Reviews in Environmental Science and Bio/Technology最新文献

The high metabolic flexibility and biodiversity of microalgae make them promising systems for the production of chemicals and high-value metabolites to be utilized in various industrial applications. Currently, microalgae are primarily cultivated in phototrophic processes or in fermenters using glucose as substrate. However, such configurations are often too costly for the majority of potential applications and require improvements. The use of acetate as substrate to enhance biomass productivity and reduce cost and environmental impacts is a promising solution. In a future bio-based economy, acetate can serve as an excellent intermediate to link many industrial facilities, as it can be synthesized using different technologies from renewable resources as CO₂ and waste. This work provides a detailed description of acetate synthesis processes alternative to the conventional methanol carbonylation, including the pros and cons of each: aerobic and anaerobic fermentations; thermochemical treatments; C1 gas fermentation; microbial electrosynthesis and artificial photosynthesis. Additionally, the utilization of acetate as substrate for microalgae growth in mixotrophic and heterotrophic conditions is reviewed, covering key metabolic and engineering aspects (strains, yields, growth rate, inhibition, productivity, process configuration). These aspects serve as guidelines for a rationale design of an algal cultivation process based on acetate as a carbon source. Finally, the review critically assesses the state of the art of coupling of acetate-rich streams with algal biomass production, highlighting the pros and cons and addressing the main knowledge gaps to be filled through future research.

Copper (Cu) is a bio-essential element and a potentially toxic pollutant in the plant–soil systems. Analysis of stable Cu isotopes can be a powerful tool for tracing the biogeochemical cycling of Cu in plant–soil systems. In this review, we examined the analysis method of stable Cu isotope ratios in plants and soils, and discussed the biogeochemical processes, including redox reactions, mineral dissolution, abiotic and biotic sorption, which fractionate Cu isotopes in plant–soil systems. We also reviewed the variability of the isotopic signature in different plants and plant tissues, as well as different soil types and profiles to discuss the relationship between the biogeochemical transformation of Cu and its isotope fractionation in plant–soil systems. The collected data show that δ⁶⁵Cu values range from − 2.59 to + 1.73‰ in plant–soil systems, and ∆⁶⁵Cu values range from − 1.00 to − 0.11‰ between the plant and soil. The variation in the ∆⁶⁵Cu value between the plant and soil is mainly in response to the different uptake strategies during the acquisition of Cu from soils. Cu isotope analyses are proved to be a suitable technique during the biogeochemical transformation of Cu in plant–soil systems, especially during redox reactions. Ultimately, research challenges and future directions for Cu isotope techniques as a proxy for Cu biogeochemical cycles are also proposed. This review is beneficial for soil safety, food safety, and the sustainable development of agriculture and human health.

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Biotechnological fermentation of polyhydroxyalkanoates (PHAs) from microbes is rooted in decelerating the reliance on synthetic plastics, one of the predominant challenges for the sustainable development goals (SDGs) of recent decades. The multifaceted inherent properties of these PHAs also exert wide spectrum applicability in numerous industrial, environmental, and healthcare sectors. However, conventional producers include gram-negative microbes with stringent nutrient requirements, low PHA productivities, and endotoxin-contaminated products thereby limiting large-scale production. We hereby critically review the inherent potential of developing non-pathogenic gram-positive Bacillus cereus clade as the chassis for PHA biosynthesis and growth-dependent (exponential) accumulation with high purity. Integration of these microbes as PHA producers in mainstream industries requires in-depth and precise knowledge that is provided within this review in coordination with (i) key operons/pathways, (ii) evolved regulatory mechanisms, (iii) toxigenicity evasion, (iv) carbon flux engineering, and (v) -omics-supported bioprocesses. Among them, the review reports newly updated Bacillus emend cereus members with class IV PhaC ‘synthase’ demonstrating superior properties such as broad substrate specificity, structurally unrelated waste carbon catalysis, diverse monomeric copolymerization and unique alcoholytic cleavage. Moreover, the obtained biopolymer naturally lacks pyrogenic contamination meaning that the end polymer is in compliance with the Food and Drug Administration (FDA). Accordingly, this can propel the industrial B. cereus clade PHAs in advanced biorefinery domains using second-generation (waste) feedstocks to promote a circular economy, reduce the carbon footprint and an increase in practical applications as both social and environmentally friendly polymers.

Selenium, the essential toxin, is an indispensable nutrient for many organisms but quickly becomes a significant environmental concern at slightly higher concentrations, particularly in aquatic environments. Water treatment technologies have been developed over decades for industrial Se removal, but invariably result in Se-laden residuals. These Se-laden residuals represent a significant environmental liability and require careful management, which in turn represents a real, but often overlooked, operating cost. Conversely, Se sees commercial use across many industries and may be considered a vulnerable element in that its economic importance far outweighs its global supply chain stability. Thus, the recovery of Se from non-conventional sources, including solid (electronic waste) and water-based sources (mine tailings, leachates, flue gas desulphurization water, agricultural waste) is desirable. Industrial wastewater represents a unique opportunity to pair wastewater treatment techniques with resource recovery towards circular economy principles. This review highlights conventional and emerging uses of Se, along with an overview of its current supply, and potential sources. Next, a summary of existing and emerging wastewater treatment technologies for Se removal from industrial wastewater streams is provided. Finally, this review also includes progress and developments towards Se recovery from the same industrial wastewater streams, with a focus on integrating Se wastewater treatment and Se recovery towards a circular economy.

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Microalgae are well-known photosynthetic microorganisms used as cell factories for the production of relevant biotechnological compounds. Despite the outstanding characteristics attributed to microalgae, their industrial-scale production still struggles with scale-up problems and economic feasibility. One important bottleneck is the lack of suitable online sensors for the reliable monitoring of biological parameters, mostly concentrations of intracellular components, in microalgae bioprocesses. Software sensors provide an approach to improving the monitoring of those process parameters that are difficult to quantify directly and are therefore only indirectly accessible. Their use aims to improve the productivity of microalgal bioprocesses through better monitoring, control and automation, according to the current demands of Industry 4.0. In this review, a description of the microalgae components of interest as candidates for monitoring in a cultivation, an overview of software sensors, some of the available approaches and tools, and the current state-of-the-art of the design and use of software sensors in microalgae cultivation are presented. The latter is grouped on the basis of measurement methods used as software sensor inputs, employing either optical or non-optical techniques, or a combination of both. Some examples of software sensor design using simulated process data are also given, grouped according to their design, either as model-driven or data-driven estimators.

Hybrid ion exchange (IX) and biological processes have been developed for various water and wastewater treatment applications. These hybrid systems integrate multiple physical, chemical, biological, hydrodynamics, and substrate transport processes to improve the treatment efficiencies and system stability. The mathematical description of the individual process has been well established previously; however, there is a lack of a holistic review and guidelines to develop hybrid models for different treatment systems. In this paper, we summarize the applications of hybrid IX and biological systems, critically review the representative individual process models, and propose the framework to integrate these models for the hybrid process. Additionally, we provide a comprehensive review of the equilibrium, kinetic, and thermodynamic models for the IX process and the key biological process models, along with their applied scenarios. Advanced data-driven modelling and its combination with mechanistic models are also discussed to overcome the drawbacks in conventional modeling approach. We highlight emerging techniques that would lead to higher fidelity models. This review provides a comprehensive guideline for the model development of hybrid systems and presents future research directions to build robust systems.

The occurrence of antibiotics in surface waters is an alarming issue that can be addressed by advanced wastewater treatment technologies. Among them, enzymatic treatment is an emerging technology claimed to provide prospective benefits in terms of efficiency, controllability, and safety. This review illustrates the current state of research focused on enzyme-based approaches for pollutant abatement, specifically on the most critical classes of antibiotics (e.g. tetracyclines, sulfonamides, fluoroquinolones). In addition to providing an overview of the efficiency both in terms of compound removal as well as toxicity reduction, we critically analyze if selected reaction conditions, such as the pH, temperature and water matrix are representative for real-case scenarios. Enzyme immobilization strategies onto inorganic, organic and composite materials are analyzed in terms of their effect on enzyme stability and activity. Their feasibility to be applied in future processes was also evaluated. We found that adequate kinetic description of target compound removal by sufficiently detailed models is still scarce even though it will be key for successful conceptualization of treatment processes. Considering that only a few studies have been conducted at scales above 100 mL, we present the investigated reactor configurations which are at the forefront of further scale-up. The systematic approach presented in this manuscript, which aims to critically evaluate the feasibility to implement enzymatic processes for the removal of antibiotics, can be adapted for other types of recalcitrant compounds targeted by oxidoreductases. Intensified research in the recommended areas will contribute to the development of enzyme-based processes which can complement other advanced wastewater treatment processes.

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A progressive shift from energy-intensive wastewater treatment plants toward sustainable water resource recovery facilities (WRRFs) has gained traction over the years. The A-stage coupled with the B-stage shortcut biological nitrogen removal is enticing, owing to its efficacy in terms of land and energy conservation. This paper is a critical review of the A-stage process that provides a mechanistic understanding of its performance in terms of removal mechanisms, and the influence of its operational parameters. In accordance, future research directions are suggested to deepen the current understanding of the process, develop alternative technologies, and build more efficient WRRFs. Several factors such as HRT, SRT, DO concentration, OLR, chemical oxygen demand (COD) mass load, reactor VSS, feeding regime (i.e., feast/famine), and feast-to-famine retention time ratio independently affect the A-stage process. These factors alternate the substrate acquisition-based mechanisms from being transitional/preparatory mechanisms and typically overlooked in the conventional activated sludge process to critical removal mechanisms in the A-stage process. Although the influence of SRT on the A-stage process has been widely studied, this study demonstrated that SRT should be determined according to the influent COD fractionation and mass load. Moreover, it was inferred that a high DO concentration allows for high bioflocculation and storage under controlled SRT and HRT. Further research is needed to better understand the influence of HRT and feast-to-famine retention time ratio. Furthermore, there are discrepancies regarding the actual selection pressures that induce the substrate acquisition-based mechanisms which require further investigation and resolution.

Based on the most recently published data, we definitively estimated that the annual global production of sewage sludge may rise from ~ 53 million tons dry solids currently to ~ 160 million tons if global wastewater were to be treated to a similar level as in the 27 European Union countries/UK. It is widely accepted that the agricultural application is a beneficial way to recycle the abundant organic matter and plant nutrients in sewage sludge. However, land application may need to be limited due to the presence of metals. This work presents a meticulous and systematic review of the sources, concentrations, partitioning, and speciation of metals in sewage sludge in order to determine the impacts of sludge application on metal behavior in soils. It identifies that industrial wastewater, domestic wastewater and urban runoff are main sources of metals in sludge. It shows conventional treatment processes generally result in the partitioning of over 70% of metals from wastewater into primary and secondary sludge. Typically, the order of metal concentrations in sewage sludge is Zn > Cu > Cr ≈ Pb ≈ Ni > Cd. The proportion of these metals that are easily mobilised is highest for Zn and Ni, followed by Cd and Cu, then Pb and Cr. Sludge application to land will lead to elevated metal concentrations, and potentially to short-term changes to the dominant metal species in soils. However, the speciation of sludge-associated metals will change over time due to interactions with plant roots and soil minerals and as organic matter is mineralised by rhizo-microbiome.

The interaction of bio–geosphere dates to the formation of first unicellular microbes on earth. However, it is only relatively recently that the complex biological interactions are observed, characterised, and simulated for its use in the domain of geotechnical engineering. Also, many bioinspired approaches have been utilised in computational geotechnics for optimisation and data analysis process. The living phase present in the soil system hold a bearing on the majority of geochemical reactions and assist in modifying its fundamental and engineering behaviour. It necessitates revaluation and rescrutinisation of the conventional theories and formulations in geotechnical engineering, where soil has always been considered as an inert engineering material from biological perspective. To that end, this manuscript provides a critical review on biological approaches used in geotechnical engineering by highlighting the ongoing developments, achievements, and challenges to implement the processes. The review further emphasises the role of biological systems on the alteration of fundamental properties of soils and their consequences on effective stress, strength and stiffness, volume change and conduction properties of soils. Overall, the manuscript provides a basic understanding on the biological intervention in the soil system and the importance of consideration of the fourth phase in the soil system, i.e., the living phase, while describing such interventions.