite was 5% (w/w), and agitation and oxygen flow rates were set to 250 rpm and 1.5 LO2 min-1, respectively. On the other hand, we utilized a waste of computer printed circuit board (WPCB) with a pulp density of 10% (w/w), agitation at 400 rpm, and an oxygen flow rate of 3.0 LO2 min-1. Metal concentration analyses post-fermentation showed that R. erythropolis ATCC 4277 was able to leach about 38% of the Cu present in the chalcopyrite residue (in ~ 24 h), and 49.5% of Fe, 42.3% of Ni, 27.4% of Al, and 15% Cu present in WPCB (in ~ 24 h). In addition, the strain survived well in the environment containing such metals, demonstrating the potential of using this bacterium for waste biomining processes as well as in other processes with these metals.

Synergistic remediation of phenanthrene-cadmium co-contaminants by an immobilized acclimated bacterial-fungal consortium and its community response

Bioremediation has tremendous potential to mitigate the serious threats posed by polycyclic aromatic hydrocarbons (PAHs) and heavy metals (HMs). In the present study, nine bacterial-fungal consortia were progressively acclimated under different culture conditions. Among them, a microbial consortium 1, originating from activated sludge and copper mine sludge microorganisms, was developed through the acclimation of a multi-substrate intermediate (catechol)-target contaminant (Cd²⁺, phenanthrene (PHE)). Consortium 1 exhibited the best PHE degradation, with an efficiency of 95.6% after 7 d of inoculation, and its tolerance concentration for Cd²⁺ was up to 1800 mg/L within 48 h. Bacteria Pandoraea and Burkholderia-Caballeronia-Paraburkholderia, as well as fungi Ascomycota and Basidiomycota predominated in the consortium 1. Furthermore, a biochar-loaded consortium was constructed to better cope with the co-contamination behavior, which exhibited excellent adaptation to Cd²⁺ ranging of 50-200 mg/L. Immobilized consortium efficiently degraded 92.02-97.77% of 50 mg/L PHE within 7 d while removing 93.67-99.04% of Cd²⁺. In remediation of co-pollution, immobilization technology improved the bioavailability of PHE and dehydrogenase activity of the consortium to enhance PHE degradation, and the phthalic acid pathway was the main metabolic pathway. As for Cd²⁺ removal, oxygen-containing functional groups (-OH, C=O, and C-O) of biochar or microbial cell walls and EPS components, fulvic acid and aromatic proteins, participated through chemical complexation and precipitation. Furthermore, immobilization led to more active consortium metabolic activity during the reaction, and the community structure developed in a more favorable direction. The dominant species were Proteobacteria, Bacteroidota, and Fusarium, and the predictive expression of functional genes corresponding to key enzymes was elevated. This study provides a basis for combining biochar and acclimated bacterial-fungal consortia for co-contaminated site remediation.

Optimization Study of the Capacity of Chlorella vulgaris as a Potential Bio-Remediator for the Bio-Adsorption of Arsenic (III) from Aquatic Environments

This study examined the ability of the green microalgae Chlorella vulgaris to remove arsenic from aqueous solutions. A series of studies was conducted to determine the optimal conditions for biological arsenic elimination, including biomass amount, incubation time, initial arsenic level, and pH values. At 76 min, pH 6, 50 mgL^-1 metal concentration, and 1 gL^-1 bio-adsorbent dosage, the maximum removal of arsenic from an aqueous solution was 93%. The uptake of As (III) ions by C. vulgaris reached an equilibrium at 76 min of bio-adsorption. The maximum adsorptive rate of arsenic (III) by C. vulgaris was 55 mg/gm. The Langmuir, Freundlich, and Dubinin-Radushkevich equations were used to fit the experimental data. The best theoretical isotherm of Langmuir, Freundlich, or/and Dubinin-Radushkevich for arsenic bio-adsorption by Chlorella vulgaris was determined. To choose the best theoretical isotherm, the coefficient of correlation was used. The data on absorption appeared to be linearly consistent with the Langmuir (q_max = 45 mgg^-1; R² = 0.9894), Freundlich (k_f = 1.44; R² = 0.7227), and Dubinin-Radushkevich (q_D-R = 8.7 mg/g; R² = 0.951) isotherms. The Langmuir and Dubinin-Radushkevich isotherms were both good two-parameter isotherms. In general, Langmuir was demonstrated to be the most accurate model for As (III) bio-adsorption on the bio-adsorbent. Maximum bio-adsorption values and a good correlation coefficient were observed for the first-order kinetic model, indicating that it was the best fitting model and significant in describing the arsenic (III) adsorption process. SEM micrographs of treated and untreated algal cells revealed that ions adsorbed on the algal cell's surface. A Fourier-transform infrared spectrophotometer (FTIR) was used to analyze the functional groups in algal cells, such as the carboxyl group, hydroxyl, amines, and amides, which aided in the bio-adsorption process. Thus, C. vulgaris has great potential and can be found in eco-friendly biomaterials capable of adsorbing arsenic contaminants from water sources.

Aquatic Bacteria Rheinheimera tangshanensis New Ability for Mercury Pollution Removal

To explore the strong tolerance of bacteria to Hg pollution, aquatic Rheinheimera tangshanensis (RTS-4) was separated from industrial sewage, with a maximum Hg(II) tolerant concentration of 120 mg/L and a maximum Hg(II) removal rate of 86.72 ± 2.11%, in 48 h under optimum culture conditions. The Hg(II) bioremediation mechanisms of RTS-4 bacteria are as follows: (1) the reduction of Hg(II) through Hg reductase encoded by the mer operon; (2) the adsorption of Hg(II) through the production of extracellular polymeric substances (EPSs); and (3) the adsorption of Hg(II) using dead bacterial biomass (DBB). At low concentrations [Hg(II) ≤ 10 mg/L], RTS-4 bacteria employed Hg(II) reduction and DBB adsorption to remove Hg(II), and the removal percentages were 54.57 ± 0.36% and 45.43 ± 0.19% of the total removal efficiency, respectively. At moderate concentrations [10 mg/L < Hg(II) ≤ 50 mg/L], all three mechanisms listed above coexisted, with the percentages being 0.26 ± 0.01%, 81.70 ± 2.31%, and 18.04 ± 0.62% of the total removal rate, respectively. At high concentrations [Hg(II) > 50 mg/L], the bacteria primary employed EPS and DBB adsorption to remove Hg(II), where the percentages were 19.09 ± 0.04% and 80.91 ± 2.41% of the total removal rate, respectively. When all three mechanisms coexisted, the reduction of Hg(II) occurred within 8 h, the adsorption of Hg(II) by EPSs and DBB occurred within 8-20 h and after 20 h, respectively. This study provides an efficient and unused bacterium for the biological treatment of Hg pollution.

Effective removal of fluoride ions from aqueous solution by marine microalgae as natural biosorbent

In this study, the phytoremediation technology from marine source Dunaliella salina was chosen to eliminate fluoride ions from aqueous solution by Adsorption isotherm, Kinetics and RSM optimization methods. Marine microalgae were collected, identified and mass cultured then its physical characteristics, functional groups and surface microstructure was examined by FT-IR, NMR, XRD and SEM analysis also the same was performed on post treated bioadsorbent. Fluoride removal was optimized by different conditions through response surface methodology and kinetics modelling also performed. Several active functional groups were noticed in IR spectra and NMR of pre and post treated microalgal biosorbent. Many micropores, crystalline structure, voids were observed in pre-treated and lesser in post treated bioadsorbent, removal process was optimized by temperature, pH, dose and time and its showed high influence of removal process. The fluoride removal process was optimized by response surface methodology, Langmuir Isotherm, Freundlich Isotherm, Temkin isotherm, Pseudo I order, Pseudo II order and Intra particle diffusion and revealed that the F ions removal mechanism clearly. Microalgae are novel, low-cost and effective bio based innovative methods which are sustainable for the bioremediation of fluoride from water bodies and industrial wastewaters.

Simultaneous removal of ternary heavy metal ions by a newly isolated Microbacterium paraoxydans strain VSVM IIT(BHU) from coal washery effluent

In the present work, the removal of Cr (VI), Cd (II) and Pb (II) at 50 mg/L of each metal ion concentration was investigated by Microbacterium paraoxydans strain VSVM IIT(BHU). The heavy metal binding on the bacterial cell surface was confirmed through X-ray photoelectron spectroscopy and energy dispersive X-ray. X-ray photoelectron spectroscopy analysis also confirmed the reduction of Cr (VI) to Cr (III). Heavy metal removal dynamics was investigated by evaluating dimensionless, and the value of N_k (9.49 × 10^-3, 9.92 × 10^-3 and 1.23 × 10^-2 for Cr (VI), Cd (II) and Pb (II) ions) indicated that the removal of heavy metals by bacterial isolate was mixed diffusion and transfer controlled. It was found that both the experimental and predicted values for isolated bacterial strain coincided with each other with a good R² value in the L-M Algorithm range of 0.94-0.98 for the ternary metal ion system. The bacterial isolate presented a maximum heavy metal ion removal efficiency of 91.62% Cr (VI), 89.29% Pb (II), and 83.29% Cd (II) at 50 mg/L.

Biochar Effect on the Benzo[a]pyrene Degradation Rate in the Cu Co-Contaminated Haplic Chernozem under Model Vegetation Experiment Conditions

The research of the fundamentals of the behavior of behavior in the soil–plant system during their co-contamination is of high interest because of the absence of technologies for the creation of effective, environmentally friendly and cost-effective remediation methods, as well as integrated systems for predicting the quality of soils co-contaminated with HMs and PAHs. The unique model vegetation experiment was studied with Haplic Chernozem contaminated by one of the priority organic toxicants, benzo[a]pyrene (BaP), applied alone and co-contaminated with Cu with the subsequent vegetation of tomato (Solanum lycopersicum) and spring barley plants (Hordeum sativum Distichum). Biochar obtained from sunflower husks was used as a sorbent for the remediation of the contaminated soil. It was established that by increasing the BaP amount applied to the soil, the rate of BaP degradation improved. The effect was enhanced in the presence of biochar and decreased in the case of joint co-contamination with Cu, which is especially expressed for the soil of tomato plants. The half-degradation time of the BaP molecule varied from 8 up to 0.2 years for tomatoes and barley.

Adsorption mechanism of Pb2+ in montmorillonite nanopore under various temperatures and concentrations

Adsorption of lead (Pb²⁺) onto the montmorillonite (Mt) surface is one of the key approaches to remove Pb²⁺ in geological and environmental engineering. Temperature and initial Pb²⁺ concentration are two essential factors that influence the adsorption capacity of Mt on absorbing Pb²⁺. However, the nanoscale governing mechanism of temperature and initial concentration on Pb²⁺ adsorbing of Mt is still unclear. This research performed comprehensively molecular dynamics (MD) simulations to investigate how temperature and initial concentration affect the dynamic Pb²⁺ adsorption of Mt nanopore. The Pb²⁺ removal ratio shows a two-stage variation with the increase of initial Pb²⁺ concentration. Temperature controls the maximum initial Pb²⁺ concentration for complete Pb²⁺ removal by changing the maximum adsorption energy of Mt. Temperature also influences the maximum adsorption capacity and Pb²⁺ removal ratio of Mt nanopore indirectly by changing diffusion and hydration state of Pb²⁺. The initial Pb²⁺ concentration corresponding to the maximum adsorption energy coincides with the maximum initial Pb²⁺ concentration determined by the Pb²⁺ removal ratio. Lower adsorption energy and higher level of hydration and diffusion make Pb²⁺ absorbing on Mt surface become more difficult, reducing the Pb²⁺ adsorbing capacity of Mt. The initial Pb²⁺ concentration influences adsorption capacity and Pb²⁺ removal ratio not only via altering the quantity of Pb²⁺ but also through controlling the adsorption energy of Mt, as well as the diffusion and hydration state of Pb²⁺. With the increase of initial Pb²⁺ concentration, the hydration of Pb²⁺ is weakened while the adsorption energy of Mt and diffusion of Pb²⁺ are enhanced.

Application of mixotrophic acidophiles for the bioremediation of cadmium-contaminated soils elevates cadmium removal, soil nutrient availability, and rice growth

A major challenge in radically alleviating the threats posed by Cd-contaminated paddy fields to human health is to reduce the Cd levels in both soils and rice grains. In this study, the microbial extraction (ME) treatment using a mixotrophic acidophilic consortium was used for the bioremediation of Cd-contaminated soils. The results showed that the ME treatment enhanced the total Cd (40%) and diethylenetriamine pentaacetic acid-soluble Cd (DTPA-Cd, 64%) removal efficiencies in contaminated soils. In addition, ME treatment decreased the levels of Cd acid-soluble and reducible fractions and thereby reduced Cd uptake in rice tissues. Microbial community analysis indicated that the indigenous soil microbial diversity and composition were not changed after the ME treatment, but the relative abundance of functional microbes associated with Cd removal was improved. Notably, soil available nutrient levels were elevated upon inoculation with mixotrophic acidophiles, resulting in an increase in rice growth and grain weight. This study provides a scientific basis for the potential application and evaluation of ME treatment in the field for remediating Cd-contaminated paddy soils.

State-of-the-Art Review on the Application of Membrane Bioreactors for Molecular Micro-Contaminant Removal from Aquatic Environment

In recent years, the emergence of disparate micro-contaminants in aquatic environments such as water/wastewater sources has eventuated in serious concerns about humans’ health all over the world. Membrane bioreactor (MBR) is considered a noteworthy membrane-based technology, and has been recently of great interest for the removal micro-contaminants. The prominent objective of this review paper is to provide a state-of-the-art review on the potential utilization of MBRs in the field of wastewater treatment and micro-contaminant removal from aquatic/non-aquatic environments. Moreover, the operational advantages of MBRs compared to other traditional technologies in removing disparate sorts of micro-contaminants are discussed to study the ways to increase the sustainability of a clean water supplement. Additionally, common types of micro-contaminants in water/wastewater sources are introduced and their potential detriments on humans’ well-being are presented to inform expert readers about the necessity of micro-contaminant removal. Eventually, operational challenges towards the industrial application of MBRs are presented and the authors discuss feasible future perspectives and suitable solutions to overcome these challenges.

Nano-Biochar as a Sustainable Catalyst for Anaerobic Digestion: A Synergetic Closed-Loop Approach

Nowadays, the valorization of organic wastes using various carbon-capturing technologies is a prime research area. The anaerobic digestion (AD) technology is gaining much consideration in this regard that simultaneously deals with waste valorization and bioenergy production sustainably. Biochar, a well-recognized carbonaceous pyrogenic material and possessing a broad range of inherent physical and chemical properties, has diverse applications in the fields of agriculture, health-care, sensing, catalysis, carbon capture, the environment and energy. The nano-biochar-amended anaerobic digestion approach has intensively been explored for the past few years. However, an inclusive study of multi-functional roles of biochar and the mechanism involved for enhancing the biogas production via the AD process still need to be evaluated. The present review inspects the significant role of biochar addition and the kinetics involved, further focusing on the limitations, perspectives, and challenges of the technology. Additionally, the techno-economic analysis and life-cycle assessment of biochar-aided AD process for the closed-loop integration of biochar and AD and possible improvement practices are discussed.

Ultrasonic seed treatment improved morpho-physiological and yield traits and reduced grain Cd concentrations in rice

Rice cultivation under cadmium (Cd) contaminated soil often results in reduced growth with excess grain Cd concentrations. A pot experiment was conducted to assess the potential of ultrasonic seed treatment to alleviate Cd stress in rice. Seeds of two aromatic rice cultivars i.e., Xiangyaxiangzhan and Meixiangzhan 2 and two non-aromatic rice cultivars i.e., Huahang 31 and Guangyan 1 were exposed to ultrasonic waves for 1.5 min in 20-40 KHz mixing frequency. The experimental treatments were comprised of untreated seeds (U0) and ultrasonic treated seeds (U1) transplanted in un-contaminated soil (H0) and Cd-contaminated soil (H1). Results revealed that Cd contents and Cd accumulation in grain in U1 were 33.33-42.31% and 12.86-57.58% lower than U0 for fragrant rice cultivars under H1. Meanwhile, biomass production was higher in U1 than U0 under H0 and better yield was assessed in U1 for all cultivars under H1. The activity of peroxidase (POD) in flag leaves was increased by 8.28-115.65% for all cultivars while malondialdehyde (MDA) contents were significantly decreased in U1 compared with U0 under H0. Conclusively, ultrasonic treatment modulated Cd distribution and accumulation in different parts while improved physiological performance as well as yield and grain quality of rice under Cd contaminated conditions.

Cyanobacterial Extracellular Polymeric Substances for Heavy Metal Removal: A Mini Review

Heavy metals from various natural and anthropogenic sources are becoming a chief threat to the aquatic system owing to their toxic and lethal effect. The treatment of such contaminated wastewater is one of the prime concerns in this field. For decades, a huge array of innovative biosorbents is used for heavy metal removal. Though extensive microbes and their biomolecules have been experimented and have showed great potential but most of them have failed to have the substantial breakthrough for the practical application. The present review emphasis on the potential utilization of the cyanobacteria for the heavy metal removal along with the toxic effect imposed by the pollutant. Furthermore, the effect of significant parameters, plausible mechanistic insights of the heavy metal toxicity imposed onto the cyanobacteria is also discussed in detail. The role of extrapolymeric substances and metallothionein secreted by the microbes are also elaborated. The review was evident that the cyanobacterial species have a huge potential towards the heavy metal removal from the aqueous system ranging from very low to very high concentrations.

Toxicity mechanism of Cu2+ ion individually and in combination with Zn2+ ion in characterizing the molecular changes of Staphylococcus aureus studied using FTIR coupled with chemometric analysis

Copper and zinc have a high binding affinity with a Staphylococcus aureus bacterial community. This causes a change in the biomolecular composition of S. aureus. Our study aims at understanding the resistance mechanism of Cu and Zn either or in various combinations using FTIR and chemometric techniques. Zn toxicity resulted in a significant change in lipid content (3100-2800 cm-1) compared to Cu. A significant decrease in protein content is observed for Cu treatment in the amide region. The bio-concentration factor shows a higher value for Cu compared to Zn. The increase in band area of carbohydrates moieties 1059 cm-1 shows the secretion of EPS due to Cu toxicity. A significant change in nucleic acid compositions was noted in the region1200-900 cm-1 due to Zn treatment. Secondary structural change in protein shows β sheet formation. The result of the finding shows Cu has greater toxicity than Zn. Further toxicity effects were greatly enhanced for metal mixtures ratio (Cu:2Zn). This shows Zn exhibits synergism effect with Cu. The obtained ROC (receiver operating characteristic) curve area gives good reliability of the experiments. The study attempts to understand the mechanism of toxicity removal of Cu and Zn metal mixtures by bacterial population using FTIR coupled with chemometric techniques. Graphical abstract.

An overview on heavy metal resistant microorganisms for simultaneous treatment of multiple chemical pollutants at co-contaminated sites, and their multipurpose application

Anthropogenic imbalance of chemical pollutants in environment raises serious threat to all life forms. Contaminated sites often possess multiple heavy metals and other types of pollutants. Elimination of chemical pollutants at co-contaminated sites is imperative for the safe ecosystem functions, and simultaneous removal approach is an attractive scheme for their remediation. Different conventional techniques have been applied as concomitant treatment solution but fall short at various parameters. In parallel, use of microorganisms offers an innovative, cost effective and ecofriendly approach for simultaneous treatment of various chemical pollutants. However, microbiostasis due to harmful effects of heavy metals or other contaminants is a serious bottleneck facing remediation practices in co-contaminated sites. But certain microorganisms have unique mechanisms to resist heavy metals, and can act on different noxious wastes. Considering this significant, my review provides information on different heavy metal resistant microorganisms for bioremediation of different chemical pollutants, and other assistance. In this favour, the integrated approach of simultaneous treatment of multiple heavy metals and other environmental contaminants using different heavy metal resistant microorganisms is summarized. Further, the discussion also intends toward the use of heavy metal resistant microorganisms associated with industrial and environmental applications, and healthcare. PREFACE: Simultaneous treatment of multiple chemical pollutants using microorganisms is relatively a new approach. Therefore, this subject was not well received for review before. Also, multipurpose application of heavy metal microorganisms has certainly not considered for review. In this regard, this review attempts to gather information on recent progress on studies on different heavy metal resistant microorganisms for their potential of treatment of co-contaminated sites, and multipurpose application.

Adsorption characteristics of Barmer bentonite for hazardous waste containment application

Low hydraulic conductivity and high chemical immobilization are the two characteristics that make bentonite a mandatory construction material for hazardous waste containment applications. We performed a comprehensive batch sorption study on Barmer bentonite (BB), an exclusive construction clay mined in India, using lead (Pb²⁺) as a model contaminant. The maximum adsorption capacity of BB was obtained as 55 mg g^-1 at pH 5 and 27 ± 2℃. Adsorption was extremely rapid, with equilibrium attained <5 min for the BB. Increased adsorbent dosage resulted in higher Pb²⁺ percentage removal, while adsorption capacity decreased. Ionic strength, salt concentration, valency and ionic radius played a critical role in suppressing the adsorption of Pb²⁺. Clay fabric change was observed to be dispersed at low ionic strength and gradually attained aggregated face-to-face structures at high ionic strength. The simultaneous presence of other metals/salts strongly influenced Pb²⁺ removal by BB, while divalent salt exhibited high suppression of adsorptive reaction at low concentrations. Sorption isotherm and kinetic modeling results indicated the possibility of chemisorption of Pb²⁺ on BB. Based on the thermodynamic analysis, it was noted that Pb²⁺ adsorption on BB is exothermic, spontaneous and adsorption reaction is less favorable at a higher temperature.

Analysis of the biodegradative and adaptive potential of the novel polychlorinated biphenyl degrader Rhodococcus sp. WAY2 revealed by its complete genome sequence

The complete genome sequence of Rhodococcus sp. WAY2 (WAY2) consists of a circular chromosome, three linear replicons and a small circular plasmid. The linear replicons contain typical actinobacterial invertron-type telomeres with the central CGTXCGC motif. Comparative phylogenetic analysis of the 16S rRNA gene along with phylogenomic analysis based on the genome-to-genome blast distance phylogeny (GBDP) algorithm and digital DNA–DNA hybridization (dDDH) with other Rhodococcus type strains resulted in a clear differentiation of WAY2, which is likely a new species. The genome of WAY2 contains five distinct clusters of bph, etb and nah genes, putatively involved in the degradation of several aromatic compounds. These clusters are distributed throughout the linear plasmids. The high sequence homology of the ring-hydroxylating subunits of these systems with other known enzymes has allowed us to model the range of aromatic substrates they could degrade. Further functional characterization revealed that WAY2 was able to grow with biphenyl, naphthalene and xylene as sole carbon and energy sources, and could oxidize multiple aromatic compounds, including ethylbenzene, phenanthrene, dibenzofuran and toluene. In addition, WAY2 was able to co-metabolize 23 polychlorinated biphenyl congeners, consistent with the five different ring-hydroxylating systems encoded by its genome. WAY2 could also use n-alkanes of various chain-lengths as a sole carbon source, probably due to the presence of alkB and ladA gene copies, which are only found in its chromosome. These results show that WAY2 has a potential to be used for the biodegradation of multiple organic compounds.

Structural Determination of a New Peptidolipid Family from Rhodococcus opacus and the Pathogen Rhodococcus equi by Multiple Stage Mass Spectrometry

The cell walls of the genus Rhodococcus including the pathogenic bacterium Rhodococcus equi (R. equi) and biotechnologically important bacterium Rhodococcus opacus (R. opacus) contain an abundant peptidolipid (or termed lipopeptide) family whose structures have not been reported previously. Here, we describe a linear ion-trap multiple-stage mass spectrometric (LIT MSⁿ) approach with high resolution mass spectrometry (HRMS), in conjunction with NMR spectroscopy, chemical reactions, and GC/MS analysis to define the structures of these compounds. We employed LIT MSⁿ (n = 2-8) on the [M + Na]⁺ ion species to establish the peptide sequence, the identity of the fatty acyl substituent, and its location within the molecule, while NMR spectroscopy and GC/MS were used to recognize the Leu and Ile moieties. The major new lipopeptide found in R. opacus is defined as C₁₇H₃₅CH(OH)CH₂CO-NHLeu-Ser-Leu-Ile-Thr-Ile-PheCOOH, where a β-OH fatty acyl (C₁₈-C₂₂) substituent is attached to the N-terminal of the LSLITIF peptide chain via a NH-CO bond. By contrast, the main peptidolipids found in R. equi belong to the cyclopeptidolipid family, which possesses the same peptide sequence and lipid chain, but the β-OH group of the fatty acyl moiety and the C-terminus of the peptide (i.e., the -COOH) are cyclized by an ester bond formation to a lactone, with a structure similar to iturin-A (Peypoux, F. et al. Biochemistry 1978, 17, 3992-3996). The antibiotic activity test of these new lipids did not reveal an activity against any of seven microorganisms tested.

Biosorption of Hg (II) from aqueous solution using algal biomass: kinetics and isotherm studies

The present work investigated the ability of algal biomass Chlorella vulgaris to remove mercury from aqueous solutions. The mercury biosorption process was studied through batch experiments 35 °C temperature with regard to the influence of contact time, initial mercury concentration, pH and desorption. The maximum adsorption capacity was registered at pH 6. The adsorption conduct of Hg(II) was defined by pseudo second order well rather pseudo first order as the experimental data (q_e) come to an agreement with the calculated value. The kinetics of adsorption was fast and a high capacity of adsorption occurred within only 90 min. The adsorption data were signified by many models but Langmuir (q_max = 42. mg g⁻¹) & Freundlich fitted well having regression coefficients near to unity. The thermodynamic parameters were also suited well as negative value of free energy cope up to spontaneity, positive value of the randomness described by ΔS attributed to affinity of Hg⁺² towards algal bioadsorbant and high positive value of heat of enthalpy designates that the adsorption process is expected due to robust interactions between the Hg(II) ions and various functional groups on surface of algal bioadsorbant. Field emission scanning electron microscopy integrated with energy dispersive X-ray spectroscopy analysis before and after adsorption of Hg(II) reveals the adsorption of metallic ions over the surface. FTIR study supported the existence of various functional groups (carboxylix, amines, hydroxyls, amides etc.) helped in adsorption. Continuous adsorption desorption experiments proved that algal cells was excellent biosorbents with potential for further development.

Manipulation of Culture Conditions: Tool for Correlating/Improving Lipid and Carotenoid Production by Rhodotorula glutinis

The coproduction of lipid and carotenoid by red yeasts in one cycle is more convenient and economical for the industrial sectors, while the kinetics correlation between both products under different culture conditions has been scarcely studied. This study is aiming to correlate the impact of different carbon sources, carbon to phosphorus ratio (C/P), temperature, aeration, pH, and metals on dry cell weight, lipid (GC and fluorescence microscope), and carotenoid (HPLC) production by Rhodotorula glutinis, and applying a novel feeding approach using a 5 L bioreactor to enhance carotenoid and unsaturated fatty acid production by R. glutinis. Whatever the culture condition is, the reversible correlation between lipid and carotenoid production was detected. Remarkably, when adding 0.1 mM BaCl2, cellular lipid was significantly increased 14% more than the control, with 79.3% unsaturated fatty acid (46% C18:2 and C18:3) and 50% γ-carotene, while adding 1 mM NiSO4, cellular carotenoid was enhanced around 53% than the control (torulene 88%) with 81% unsaturated fatty acid (61% oleic acid). Excitingly, 68.8 g/l biomass with 41% cellular lipid (79% unsaturated fatty acid) and 426 µgpigment/gdcw cellular carotenoid (29.3 mg/L) (71% torulene) were obtained, when the pH-temperature dual controlled process combined with metallo-sulfo-phospho-glucose feeding approach in the 5 L bioreactor during the accumulation phase was conducted. This is the first study on the kinetic correlation between lipid and carotenoid under different C/P ratio and the dual effect of different metals like NiSO4 on lipid and carotenoid production by red oleaginous yeasts, which in turn significant for enhancing the coproduction of lipid and carotenoid by R. glutinis.

Biodegradation of hydrocarbons by microbial strains in the presence of Ni and Pb

Microbial strains capable of degrading petroleum hydrocarbons were isolated from the Yellow River Delta and screened for bio-surfactant production. The bio-surfactant-producing characteristics of the isolates were evaluated, and all the isolates which could produce bio-surfactant were identified by 16S rRNA gene sequencing. The results showed that the isolates belong to Bacillus sp. (72%), Ochrobactrum sp. (0.16%), Brevundimonas sp. (0.06%) and Brevibacterium sp. (0.06%). The biodegradability of crude oil, gasoline, diesel oil and other hydrocarbons by microbial strains were studied, among which the biodegrading ability of strain P1 and strain P19 is higher than other strains. Both strains P1 and P19 can degrade n-hexane and n-hexadecane effectively and have wide substrate extensiveness. In addition, Ni promoted the biodegradability of toluene by both strain P1 and strain P19, while Pb inhibited the growth of strain P19 and decreased its ability to biodegrade toluene. The studies revealed that microbes including strain P1 and strain P19 can be utilized in bioremediation of co-contaminated water with petroleum and heavy metals including Ni and Pb.

Valorization of coal fired-fly ash for potential heavy metal removal from the single and multi-contaminated system

In this study, adsorption of three different heavy metals i.e. cadmium (Cd (II)), copper (Cu (II)) and nickel (Ni (II)) was carried out in single and multi-contaminated system using coal-fired fly ash (CFFA). Initially, for the single contaminated system, various physical process parameters were selected for optimization by deploying Box–Behnken design of experiments. Further, the evaluation of CFFA for removal of heavy metals in a multi-component system from aqueous solution was performed by employing Plackett-Burman design of experiments with all the three heavy metals at two different levels by varying their initial concentration (10–50 mg L⁻¹). In both the aforementioned cases, CFFA showed its great potential for heavy metal removal, i.e. single and multi-component system and followed the order: Cu (II) > Ni (II) > Cd (II). Further, FTIR study confirmed the involvement of amide, aldehyde, alkoxy, alkanes, and alkene groups for heavy metal adsorption by CFFA.

Novel waste-derived biochar from biomass gasification effluent: preparation, characterization, cost estimation, and application in polycyclic aromatic hydrocarbon biodegradation and lipid accumulation by Rhodococcus opacus

This study evaluated an enhancement of simultaneous polycyclic aromatic hydrocarbon (PAH) biodegradation and lipid accumulation by Rhodococcus opacus using biochar derived cheaply from biomass gasification effluent. The chemical, physical, morphological, thermal, and magnetic properties of the cheaply derived biochar were initially characterized employing different techniques, which indicated that the material is easy to separate, recover, and reuse for further application. Batch experiments were carried out to study biochar-aided PAH biodegradation by R. opacus clearly demonstrating its positive effect on PAH biodegradation and lipid accumulation by the bacterium utilizing the synthetic media containing 2-, 3- or 4-ring PAH compounds, at an initial concentration in the range 50-200 mg L^-1, along with 10% (w/v) inoculum. An enhancement in PAH biodegradation from 79.6 to 92.3%, 76.1 to 90.5%, 74.1 to 88.2%, and 71.6 to 82.3% for naphthalene, anthracene, phenanthrene, and fluoranthene, respectively, were attained with a corresponding lipid accumulation of 68.1%, 74.2%, 72.4%, and 63% (w/w) of cell dry weight (CDW). From contact angle measurements carried out in the study, enhancement in PAH biodegradation and lipid accumulation due to the biochar was attributed to an improved bioavailability of PAH to the degrading bacterium.

Bioleaching of Al from spent fluid catalytic cracking catalyst using Aspergillus species

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Biogenically produced organic acids (citric acid) are used for the bioleaching of spent fluid catalytic cracking catalyst.

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Aspergillus strains-A. niger, A. foetidus, and A. carbonarius, were studied with varying catalyst loading for Al bioleaching.

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The highest Al leaching efficiency of 88.43% was obtained at 0.8% (w/v) catalyst loading using A. foetidus.

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A different carbon source, molasses was also investigated for Al bioleaching.

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Highest bioleaching efficiency of 60% (in molasses) for Al was obtained at 40 g/L sugar concentration.

Bioleaching uses biodegradable organic acids, thereby making the process environmental friendly as compared to chemical leaching. In this work, bioleaching of aluminium (Al) metal from spent catalyst was investigated by using three Aspergillus strains (A. niger, A. foetidus, and A. carbonarius). Bioleaching was performed in batch culture mode at different loading densities of spent catalyst (i.e., 0.4%, 0.8% and 1.2% (w/v)). The highest Al leaching efficiency of 88.43% was obtained at 0.8% ((w/v)) catalyst loading using A. foetidus, further increase in the catalyst loading decreased the efficiency. In addition to this, molasses was used as a carbon source (low-cost) at various concentrations for bioleaching of spent catalyst and the results were found to be significant at 40 g/L sugar concertation with 60% bioleaching efficiency. Overall, this study indicates that A. foetidus have the potential for leaching of Al from spent catalysts. Therefore, present research findings suggested that, instead of using mineral acids, organic acids (biodegradable) usage for metal leaching process is highly reliable and eco-friendly as well.

A novel integrated biodegradation-microfiltration system for sustainable wastewater treatment and energy recovery

This work assessed the treatment of wastewater generated from three different industries viz., paper and pulp, biomass gasification and dairy by biodegradation followed by membrane filtration. Batch biodegradation was first carried out using wastewater as the potential substrate for oleaginous Rhodococcus opacus with lipid accumulation intracellular; subsequently, a microfiltration system was applied to recover the bacterial biomass grown as well as for residual chemical oxygen demand (COD) removal from the effluent. The combined process showed excellent results in terms of COD removal from the industrial wastewaters, with the values 56.8%, 46.1% and 68.9% for dairy, paper and pulp and biomass gasification wastewaters, respectively, by biodegradation. These values were further improved to 92.7%, 87.6% and 88.2%, respectively, following the microfiltration step performed by employing a low-cost ceramic membrane. In addition, lipids accumulated by the bacterium were extracted and characterized for biodiesel production potential. Lipid characterization using ¹H NMR confirmed the presence of saturated fatty acids. Gas chromatography analysis of the transesterified lipids revealed the presence of methyl palmitate and methyl stearate. In addition, the estimated properties of the transesterified product affirmed its potential for biofuel application.

Groundwater flow and arsenic contamination transport modeling for a multi aquifer terrain: Assessment and mitigation strategies

Arsenic contaminated shallow aquifers evaluation, mitigation, and management strategies are the challenging task to all the hydrologist and provide a safe drinking water demand in the Holocene age, alluvial aquifers. To manage and mitigate such problems, we used numerical groundwater modeling software (GMS 10.2), for the development of 3D transient state predictive (groundwater flow and contaminant transport) conceptual model for two topographically different arsenic contaminated regions. The models were built by using the measured hydro-geological data, empirical values, and equations. Groundwater flow calibration, sensitivity analyses, and validation were performed for each soil parameters, varying boundary conditions and for alternate meteorological scenarios. The MODFLOW results suggested that, the distribution of As contaminant was directly controlled by the complex hydrostratigraphy, surface water bodies and indirectly controlled by the change in meteorological conditions. The MT3DMS model, for As contaminant transport, used for the assessment of shallow and deeper aquifers. The results showed that the downward movement of As has made the deeper aquifer unsafe for drinking water and irrigation purposes. However, the aquifers and regions with high flushing capability, negligible vertical hydraulic conductivity can be delineated as As safe groundwater source, irrespective of their sediment color. Therefore, for the geogenic source of As, both the simulation results inferred that to estimate and mitigate As contaminant groundwater aquifers or regions, the numerical modeling solution is a technically viable means an effective decision-making tool.

Screening and identification of Lactic acid bacteria from Ya'an pickle water to effectively remove Pb2

Heavy metal lead, which enters the human body through food intake, endangers human health. Microbe has the ability of adsorbing heavy metal, among which lactic acid bacteria are promising microbes to adsorb and remove Pb2+. The purpose of this study was to screen lactic acid bacteria from Ya'an pickle water to effectively remove Pb2+. The 7 strains having strong ability to effectively remove Pb2+ were detected. These strains were identified by microscopic examination and 16S rDNA sequencing, 4 strains of Lactobacillus plantarum and 3 strains of Lactobacillus brevis were obtained. Then the bacteria had a blind adsorption effect on Pb2+. After microwave digestion, the Pb2+ concentration was measured by flame atomic absorption spectrometry. The highest removal reached 82.25%. The adsorption mechanism of lactic acid bacteria was mainly divided into biosorption and bioaccumulation. The 7 strains of lactic acid bacteria could provide potential for detoxification of contaminated foods and reduction of the Pb2+ accumulation in the human diet and animal feed. At the same time, this study was helpful to further understand the mechanism of Pb2+ being adsorbed by lactic acid bacteria.

Evaluation of the cytotoxicity and interaction of lead with lead resistant bacterium Acinetobacter junii Pb1

This study explores the potential of lead resistant bacterium Acinetobacter junii Pb1 for adsorption/accumulation of lead using various techniques. In the present work, growth of A. junii Pb1 was investigated in the presence of a range of Pb(II) concentrations (0, 100, 250, 500, and 1000 mg l^-1). Lead was found to have no toxic effect on the growth of A. junii Pb1 at 100 and 250 mg l^-1 concentrations. However, further increase in Pb(II) concentration (500 mg l^-1) showed increase in lag phase, though growth remained unaffected and significant growth inhibition was observed when concentration was increased to 1000 mg l^-1. Same was confirmed by the observations of flow cytometry. Further, the effect of Pb(II) on A. junii Pb1 was evaluated by using fluorescence microscopy, spectrofluorimetry, and flow cytometry. The spectrofluorimetry and fluorescence microscopy results revealed the accumulation of Pb(II) inside the bacterial cells as evident by green fluorescence due to lead binding fluorescent probe, Leadmium Green AM dye. Flow cytometry observations indicate an increase in cell size and granularity of exposure to lead. Thus, present work provides a new understanding of Pb(II) tolerance in A. junii Pb1 and its potential use in remediation of lead from contaminated soil.

Genome Sequencing and Comparative Transcriptomics Provide a Holistic View of 4-Nitrophenol Degradation and Concurrent Fatty Acid Catabolism by Rhodococcus sp. Strain BUPNP1

Rhodococcus sp.strain BUPNP1 can utilize the priority environmental pollutant 4-nitrophenol (4-NP) as its sole source of carbon and energy. In this study, genome and transcriptome sequencing were used to gain mechanistic insights into 4-NP degradation. The draft BUPNP1 genome is 5.56 Mbp and encodes 4,963 proteins, which are significantly enriched in hypothetical proteins compared to other Rhodococcus sp. A novel 4-NP catabolic 43 gene cluster “nph” was identified that encodes all the genes required for the conversion of 4-NP into acetyl-CoA and succinate, via 4-nitrocatechol. The cluster also encodes pathways for the catabolism of other diverse aromatic compounds. Comparisons between BUPN1 growing on either 4-NP or glucose resulted in significant changes in the expression of many nph cluster genes, and, during 4-NP growth, a loss of lipid inclusions. Moreover, fatty acid degradation/synthesis genes were found within the nph cluster, suggesting fatty acids may be concurrently catabolised with 4-NP. A holistic model for the action of the nph gene cluster is proposed which incorporates genetic architecture, uptake and metabolism of aromatic compounds, enzymatic activities and transcriptional regulation. The model provides testable hypotheses for further biochemical investigations into the genes of the nph cluster, for potential exploitation in bioremediation.

Effect of Growing Miscanthus x giganteus on Soil Microbial Communities in Post-Military Soil

Growing a second generation energetic plant Miscanthus x giganteus (Mxg) in former military sites appears to be a promising way to use such areas with synergic phytoremediation of contaminants (organic pollutants, potential toxic metals). Effect of Mxg growth on soil microbial communities during a two-year pot experiment with real post-military soil (Sliač, Slovakia) and the effect of potential toxic metal concentration was studied by analyses of microbial activities and phospholipid fatty acids (PLFA). Year-on-year positive changes in microbial community structure and state were detected (higher ratios of G+/G− bacteria and fungal/bacterial PLFA, and a decrease of stress indicators trans/cis and cy/pre PLFA). Portion of gram-positive bacteria correlated negatively with potential toxic metal concentrations; however, the concentration of potential toxic metals was not identified as the main stress factor—the access to bioavailable nutrients was more important. Overall, Mxg growth generally exhibited a positive effect on soil microorganisms.