Assessment of environmental and carcinogenic health hazards from heavy metal contamination in sediments of wetlands.

Sediment contamination jeopardizes wetlands by harming aquatic organisms, disrupting food webs, and reducing biodiversity. Carcinogenic substances like heavy metals bioaccumulate in sediments and expose consumers to a greater risk of cancer. This study reports Pb, Cr, Cu, and Zn levels in sediments from eight wetlands in India. The Pb (51.25 ± 4.46 µg/g) and Cr (266 ± 6.95 µg/g) concentrations were highest in Hirakud, Cu (34.27 ± 2.2 µg/g) in Bhadrak, and Zn (55.45 ± 2.93 µg/g) in Koraput. The mean Pb, Cr, and Cu values in sediments exceeded the toxicity reference value. The contamination factor for Cr was the highest of the four metals studied at Hirakud (CF = 7.60) and Talcher (CF = 6.97). Furthermore, high and moderate positive correlations were observed between Cu and Zn (r = 0.77) and Pb and Cr (r = 0.36), respectively, across all sites. Cancer patients were found to be more concentrated in areas with higher concentrations of Pb and Cr, which are more carcinogenic. The link between heavy metals in wetland sediments and human cancer could be used to make policies that limit people's exposure to heavy metals and protect their health.

Recent advances and challenges in the utilization of nanomaterials in transesterification for biodiesel production.

Due to diminishing fossil fuel supplies and rising energy needs, there has been an ever-increasing demand for renewable energy sources. The available renewable energy resources, such as solar, wind, hydropower, and biofuels, provide a new way of supplying the world's energy needs. Biofuels stand out among them because they are sustainable and have the potential to bring the idea of a global bioeconomy to life. As a result of their production of biofuels like biomethane, biohydrogen, and biodiesel, atmospheric CO2 is being fixed, eventually lowering the world's carbon footprint. Current developments in the production of bioenergy have concentrated on producing biodiesel among other biofuels. Biodiesel is being produced from a variety of feedstocks using a number of processes, including transesterification, micro-emulsion, direct mixing, and pyrolysis. The most popular method among these is transesterification, which makes use of a variety of catalysts. As a result of the development of nanotechnology, nanocatalysts with desirable properties, such as increased catalytic activity, increased surface area, and superior thermal stability, have been made and modified. In this review, various nanocatalyst types and manufacturing processes are examined in relation to transesterification. It explores how crucial nanocatalysts are in boosting biodiesel production, highlights potential barriers, and makes recommendations for their widespread use in the future.

Comparative assessment on lignocellulose degrading enzymes and bioethanol production from spent mushroom substrate of Calocybe indica and Volvariella volvacea.

In the current study, we compared the production of extracellular lignocellulose degrading enzymes and bioethanol from the spent mushroom substrate (SMS) of Calocybe indica and Volvariella volvacea. From SMS at different stages of the mushroom development cycle, ligninolytic and hydrolytic enzymes were analysed. The activities of lignin-degrading enzymes, including lignin peroxidase (LiP), laccase, and manganese peroxidase (MnP) were maximal in the spawn run and primordial stages, while hydrolytic enzymes including xylanase, cellobiohydrolase (CBH), and carboxymethyl cellulase (CMCase) showed higher activity during fruiting bodies development and at the end of the mushroom growth cycle. SMS of V. volvacea showed relatively lower ligninase activity than the SMS of C. indica, but had the maximum activity of hydrolytic enzymes. The enzyme was precipitated with acetone and further purified with the DEAE cellulose column. The maximum yield of reducing sugars was obtained after hydrolysis of NaOH (0.5 M) pretreated SMS with a cocktail of partially purified enzymes (50% v/v). After enzymatic hydrolysis, the total reducing sugars were 18.68 ± 0.34 g/l (SMS of C. indica) and 20.02 ± 0.87 g/l (SMS of V. volvacea). We observed the highest fermentation efficiency and ethanol productivity (54.25%, 0.12 g/l h) obtained from SMS hydrolysate of V. volvacea after 48 h at 30 ± 2 °C, using co-culture of Saccharomyces cerevisiae MTCC 11,815 and Pachysolen tannophilus MTCC 1077.

Soil treatment using a biosurfactant producing bacterial consortium in rice fields contaminated with oily sludge- a sustainable approach.

A consortium of two biosurfactant-producing bacteria (Bacillus pumilus KS2 and Bacillus cereus R2) was developed to remediate petroleum hydrocarbon-contaminated paddy soil. Soil samples from a heavily contaminated rice field near Assam's Lakwa oilfield were collected and placed in earthen pots for treatment. After each month of incubation, 50 g of soil from each earthen pot was collected, and the soil TPH (ppm) in each sample was determined. The extracted TPH samples were analysed by Gas chromatography-mass spectrometry (GC-MS) to confirm microbial degradation. The soil samples were examined for changes in pH, conductivity, total organic content (TOC), water holding capacity, and total nitrogen content in addition to TPH degradation. An increasing trend in TPH degradation was observed with each passing month. After six months of treatment, the sample with the lowest initial TPH concentration (1735 ppm) had the highest degradation (91.24%), while the soil with the highest amount of TPH (5780 ppm) had the lowest degradation (74.35%). A wide range of aliphatic hydrocarbons found in soil samples was degraded by the bacterial consortium. The soil samples contained eight different low- and high-molecular-weight PAHs. Some were fully mineralized, while others were significantly reduced. With the decrease in the TPH level in the polluted soil, a significant improvement in the soil's physicochemical qualities (such as pH, electrical conductivity, total organic content, and water-holding capacity) was observed.

Fungi-derived agriculturally important nanoparticles and their application in crop stress management - Prospects and environmental risks.

Nanotechnology has a wide range of agricultural applications, with emphasize on the development of novel nano-agrochemicals such as, nano-fertilizer and nano-pesticides. It has a significant impact on sustainable agriculture by increasing agricultural productivity, while reducing the use of inorganic fertilizers, pesticides, and herbicides. Nano-coating delivery methods for agrochemicals have improved agrochemical effectiveness, safety, and consistency. Biosynthesis of nanoparticles (NPs) has recently been recognized as an effective tool, contrary to chemically derived NPs, for plant abiotic and biotic stress control, and crop improvement. In this regard, fungi have tremendous scope and importance for producing biogenic NPs of various sizes, shapes, and characteristics. Fungi are potential candidates for synthesis of biogenic NPs due to their enhanced bioavailability, biological activity, and higher metal tolerance. However, their biomimetic properties and high capacity for dispersion in soil, water environments, and foods may have negative environmental consequences. Furthermore, their bioaccumulation raises significant concerns about the novel properties of nanomaterials potentially causing adverse biological effects, including toxicity. This review provides a concise outline of the growing role of fungal-mediated metal NPs synthesis, its potential applications in crop field, and associated issues of nano-pollution in soil and its future implications.

Biodegradation of hazardous naphthalene and cleaner production of rhamnolipids - Green approaches of pollution mitigation.

Toxic and hazardous waste poses a serious threat to human health and the environment. Green remediation technologies are required to manage such waste materials, which is a demanding and difficult task. Here, effort was made to explore the role of Pseudomonas aeruginosa SR17 in alleviating naphthalene via catabolism and simultaneously producing biosurfactant. The results showed up to 89.2% naphthalene degradation at 35 °C and pH 7. The GC/MS analysis revealed the generation of naphthalene degradation intermediates. Biosurfactant production led to the reduction of surface tension of the culture medium to 34.5 mN/m. The biosurfactant was further characterized as rhamnolipids. LC-MS of the column purified biosurfactant revealed the presence of both mono and di rhamnolipid congeners. Rhamnolipid find tremendous application in medical field and as well as in detergent industry and since they are of biological origin, they can be used as favorable alternative against their chemical counterparts. The study demonstrated that catabolism of naphthalene and concurrent formation of rhamnolipid can result in a dual activity process, namely environmental cleanup and production of a valuable microbial metabolite. Additionally, the present-day application of rhamnolipids is highlighted.

Metagenomics Combined with Stable Isotope Probe (SIP) for the Discovery of Novel Dehalogenases Producing Bacteria.

Halogenated compounds are one of the largest groups of environmental-hazardous chemicals. The removal of the halogen atom from the substrate is possible by the catalytic activity of a type of enzyme called dehalogenase. Hydrolytic dehalogenases are suggested to be a good biodegradation catalyst for halogenated compounds with potential bioremediation applications. Therefore, the identification of possible bacterial strains that produce dehalogenase is of great importance. Soil microorganisms that are regularly exposed to halogenated pesticides are a major source of hydrolytic dehalogenase. Their proper identification may be useful in the production of high-quality dehalogenase. DNA stable isotope probing (DNA-SIP) is quite a useful technique for the identification of active microorganisms that assimilate specific carbon substrates and nutrients. Metagenomics combined with a stable isotope probe (SIP) technique could therefore be used to detect bacterial dehalogenases in pesticides exposed agricultural soil.

Analysis of Bacterial Diversity in Different Heavy Oil Wells of a Reservoir in South Oman with Alkaline pH.

The identification of potential hydrocarbon utilizing bacteria is an essential requirement in microbial enhanced oil recovery (MEOR). Molecular approaches like proteomic and genomic characterization of the isolates are replacing the traditional method of identification with systemic classification. Genotypic profiling of the isolates includes fingerprint or pattern-based technique and sequence-based technique. Understanding community structure and dynamics is essential for studying diversity profiles and is challenging in the case of microbial analysis. The present study aims to understand the bacterial community composition from different heavy oil contaminated soil samples collected from geographically related oil well areas in Oman and to identify spore-forming hydrocarbon utilizing cultivable bacteria. V4 region of 16S rDNA gene was the target for Ion PGM™. A total of 825081 raw sequences were obtained from Ion torrent from all the 10 soil samples. The species richness and evenness were found to be moderate in all the samples with four main phyla, Firmicutes, Bacteroidetes, Proteobacteria, and Actinobacteria, the most abundant being Firmicutes. Bacillus sp. ubiquitously dominated in all samples followed by Paenibacillus, which was followed by Brevibacillus, Planococcus, and Flavobacterium. Principal Coordinate Analysis (PCoA) and UPGMA dendrogram clustered the 10 soil samples into four main groups. Weighted UniFrac significance test determined that there was significant difference in the communities present in soil samples examined. It can be concluded that the microbial community was different in all the 10 soil samples with Bacillus and Paenibacillus sp. as predominating genus. The 16S rDNA sequencing of cultivable spore-forming bacteria identified the hydrocarbon utilizing bacteria as Bacillus and Paenibacillus sp. and the nucleotide sequences were submitted to NCBI GenBank under accession numbers KP119097-KP119115. Bacillus and Paenibacillus sp., which were relatively abundant in the oil fields, can be recommended to be chosen as candidates for hydrocarbon utilization study.

The potential of indigenous Paenibacillus ehimensis BS1 for recovering heavy crude oil by biotransformation to light fractions.

Microbial Enhanced Oil Recovery (MEOR) is a potential technology for residual heavy oil recovery. Many heavy oil fields in Oman and elsewhere have difficulty in crude oil recovery because it is expensive due to its high viscosity. Indigenous microbes are capable of improving the fluidity of heavy oil, by changing its high viscosity and producing lighter oil fractions. Many spore-forming bacteria were isolated from soil samples collected from oil fields in Oman. Among the isolates, an autochthonous spore-forming bacterium was found to enhance heavy oil recovery, which was identified by 16S rDNA sequencing as Paenibacillus ehimensis BS1. The isolate showed maximum growth at high heavy oil concentrations within four days of incubation. Biotransformation of heavy crude oil to light aliphatic and aromatic compounds and its potential in EOR was analyzed under aerobic and anaerobic reservoir conditions. The isolates were grown aerobically in Bushnell-Haas medium with 1% (w/v) heavy crude oil. The crude oil analyzed by GC-MS showed a significant biotransformation from the ninth day of incubation under aerobic conditions. The total biotransformation of heavy crude oil was 67.1% with 45.9% in aliphatic and 85.3% in aromatic fractions. Core flooding experiments were carried out by injecting the isolates in brine supplemented with Bushnell-Haas medium into Berea sandstone cores and were incubated for twelve days under oil reservoir conditions (50°C). The extra recovered oil was analyzed by GC-MS. The residual oil recovered from core flood experiments ranged between 10-13% compared to the control experiment. The GC-MS analyses of the extra recovered oil showed 38.99% biotransformation of heavy to light oil. The results also indicated the presence of 22.9% extra aliphatic compounds in the residual crude oil recovered compared to that of a control. The most abundant compound in the extra recovered crude oil was identified as 1-bromoeicosane. The investigations showed the potential of P. ehimensis BS1 in MEOR technology by the biotransformation of heavy to lighter crude oil under aerobic and reservoir conditions. Heavy oil recovery and biotransformation to lighter components are of great economic value and a few studies have been done.

Production, Characterization, and Application of Bacillus licheniformis W16 Biosurfactant in Enhancing Oil Recovery.

The biosurfactant production by Bacillus licheniformis W16 and evaluation of biosurfactant based enhanced oil recovery (EOR) using core-flood under reservoir conditions were investigated. Previously reported nine different production media were screened for biosurfactant production, and two were further optimized with different carbon sources (glucose, sucrose, starch, cane molasses, or date molasses), as well as the strain was screened for biosurfactant production during the growth in different media. The biosurfactant reduced the surface tension and interfacial tension to 24.33 ± 0.57 mN m-1 and 2.47 ± 0.32 mN m-1 respectively within 72 h, at 40°C, and also altered the wettability of a hydrophobic surface by changing the contact angle from 55.67 ± 1.6 to 19.54°± 0.96°. The critical micelle dilution values of 4X were observed. The biosurfactants were characterized by different analytical techniques and identified as lipopeptide, similar to lichenysin-A. The biosurfactant was stable over wide range of extreme environmental conditions. The core flood experiments showed that the biosurfactant was able to enhance the oil recovery by 24-26% over residual oil saturation (Sor). The results highlight the potential application of lipopeptide biosurfactant in wettability alteration and microbial EOR processes.

Lipopeptide production by Bacillus subtilis R1 and its possible applications

Abstract The possible application of a bacterial strain - Bacillus subtilis R1, isolated from an oil contaminated desert site in India, as biocontrol agent and its biosurfactant in microbial enhanced oil recovery are discussed. The biosurfactant production in minimal medium was carried out at different temperatures and salt concentrations, where it produced an efficient biosurfactant at 30-45 °C and in presence of up to 7% salt. It significantly reduced the surface tension from 66 ± 1.25 mN/m to 29 ± 0.85 mN/m within 24 h. In order to enhance the biosurfactant production, random mutagenesis of B. subtilis R1 was performed using chemical mutagen - ethyl methanesulfonate. Majority of the isolated 42 mutants showed biosurfactant production, but the difference was statistically insignificant as compared with parent strain R1. Therefore none of the mutants were selected for further study, and only parent strain R1 was studied. The biosurfactant was quite stable under harsh conditions for up to 10 days. The biosurfactant was extracted and characterized as similar to the lipopeptide group - surfactins and fengycin. The crude oil displacement experiments using biosurfactant broth in sand pack glass columns showed 33 ± 1.25% additional oil recovery. The strain also showed inhibition of various plant pathogenic fungi on potato dextrose agar medium.

Lipopeptide production by Bacillus subtilis R1 and its possible applications.

The possible application of a bacterial strain - Bacillus subtilis R1, isolated from an oil contaminated desert site in India, as biocontrol agent and its biosurfactant in microbial enhanced oil recovery are discussed. The biosurfactant production in minimal medium was carried out at different temperatures and salt concentrations, where it produced an efficient biosurfactant at 30-45°C and in presence of up to 7% salt. It significantly reduced the surface tension from 66±1.25mN/m to 29±0.85mN/m within 24h. In order to enhance the biosurfactant production, random mutagenesis of B. subtilis R1 was performed using chemical mutagen - ethyl methanesulfonate. Majority of the isolated 42 mutants showed biosurfactant production, but the difference was statistically insignificant as compared with parent strain R1. Therefore none of the mutants were selected for further study, and only parent strain R1 was studied. The biosurfactant was quite stable under harsh conditions for up to 10 days. The biosurfactant was extracted and characterized as similar to the lipopeptide group - surfactins and fengycin. The crude oil displacement experiments using biosurfactant broth in sand pack glass columns showed 33±1.25% additional oil recovery. The strain also showed inhibition of various plant pathogenic fungi on potato dextrose agar medium.

Sophorolipids Production by Candida bombicola ATCC 22214 and its Potential Application in Microbial Enhanced Oil Recovery.

Biosurfactant production using Candida bombicola ATCC 22214, its characterization and potential applications in enhancing oil recovery were studied at laboratory scale. The seed media and the production media were standardized for optimal growth and biosurfactant production. The production media were tested with different carbon sources: glucose (2%w/v) and corn oil (10%v/v) added separately or concurrently. The samples were collected at 24 h interval up to 120 h and checked for growth (OD660), and biosurfactant production [surface tension (ST) and interfacial tension (IFT)]. The medium with both glucose and corn oil gave better biosurfactant production and reduced both ST and IFT to 28.56 + 0.42mN/m and 2.13 + 0.09mN/m, respectively within 72 h. The produced biosurfactant was quite stable at 13-15% salinity, pH range of 2-12, and at temperature up to 100°C. It also produced stable emulsions (%E24) with different hydrocarbons (pentane, hexane, heptane, tridecane, tetradecane, hexadecane, 1-methylnaphthalene, 2,2,4,4,6,8-heptamethylnonane, light and heavy crude oil). The produced biosurfactant was extracted using ethyl acetate and characterized as a mixture of sophorolipids (SPLs). The potential of SPLs in enhancing oil recovery was tested using core-flooding experiments under reservoir conditions, where additional 27.27% of residual oil (Sor) was recovered. This confirmed the potential of SPLs for applications in microbial enhanced oil recovery.

Characterization and Application of Biosurfactant Produced by Bacillus licheniformis R2.

The biosurfactant produced by Bacillus licheniformis R2 was characterized and studied for enhancing the heavy crude oil recovery at 80 °C in coreflood experiments. The strain was found to be nonpathogenic and produced biosurfactant, reducing the surface tension of medium from 70 to 28 mN/m with 1.1 g/l yield. The biosurfactant was quite stable during exposure to elevated temperatures (85 °C for 90 days), high salinity (10 % NaCl), and a wide range of pH (5-12) for 10 days. It was characterized as lipopeptide similar to lichenysin-A, with a critical micelle concentration of about 19.4 mg/l. The efficiency of crude biosurfactant for enhanced oil recovery by core flood studies revealed it to recovering additional 37.1 % oil from Berea sandstone cores at 80 °C. The results are indicative of the potential for the development of lipopeptide biosurfactant-based ex situ microbial enhanced heavy oil recovery from depleting oil fields with extreme temperatures.

Production of bioethanol using agricultural waste: banana pseudo stem.

India is amongst the largest banana (Musa acuminata) producing countries and thus banana pseudo stem is commonly available agricultural waste to be used as lignocellulosic substrate. Present study focuses on exploitation of banana pseudo stem as a source for bioethanol production from the sugars released due to different chemical and biological pretreatments. Two fungal strains Aspergillus ellipticus and Aspergillus fumigatus reported to be producing cellulolytic enzymes on sugarcane bagasse were used under co-culture fermentation on banana pseudo stem to degrade holocellulose and facilitate maximum release of reducing sugars. The hydrolysate obtained after alkali and microbial treatments was fermented by Saccharomyces cerevisiae NCIM 3570 to produce ethanol. Fermentation of cellulosic hydrolysate (4.1 g%) gave maximum ethanol (17.1 g/L) with yield (84%) and productivity (0.024 g%/h) after 72 h. Some critical aspects of fungal pretreatment for saccharification of cellulosic substrate using A. ellipticus and A. fumigatus for ethanol production by S. cerevisiae NCIM 3570 have been explored in this study. It was observed that pretreated banana pseudo stem can be economically utilized as a cheaper substrate for ethanol production.

Production of bioethanol using agricultural waste: banana pseudo stem

India is amongst the largest banana (Musa acuminata) producing countries and thus banana pseudo stem is commonly available agricultural waste to be used as lignocellulosic substrate. Present study focuses on exploitation of banana pseudo stem as a source for bioethanol production from the sugars released due to different chemical and biological pretreatments. Two fungal strains Aspergillus ellipticus and Aspergillus fumigatus reported to be producing cellulolytic enzymes on sugarcane bagasse were used under co-culture fermentation on banana pseudo stem to degrade holocellulose and facilitate maximum release of reducing sugars. The hydrolysate obtained after alkali and microbial treatments was fermented by Saccharomyces cerevisiae NCIM 3570 to produce ethanol. Fermentation of cellulosic hydrolysate (4.1 g%) gave maximum ethanol (17.1 g/L) with yield (84%) and productivity (0.024 g%/h) after 72 h. Some critical aspects of fungal pretreatment for saccharification of cellulosic substrate using A. ellipticus and A. fumigatus for ethanol production by S. cerevisiae NCIM 3570 have been explored in this study. It was observed that pretreated banana pseudo stem can be economically utilized as a cheaper substrate for ethanol production.

Microbial enhanced heavy oil recovery by the aid of inhabitant spore-forming bacteria: an insight review.

Crude oil is the major source of energy worldwide being exploited as a source of economy, including Oman. As the price of crude oil increases and crude oil reserves collapse, exploitation of oil resources in mature reservoirs is essential for meeting future energy demands. As conventional recovery methods currently used have become less efficient for the needs, there is a continuous demand of developing a new technology which helps in the upgradation of heavy crude oil. Microbial enhanced oil recovery (MEOR) is an important tertiary oil recovery method which is cost-effective and eco-friendly technology to drive the residual oil trapped in the reservoirs. The potential of microorganisms to degrade heavy crude oil to reduce viscosity is considered to be very effective in MEOR. Earlier studies of MEOR (1950s) were based on three broad areas: injection, dispersion, and propagation of microorganisms in petroleum reservoirs; selective degradation of oil components to improve flow characteristics; and production of metabolites by microorganisms and their effects. Since thermophilic spore-forming bacteria can thrive in very extreme conditions in oil reservoirs, they are the most suitable organisms for the purpose. This paper contains the review of work done with thermophilic spore-forming bacteria by different researchers.

Engineering rhizobial bioinoculants: a strategy to improve iron nutrition.

Under field conditions, inoculated rhizobial strains are at a survival disadvantage as compared to indigenous strains. In order to out-compete native rhizobia it is not only important to develop strong nodulation efficiency but also increase their competence in the soil and rhizosphere. Competitive survival of the inoculated strain may be improved by employing strain selection and by genetic engineering of superior nitrogen fixing strains. Iron sufficiency is an important factor determining the survival and nodulation by rhizobia in soil. Siderophores, a class of ferric specific ligands that are involved in receptor specific iron transport into bacteria, constitute an important part of iron acquisition systems in rhizobia and have been shown to play a role in symbiosis as well as in saprophytic survival. Soils predominantly have iron bound to hydroxamate siderophores, a pool that is largely unavailable to catecholate-utilizing rhizobia. Outer membrane receptors for uptake of ferric hydroxamates include FhuA and FegA which are specific for ferrichrome siderophore. Increase in nodule occupancy and enhanced plant growth of the fegA and fhuA expressing engineered bioinoculants rhizobial strain have been reported. Engineering rhizobia for developing effective bioinoculants with improved ability to utilize heterologous siderophores could provide them with better iron acquisition ability and consequently, rhizospheric stability.