A critical review on the ecotoxicity of heavy metal on multispecies in global context: A bibliometric analysis.

Heavy metals (HMs) have become a significant concern in the current era, with deleterious effects on diverse living organisms when exposed beyond threshold concentrations. Both nature and human beings have been constantly casting out HMs into environmental matrices through various activities. Innumerable cases of threatened diseases such as cancer, respiratory ailments, reproductive defects, skin diseases, and several others have been a cause of significant concern for humans as the number of instances has been increasing with each decade. HMs migrates via several pathways to infiltrate biological organisms and amass within them. Even though numerous treatment approaches are available for remediating HM pollution, however, they are expensive, along with other setbacks. Due to such constraints, combating HM contamination requires environmentally conscious strategies like bioremediation, which employs an array of biological systems to remove HMs from the environment. Nonetheless, to address the current global HM pollution situation, it is critical to comprehend not only how these hazardous HMs cause toxicity in various living organisms but also the knowledge gaps that currently exist concerning the subject of HM ecotoxicity. In the present investigation, data was extracted from Google Scholar using software program called Harzing's Publish or Perish. The collected information has been subsequently displayed as a network file using the VOSViewer software tool. Thus, the current review presents a significant insight with the inclusion of a readily accessible bibliometric analysis to comprehend the present status of HMs research, global research trends, existing knowledge discrepancies, and research challenges. Further, it also provides an in-depth review of HMs ecotoxicity, with a focus on arsenic (As), cadmium (Cd), and lead (Pb). Thus, as indicated by the bibliometric study, the present review will assist future investigators studying HMs ecotoxicity by providing baseline data concerning a wide range of living organisms and by addressing research gaps.

Autochthonous psychrophilic hydrocarbonoclastic bacteria and its ecological function in contaminated cold environments.

Petroleum hydrocarbon (PH) pollution has mostly been caused by oil exploration, extraction, and transportation activities in colder regions, particularly in the Arctic and Antarctic regions, where it serves as a primary source of energy. Due to the resilience feature of nature, such polluted environments become the realized ecological niches for a wide community of psychrophilic hydrocarbonoclastic bacteria (PHcB). In contrast, to other psychrophilic species, PHcB is extremely cold-adapted and has unique characteristics that allow them to thrive in greater parts of the cold environment burdened with PHs. The stated group of bacteria in its ecological niche aids in the breakdown of litter, turnover of nutrients, cycling of carbon and nutrients, and bioremediation. Although such bacteria are the pioneers of harsh colder environments, their growth and distribution remain under the influence of various biotic and abiotic factors of the environment. The review discusses the prevalence of PHcB community in colder habitats, the metabolic processes involved in the biodegradation of PH, and the influence of biotic and abiotic stress factors. The existing understanding of the PH metabolism by PHcB offers confirmation of excellent enzymatic proficiency with high cold stability. The discovery of more flexible PH degrading strategies used by PHcB in colder environments could have a significant beneficial outcome on existing bioremediation technologies. Still, PHcB is least explored for other industrial and biotechnological applications as compared to non-PHcB psychrophiles. The present review highlights the pros and cons of the existing bioremediation technologies as well as the potential of different bioaugmentation processes for the effective removal of PH from the contaminated cold environment. Such research will not only serve to investigate the effects of pollution on the basic functional relationships that form the cold ecosystem but also to assess the efficacy of various remediation solutions for diverse settings and climatic conditions.

Optimization of Nutrient Requirements and Culture Conditions for the Production of Rhamnolipid from Pseudomonas aeruginosa (MTCC 7815) using Mesua ferrea Seed Oil.

Environmental awareness has led to a serious consideration for biological surfactants and hence non-edible vegetable oils may serve as a substitute carbon source for bio-surfactant production (rhamnolipid) which might be an alternative to complex synthetic surfactants. There are reports of rhamnolipid production from plant based oil giving higher production than that of glucose because of their hydrophobicity and high carbon content. Therefore the contribution of non-edible oil such as Mesua ferrea seed oil could serve as a good carbon source for rhamnolipid production. Moreover the use of rhamnolipid production from non-edible plant based seed oil has not been reported elsewhere. The present work focus on the optimal production of rhamnolipid by considering both micro and macro nutrients and culture conditions using response surface methodology. The study observes that micronutrients play a significant role in rhamnolipid production from Pseudomonas aeruginosa (MTCC 7815). The investigation results with the statistically optimize parameters able to produce a higher rhamnolipid production and this methodology could be used to optimize the nutrients requirements and culture conditions. The present findings would assist in bioremediation of crude oil contaminated ecosystems.

PHA-Based Bioplastic: a Potential Alternative to Address Microplastic Pollution.

Petroleum-derived plastics are linked to a variety of growing environmental issues throughout their lifecycle, including emission of greenhouse gases, accumulation in terrestrial and marine habitats, pollution, among others. There has been a lot of attention over the last decade in industrial and research communities in developing and producing eco-friendly polymers to deal with the current environmental issues. Bioplastics preferably are a fast-developing family of polymeric substances that are frequently promoted as substitutes to petroleum-derived plastics. Polyhydroxyalkanoates (PHAs) have a number of appealing properties that make PHAs a feasible source material for bioplastics, either as a direct replacement of petroleum-derived plastics or as a blend with elements derived from natural origin, fabricated biodegradable polymers, and/or non-biodegradable polymers. Among the most promising PHAs, polyhydroxybutyrates (PHBs) are the most well-known and have a significant potential to replace traditional plastics. These biodegradable plastics decompose faster after decomposing into carbon dioxide, water, and inorganic chemicals. Bioplastics have been extensively utilized in several sectors such as food-processing industry, medical, agriculture, automobile industry, etc. However, it is also associated with disadvantages like high cost, uneconomic feasibility, brittleness, and hydrophilic nature. A variety of tactics have been explored to improve the qualities of bioplastics, with the most prevalent being the development of gas and water barrier properties. The prime objective of this study is to review the current knowledge on PHAs and provide a brief introduction to PHAs, which have drawn attention as a possible potential alternative to conventional plastics due to their biological origin, biocompatibility, and biodegradability, thereby reducing the negative impact of microplastics in the environment. This review may help trigger further scientific interest to thoroughly research on PHAs as a sustainable option to greener bioplastics.

In-situ biofabrication of bacterial nanocellulose (BNC)/graphene oxide (GO) nano-biocomposite and study of its cationic dyes adsorption properties.

In the present study, bacterial nanocellulose/graphene oxide nano-biocomposites (BNC-GO-NBCs) were fabricated by Komagataeibacter saccharivorans NUWB1 using an in-situ method involving three time-dependent approaches. Physicochemical studies showed that the chosen dried BNC-GO-NBC possessed a three-dimensional interconnected porous structure of BNC with GO layers embedded within the BNC fibrils. BNC-GO-NBC had a crystallinity index of 74.21 %, higher thermostability up to 380 °C and could withstand a tensile load of 84.72 MPa. N2 adsorption-desorption isotherm of the BNC-GO-NBC was found to be of type IV, suggesting a mesoporous type structure with a total pore volume and surface area of 6.232e-04 cc g-1 and 10.498 m2. BNC-GO-NBC exhibited remarkable adsorption capacity for two cationic dyes, Rhodamine B (RhB) and Acridine Orange (AO), and the adsorption data conformed well to the Langmuir isotherm (R2 = 0.99) and pseudo-second-order model. Thermodynamic studies indicated that the adsorption process was spontaneous and endothermic. Additionally, the BNC-GO-NBC displayed the potential for regeneration, with the ability to be recycled up to five times. Further, the antibacterial activity, cell cytotoxicity and oxidative stress assays of the BNC-GO-NBC revealed its non-cytotoxic nature. The findings of the present investigation evidently suggest the potentiality of BNC-GO-NBC in the application of dye adsorption and other environmental applications.

Bioprospecting of indigenous biosurfactant-producing oleophilic bacteria for green remediation: an eco-sustainable approach for the management of petroleum contaminated soil.

In the present study, the efficiency of four different strains of Pseudomonas aeruginosa and their biosurfactants in the bioremediation process were investigated. The strains were found to be capable of metabolizing a wide range of hydrocarbons (HCs) with preference for high molecular weight aliphatic (ALP) over aromatic (ARO) compounds. After treating with individual bacteria and 11 different consortia, the residual crude oils were quantified and qualitatively analyzed. The bacterial strains degraded ALP, ARO, and nitrogen, sulphur, oxygen (NSO) containing fractions of the crude oil by 73-67.5, 31.8-12.3 and 14.7-7.3%, respectively. Additionally, the viscosity of the residual crude oil reduced from 48.7 to 34.6-39 mPa s. Further, consortium designated as 7 and 11 improved the degradation of ALP, ARO, and NSO HCs portions by 80.4-78.6, 42.7-42.4 and 21.6-19.2%, respectively. Moreover, addition of biosurfactant further increased the degradation performance of consortia by 81.6-80.7, 43.8-42.6 and 22.5-20.7%, respectively. Gas chromatographic analysis confirmed the ability of the individual strains and their consortium to degrade various fractions of crude oil. Experiments with biosurfactants revealed that polyaromatic hydrocarbons (PAHs) are more soluble in the presence of biosurfactants. Phenanthrene had the highest solubility among the tested PAHs, which further increased as biosurfactant doses raised above their respective critical micelle concentrations (CMC). Furthermore, biosurfactants were able to recover 73.5-63.4% of residual oil from the sludge within their respective CMCs. Hence, selected surfactant-producing bacteria and their consortium could be useful in developing a greener and eco-sustainable way for removing crude oil pollutants from soil.

Green Synthesis of Bromo Organic Molecules and Investigations on Their Antibacterial Properties: An Experimental and Computational Approach.

A simple, environmentally benign methodology has been developed to synthesize some bromoorganic compounds which have potential as antimicrobial agents. The required compounds were obtained through microwave (MW) irradiation, on-water reactions and using cetyltrimethylammonium tribromide (CTMATB) as the bromine source. The high yield of the product could be achieved within short reaction times, thus representing the main attribute of the present synthetic approach. The compounds were evaluated for in vitro antibacterial activity against Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus and Bacillus subtilis. Further, in silico studies were carried out to elucidate the interactions of the compounds with the bacterial proteins.

Antimicrobial hyperbranched poly(ester amide)/polyaniline nanofiber modified montmorillonite nanocomposites.

There has been growing interest in the use of nanomaterials featuring potent of antimicrobial activity in the biomedical domain. It still remains a challenge for the researchers to develop an efficient nanocomposite possessing antimicrobial efficacy against broad spectrum microbes including bacteria, fungi as well as algal consortium, posing serious challenges for the human survival. In addressing the above problem, we report the fabrication of bio-based hyperbranched poly(ester amide) (HBPEA)/polyaniline nanofiber modified montmorillonite (MMT) nanocomposites by an ex-situ polymerization technique at varied weight percentages (1, 2.5, 5 wt.%) of the modified MMT (nanohybrid). The Fourier transform infrared spectroscopy confirmed the structural changes upon interaction of the nanohybrid with HBPEA. A probable mechanism is proposed for the formation of nanocomposites with partially exfoliated nanoplatelet structure, which was further confirmed from the high resolution transmission electron microscopic analyses. The prepared nanocomposites exhibited potent efficacy against gram positive bacteria like Bacillus subtilis and Staphylococcus aureus as compared to the gram negative ones like Pseudomonas aeruginosa and Escherichia coli. The nanocomposites showed significant antifungal activity against Aspergillus niger, Fusarium oxysporum and Coleotricum capcii and antialgal activity against algal consortium comprising of Chlorella, Hormidium and Cladophorella species. The formation of thermosetting nanocomposites resulted in the acceptable improvement of desired physico-chemical and mechanical properties including thermostability. Thus pronounced antimicrobial activity of the nanocomposites against a spectrum of bacterial and fungal strains as well as a consortium of algal species along with other desired performance vouched them as potent antimicrobial materials in the realm of health and biomedical industry.

Possible protection of silver nanoparticles against salt by using rhamnolipid.

Rhamnolipid (RL) from Pseudomonas aeruginosa was dissolved in distilled water with concentration equivalent to its critical micelle concentration (CMC). Silver nanoparticles (SNP) synthesized in the RL colloid were found to be stable for more than 1 month. Further, after 1 month when the SNP in RL colloid (SNPRL) were exposed to NaCl solution it took about 60 mg/ml as compared to 2 mg NaCl/ml in the case of SNP colloid for degrading silver nanoparticles. The inference suggests that the RL must undergo vesicle formation and to prevent silver nanoparticle exposure to NaCl.

Silver-embedded modified hyperbranched epoxy/clay nanocomposites as antibacterial materials.

Silver-embedded modified hyperbranched epoxy/clay nanocomposites were prepared at different wt.% of octadecyl amine-modified montmorillonite at a constant silver concentration (1 wt.%). UV-visible, XRD and TEM studies confirmed the formation of silver nanoparticles. Compared to the system without silver and clay, the gloss from 70° to 94°, scratch hardness from 4 to 5.8 kg, impact strength from 60 to 90 cm, tensile strength from 8.5 to 15.5 MPa, adhesive strength from 5 to 7.1 × 10(9)N/m, flexibility from >6 to <4mm, and thermostability from 230 to 260 °C increased for the modified system. Resistance to aqueous 10% HCl, 0.5% NaOH, 10% NaCl also increased. The nanocomposites showed antibacterial activity in well diffusion assays against Staphylococcus aureus (ATCC11632), Bacillus subtilis (ATCC11774), Escherichia coli (MTCC40), Pseudomonas aeruginosa (MTCC7814) and Klebsiella pneumoniae (ATCC10031). The results showed that these nanocomposites have potential to be used as antimicrobial materials.

Production and physico-chemical characterization of a biosurfactant produced by Pseudomonas aeruginosa OBP1 isolated from petroleum sludge.

Pseudomonas aeruginosa strain OBP1, isolated from petroleum sludge, was used to produce biosurfactant from a modified mineral salt medium with 2% n-hexadecane as sole source of carbon. The crude biosurfactant was fractionated using TLC and HPLC. Using FTIR spectroscopy, ¹H NMR, and LC-MS analyses, the chemical structure of the purified fraction of crude biosurfactant was identified as rhamnolipid species. The LC-MS spectra show that monorhamnolipid (L-rhamnopyranosyl-ß-hydroxydecanoyl-ß- hydroxydecanoate, Rha-C10-C10) was produced in abundance with the predominant congener [M-H]⁻ ions for L-rhamnopyranosyl-L-rhamnopyranosyl-3-hydroxydecanoyl-3-hydroxydecanoate (Rha-Rha-C10-C10). Seven different carbon substrates and five nitrogen sources were examined for their effect on rhamnolipid production. Using n-hexadecane (20 g/l) as carbon substrate and urea along with (NH4)2SO4 (2 g/l each) as nitrogen source was found to be the best, with a maximum yield of 4.8 g/l. The biosurfactant reduced the surface tension of water to 31.1 mN m⁻¹ with a critical micelle concentration of 45 mg/l. The biosurfactant showed a better emulsifying activity against a variety of hydrocarbon and achieved a maximum emulsion index of 82% for diesel. The purified biosurfactant showed a significant antibacterial activity against Staphylococcus aureus at a minimum inhibitory concentration of 8 µg/ml.