Search Results (168)

Soil respiration (Rt), consisting of heterotrophic (Rh) and autotrophic respiration (Ra), plays a vital role in terrestrial carbon cycling and is sensitive to soil temperature and moisture. In dryland agriculture, plastic film mulching (PM) is widely used to regulate soil hydrothermal conditions, but its effects on Rt components and their temperature sensitivity (Q₁₀) across regions remain unclear. A two-year field study was conducted at two rain-fed maize sites: Anding (warmer, semi-arid) and Yuzhong (colder, drier). PM significantly increased Rt, Rh, and Ra, especially Ra, due to enhanced root biomass and improved microclimate. Yield increased by 33.6–165%. Peak respiration occurred earlier in Anding, aligned with maize growth and soil temperature. PM reduced Q₁₀ of Rt and Ra in Anding, but only Ra in Yuzhong. Rh Q₁₀ remained stable, indicating microbial respiration was less sensitive to temperature changes. Structural equation modeling revealed that Rt and Ra were mainly driven by soil temperature and root biomass, while Rh was more influenced by microbial biomass carbon (MBC) and dissolved organic carbon (DOC). Despite increased CO₂ emissions, PM improved carbon emission efficiency (CEE), particularly in Yuzhong (+67%). The application of PM is recommended to enhance yield while optimizing carbon efficiency in dryland farming systems. Full article

In recent years, microalgae have gained significant biotechnological importance as a sustainable source of various metabolites of industrial interest. Among these, paramylon, a polysaccharide produced by the microalga Euglena gracilis, stands out for its diverse applications in biomedicine and pharmaceuticals. E. gracilis is an adaptable secondary eukaryote capable of growing photoautotrophically, heterotrophically and mixotrophically. During photoautotrophic growth, varying light conditions impact biomass and paramylon production. To investigate the effects of varying illumination more thoroughly, we designed and built a modular photobioreactor that allowed us to simultaneously evaluate the photoautotrophic growth of E. gracilis under twelve different light conditions: seven single-spectrum lights (ultraviolet, royal blue, blue, green, red, far-red, and infrared) and five composite-spectrum lights (3000 K, 10,000 K, and 30,000 K white lights, amber light, and “Full-spectrum” light). The 24-day growing kinetics were recorded, and the growth parameters were calculated for each light regime. Both growth curves and pigment composition present differences attributable to the light regime used for cell culture. Additionally, photosynthetic and respiratory machinery functionality were proven by oximetry. Finally, our results strongly suggest that the far-red component enhances paramylon production during the stationary phase. Full article

The structure of microbial communities in sponge-sand filters, used for the treatment of real domestic sewage with elevated ammonium nitrogen concentrations (approximately 155 mg·dm⁻³), was characterized using 16S rRNA gene sequencing. Analyses using the Illumina technique allowed us to perform a comparison of filters by layer (two or three layers) and type of fill (waste PUR foams with 95% open porosity, sand). Proteobacteria, actinobacteria, and firmicutes were shown to be the most abundant phyla. The number and type of fill layers had a significant impact on the diversity of nitrifying bacteria. The presence of Nitrosomonas and Nitrospira was observed in every sponge fill sample, but the abundance of autotrophic nitrifiers was negligible in the two-layer filter. The conditions there proved more favorable for the growth of aerobic heterotrophic bacteria. Also in the Schmutzdecke layer, a dominance of heterotrophic nitrifiers was found. The abundance of bacteria with nitrifying activity (AOB, comammox, HNAD) in the biomass of spongy fill placed in casings was 1.7 times lower than in foams without casings. In addition, anammox bacteria (unidentified Planctomycetes), found mainly in the sponge fill and Schmutzdecke of the three-layer filters, may have been responsible for NH4⁺-N removal exceeding 70%. In the case of the two-layer filter, the removal of this pollutant reached 92%. Burkholderia and Sphingopyxis were identified as the predominant denitrifying bacteria. The foam-filled filter in the casings showed an increase in o_Caldilineaceae, involved in nitrate removal as non-denitrifiers. Actinomycetes Pseudonocardia and Amycolatopsis, as well as Proteobacteria Devosia, Acinetobacter, and Bdellovibrio, were found to be involved in phosphorus removal in the waste PUR foams. Full article

We propose an adaptive multi-timescale particle filter (AMTS-PF) for nonlinear state estimation in wastewater treatment plants (WWTPs) to address multi-scale temporal dynamics. The AMTS-PF decouples the problem into minute-level state updates and hour-level parameter refinements, integrating adaptive noise tuning, multi-scale entropy-driven feature extraction, and dual-timescale particle weighting. It dynamically adjusts noise covariances via Bayesian fusion and uses wavelet-based entropy analysis for adaptive resampling. The method interfaces seamlessly with existing WWTP control systems, providing real-time state estimates and refined parameters. Implemented on a heterogeneous computing architecture, it combines edge-level parallelism and cloud-based inference. Experimental validation shows superior performance over extended Kalman filters and single-timescale particle filters in handling nonlinearities and time-varying dynamics. The proposed AMTS-PF significantly enhances the accuracy of state estimation in WWTPs compared to traditional methods. Specifically, during the 14-day evaluation period using the Benchmark Simulation Model No. 1 (BSM1), the AMTS-PF achieved a root mean square error (RMSE) of 54.3 mg/L for heterotroph biomass (XH) estimation, which is a 37% reduction compared to the standard particle filter (PF) with an RMSE of 68.9 mg/L. For readily biodegradable substrate (Ss) and particulate products (Xp), the AMTS-PF also demonstrated superior performance with RMSE values of 7.2 mg/L and 9.8 mg/L, respectively, representing improvements of 24% and 21% over the PF. In terms of slow parameters, the AMTS-PF showed a 37% reduction in RMSE for the maximum heterotrophic growth rate (μH) estimation compared to the PF. These results highlight the effectiveness of the AMTS-PF in handling the multi-scale temporal dynamics and nonlinearities inherent in WWTPs. This work advances the state-of-the-art in WWTP monitoring by unifying multi-scale temporal modeling with adaptive Bayesian estimation, offering a practical solution for improving operational efficiency and process reliability. Full article

With the rapid development of the global aquaculture industry, the issue of effluent pollution from aquaculture has become increasingly severe. Effective management of aquaculture effluent is an urgent requirement for the sustainable development of the aquaculture industry, with a key focus on the efficient removal of nitrogen. Heterotrophic bacteria assimilation technology offers advantages such as high efficiency and resource recovery; however, its application in effluent treatment remains limited. Therefore, this study aimed to identify the optimal carbon source for the heterotrophic bacteria assimilation process and to optimize its operating parameters using response surface methodology (RSM). The results revealed that the sucrose group achieved the highest total ammonia nitrogen (TAN) removal rate of 85.1%, significantly outperforming molasses (77.0%) and glucose (62.9%), with microbial biomass also significantly higher than in the other groups. Metagenomic analysis indicated that sucrose promotes the formation of efficient denitrifying microbial communities by enriching the phylum Bacteroidota and the denitrifying functional bacteria Xanthomarina, thereby significantly enhancing denitrification efficiency. The optimal carbon source was determined to be sucrose. Using the optimal parameters of microbial biomass at 1.7 g/L, a hydraulic retention time of 36 h, and a chemical oxygen demand-to-total nitrogen (COD/TN) ratio of 26, the removal rates of total nitrogen (TN), TAN, and nitrite nitrogen (NO₂⁻-N) exceeded 85%, while the removal rate of nitrate nitrogen (NO₃⁻-N) surpassed 60%. A significant interaction was observed between microbial biomass and hydraulic retention time, which notably affected denitrification efficiency (p < 0.05). This study provides theoretical support for the harmless and resourceful treatment of aquaculture effluent, contributing to the green and sustainable development of the aquaculture industry. Full article

Antarctica and the Southern Ocean are important sinks in the global mercury (Hg) cycle, and in the marine environment, inorganic Hg can be converted by bacteria to monomethylmercury (MeHg), a highly bioavailable and toxic compound that biomagnifies along food webs. In the Southern Ocean, higher concentrations of Hg and MeHg have typically been reported in the coastal waters of the Ross and Amundsen Seas, where katabatic winds can transport Hg from the Antarctic Plateau and create coastal polynyas, which results in spring depletion events of atmospheric Hg. However, some studies on MeHg biomagnification in Antarctic marine food webs have reported higher Hg concentrations in penguins from sub-Antarctic waters and, unexpectedly, higher levels in juvenile krill than those in adult Antarctic krill. In light of recent estimates of the phytoplankton and zooplankton biomass and distribution in the Southern Ocean, this review suggests that although most studies on MeHg biomagnification refer to the short diatom–krill–vertebrate food chain, alternative and more complex pelagic food webs exist in the Southern Ocean. Thus, juvenile krill and micro- and mesozooplankton grazing on very small autotrophs and heterotrophs, which have high surface-to-volume ratios for MeHg ad-/absorption, may accumulate more Hg than consumers of large diatoms, such as adult krill. In addition, the increased availability of Hg and the different diet contribute to a greater metal accumulation in the feathers of Adélie penguins from the Ross Sea than that of those from the sub-Antarctic. Full article

Biochar may represent a sustainable and eco-friendly strategy to recycle agroforestry wastes, sequester carbon and improve soil health. With the aim of proving these benefits in a real scenario, we treated several soil parcels with 0 (CTRL), 1 (LOW) and 3 (HIGH) kg/m² of wood biochar, in open-field trials. The heterotrophic soil respiration (SR) was monitored continuously for two months via a Closed Dynamic Chamber (CDC) associated with an innovative pilot system, and the most important soil chemical parameters were measured 9 and 54 days after biochar application. Biochar induced an immediate dose-dependent increase in organic matter content and CEC (up to 41.6% and 36.8% more than CTRL, respectively), which tended to slightly and gradually decrease after 54 days. In all cases, biochar induced a more pronounced SR, although the most enhanced microbial response was detected for the LOW parcel (19.3% higher than CTRL). Fennels were grown in treated soils and only LOW microplots gave a significantly better response (weight and size). Finally, NMR, FT-IR and Pyr-GC/MS analyses of LOW SOM extracts revealed a relevant impact on the composition, which was accompanied by a higher content of carbohydrates, indole-based compounds and FAME species correlating with enhanced microbial activity. Our findings demonstrate that the proper biochar dose improves soil fertility by creating an environment favorable to plants and promoting microbial activity. Full article

Purple phototrophic bacteria (PPB) have great potential in treating nitrogen-contaminated wastewater. Unlike conventional heterotrophic denitrification, PPB-driven denitrification utilizes light-driven metabolism, concurrently improving nitrogen removal and carbon management efficiency. This work aimed to develop a PPB denitrification process for nitrogen removal, carbon emission mitigation, and resource recovery. The PPB growth was first optimized and the most desirable light and carbon sources (i.e., incandescent light and sodium acetate) were pinpointed. PPB denitrification could reach a nitrate removal rate of 0.68 mg N/L/h, while no nitrite was detected during the process, regardless of the amount of external electron donors. This was attributed to the fact that the true reduction rate of nitrite (4.42 mg N/gVSS/h) was significantly higher than that of nitrate (1.51 mg N/gVSS/h). In the presence of a sufficient carbon source, PPB denitrification was found to be a low-carbon process, with only ~0.17% of converted nitrate being emitted as nitrous oxide. Meanwhile, PPB biomass for denitrification was rich in value-added products (e.g., protein and pigment), which potentially generated additional benefits over the biomass valued at USD 17 kg⁻¹. These results provide a theoretical basis for implementing PPB denitrification for carbon-neutral and resource-efficient wastewater treatment. Full article

Aerobic denitrifying microorganisms, with their strong environmental adaptability, low dissolved oxygen concentration requirements, rapid growth rate, and high nitrogen removal efficiency, significantly compensate for the shortcomings of traditional aerobic chemolithoautotrophic nitrification and anaerobic heterotrophic denitrification models. The introduction of aerobic denitrifiers can effectively enhance the removal of nitrate nitrogen. However, directly inoculating aerobic denitrifiers into wastewater leads to issues such as easy loss of bacterial cells and difficulty in forming a dominant flora, thus preventing the long-term maintenance of their enhancing effect on denitrification performance. To address this problem, microbial immobilization technology has been introduced into the remediation process of nitrogen-polluted water bodies. This technology can maintain a high biomass concentration, provide a stable breeding ground for microorganisms, and effectively prevent the rapid loss of microorganisms. This article systematically reviews the current status of the isolation of aerobic denitrifying bacteria, key enzymes, and genes, as well as the application progress of aerobic denitrifying bacteria and their immobilization technology, aiming to provide solid theoretical support for the practical application of aerobic denitrification technology and promote its further development in the field of nitrogen pollution control. Full article

Biochar application as a soil amendment is gaining attention as a stable, long-term carbon sequestration strategy for the mitigation of climate change. However, biochar applied to the soil may increase soil carbon efflux. This study aimed to determine the long-term (8 years) effects of biochar application to the forest floor on soil carbon effluxes (soil respiration [SR] and heterotrophic respiration [HR]) in a warm–temperate oak forest. Biochar was applied at the rate of 0, 5, or 10 Mg ha⁻¹ to 20 m × 20 m plots (n = 4). The SR and HR rates were determined using the closed chamber method and the trenching method. The annual SR tended to increase over 8 years following biochar application, whereas a significant increase in the annual HR (+31%–37%) was observed in the short term (<3 years). The increased HR likely included CO₂ emissions from the decomposition of the labile fraction of biochar carbon and from the microbial decomposition of the original soil organic matter stimulated through changes in the soil physicochemical environment, such as soil moisture and pH. The results suggest that a short-term increase in HR should be considered in the evaluation of carbon sequestration in response to biochar addition to forest ecosystems. Full article

Microalgae are photosynthetic microorganisms that have a rapid growth cycle and carbon fixation ability. They have diverse cellular structures, ranging from prokaryotic cyanobacteria to more complex eukaryotic forms, which enable them to thrive in a variety of environments and support biomass production. They utilize both photosynthesis and heterotrophic pathways, indicating their ecological importance and potential for biotechnological applications. Reproducing primarily through asexual means, microalgae have complex cell cycles that are crucial for their growth and ability to adapt to changing conditions. Additionally, microalgae possess bioactive compounds that make them both nutritious and functional. Thanks to their content of proteins, lipids, carbohydrates, vitamins, and minerals, they play an important role in the development of functional food products, particularly by enhancing nutritional content and product quality. Furthermore, studies have demonstrated that algae and algal bioactive compounds support cardiovascular health, immune function, and gut health, especially in relation to obesity and other metabolic diseases. They also contribute to skin health and cognitive functions, including memory. This review article explores the biological, nutritional, and functional properties of microalgae based on the studies conducted. Full article

Microzooplankton grazing is widely recognized as an important process of heterotrophic prokaryote and phytoplankton biomass removal. However, few studies have specifically addressed microbial mortality in the Ria Formosa coastal lagoon. This study aimed to assess the growth and mortality of heterotrophic prokaryotes and phytoplankton in this ecosystem using the dilution technique. The results revealed significant seasonal variations in the growth and grazing rates of both heterotrophic prokaryotes and phytoplankton, with mean grazing rates slightly exceeding the mean potential instantaneous growth rates. This indicates that microzooplankton consume a substantial proportion of both microbial groups in the lagoon. For specific phytoplankton taxa, the wide range of observed grazing rates suggests grazer selectivity, highlighting the need for future research to examine the dynamics of each phytoplankton group more closely. Full article

With the increasing awareness of socio-environmental issues, a global trend has emerged emphasizing the valorization of natural ingredients that promote health and well-being within sustainable production systems, such as microalgae-based carotenoids. Currently, little is understood about the correlation between biomass productivity and carotenoid content, which is a fundamental parameter for facilitating the immediate expansion of microalgae bioprocesses and ensuring the availability and industrial viability of these compounds. In this context, this study aims to investigate the carotenoid profile of Chlorella vulgaris through growth curve experiments conducted under photoautotrophic and heterotrophic regimes. Additionally, a trade-off analysis was performed for the production of carotenoids from microalgae. Carotenoids were quantified using high-performance liquid chromatography coupled with diode array and mass spectrometry detectors (HPLC-PDA-MS/MS). The performance of kinetic phases and energy demands across growth regimes was assessed to provide insights into production trade-offs. The results indicated that a total of 22 different carotenoids were identified in all the extracts. The all-trans-lutein and all-trans-β-carotene were the majority compounds. The total carotenoid content of Chlorella vulgaris revealed significant differences in the kinetic phases of carotenoid production, indicating that carotenoid volumetric production is only viable if the cultures are conducted until the log and stationary phases, based on the function of the biomass volumetric production (weight.volume⁻¹). Therefore, the best trade-off for the process was to provide photoautotrophic growth until the exponential phase (log). Under this condition, the maximum carotenoid and lutein content was 2921.70 µg.L⁻¹, reaching a maximum cell biomass of 1.46 g.L⁻¹. From an environmental/economic point of view, the energy demand was 7.74 kWh.L⁻¹. Finally, the scientific advances achieved in this study provide a holistic view of the influence of the main cultivation methods on the production of microalgae carotenoids, suggesting a viable initial direction for different industrial applications. Full article

Global climate warming has led to the deepening of the active layer of permafrost on the Tibetan Plateau, further triggering thermal subsidence phenomena, which have profound effects on the carbon cycle of regional ecosystems. This study conducted warming (W) and thermal subsidence (RR) control experiments using an Open-Top Chamber (OTC) device in the river source wetlands of the Qinghai Lake basin. The aim was to assess the impacts of warming and thermal subsidence on soil temperature, volumetric water content, biomass, microbial diversity, and soil respiration (both autotrophic and heterotrophic respiration). The results indicate that warming significantly increased soil temperature, especially during the colder seasons, and thermal subsidence treatment further exacerbated this effect. Soil volumetric water content significantly decreased under thermal subsidence, with the RRW treatment having the most pronounced impact on moisture. Additionally, a microbial diversity analysis revealed that warming promoted bacterial richness in the surface soil, while thermal subsidence suppressed fungal community diversity. Soil respiration rates exhibited a unimodal curve during the growing season. Warming treatment significantly reduced autotrophic respiration rates, while thermal subsidence inhibited heterotrophic respiration. Further analysis indicated that under thermal subsidence treatment, soil respiration was most sensitive to temperature changes, with a Q₁₀ value reaching 7.39, reflecting a strong response to climate warming. In summary, this study provides new scientific evidence for understanding the response mechanisms of soil carbon cycling in Tibetan Plateau wetlands to climate warming. Full article

Microalgae are considered to be a promising and prospective source of lipids for the production of biocomponents for conventional liquid fuels. The available sources contain a lot of information about the cultivation of biomass and the amounts and composition of the resulting bio-oils. However, there is a lack of reliable and verified data on the impact of fuel blends based on microalgae biodiesel on the quality of the emitted exhaust gas. Therefore, the main objective of the study was to present the emission characteristics of a compression-ignition engine fuelled with a blend of diesel fuel and biodiesel produced from the lipids accumulated in the biomass of a heterotrophic culture of Schizochytrium sp. The final concentrations of microalgal biomass and lipids in the culture were 140.7 ± 13.9 g/L and 58.2 ± 1.1 g/L, respectively. The composition of fatty acids in the lipid fraction was dominated by decosahexaenoic acid (43.8 ± 2.8%) and palmitic acid (40.4 ± 2.8%). All parameters of the bio-oil met the requirements of the EN 14214 standard. It was found that the use of bio-components allowed lower concentrations of hydrocarbons in the exhaust gas, ranging between 33 ± 2 ppm and 38 ± 7 ppm, depending on the load level of the engine. For smoke opacity, lower emissions were found in the range of 50–100% engine load levels, where the observed content was between 23 ± 4% and 53 ± 8%. Full article