Microalgae have drawn significant interest worldwide, owing to their enormous application potential in the green energy, biopharmaceutical, and nutraceutical industries. Many studies have proved and stated the potential of microalgae in the area of biofuel which is economically effective and environmentally friendly. Besides the commercial value, the potential of microalgae in environmental protection has also been investigated. Microalgae-based process is one of the most effective way to treat heavy metal pollution, compared to conventional methods, it does not release any toxic waste or harmful gases, and the aquatic organism will not receive any harmful effects. The potential dual role of microalge in phytoremedation and energy production has made it widely explored for its capability. The interest of microalgae in various application has motivated a new focus in green technologies. Considering the rapid population growth with the continuous increase on the global demand and the application of biomass in diverse field, significant upgrades have been performed to accommodate green technological advancement. In the past decade, noteworthy advancement has been made on the technology involving the diverse application of microalgae biomass. This review aims to explore on the application of microalgae and the development of green technology in various application for microalgae biomass. There is great prospects for researchers in this field to delve into other potential utilization of microalgae biomass not only for bioremediation process but also to generate revenues from microalgae by incorporating clean and green technology for long-term sustainability and environmental benefits.
One of the challenges of integrating phytoremediation into a waste treatment system is the sensitivity of plant species to fluctuations in environmental conditions and the difficulty in estimating subsequent changes to their rates of uptake. In this study, we examine a method using the exponential decay equation to approximate the median uptake rate (MUR) of nutrients for three aquatic macrophyte species, Salvinia molesta, Spirodela polyrhiza, and Lemna minor. These MUR values were then used to directly evaluate the phytoremediation performance between species and at varying levels of salinity stress. The results of this study indicate that an exponential decay relationship produced the most accurate models of the nutrient uptake profile for each species, with highest correlation values in 74.1% of tests for the three species at increasing salinity over a period of 14 d. S. polyrhiza and L. minor began to show significant reductions in nutrient uptake and growth at salinity concentration above 10 g/L. Using MUR, direct comparisons can be made between species in a time and mass-independent manner, allowing for the rapid assessment of phytoremediation performance under conditions of increasing salinity stress. Novelty statementIn this study, we propose the use of an exponential decay model and the use of median uptake rate (MUR) obtained from the model coefficients as a method for directly comparing species performance under different conditions. Subsequently, we show how the use of MUR values obtained from three species of aquatic macrophytes allows for the direct comparison of species performance under increasing salinity stress. The method proposed in this study would improve the ability for easy comparison between species performance under varying environmental conditions. Future works could further build on the parameters proposed in this study and optimize the performance of phytoremediation systems developed for nutrient-affected wastewater management. This study is especially beneficial to phytoremediation researchers and environmental engineers who are implementing or designing macrophyte phytoremediation systems.
Molybdenum (Mo) microbial bioreduction is a phenomenon that is beginning to be recognized globally as a tool for the remediation of molybdenum toxicity. Molybdenum toxicity continues to be demonstrated in many animal models of spermatogenesis and oogenesis, particularly those of ruminants. The phenomenon has been reported for more than 100 years without a clear understanding of the reduction mechanism, indicating a clear gap in the scientific knowledge. This knowledge is not just fundamentally important-it is specifically important in applications for bioremediation measures and the sustainable recovery of metal from industrial or mine effluent. To date, about 52 molybdenum-reducing bacteria have been isolated globally. An increasing number of reports have also been published regarding the assimilation of other xenobiotics. This phenomenon is likely to be observed in current and future events in which the remediation of xenobiotics requires microorganisms capable of degrading or transforming multi-xenobiotics. This review aimed to comprehensively catalogue all of the characterizations of molybdenum-reducing microorganisms to date and identify future opportunities and improvements.
Researchers and companies have increasingly been drawn to biodegradable polymers and composites because of their environmental resilience, eco-friendliness, and suitability for a range of applications. For various uses, biodegradable fabrics use biodegradable polymers or natural fibers as reinforcement. Many approaches have been taken to achieve better compatibility for tailored and improved material properties. In this article, PBS (polybutylene succinate) was chosen as the main topic due to its excellent properties and intensive interest among industrial and researchers. PBS is an environmentally safe biopolymer that has some special properties, such as good clarity and processability, a shiny look, and flexibility, but it also has some drawbacks, such as brittleness. PBS-based natural fiber composites are completely biodegradable and have strong physical properties. Several research studies on PBS-based composites have been published, including physical, mechanical, and thermal assessments of the properties and its ability to replace petroleum-based materials, but no systematic analysis of up-to-date research evidence is currently available in the literature. The aim of this analysis is to highlight recent developments in PBS research and production, as well as its natural fiber composites. The current research efforts focus on the synthesis, copolymers and biodegradability for its properties, trends, challenges and prospects in the field of PBS and its composites also reviewed in this paper.
A reedbed system planted with Phragmites australis was implemented to treat chlorinated hydrocarbon-contaminated groundwater in an industrial plant area. Reedbed commissioning was conducted from July 2016 to November 2016 to treat contaminated groundwater via a pump-and-treat mechanism. Combination of horizontal and vertical reedbed systems was applied to treat 1,2-dichloroethane (1,2 DCA) under four parallel installations. The 2-acre horizontal and vertical reedbed systems were designed to treat approximately 305 m3/day of pumped groundwater. Initial concentration of 1,2 DCA was observed at 0.362 mg/L to 4320 mg/L, and the reedbed system successfully reduced the concentration up to 67.9%. The average outlet concentration was measured to be 2.08 mg/L, which was lower than the site-specific target level of 156 mg/L. Natural attenuation analysis was conducted using first-order decay kinetics, showing an average natural attenuation rate of 0.00372/year. Natural attenuation of 1,2 DCA was observed in shallow monitoring wells, which was indicated by the reduction trend of 1,2 DCA concentration, thereby confirming that the reedbed system worked well to remove 1.2 DCA from contaminated groundwater at the shallow profile.
The emergence and continual accumulation of industrial micropollutants such as dyes, heavy metals, organic matters, and pharmaceutical active compounds (PhACs) in the ecosystem pose an alarming hazard to human health and the general wellbeing of global flora and fauna. To offer eco-friendly solutions, living and non-living algae have lately been identified and broadly practiced as promising agents in the bioremediation of micropollutants. The approach is promoted by recent findings seeing better removal performance, higher efficiency, surface area, and binding affinity of algae in various remediation events compared to bacteria and fungi. To give a proper and significant insight into this technology, this paper comprehensively reviews its current applications, removal mechanisms, comparative efficacies, as well as future outlooks and recommendations. In conducting the review, the secondary data of micropollutants removal have been gathered from numerous sources, from which their removal performances are analyzed and presented in terms of strengths, weaknesses, opportunities, and threats (SWOT), to specifically examine their suitability for selected micropollutants remediation. Based on kinetic, isotherm, thermodynamic, and SWOT analysis, non-living algae are generally more suitable for dyes and heavy metals removal, meanwhile living algae are appropriate for removal of organic matters and PhACs. Moreover, parametric effects on micropollutants removal are evaluated, highlighting that pH is critical for biodegradation activity. For selective pollutants, living and non-living algae show recommendable prospects as agents for the efficient cleaning of industrial wastewaters while awaiting further supporting discoveries in encouraging technology assurance and extensive applications.
Plastic throughout the years is now one of the biggest world commodities and also the largest pollution to have an environmental impact, accumulating in landfills and also leaching into water systems and oceans. Especially with the shift to single-use disposable plastic, evermore positions plastics as the number one novel entity that pollutes the earth. This shift is also consistent in the food packaging industry. Managing plastic waste is still an issue at large, while the process of pyrolysis incineration still requires an obscene amount of energy that also does not resolve the problems with its environmental impact, the cost of mechanical-chemical degradation even outweighs the cost of producing the materials, and biodegradation process is a very slow and long process. Converting to bioplastics is one of the potential solutions to the global plastic issue. This review covers the potentials, limitations, challenges, progress and advancements of bioplastics, especially thermoplastic starch (starch-based bioplastic) in their efforts to replace petroleum plastics in food packaging and smart food packaging, especially for single-use (disposable) food packaging.
Over the past few decades, extensive research has been conducted to develop cost-effective and high-quality biochar for environmental biodegradation purposes. Pyrolysis has emerged as a promising method for recovering biochar from biomass and waste materials. This study provides an overview of the current state-of-the-art biochar production technology, including the advancements and biochar applications in organic pollutants remediation, particularly wastewater treatment. Substantial progress has been made in biochar production through advanced thermochemical technologies. Moreover, the review underscores the importance of understanding the kinetics of pollutant degradation using biochar to maximize its synergies for potential environmental biodegradation. Finally, the study identifies the technological gaps and outlines future research advancements in biochar production and its applications for environmental biodegradation.
Crude oil pollution is one of the most serious environmental issues today, and the clean-up procedure is perhaps the most difficult. Within one to three weeks, the vast majority of oil bacteria may degrade approximately 60% of the crude oil, leaving approximately 40% intact. The by-product metabolites produced during the breakdown of oil are essentially organic molecules in nature. These metabolites inhibit its enzymes, preventing the oil bacteria from further degrading the oil. By combining a variety of different oils with heterotrophic bacteria in a bioreactor, the rate of crude oil biodegradation was accelerated. In this study, two strains of oil-resistant, heterotrophic bacteria (OG1 and OG2-Erythrobacter citreus) and a bacterium that uses hydrocarbons (AR3-Pseudomonas pseudoalcaligenes) were used. Gas chromatography-mass spectroscopy was used to investigate the effectiveness of this consortium of symbiotic bacteria in the biodegradation of crude oil. According to gravimetric and gas chromatography analyses, the consortium bacteria digested 69.6% of the crude oil in the bioreactor, while the AR3 single strain was only able to destroy 61.9% of it. Under the same experimental conditions, consortium bacteria degraded approximately 84550.851 ppb (96.3%) of 16 aliphatic hydrocarbons and 9333.178 ppb (70.5%) of 16 aromatic hydrocarbons in the bioreactor. It may be inferred that the novel consortium of symbiotic bacteria accelerated the biodegradation process and had great potential for use in increasing the bioremediation of hydrocarbon-contaminated locations.
Heavy metal wastes, particularly hexavalent chromium [Cr(VI)], are generated from anthropogenic activities, and their increasing abundance has been a research concern due to their toxicity, genotoxicity, carcinogenicity and mutagenicity. Exposure to these dangerous pollutants could lead to chronic infections and even mortality in humans and animals. Bioremediation using microorganisms, particularly bacteria, has gained considerable interest because it can remove contaminants naturally and is safe to the surrounding environment. Bacteria, such as Pseudomonas putida and Bacillus subtilis, can reduce the toxic Cr(VI) to the less toxic trivalent chromium Cr(III) through mechanisms including biotransformation, biosorption and bioaccumulation. These mechanisms are mostly linked to chromium reductase and nitroreductase enzymes, which are involved in the Cr(VI) reduction pathway. However, relevant data on the nitroreductase route remain insufficient. Thus, this work proposes an alternative metabolic pathway of nitroreductase, wherein nitrate activates the reaction and indirectly reduces toxic chromium. This nitroreductase pathway occurs concurrently with the chromium reduction pathway.
Heavy metal toxicity affects aquatic plants and animals, disturbing biodiversity and ecological balance causing bioaccumulation of heavy metals. Industrialization and urbanization are inevitable in modern-day life, and control and detoxification methods need to be accorded to meet the hazardous environment. Microorganisms and plants have been widely used in the bioremediation of heavy metals. Sporosarcina pasteurii, a gram-positive bacterium that is widely known for its calcite precipitation property in bio-cementing applications has been explored in the study for its metal tolerance ability for the first time. S. pasteurii SRMNP1 (KF214757) can tolerate silver stress to form nanoparticles and can remediate multiple heavy metals to promote the growth of various plants. This astounding property of the isolate warranted extensive examinations to comprehend the physiological changes during an external heavy metal stress condition. The present study aimed to understand various physiological responses occurring in S. pasteuriiSRMNP1 during the metal tolerance phenomenon using electron microscopy. The isolate was subjected to heavy metal stress, and a transmission electron microscope examination was used to analyze the physiological changes in bacteria to evade the metal stress. S. pasteurii SRMNP1 was tolerant against a wide range of heavy metal ions and can withstand a broad pH range (5-9). Transmission Electron Microscopy (TEM) examination of S. pasteurii SRMNP1 followed by 5 mM nickel sulfate treatment revealed the presence of nanovesicles encapsulating nanosized particles in intra and extracellular spaces. This suggests that the bacteria evade the metal stress by converting the metal ions into nanosized particles and encapsulating them within nanovesicles to efflux them through the vesicle budding mechanism. Moreover, the TEM images revealed an excessive secretion of extracellular polymeric substances by the strain to discharge the metal particles outside the bacterial system. S. pasteurii can be foreseen as an effective bioremediation agent with the potential to produce nanosized particles, nanovesicles, and extracellular polymeric substances. This study provides physiological evidence that, besides calcium precipitation applications, S. pasteurii can further be explored for its multidimensional roles in the fields of drug delivery and environmental engineering.
Remediation by algae is a very effective strategy for avoiding the use of costly, environmentally harmful chemicals in wastewater treatment. Recently, industries based on biomass, especially the bioenergy sector, are getting increasing attention due to their environmental acceptability. However, their practical application is still limited due to the growing cost of raw materials such as algal biomass, harvesting and processing limitations. Potential use of algal biomass includes nutrients recovery, heavy metals removal, COD, BOD, coliforms, and other disease-causing pathogens reduction and production of bioenergy and valuable products. However, the production of algal biomass using the variable composition of different wastewater streams as a source of growing medium and the application of treated water for subsequent use in agriculture for irrigation has remained a challenging task. The present review highlights and discusses the potential role of algae in removing beneficial nutrients from different wastewater streams with complex chemical compositions as a biorefinery concept and subsequent use of produced algal biomass for bioenergy and bioactive compounds. Moreover, challenges in producing algal biomass using various wastewater streams and ways to alleviate the stress caused by the toxic and high concentrations of nutrients in the wastewater stream have been discussed in detail. The technology will be economically feasible and publicly accepted by reducing the cost of algal biomass production and reducing the loaded or attached concentration of micropollutants and pathogenic microorganisms. Algal strain improvement, consortium development, biofilm formation, building an advanced cultivation reactor system, biorefinery concept development, and life-cycle assessment are all possible options for attaining a sustainable solution for sustainable biofuel production. Furthermore, producing valuable compounds, including pharmaceutical, nutraceutical and pigment contents generated from algal biomass during biofuel production, could also help reduce the cost of wastewater management by microalgae.
Bioaugmentation helps to obtain a microbiome capable of remediating polycyclic aromatic hydrocarbons (PAHs). In this study, acclimation of microorganisms to soil supplemented with phenanthrene (PHE) led to enrichment with PAH-degraders, including those in Actinobacteriota and in the genera Streptomyces, Rhodococcus, Nocardioides, Sphingomonas, and Mycobacterium. Aqueous (28 °C, pH 6.5) and soil cultures inoculated with PHE-acclimated soil showed a high PHE (ca. 50 mg L-1) degradation efficiency. The PHE degradation kinetics in aqueous and soil incubations fitted to the Gompertz equation and the first-order kinetic equation, respectively. Indigenous microorganisms adapted to PHE in their environment, and this increased their capacity to degrade PHE. The effect of co-contaminants and pathway intermediates on PHE degradation showed that the degradation of PHE improved in the presence of diesel while being hindered by lubricant oil, catechol, salicylic and phthalic acid. Our findings provide theoretical and practical support for bioremediationof PAHs in the environment.
Biodegradation is an eco-friendly measure to address plastic pollution. This study screened four bacterial isolates that were capable of degrading recalcitrant polymers, i.e., low-density polyethylene, polyethylene terephthalate, and polystyrene. The unique bacterial isolates were obtained from plastic polluted environment. Dermacoccus sp. MR5 (accession no. OP592184) and Corynebacterium sp. MR10 (accession no. OP536169) from Malaysian mangroves and Bacillus sp. BS5 (accession no. OP536168) and Priestia sp. TL1 (accession no. OP536170) from a sanitary landfill. The four isolates showed a gradual increase in the microbial count and the production of laccase and esterase enzymes after 4 weeks of incubation with the polymers (independent experiment set). Bacillus sp. BS5 produced the highest laccase 15.35 ± 0.19 U/mL and showed the highest weight loss i.e., 4.84 ± 0.6% for PS. Fourier transform infrared spectroscopy analysis confirmed the formation of carbonyl and hydroxyl groups as a result of oxidation reactions by enzymes. Liquid chromatography-mass spectrometry analysis showed the oxidation of the polymers to small molecules (alcohol, ethers, and acids) assimilated by the microbes during the degradation. Field emission scanning electron microscopy showed bacterial colonization, biofilm formation, and surface erosion on the polymer surface. The result provided significant insight into enzyme activities and the potential of isolates to target more than one type of polymer for degradation.
Microplastic pollution is one of the most pressing global environmental problems due to its harmful effects on living organisms and ecosystems. To address this issue, researchers have explored several techniques to successfully eliminate microplastics from water sources. Chemical coagulation, electrocoagulation, magnetic extraction, adsorption, photocatalytic degradation, and biodegradation are some of the recognized techniques used for the removal of microplastics from water. In addition, membrane-based techniques encompass processes propelled by pressure or potential, along with sophisticated membrane technologies like the dynamic membrane and the membrane bioreactor. Recently, researchers have been developing advanced membranes composed of metal-organic frameworks, MXene, zeolites, carbon nanomaterials, metals, and metal oxides to remove microplastics. This paper aims to analyze the effectiveness, advantages, and drawbacks of each method to provide insights into their application for reducing microplastic pollution.
The treatment of biodegradable plastics through composting has garnered increasing attention. This study aimed to investigate the effects of Biochar FN1 bacteria and ferrous sulfate on nitrogen retention, greenhouse gas emissions, and degradable plastics during composting and to elucidate their synergistic mechanisms on microbial communities. Compared with the control, applying biochar-loaded FN1 bacteria composites combined with Ferrous sulfate (SGC) markedly accelerated organic matter degradation and reduced cumulative CO2 and NH3 emissions. The synergistic interaction between the composites and Ferrous sulfate significantly enhanced NH4+-N levels in the thermophilic phase and NO3--N levels in the cooling phase, ultimately decreasing nitrogen loss by 14.9% (P
This study revealed Streptomyces bacillaris as an efficient biological agent for the removal of triphenylmethane (TPM) dyes. The isolate decolorized Malachite Green (MG), Methyl Violet (MV), Crystal Violet (CV), and Cotton Blue (CB) effectively. S. bacillaris in the treated dye solutions were analyzed for enzyme production, and the cell biomass was observed for functional groups and cell morphology. The treated dye solutions were also analyzed for degraded compounds and their toxicity. Results revealed high decolorization activities for MG (94.7%), MV (91.8%), CV (86.6%), CB (68.4%), attributed to both biosorption and biodegradation. In biosorption, dye molecules interacted with the hydroxyl, amino, phosphoryl, and sulfonyl groups present on the cell surface. Biodegradation was associated with induced activities of MnP and NADH-DCIP reductase, giving rise to various simpler compounds. The degraded compounds in the treated dyes were less toxic, as revealed by the significant growth of Vigna radiata in the phytotoxicity test. There were no significant changes in cell morphology before and after use in dye solutions, suggesting S. bacillaris is less susceptible to dye toxicity. This study concluded that S. bacillaris demonstrated effective removal of TPM dyes via biosorption and biodegradation, rendering the treated dyes less toxic than untreated dyes. Findings in this study enabled further explorations into the potential application of lesser-known actinobacteria (i.e. Streptomyces sp.) for dye removal.
Transportation of crude oil and refined petroleum is the main function of pipeline system in petroleum industry. Unfortunately, wax precipitation has become a serious problem for the petroleum industry where it causes pipeline blockage and eventually results in operational catastrophe. Up-to-date, the technique used to mitigate wax deposition by injecting chemical wax inhibiting agent remains a debate amongst researchers. This review addresses the evolution of chemical wax inhibitor generations started from polymer-based in the early 1980s, followed by biosurfactant-based in the late 1990s and finally plant-based or agricultural-based in recent years. Pivoting to environmental impact, petroleum industry is amidst finding a green wax inhibiting agent to solve wax deposition problem that occurs during the transportation of crude oil whilst facilitating the remediation process of contaminated groundwater.
The proliferation of heavy metal contamination necessitates sustainable, cost-effective remediation strategies capable of discriminating between toxic co-existing cations in complex matrices. This study presents the first systematic investigation employing phosphoric acid-modified Eucalyptus camaldulensis leaf biochar (EC-biochar) for the simultaneous and selective removal of Pb(II) and Cd(II) from competitive multicomponent systems a critical advancement beyond conventional single-metal studies. Characterization analyses confirmed a hierarchically porous architecture (SEM), semi-crystalline structure (crystallinity index ∼35%), and abundant oxygenated surface functional groups. Maximum adsorption capacities in monocomponent systems reached 17.90 mg g-1 for Pb(II) and 18.35 mg g-1 for Cd(II) under optimal conditions (pH 4.5, 25 °C, 120 min contact time, 1 g L-1 adsorbent dose). Notably, although Cd(II) exhibited marginally higher capacity in single-metal solutions, competitive experiments revealed preferential affinity for Pb(II) over Cd(II) in binary and multimetallic matrices, with significant interference from co-existing Zn(II), Cu(II), and electrolytes (NaCl and NaClO4). The extent of competitive suppression was rigorously quantified using the steady-state adsorption capacity ratio (q'e/qe), where qe represents the equilibrium adsorption capacity (mg g-1) in single-component systems and q'e denotes the corresponding equilibrium capacity (mg g-1) obtained under competitive multicomponent conditions. While the competitive Langmuir model adequately described Pb(II) removal, it poorly fitted Cd(II) adsorption isotherms suggesting that Cd(II) exhibits non-ideal competitive behavior involving heterogeneous site interactions or multi-layer formation, consistent with its softer Lewis acid characteristics and explaining its inferior performance relative to Pb(II) in mixed systems. Thermodynamic analysis confirmed spontaneous, endothermic adsorption processes. Mechanistic studies identified hydrogen bonding, electrostatic attraction, π-π interactions, and inner-sphere surface complexation as primary removal pathways. These findings demonstrate that EC-biochar is a promising eco-friendly adsorbent for the selective retention of Pb(II) and Cd(II) from complex wastewater matrices.
Microbial fuel cells (MFCs) offer a promising approach to remediate organic pollutants while generating energy. Despite significant advancements, generating electrons remains a major challenge for MFCs. This study addresses the electron production challenges in MFCs using pineapple waste as an organic substrate and resorcinol as a pollutant and carbon source. At a constant 1000 Ω external resistance, the maximum power density (PD) achieved was 2.69 mW/m2. Electrochemical studies, including cyclic voltammetry (CV), indicated efficient oxidation and reduction of the substrate, with a specific capacitance of 1.36 × 10⁻⁷ F/g, suggesting gradual biofilm formation. The electrochemical impedance spectroscopy (EIS) findings confirmed efficient electron transport and resorcinol biodegradation reached 84.66%. Bacterial identification revealed that Proteus vulgaris, Hafnia alvei, and Yersinia enterocolitica significantly contributed to resorcinol degradation and energy generation. Optimal MFC operation was observed at pH 7 and temperatures of 25-30 °C. Overall, pineapple substrates, with their polysaccharide composition, maintained stability for 40 days. The study concludes by highlighting future challenges and potential improvements.