Bioremediation Agents Research Articles

Application of Green Surfactants in the Remediation of Soils Contaminated by Hydrocarbons

Among the innovative technologies utilized for the treatment of contaminated soils, the use of green surfactants appears to be a biocompatible, efficient, and attractive alternative, since the cleaning processes that normally use synthetic surfactants as additives cause other problems due to toxicity and the accumulation of by-products. Three green surfactants, i.e., two biobased (biobased 1 and biobased 2) surfactants produced by chemical synthesis and a microbial surfactant produced from the yeast Starmerella bombicola ATCC 22214, were used as soil remediation agents and compared to a synthetic surfactant (Tween 80). The three surfactants were tested for their ability to emulsify, disperse, and remove different hydrophobic contaminants. The biosurfactant, which was able to reduce the water surface tension to 32.30 mN/m at a critical micelle concentration of 0.65 g/L, was then used to prepare a commercial formulation that showed lower toxicity to the tested environmental bioindicators and lower dispersion capacity than the biobased surfactants. All the green surfactants showed great emulsification capacity, especially against motor oil and petroleum. Therefore, their potential to remove motor oil adsorbed on different types of soils (sandy, silty, and clay soil and beach sand) was investigated either in kinetic (flasks) or static (packed columns) experiments. The commercial biosurfactant formulation showed excellent effectiveness in removing motor oil, especially from contaminated sandy soil (80.0 ± 0.46%) and beach sand (65.0 ± 0.14%) under static conditions, while, in the kinetic experiments, the commercial biosurfactant and the biobased 2 surfactant were able to remove motor oil from all the contaminated soils tested more effectively than the biobased 1 surfactant. Finally, the S. bombicola commercial biosurfactant was evaluated as a soil bioremediation agent. In degradation experiments carried out on motor oil-contaminated soils enriched with sugarcane molasses, oil degradation yield in the sandy soil reached almost 90% after 60 days in the presence of the commercial biosurfactant, while it did not exceed 20% in the presence of only S. bombicola cells. These results promise to contribute to the development of green technologies for the treatment of hydrophobic pollutants with economic gains for the oil industries.

Petroleum Hydrocarbon Impacted Aquatic Ecosystem Reveals Methylotenera as the Dominant Genera in the Niger Delta Region of Nigeria

Petroleum pollution of coastal areas such as Nigeria’s Niger Delta is increasingly alarming. After an oil spill, aquatic organisms, including indigenous microbial communities are affected, leading to an increased abundance of oil degraders in the affected environment. During the last decade, microbial ecology research has shifted from cultivation and characterization of individual environmental isolates to metagenomics studies that are focused on the characterization of community dynamics and composition. In this study, we determined the indigenous bacterial community in water bodies polluted with crude oil in Delta State, Nigeria by Next Generation Sequencing (NGS). Oil hydrocarbon composition was determined by Gas Chromatography–Mass Spectrometry analysis (GC–MS) and the physical-chemical dynamics were assessed using standard procedures. Results revealed Proteobacteria (76.9%), Bacteroidetes (8.5%) and Firmicutes (1.1%) as the dominant phyla. GC–MS data revealed different petroleum hydrocarbon concentrations across the seasons and locations sampled. The indigenous bacterial community included the prevalence of oil degrades with Methylotenera as the major genus. This study suggests that Methylotenera could be a useful agent for bioremediation in the Niger Delta.

Phenotype Switching in Metal-Tolerant Bacteria Isolated from a Hyperaccumulator Plant.

Simple SummaryAzolla filiculoides L. is an aquatic fern with the potential for degradation and accumulation of pollutants. It is accompanied by microorganisms (a microbiome) that may participate in these processes. Microorganisms showing specific phenotypes may promote plant growth in the presence of pollutants. We intended to identify such beneficial strains by studying their potential for the degradation of given organic compounds and the production of hydrolytic enzymes and phytohormones under heavy metal stress (Pb, Cd, Cr (VI), Ni, Ag, and Au). We found 10 isolates displaying varying phenotypes depending on the stress factor. The most efficient was Delftia sp., which showed potential for both degradation of organics and plant growth promotion. Other strains were more efficient at metabolizing organics or exhibited enzymatic responses in the presence of the studied metals. These identified phenotypes made all strains beneficial in both supporting plants in unfavorable conditions and degradation of organic compounds. A biopreparation containing these strains may be valuable as both a biofertilizer and a bioremediation agent.As an adaptation to unfavorable conditions, microorganisms may represent different phenotypes. Azolla filiculoides L. is a hyperaccumulator of pollutants, but the functions of its microbiome have not been well recognized to date. We aimed to reveal the potential of the microbiome for degradation of organic compounds, as well as its potential to promote plant growth in the presence of heavy metals. We applied the BiologTM Phenotypic Microarrays platform to study the potential of the microbiome for the degradation of 96 carbon compounds and stress factors and assayed the hydrolytic potential and auxin production by the microorganisms in the presence of Pb, Cd, Cr (VI), Ni, Ag, and Au. We found various phenotype changes depending on the stress factor, suggesting a possible dual function of the studied microorganisms, i.e., in bioremediation and as a biofertilizer for plant growth promotion. Delftia sp., Staphylococcus sp. and Microbacterium sp. exhibited high efficacy in metabolizing organic compounds. Delftia sp., Achromobacter sp. and Agrobacterium sp. were efficient in enzymatic responses and were characterized by metal tolerant. Since each strain exhibited individual phenotype changes due to the studied stresses, they may all be beneficial as both biofertilizers and bioremediation agents, especially when combined in one biopreparation.

Potential of Variovorax paradoxus isolate BFB1_13 for bioremediation of BTEX contaminated sites

Here, we report and discuss the applicability of Variovorax paradoxus strain BFB1_13 in the bioremediation of BTEX contaminated sites. Strain BFB1_13 was capable of degrading all the six BTEX-compounds under both aerobic (O2 conc. 8 mg l−1) and micro-aerobic/oxygen-limited (O2 conc. 0.5 mg l−1) conditions using either individual (8 mg‧l−1) or a mixture of compounds (~ 1.3 mg‧l−1 of each BTEX compound). The BTEX biodegradation capability of SBP-encapsulated cultures (SBP—Small Bioreactor Platform) was also assessed. The fastest degradation rate was observed in the case of aerobic benzene biodegradation (8 mg l−1 per 90 h). Complete biodegradation of other BTEX occurred after at least 168 h of incubation, irrespective of the oxygenation and encapsulation. No statistically significant difference was observed between aerobic and microaerobic BTEX biodegradation. Genes involved in BTEX biodegradation were annotated and degradation pathways were predicted based on whole-genome shotgun sequencing and metabolic analysis. We conclude that V. paradoxus strain BFB1_13 could be used for the development of reactive biobarriers for the containment and in situ decontamination of BTEX contaminated groundwater plumes. Our results suggest that V. paradoxus strain BFB1_13—alone or in co-culture with other BTEX degrading bacterial isolates—can be a new and efficient commercial bioremediation agent for BTEX contaminated sites.

Antioxidant capacity and DNA damage in Nile tilapia (Oreochromis niloticus) exposed to Ethidium bromide: A protective role for Spirulina Platensis

Negative impacts of chemicals are documented in the environment, but a shortage exists in bioremediation studies for residues of such chemicals in aquatic systems. This study focused on the effects of Ethidium Bromide (EtBr) on fry of Oreochromis niloticus and the role of Spirulina platensis (SP) as a bioremediation agent. Five groups of fish were divided into (1) control, and four treatment groups: (2)10 µg L − 1 EtBr, (3)10 µg L − 1 EtBr with 200 mg L − 1 SP, (4)100 µg L − 1 EtBr, and (5)100 µg L − 1 EtBr with 200 mg L − 1 SP for 15 days. Antioxidant biomarkers–total antioxidant capacity; TAC, Superoxide dismutase; SOD, and catalase; CAT–were assessed. Exposure to EtBr led to a decrease in TAC after exposure to 100 µg L − 1 EtBr and 100 µg L − 1 EtBr +200 mg L − 1 SP. No significant change in SOD and CAT activity was observed compared with control fish, except for fish treated with 100 µg L − 1 EtBr. This treatment induces an increase in activity of SOD and CAT. DNA fragmentation increased significantly after exposure to EtBr alone and this increase was counteracted by combined exposure to SP. Exposure to EtBr induced alteration in antioxidant capacity and DNA damage. SP protects against these negative impacts.

Growth Performance of Grain Amaranth (Amaranthus Cruentus L.) on Spent Engine Oil Contaminated Soil Bioremediated With Two Bacterial Co-Cultures and Organic Amendments

The advent of bioremediation technology has helped scientists to proffer sustainable solutions to problems associated with environmental pollution. This study was staged to assess the growth of Amaranthus cruentus L. on spent engine oil (SEO) contaminated soil that had been subjected to bioremediation. Two bacterial co-cultures; Pseudomonas aeruginosa+Alcaligenes faecalis and Streptococcus pyogenes + Enterococcus faecalis were bio-enhanced with organic amendments; powdered cow dung (PCD), powdered cocoa pod husk (PCPH) and compost made from cow dung (CD) and cocoa pod husk (CPH) with a view to reclaiming SEO soil at three levels of contamination. It was a factorial experiment laid out with completely randomized design (CRD). Subsequently, amaranth seeds were sown on the experimental pots in the screen house. Results indicated that at two weeks after sowing (2WAS), compost produced significant (P < 0.05) and the highest plant heights (6.5, 7.5 and 6.1 cm) on all the SEO contamination levels studied compared with other organic amendments. Compost produced the highest (6.0) number of leaves compared with other organic amendments on 10% SEO contamination level while all the other organic amendments produced the same number of leaves (4.0) on 15% SEO contamination level. In respect of the stem girths measured in this study, significant performance was recorded at 2WAS, four weeks after sowing (4WAS) and six weeks after sowing (6WAS) (P < 0.05). The significant feat that the bioremediation agents utilized in this study recorded has further confirmed these agents as good candidates that can be adopted in ensuring the reclamation and restoration of SEO ravaged agricultural land.

Potential of microalgae Parachlorella kessleri Bh-2 as bioremediation agent of heavy metals cadmium and chromium

The basis of biological remediation basically refers to environmentally friendly methods of extracting various xenobiotics, including heavy metals, from the wastewater of various industrial facilities, using the biochemical capabilities of naturally occurring organisms or their metabolites. In this regard, the assessment of the contribution of microalgae to the transformation of heavy metal compounds and the detoxification of the natural environment is very important and necessary. This paper presents an investigation of the effect of different concentrations of cadmium Cd2+ and chromium Cr2O72− ions on the survival and ultrastructure of microalgae cells of Parachlorella kessleri Bh-2 and its ability to accumulate these metals in order to determine its bioremediational potential against these metals. It was determined that the culture of Parachlorella kessleri Bh-2 is resistant to concentrations of cadmium (0.3 mg l−1) and chromium (30 mg l−1) ions. It was found that heavy metals in these concentrations are actively transported through the cell membrane and accumulate in the cytoplasm of cells, causing an increase in the number of vacuoles with electron-dense deposits, granulation of the cytoplasm and an increase in the number of starch grains in the microalgae cells. Analysis of the content of total polysaccharides showed a noticeable increase in the concentration of polysaccharides by of exposure to concentrations of Cd (II) - 0,3 mg l−1 and Cr (VI) - 30 mg l−1.

Assessment of Heavy Metal Bioaccumulation Capacity of Calopogonium muconoides and Senna obtusifolia as Potential Bioremediation Agents

A wide range of inorganic and organic compounds such as combustibles, and putrescible substances, hazardous waste, explosives, petroleum products and heavy metals (HM) can cause contamination. In addition, the non-biodegradability of heavy metals further exacerbates environmental pollution with its attendant health consequences on the biotic components of the ecosystem including humans. The use of living organisms such as plants and microbes is increasingly becoming acceptable practice of sustainable environmental sanitation. However, identification of potential bioremediation agents is still challenging. This study was carried out to bridge this gap by assessing heavy metal bioaccumulation properties of Calopogoniun Muconoides and Senna obtusifolia plants at contaminated site of mechanic workshop (site 1) in comparative to a physically non-contaminated site (site 2) within Makurdi metropolis of Benue State Nigeria. The selected plants were obtained from both sites and evaluated for their bioaccumulation capacities using standard procedures. The results revealed the sample plants accumulated high levels of heavy metals particularly in the leaves and roots, suggesting the utilization of phytoextraction, phytostabilization and phytovolatilization mechanisms of remediation. The plants and HM generally presented an order of concentration and bioaccumulation as: Senna obtusifolia > Calopogonium Muconoides; Zn > Fe > Pb > Cu > Cd > Cr > Ni. These findings suggest that these novel plants, especially Senna obtusifolia are good agents of bioremediation of heavy metals. Studies involving isotopic labeling to determine the exact mechanism of remediation as well molecular techniques such as transcriptomics and proteomics to identify genes/molecules that confer phytoremediation potential on the plants would be the next focus of our research in this emerging field of environmental biochemistry.

Sustainable aquaculture and animal feed from microalgae – Nutritive value and techno-functional components

Microalgae are being promoted as a superior alternative feedstock for sustainable biofuel production and recently they are also being increasingly recognized as phytoremediation agents in bioremediation. Other than these, microalgae have been utilized as a sustainable feed in aquaculture for many years. The success of microalgae as a feed is based on the nutritional quality of microalgae, which are rich in protein, carbohydrates, fats, vitamins, minerals, and other beneficial biologically active components such as carotenoids and polyunsaturated fatty acids. Standards for the evaluation of microalgae include the assessment of various qualities such as digestibility, bioavailability, and toxicity analysis. This review provides comprehensive information regarding the current status and desirable characteristics of microalgae as a feed ingredient. Feed quality assessments such as protein quality, toxicological and microbiological analysis for microalgae are discussed. The techno-functional components of microalgae are presented in the feed perspective. The utilization of microalgae in various animal husbandry sectors and aquaculture are summarized. The advantages – disadvantages of microalgae as a feed is also presented, along with future research prospects. In short, this review will provide an overall view of the nutritional quality of microalgae and its beneficial application as a sustainable feed ingredient.

Fungal bioremediation of polyethylene: Challenges and perspectives.

Plastics have become ubiquitous in both their adoption as materials and as environmental contaminants. Widespread pollution of these versatile, man-made and largely petroleum-derived polymers has resulted from their long-term mass production, inappropriate disposal and inadequate end of life management. Polyethylene (PE) is at the forefront of this problem, accounting for one-third of plastic demand in Europe in part due to its extensive use in packaging. Current recycling and incineration processes do not represent sustainable solutions to tackle plastic waste, especially once it becomes littered, and the development of new waste-management and remediation technologies are needed. Mycoremediation (fungal-based biodegradation) of PE has been the topic of several studies over the last two decades. The utility of these studies is limited by an inconclusive definition of biodegradation and a lack of knowledge regarding the biological systems responsible. This review highlights relevant features of fungi as potential bioremediation agents, before discussing the evidence for fungal biodegradation of both high- and low-density PE. An up-to-date perspective on mycoremediation as a future solution to PE waste is provided.

Insights into the Restoration of Tributyltin Contaminated Environments Using Marine Bacteria from Portuguese Fishing Ports

Tributyltin (TBT) is an organotin chemical mainly used as biocide in marine antifouling paints. Despite the restrictions and prohibitions on its use, TBT is still an environmental problem due to its extensive application and subsequent release into the environment, being regarded as one of the most toxic chemicals released into the marine ecosystems. Microorganisms inhabiting impacted sites are crucial for their restoration since they have developed mechanisms to tolerate and break down pollutants. Nonetheless, transformation products resulting from the degradation process may still be toxic or, sometimes, even more toxic than the parent compound. The determination of the parent and degradation products by analytical methods, although necessary, may not be ecologically relevant since no information is provided regarding their ecotoxicity. In this study, marine bacteria collected from seven Portuguese fishing ports were isolated and grown in the presence of TBT. Bacteria that exhibited higher growth were used to bioremediate TBT-contaminated waters. The potential of these bacteria as bioremediation agents was evaluated through ecotoxicological assays using the sea snail Gibbula umbilicalis as model organism. Data suggested that some TBT-tolerant bacteria, such as Pseudomonas putida, can reduce the toxicity of TBT contaminated environments. This work contributes to the knowledge of TBT-degrading bacteria.

Halotolerant and metalotolerant bacteria strains with heavy metals biorestoration possibilities isolated from Uburu Salt Lake, Southeastern, Nigeria

Environmental contaminations by heavy metals are currently an increasing public health concern globally. One key challenge of these toxic metals is the extremely difficulties involved in their detoxification from the environment and effluents because of their non-degradability. An efficient biologic agent with potentials of remediating these toxic metals may ease these ever-increasing problems. We reported toxic metals tolerance and bioremediation potentials of novel bacteria sp. Strains USL2S, USL4W and USL5W isolated from Uburu salt lake, Ebonyi State, Nigeria. The phenotypic characteristics and the 16S rRNA gene analyses revealed that USL2S strain belongs to the genus Klebsiella, whereas USL4W and USL5W strains belong to the genus Pseudomonas. The bacteria isolates grew well in media containing 5–15 % of sodium chloride. The bacteria isolate showed capacity to tolerate 50.0 mM Hg+2 and Pb+2, 17.0, 12.50 and 4.0mM Ni+2, Cd+2, and Zn+2 respectively in solid media. Pseudomonas putida A4W Strain also tolerated 16.0 mM Cu+2, while Klebsiella sp. Strain USL2S, Pseudomonas putida USL5W Strain tolerated 4.0 mM each. AAS analyses showed 85, 95, and 95 % Hg; 97.13, 98.89, and 97.55 % Pb; 73.33, 77.42 and 69.72 Cd; 88.06, 99.54, and 97.91 % Ni; 100, 100 and 83.62% Cu; 42.30, 84.52 and 98.80 % Zn removal from media broth incorporated with the tested metals by Klebsiella sp. USL2S, Pseudomonas sp. Strain USL5W and Pseudomonas sp. USL4W respectively. We therefore recommend these novel moderately halophilic and metal tolerant isolates as possible biologic agents for effective bioremediation of mercury, lead, cadmium, nickel, copper and zinc in contaminated environments and effluents.

Effectiveness of indigenous local microorganisms in degrading hexavalent chromium (Cr(VI)) in Batik liquid waste

The batik industry in Indonesia has an IKM (Small and Medium Industry) scale so that it does not yet have adequate waste treatment. In the long term, waste is disposed of directly into the environment which can damage aquatic ecosystems and harm human health. Textile wastewater has a complementary picture and has a deep color. One of the most dangerous heavy metals contained in textile waste is hexavalent chromium (Cr(VI)). Several ways can be done to reduce hexavalent chromium (Cr(VI)) by bioremediation. Based on the results of the literature review, it shows that the bioremediation agents from single isolate microorganisms that are most effective in degrading chromium with high efficiency are Bacillus subtilis and Pseudomonas aeruginosa. The most effective consortium servers with constant reduction rates are the consortium of bacteria genus Mesophilobacter, Methylococcus, Agrobacterium, Neisseria, Xanthobacter, Deinococcus, Sporosarcina, and Bacillus by reducing BOD levels by 85.71%. The hexavalent chromium-degrading microorganisms are characterized by the presence of chromate reductase enzymes, mostly gram-negative bacteria, and a high growth rate.

Exhaustion of pentachlorophenol in soil microcosms with three Pseudomonas species as detoxification agents.

Pentachlorophenol (PCP) is a toxic compound, which is widely used as a wood preservative product and general biocide. It is persistent in the environment and has been classified as a persistent organic pollutant to be reclaimed in many countries. Bioremediation is an emerging approach to rehabilitating areas polluted by recalcitrant xenobiotics. In the present study, we evaluated the potential of three strains of Pseudomonas (P. putida S121, P. rhizophila S211, and P. fuscovagiceae S115) as bioremediation agents in depletion and detoxification of PCP in soil microcosms. PCP removal was effectively optimized using a central-composite experimental design and response surface methodology (RSM). The optimum conditions for maximum PCP removal yield (85 ± 5%) were: 500mg/kg PCP concentration, 108 UFC/g soil inoculum size of each strain and 55days incubation period. The bacterial strains, P. putida, P. rhizophila, and P. fuscovagiceae, showed good capability to tolerate and degrade PCP so that they could be successfully used in synergistic effect to treat PCP polluted soils.

Indigenous multiresistant bacteria of Cupriavidus pauculus IrC4 isolated from Indonesia as a heavy metal bioremediation agent

Abstract. Irawati W, Winoto SE, Kusumawati L, Pinontoan R. 2021. Indigenous multiresistant bacteria of Cupriavidus pauculus IrC4 isolated from Indonesia as a heavy metal bioremediation agent. Biodiversitas 22: 3349-3355. Heavy metal pollution is a serious environmental problem because it endangers humans, animals, and plants. Bioremediation of heavy metals using bacteria is an effective method to remove heavy metals. Cupriavidus pauculus IrC4 is an indigenous multi-resistant bacteria isolated from Indonesia. This study aims to determine the growth of this strain in a medium containing cadmium, mercury, lead, copper, and its ability to accumulate heavy metal. Bacterial resistance was observed by cultivating bacteria on a Luria Bertani medium containing various concentrations of heavy metals. Heavy metal accumulation was measured using atomic absorption spectrophotometer. The study showed that this strain could grow in a solid medium containing 5 mM cadmium, 13 mM lead, and 4 mM mercury, also in 0.5 mM of the heavy metal mixture. A high concentration of heavy metals resulted in lag phase elongation and logarithmic growth phase inhibition. C. pauculus IrC4 could accumulate copper, lead, and cadmium and lead up to 371.42 mg, 254.4 mg, 5.8 mg heavy metals per gram of dry weight of cells, respectively. In conclusion, this strain is a promising bacterium for use as a heavy metal bioremediation agent.

Biodegradation of the pyridinecarboxamide insecticide flonicamid by Microvirga flocculans and characterization of two novel amidases involved

Flonicamid (N-cyanomethyl-4-trifluoromethylnicotinamide, FLO) is a new type of pyridinecarboxamide insecticide that exhibits particularly good efficacy in pest control. However, the extensive use of FLO in agricultural production poses environmental risks. Hence, its environmental behavior and degradation mechanism have received increasing attention. Microvirga flocculans CGMCC 1.16731 rapidly degrades FLO to produce the intermediate N-(4-trifluoromethylnicotinoyl) glycinamide (TFNG-AM) and the end acid metabolite 4-(trifluoromethyl) nicotinol glycine (TFNG). This bioconversion is mediated by the nitrile hydratase/amidase system; however, the amidase that is responsible for the conversion of TFNG-AM to TFNG has not yet been reported. Here, gene cloning, overexpression in Escherichia coli and characterization of pure enzymes showed that two amidases—AmiA and AmiB—hydrolyzed TFNG-AM to TFNG. AmiA and AmiB showed only 20–30% identity to experimentally characterized amidase signature family members, and represent novel amidases. Compared with AmiA, AmiB was more sensitive to silver and copper ions but more resistant to organic solvents. Both enzymes demonstrated good pH tolerance and exhibited broad amide substrate specificity. Homology modeling suggested that residues Asp191 and Ser195 may strongly affect the catalytic activity of AmiA and AmiB, respectively. The present study furthers our understanding of the enzymatic mechanisms of biodegradation of nitrile-containing insecticides and may aid in the development of a bioremediation agent for FLO.

Optimization of biodegradation efficacy of acrylic-based paint contaminated soil by Alcaligenes faecalis

Acrylates/acrylic-containing chemicals are components of paints. During industrial production and applications, the acrylates and acrylic-containing compounds could contaminate/accumulate in water bodies and soil systems, hence the need for bioremediation. This study aimed to investigate the in vitro biodegradation of acrylic based paint; using an indigenous bacterial isolate namely; Alcaligenes faecalis and optimization of its activity in shake cultures. The bacterial isolate; A. faecalis (2 % v/v) was able to grow and effectively degrade 68 % of acrylic paints (1 %)-mended mineral salt medium after 14 d of incubation. The rate of biodegradation was significantly (p < 0.05) increased with increasing the medium concentration, inoculum size, agitation speed and nitrogen sources. The most significant biodegradation efficiencies were obtained at a pH of 7.2, temperature of 37 °C, an agitation speed of 200 rpm, an inoculum concentration of 10 %, paint concentration of 2 %; when yeast extract (10 %) was used as a major nitrogen source. Accordingly, this work provides baseline data for optimum biodegradation of acrylate by A. faecalis, and thus could be possibly exploited as an effective bioremediation agent for acrylic paint polluted sites.

Comparison of Viability and Efficacy of an Immobilized Bacterial Consortium in Four Different Carriers to Degrade Oil

This research aimed to evaluate the storage system’s effect on immobilizing bioremediation agents’ performance in four different carriers (Perlite, Silica, Vermiculite, and Zeolite). Measured parameters were the viability and efficacy of artificial bacterial consortium (Bacillus sp., B. licheniformis, and Enterobacter cloacae) immobilized in the four porous rock carriers by lyophilization. They were stored at room temperature (25-27°C) for three months. The experiment was taken place in a microcosm system with three replicates for 28 days. The results indicate that storage of immobilized bacteria for three months at room temperature will affect their viability. The efficacy of immobilized bacteria in Vermiculite and Perlite reached the highest rate until the first week, 61.44% and 60.18 %, respectively. However, the efficacy in decreasing oil concentration of immobilized cells in the four carriers was almost similar (90.53 – 91.63%), with no significant difference between each other in the late stage. This is very different with control, decreasing oil in only 10.85 - 13.57%, except in control with fertilizer (Cp) supplemented (90.63%). We conclude that bioremediation will improve oil removal. However, storage at room temperature for three months will decrease the performance of these immobilized cells.

Bioremediation of hexavalent chromium from wastewater using bacteria-a green technology.

Hexavalent chromium has high toxic effect on the ecological system. The aim of the present study is to isolate and characterize the bacteria that can reduce the toxicity of hexavalent chromium from liquid effluent. The bacterial isolate was identified as Bacillus sp. ltds1 after 16S rRNA gene sequencing, and annotation has been submitted in National Center for Biotechnology Information (NCBI) GenBank. The bacterial strain was found able to grow in Luria Broth medium at 100mg/L Cr6+ concentration. A maximum Cr6+ bioremediation (95.24 ± 2.08 %) could be achieved using the said isolate at 40mg/L, pH 7, and inoculum concentration 4 % at 24h. The residual chromium was found in the form of less toxic trivalent chromium (Cr3+), which confirms that the bacterial isolate can transform toxic Cr6+ to non-toxic Cr3+. Fourier Transform Infra-Red (FTIR) study was performed to analyze the functional groups and overall nature of chemical bonds involved in the remediation process, whereas, Energy-Dispersive Spectroscopy (EDS) studies of native and treated cells showed the changes in elemental composition in response to metal stress. Artificial Neural Network (ANN) based prediction model is developed based on experimental points. The developed model was found to predict the bioremediation of Cr6+ at various operating conditions. Particle Swarm Optimization (PSO) is used to optimize the variables like the initial concentration of metal, pH, temperature, and inoculum concentration for the said bacterial strain. The results showed that the isolate could be applied as a potential bioremediation agent for Cr6+ removal.

Thermophilic bacteria isolated from Mount Merapi, Java, Indonesia as a potential lead bioremediation agent

Abstract. Rakhmawati A, Wahyuni ET, Yuwono T. 2021. Thermophilic bacteria isolated from Mount Merapi, Java, Indonesia as a potential lead bioremediation agent. Biodiversitas 22: 3101-3110. Contamination by lead (Pb) has become a serious health and environmental problem, that has to be urgently prevented. Bioremediation is one of the environmentally friendly methods for eliminating Pb from the contaminated environment. This study was aimed to investigate the potency of lead-tolerant thermophilic bacteria isolated from solfatara Mount Merapi, Indonesia. A total of 340 isolates of thermophilic bacteria were screened for lead tolerance at 55 °C. Five bacterial isolates were found to show tolerance to 100 mg/L Pb (II), and then were further evaluated and identified as Aeribacillus pallidus strains MRP112, MRP148, MRP272, MRP278, and MRP280 based on 16S rRNA gene sequences analysis. Among the five isolates, A. pallidus MRP 280 showed highest activity in removing Pb at pH 6, 55°C for 24 h. The analysis of scanning and transmission electron microscopy, biofilm formation, and siderophore production, demonstrated that lead tolerance of A. pallidus MRP 280 strain was also accompanied by morphological changes, bioaccumulation, biosorption, biofilm, and siderophore assembly. In conclusion A. pallidus MRP 280 was demonstrated as one of the most potential bacterial strains, can be recommended as an agent for high-temperature lead bioremediation.