Evaluation of Fresh Water Actinomycete Bioflocculant and Its Biotechnological Applications in Wastewaters Treatment and Removal of Heavy Metals

Lead removal from the aqueous solution by extracellular polymeric substances produced by the marine diatom Navicula salinicola

Microbial extracellular polymeric substances (EPS) have recently emerged as significant contributors in diverse biotechnological applications. Extracellular polymeric substances (EPS), produced by a Navicula salinicola strain, have been studied for potential applications in a specific heavy metal (lead (Pb II)) removal from wastewater. The optimisation of operational parameters, mainly pH, Pb and EPS concentrations, using the Box-Behnken design (BBD) was undertaken to enhance lead uptake. The higher Pb adsorption capacity reached 2211.029 mg/g. Hydroxyl, carbonyl, carboxyl, phosphoric, and sulfhydryl groups were identified quantitatively as potential sites for Pb adsorption. EPS exhibited a notable flocculation rate of 70.20% in kaolin clay at a concentration of 15 mg/L. They demonstrated an emulsifying activity greater than 88%, showcasing their versatile potential for both sedimentation processes and stabilising liquid-liquid systems. EPS could be excellent nonconventional renewable biopolymers for treating water and wastewater.

Source apportionment based on EEM-PARAFAC combined with microbial tracing model and its implication in complex pollution area, Wujin District, China

Further improving the quality of surface water is becoming more difficult after the control of main point-sources, especially in the complex pollution area with mixed industrial and agricultural productions, whereas the pollution source apportionment might be the key to quantify different pollution sources and developing some effective measures. In this study, a technical framework for source apportionment based on three-dimensional fluorescence and microbial traceability model is developed. Based on screening of the main environmental factors and their spatiotemporal characteristics, potential pollution sources have been tentatively identified. Then, the pollution sources are further tested based on the analysis of fluorescence excitation-emission matrix (EEM) and the similarity of fluorescence components in surface water and potential pollution sources. At the same time, the correlation between microbial species and pollution sources is constructed by analyzing the spatiotemporal characteristics of microbial composition and the response of main species to environmental factors. Therefore, pollution source apportionment is quantified using PCA-APCS-MLR, Fast Expectation-maximization for Microbial Source Tracking (FEAST), and Bayesian community-wide culture-independent microbial source tracking (SourceTracker). PCA-APCS-MLR could not effectively distinguish the contributions of different industrial sources in the complex environment of this study, and the contribution of unknown sources was high (average 39.60%). In contrast, the microbial traceability model can accurately identify the contribution of 7 pollution sources and natural sources, effectively reduce the proportion of unknown sources (average of FEAST is 19.81%, SourceTracker is 16.72%), and show better pollution identification and distribution capabilities. FEAST exhibits a more sensitive potential in source apportionment and shorter calculation time than SourceTracker, thus might be used to guide the precise regional pollution control, especially in the complex pollution environments.

South Africa's indigenous microbial diversity for industrial applications: A review of the current status and opportunities

The unique metagenomic, metaviromic libraries and indigenous micro diversity within Southern Africa have the potential for global beneficiation in academia and industry. Microorganisms that flourish at high temperatures, adverse pH conditions, and high salinity are likely to have enzyme systems that function efficiently under those conditions. These attributes afford researchers and industries alternative approaches that could replace existing chemical processes. Thus, a better understanding of African microbial/genetic diversity is crucial for the development of "greener" industries. A concerted drive to exploit the potential locked in biological resources has been previously seen with companies such as Diversa Incorporated and Verenium (Badische Anilin-und SodaFabrik-BASF) both building business models that pioneered the production of high-performance specialty enzymes for a variety of different industrial applications. The market potential and accompanying industry offerings have not been fully exploited in South Africa, nor in Africa at large. Utilization of the continent's indigenous microbial repositories could create long-lasting, sustainable growth in various production sectors, providing economic growth in resource-poor regions. By bolstering local manufacture of high-value bio-based products, scientific and engineering discoveries have the potential to generate new industries which in turn would provide employment avenues for many skilled and unskilled laborers. The positive implications of this could play a role in altering the face of business markets on the continent from costly import-driven markets to income-generating export markets. This review focuses on identifying microbially diverse areas located in South Africa while providing a profile for all associated microbial/genetically derived libraries in this country. A comprehensive list of all the relevant researchers and potential key players is presented, mapping out existing research networks for the facilitation of collaboration. The overall aim of this review is to facilitate a coordinated journey of exploration, one which will hopefully realize the value that South Africa's microbial diversity has to offer.

Hyperproduction of extracellular polymeric substance in Pseudomonas fluorescens for efficient chromium (VI) absorption

A novel extracellular polymeric substance (EPS) with flocculating activity produced by Pseudomonas fluorescein isolated from soil was studied in this paper. Firstly, atmospheric and room temperature plasma (ARTP) was applied to get a mutant of P. fluorescein with higher EPS production. A mutant T4-2 exhibited a 106.48% increase in flocculating activity compared to the original strain. The maximum EPS yield from T4-2 was enhanced up to 6.42 g/L, nearly 10 times higher than the original strain on a 3.6-L bioreactor with optimized fermentation conditions. Moreover, the flocculating activity of the mutant reached 3023.4 U/mL, 10.96-fold higher than that of T4. Further identification showed that EPS from mutant T4-2 was mainly composed of polysaccharide (76.67%) and protein (15.8%) with a molecular weight of 1.17 × 105 Da. The EPS showed excellent adsorption capacities of 80.13 mg/g for chromium (VI), which was much higher than many reported adsorbents such as chitosan and cellulose. The adsorption results were described by Langmuir isotherm and pseudo-second-order kinetic model. The thermodynamic parameters (ΔG0, ΔH0 and ΔS0) revealed that the adsorption process was spontaneous and exothermic. Adsorption mechanisms were speculated to be electrostatic interaction, reduction, and chelation.

Bioflocculant produced by Bacillus velezensis and its potential application in brewery wastewater treatment

This study was designed to evaluate the potential of bioflocculant producing strains isolated from wastewater sludge. According to the Plackett–Burman design, the response surface revealed glucose, magnesium sulfate, and ammonium sulfate as critical media components of the nutritional source, whereas the central composite design affirmed an optimum concentration of the critical nutritional source as 16.0 g/l (glucose), 3.5 g/l magnesium sulfate heptahydrate (MgSO₄.7H₂O), and 1.6 g/l ammonium sulfate ( (NH₄)₂SO₄), yielding an optimal flocculation activity of 96.8%. Fourier Transformer Infrared Spectroscopy (FTIR) analysis confirmed the presence of hydroxyl, carboxyl and methoxyl in the structure of the bioflocculant. Additionally, chemical analysis affirmed the presence of mainly a polysaccharide in the main backbone of the purified bioflocculant with no detection of protein. Energy Dispersive X-ray analysis affirmed the presence of chlorine, phosphorous, oxygen and chlorine as representatives of elemental composition. Thermogravimetric (TGA) analysis revealed over 60% weight was retained at a temperature range of 700 °C. The purified bioflocculant remarkably removed chemical oxygen demand, biological oxygen demand and turbidity in brewery wastewater. This study suggested that the bioflocculant might be an alternate candidate for wastewater treatment.

Sustainable and efficient technologies for removal and recovery of toxic and valuable metals from wastewater: Recent progress, challenges, and future perspectives

Due to their numerous effects on human health and the natural environment, water contamination with heavy metals and metalloids, caused by their extensive use in various technologies and industrial applications, continues to be a huge ecological issue that needs to be urgently tackled. Additionally, within the circular economy management framework, the recovery and recycling of metals-based waste as high value-added products (VAPs) is of great interest, owing to their high cost and the continuous depletion of their reserves and natural sources. This paper reviews the state-of-the-art technologies developed for the removal and recovery of metal pollutants from wastewater by providing an in-depth understanding of their remediation mechanisms, while analyzing and critically discussing the recent key advances regarding these treatment methods, their practical implementation and integration, as well as evaluating their advantages and remaining limitations. Herein, various treatment techniques are covered, including adsorption, reduction/oxidation, ion exchange, membrane separation technologies, solvents extraction, chemical precipitation/co-precipitation, coagulation-flocculation, flotation, and bioremediation. A particular emphasis is placed on full recovery of the captured metal pollutants in various reusable forms as metal-based VAPs, mainly as solid precipitates, which is a powerful tool that offers substantial enhancement of the remediation processes' sustainability and cost-effectiveness. At the end, we have identified some prospective research directions for future work on this topic, while presenting some recommendations that can promote sustainability and economic feasibility of the existing treatment technologies.

Physicochemical factors affecting flocculating properties of the proteoglycan isolated from Rhodococcus opacus

The water-soluble fraction of proteoglycan RS-89 isolated from the Rhodococcus opacus FCL89 and composed of 64.6% polysaccharide and 9.44% protein has been studied as regards its flocculating activity. The RS-89 polysaccharide component includes mannose, galactose and glucose at the molar ratio of 2.7: 1.3: 1. The basic factors affecting flocculating activity of the RS-89 have been established. Additionally, the kinetics of kaolin sedimentation without and with the bioflocculant was investigated. The presence of divalent metal ions had a positive effect on the flocculating activity of the RS-89. The addition of Ca2+ increased the RS-89 flocculating activity in comparison to the other studied metals. It was proved that the proteoglycan RS-89 achieved the highest flocculating activity at the concentration equal to 2 mg/L and in the presence of 10 mmol/L of Ca2+. The zeta potential values are less negative when there is an interaction between the kaolin particles and metal ions without the RS-89 in the tested systems. Therefore, the proposed mechanism to describe the proteoglycan interaction with kaolin particles in the presence of divalent ions includes charge neutralization and a bridging mechanism.

Recent advances and perspectives in efforts to reduce the production and application cost of microbial flocculants

Microbial flocculants are macromolecular substances produced by microorganisms. Due to its non-toxic, harmless, and biodegradable advantages, microbial flocculants have been widely used in various industrial fields, such as wastewater treatment, microalgae harvest, activated sludge dewatering, heavy metal ion adsorption, and nanoparticle synthesis, especially in the post-treatment process of fermentation with high safety requirement. However, compared with the traditional inorganic flocculants and organic polymeric flocculants, the high production cost is the main bottleneck that restricts the large-scale production and application of microbial flocculants. To reduce the production cost of microbial flocculant, a series of efforts have been carried out and some exciting research progresses have been achieved. This paper summarized the research advances in the last decade, including the screening of high-yield strains and the construction of genetically engineered strains, search of cheap alternative medium, the extraction and preservation methods, microbial flocculants production as an incidental product of other biological processes, combined use of traditional flocculant and microbial flocculant, and the production of microbial flocculant promoted by inducer. Moreover, this paper prospects the future research directions to further reduce the production cost of microbial flocculants, thereby promoting the industrial production and large-scale application of microbial flocculants.

Wastewater treatment using plant-derived bioflocculants: green chemistry approach for safe environment

The rapid expansion of global trade and human activities has resulted in a massive increase in wastewater pollution into the atmosphere. Suspended solids, organic and inorganic particles, dissolved solids, heavy metals, dyes, and other impurities contained in wastewater from various sources are toxic to the atmosphere and pose serious health risks to humans and animals. Coagulation-flocculation technology is commonly used in wastewater treatment to remove cell debris, colloids, and contaminants in a comfortable and effective manner. Flocculants, both organic and inorganic, have long been used in wastewater treatment. However, because of their low performance, non-biodegradability, and associated health risks, their use has been limited. The use of eco-friendly bioflocculants in wastewater treatment has become essential due to the health implications of chemical flocculants. Because of their availability, biodegradability, and protection, plant-derived coagulants/flocculants and plant-based grafted bioflocculants have recently made significant progress in wastewater treatment. This study will undoubtedly provide a clearer understanding of the current state, challenges, and solutions for bioflocculation in wastewater remediation using green materials for the sake of a cleaner climate.

Investigation of micropollutants removal from landfill leachate in a full-scale advanced treatment plant in Istanbul city, Turkey

Although the levels of micropollutants in landfill leachate and municipal wastewater are well-established, the individual removal mechanisms and the fate of micropollutants throughout a landfill leachate treatment plant (LTP) were seldom investigated. Therefore, the determination of the removal efficiencies and the fates of micropollutants in a full-scale leachate treatment plant located in the largest city of Turkey were aimed in this study. Some important processes, such as equalization pond, bioreactor, ultrafiltration (UF) and nanofiltration (NF), are being operated in the treatment plant. Landfill leachate was characterized as an intense pollution source of macro and micropollutants compared to other water types. Chemical oxygen demand (COD), NH₃, suspended solids (SS) and electrical conductivity (EC) values of the landfill leachate (and their removal efficiencies in the treatment plant) were determined as 18,656 ± 12,098 mg/L (98%), 3090 ± 845 mg/L (99%), 4175 ± 1832 mg/L (95%) and 31 ± 2 mS/cm (51%), respectively. Within the scope of the study, the most frequently and abundantly detected micropollutants in the treatment plant were found as heavy metals (8 ± 1.7 mg/L), VOCs (38 ± 2 μg/L), alkylphenols (9 ± 3 μg/L) and phthalates (8 ± 3 μg/L) and the overall removal efficiencies of these micropollutants ranged from -11% to 100% in the treatment processes. The main removal mechanism of VOCs in the aerobic treatment process has been found as the volatilization due to Henry constants greater than 100 Pa·m³/mol. However, the molecular weight cut off restriction of UF membrane has caused to less or negative removal efficiencies for some VOCs. The biological treatment unit which consists of sequential anoxic and oxic units (A/O) was found effective on the removal of PAHs (62%) and alkylphenols (87%). It was inferred that both NO₃ accumulation in anoxic reactor, high hydraulic retention time (HRT) and sludge retention time (SRT) in aerobic reactor provide higher biodegradation and volatilization efficiencies as compared to the literature. Membrane processes were more effective on the removal of alkylphenols (60-80%) and pesticides (59-74%) in terms of influent and effluent loads of each unit. Removal efficiencies for Cu, Ni and Cr, which were the dominant heavy metals, were determined as 92, 91 and 51%, respectively and the main removal mechanism for heavy metals has thought to be coprecipitation of suspended solids by microbial biopolymers in the bioreactor and the separation of colloids during membrane filtration. Total effluent loads of the LTP for VOCs, semi volatiles and heavy metals were 1.0 g/day, 5.2 g/day and 1.5 kg/day, respectively. It has been concluded that the LTP was effectively removing both conventional pollutants and micropollutants with the specific operation costs of 0.27 $/(kg of removed COD), 0.13 $/(g of removed VOCs), 0.35 $/(g of removed SVOCs) and 2.6 $/(kg of removed metals).

Marine Actinobacteria Bioflocculant: A Storehouse of Unique Biotechnological Resources for Wastewater Treatment and Other Applications

The bioactive compounds produced by actinobacteria have played a major role in antimicrobials, bioremediation, biofuels, enzymes, and anti-cancer activities. Biodegradable microbial flocculants have been produced by bacteria, algae, and fungi. Microbial bioflocculants have also attracted biotechnology importance over chemical flocculants as a result of degradability and environmentally friendly attributes they possess. Though, freshwater actinobacteria flocculants have been explored in bioflocculation. Yet, there is a paucity of information on the application of actinobacteria flocculants isolated from the marine environment. Similarly, marine habitats that supported the biodiversity of actinobacteria strains in the field of biotechnology have been underexplored in bioflocculation. Hence, this review reiterates the need to optimize culture conditions and other parameters that affect bioflocculant production by using a response surface model or artificial neural network.

Wastewater Treatment by a Polymeric Bioflocculant and Iron Nanoparticles Synthesized from a Bioflocculant

Wastewater remains a global challenge. Various methods have been used in wastewater treatment, including flocculation. The aim of this study was to synthesize iron nanoparticles (FeNPs) using a polymeric bioflocculant and to evaluate its efficacy in the removal of pollutants in wastewater. A comparison between the efficiencies of the bioflocculant and iron nanoparticles was investigated. A scanning electron microscope (SEM) equipped with an energy-dispersive X-ray analyzer (EDX) and Fourier transform-infrared (FT-IR) spectroscopy were used to characterize the material. SEM-EDX analysis revealed the presence of elements such as O and C that were abundant in both samples, while FT-IR studies showed the presence of functional groups such as hydroxyl (–OH) and amine (–NH₂). Fe nanoparticles showed the best flocculation activity (FA) at 0.4 mg/mL dosage as opposed to that of the bioflocculant, which displayed the highest flocculation activity at 0.8 mg/mL, and both samples were found to be cation-dependent. When evaluated for heat stability and pH stability, FeNPs were found thermostable with 86% FA at 100 °C, while an alkaline pH of 11 favored FA with 93%. The bioflocculant flocculated poorly at high temperature and was found effective mostly at a pH of 7 with over 90% FA. FeNPs effectively removed BOD (biochemical oxygen demand) and COD (chemical oxygen demand) in all two wastewater samples from coal mine water and Mzingazi River water. Cytotoxicity results showed both FeNPs and the bioflocculant as nontoxic at concentrations up to 50 µL.

Preparation, Performances, and Mechanisms of Microbial Flocculants for Wastewater Treatment

In recent years, close attention has been paid to microbial flocculants because of their advantages, including safety to humans, environmental friendliness, and acceptable removal performances. In this review, the preparation methods of microbial flocculants were first reviewed. Then, the performances of bioflocculants in the removal of suspended solids, heavy metals, and other organic pollutants from various types of wastewater were described and commented, and the removal mechanisms, including adsorption bridging, charge neutralization, chemical reactions, and charge neutrality, were also discussed. The future research needs on microbial flocculants were also proposed. This review would lead to a better understanding of current status, challenges, and corresponding strategies on microbial flocculants and bioflocculation in wastewater treatment.