Environment and microbiome drive different microbial traits and functions in the macroscale soil organic carbon cycle.

Soil microbial traits and functions play a central role in soil organic carbon (SOC) dynamics. However, at the macroscale (regional to global) it is still unresolved whether (i) specific environmental attributes (e.g., climate, geology, soil types) or (ii) microbial community composition drive key microbial traits and functions directly. To address this knowledge gap, we used 33 grassland topsoils (0-10 cm) from a geoclimatic gradient in Chile. First, we incubated the soils for 1 week in favorable standardized conditions and quantified a wide range of soil microbial traits and functions such as microbial biomass carbon (MBC), enzyme kinetics, microbial respiration, growth rates as well as carbon use efficiency (CUE). Second, we characterized climatic and physicochemical properties as well as bacterial and fungal community composition of the soils. We then applied regression analysis to investigate how strongly the measured microbial traits and functions were linked with the environmental setting versus microbial community composition. We show that environmental attributes (predominantly the amount of soil organic matter) determined patterns of MBC along the gradient, which in turn explained microbial respiration and growth rates. However, respiration and growth normalized for MBC (i.e., specific respiration and growth) were more linked to microbial community composition than environmental attributes. Notably, both specific respiration and growth followed distinct trends and were related to different parts of the microbial community, which in turn resulted in strong effects on microbial CUE. We conclude that even at the macroscale, CUE is the result of physiologically decoupled aspects of microbial metabolism, which in turn is partially determined by microbial community composition. The environmental setting and microbial community composition affect different microbial traits and functions, and therefore both factors need to be considered in the context of macroscale SOC dynamics.

Metataxonomic characterization of the microbial present in the anaerobic digestion of turkey litter waste with the addition of two inocula: allochthonous and commercial.

Turkey litter waste is lignocellulosic waste that can be sustainably used as an energy source through anaerobic digestion (AD). The 16S ribosomal RNA technique helps to unravel microbial diversity and predominant metabolic pathways. The assays were performed in 600-mL-glass bottles with 400 mL volume, for 60 days at 37 °C. The study evaluated the physicochemical parameters, the composition of the microbiota, and the functional inference in AD of different concentrations of turkey litter (T) using two inocula: granular inoculum (S) and commercial inoculum (B). The highest accumulated methane production (633 mL CH4·L-1) was observed in the test containing 25.5 g VS·L-1 of turkey litter with the addition of the two inocula (T3BS). In tests without inoculum (T3) and with commercial inoculum (T3B), there was an accumulation of acids and consequent inhibition of methane production 239 mL CH4·L-1 and 389 mL CH4·L-1, respectively. Bacteroidota, Firmicutes, and Actinobacteria were the main phyla identified. The presence of archaea Methanobacterium, Methanocorpusculum, and Methanolinea highlighted the hydrogenotrophic metabolic pathway in T3BS. Functional prediction showed enzymes involved in three metabolic pathways in turkey litter biodigestion: acetotrophic, hydrogenotrophic, and methylotrophic methanogenesis. The predominant hydrogenotrophic pathway can be observed by analyzing the microbiota, archaea involved in this specific pathway, genes involved, and relative acid consumption for T3S and T3BS samples with higher methane production. Molecular tools help to understand the main groups of microorganisms and metabolic pathways involved in turkey litter AD, such as the use of different inocula, allowing the development of strategies for the sustainable disposal of turkey litter.

Partial nitrification and simultaneous denitrification in sequential anaerobic and aerobic reactors: performance and microbial community dynamics.

ABSTRACTThe removal of organic matter and nitrogen from domestic sewage was evaluated using a system composed of two sequential reactors: an anaerobic reactor (ANR) with suspended sludge and an aerobic (AER) reactor with suspended and adhered sludge to polyurethane foams. Nitrogen removal consisted of AER operating at low dissolved oxygen (DO) concentrations; this favoured the simultaneous nitrification and denitrification (SND) process. The concentration of COD and N were 440 mgO2.L-1 and 37 mgTN.L-1, respectively. The operation was divided into three phases (P), lasting 51, 53, and 46 days, respectively. The initial DO concentrations applied in the AER were: 3.0 (PI) and 1.5 mg.L-1 (PII and PIII). In PIII, the AER effluent was recirculated to the ANR at a ratio of 0.25. Kinetic assays were performed to determine the nitrification and denitrification rates of the biomasses (ANR and AER in PIII). Changes in the microbial community were evaluated throughout phases PI to PIII by massive sequencing. In PIII, the best results obtained for chemical oxygen demand (COD) and total nitrogen (TN-N) removal efficiencies, were close to 94% and 65%, respectively. Under these conditions, system effluent concentrations below 30 mg COD.L-1 and 15 mg TN-N.L-1 were verified. The nitritation and nitration rates were 10.5 and 6.5 mg N.g VSS-1.h-1, while the denitrification via nitrite and nitrate were 6.8 and 5.8 mg N.g VSS-1.h-1, respectively. A mixotrophic community was prevalent, with Rhodococcus, Nitrosomonas, Pseudomnas, and Porphyromonas being dominant or co-dominant in most of the samples, confirming the SND process in the AER sludge.

Comparative analysis of prokaryotic microbiomes in high-altitude active layer soils: insights from Ladakh and global analogues using In-Silico approaches.

The active layer is the portion of soil overlaying the permafrost that freezes and thaws seasonally. It is a harsh habitat in which a varied and vigorous microbial population thrives. The high-altitude active layer soil in northern India is a unique and important cryo-ecosystem. However, its microbiology remains largely unexplored. It represents a unique reservoir for microbial communities with adaptability to harsh environmental conditions. In the Changthang region of Ladakh, the Tsokar area is a high-altitude permafrost-affected area situated in the southern part of Ladakh, at a height of 4530 m above sea level. Results of the comparison study with the QTP, Himalayan, Alaskan, Russian, Canadian and Polar active layers showed that the alpha diversity was significantly higher in the Ladakh and QTP active layers as the environmental condition of both the sites were similar. Moreover, the sampling site in the Ladakh region was in a thawing condition at the time of sampling which possibly provided nutrients and access to alternative nitrogen and carbon sources to the microorganisms thriving in it. Analysis of the samples suggested that the geochemical parameters and environmental conditions shape the microbial alpha diversity and community composition. Further analysis revealed that the cold-adapted methanogens were present in the Ladakh, Himalayan, Polar and Alaskan samples and absent in QTP, Russian and Canadian active layer samples. These methanogens could produce methane at slow rates in the active layer soils that could increase the atmospheric temperature owing to climate change.

Imprints of ecological processes in the taxonomic core community: an analysis of naturally replicated microbial communities enclosed in oil.

It is widely assumed that a taxonomic core community emerges among microbial communities from similar habitats because similar environments select for the same taxa bearing the same traits. Yet, a core community itself is no indicator of selection because it may also arise from dispersal and neutral drift, i.e. by chance. Here, we hypothesize that a core community produced by either selection or chance processes should be distinguishable. While dispersal and drift should produce core communities with similar relative taxon abundances, especially when the proportional core community, i.e. the sum of the relative abundances of the core taxa, is large, selection may produce variable relative abundances. We analyzed the core community of 16S rRNA gene sequences of 193 microbial communities occurring in tiny water droplets enclosed in heavy oil from the Pitch Lake, Trinidad and Tobago. These communities revealed highly variable relative abundances along with a large proportional core community (68.0 ± 19.9%). A dispersal-drift null model predicted a negative relationship of proportional core community and compositional variability along a range of dispersal probabilities and was largely inconsistent with the observed data, suggesting a major role of selection for shaping the water droplet communities in the Pitch Lake.

Uncovering potential mangrove microbial bioindicators to assess urban and agricultural pressures on Martinique island in the eastern Caribbean Sea.

Martinique's mangroves, which cover 1.85 ha of the island (<0.1 % of the total area), are considerably vulnerable to local urban, agricultural, and industrial pollutants. Unlike for temperate ecosystems, there are limited indicators that can be used to assess the anthropogenic pressures on mangroves. This study investigated four stations on Martinique Island, with each being subject to varying anthropogenic pressures. An analysis of mangrove sediment cores approximately 18 cm in depth revealed two primary types of pressures on Martinique mangroves: (i) an enrichment in organic matter in the two stations within the highly urbanized bay of Fort-de-France and (ii) agricultural pressure observed in the four studied mangrove stations. This pressure was characterized by contamination, exceeding the regulatory thresholds, with dieldrin, total DDT, and metals (As, Cu and Ni) found in phytosanitary products. The mangroves of Martinique are subjected to varying degrees of anthropogenic pressure, but all are subjected to contamination by organochlorine pesticides. Mangroves within the bay of Fort-de-France experience notably higher pressures compared to those in the island's northern and southern regions. In these contexts, the microbial communities exhibited distinct responses. The microbial biomass and the abundance of bacteria and archaea were higher in the two less-impacted stations, while in the mangrove of Fort-de-France, various phyla typically associated with polluted environments were more prevalent. These differences in the microbiota composition led to the identification of 65 taxa, including Acanthopleuribacteraceae, Spirochaetaceae, and Pirellulaceae, that could potentially serve as indicators of an anthropogenic influence on the mangrove sediments of Martinique Island.

Microbial diversity and abundance of Hg related genes from water, sediment and soil the Colombian amazon ecosystems impacted by artisanal and small-scale gold mining.

The Amazon region abounds in precious mineral resources including gold, copper, iron, and coltan. Artisanal and small-scale gold mining (ASGM) poses a severe risk in this area due to considerable mercury release into the surrounding ecosystems. Nonetheless, the impact of mercury on both the overall microbiota and the microbial populations involved in mercury transformation is not well understood. In this study we evaluated microbial diversity in samples of soil, sediment and water potentially associated with mercury contamination in two localities (Taraira and Tarapacá) in the Colombian Amazon Forest. To this end, we characterized the bacterial community structure and mercury-related functions in samples from sites with a chronic history of mercury contamination which today have different levels of total mercury content. We also determined mercury bioavailability and mobility in the samples with the highest THg and MeHg levels (up to 43.34 and 0.049 mg kg-1, respectively, in Taraira). Our analysis of mercury speciation showed that the immobile form of mercury predominated in soils and sediments, probably rendering it unavailable to microorganisms. Despite its long-term presence, mercury did not appear to alter the microbial community structure or composition, which was primarily shaped by environmental and physicochemical factors. However, an increase in the relative abundance of merA genes was detected in polluted sediments from Taraira. Several Hg-responsive taxa in soil and sediments were detected in sites with high levels of THg, including members of the Proteobacteria, Acidobacteria, Actinobacteria, Firmicutes and Chloroflexi phyla. The results suggest that mercury contamination at the two locations sampled may select mercury-adapted bacteria carrying the merA gene that could be used in bioremediation processes for the region.

Bacterial community composition in the Northern Gulf of Mexico intertidal sediment bioturbated by the ghost shrimp Lepidophthalmus louisianensis.

Bioturbation plays an important role in structuring microbial communities in coastal sediments. This study investigates the bacterial community composition in sediment associated with the ghost shrimp Lepidophthalmus louisianensis at two locations in the Northern Gulf of Mexico (Bay St. Louis, MS, and Choctawhatchee Bay, FL). Bacteria were analysed for shrimp burrows and for three different depths of bioturbated intertidal sediment, using second-generation sequencing of the 16S rRNA gene. Burrow walls held a unique bacterial community, which was significantly different from those in the surrounding sediment communities. Communities in burrow walls and surrounding sediment communities also differed between the two geographic locations. The burrow wall communities from both locations were more similar to each other than to sediment communities from same location. Alpha- and Gammaproteobacteria were more abundant in burrows and surface sediment than in the subsurface, whereas Deltaproteobacteria were more abundant in burrows and subsurface sediment, suggesting sediment mixing by the bioturbator. However, abundance of individual ASVs was geographic location-specific for all samples. Therefore, it is suggested that the geographic location plays an important role in regional microbial communities distinctiveness. Bioturbation appears to be an important environmental driver in structuring the community around burrows. Sampling was conducted during times of the year and water salinity, tidal regime and temperature were variable, nevertheless the structure microbial communities appeared to remain realatively stable suggesting that these environmental variable played only a minor role.

Different microbial communities in paddy soils under organic and nonorganic farming.

Organic agriculture is a farming method that provides healthy food and is friendly to the environment, and it is developing rapidly worldwide. This study compared microbial communities in organic farming (Or) paddy fields to those in nonorganic farming (Nr) paddy fields based on 16S rDNA sequencing and analysis. The predominant microorganisms in both soils were Proteobacteria, Chloroflexi, Acidobacteria, Actinobacteria, and Nitrospirota. The alpha diversity of the paddy soil microbial communities was not different between the nonorganic and organic farming systems. The beta diversity of nonmetric multidimensional scaling (NMDS) revealed that the two groups were significantly separated. Distance-based redundancy analysis (db-RDA) suggested that soil pH and electrical conductivity (EC) had a positive relationship with the microbes in organic paddy soils. There were 23 amplicon sequence variants (ASVs) that showed differential abundance. Among them, g_B1-7BS (Proteobacteria), s_Sulfuricaulis limicola (Proteobacteria), g_GAL15 (p_GAL15), c_Thermodesulfovibrionia (Nitrospirota), two of f_Anaerolineaceae (Chloroflexi), and two of g_S085 (Chloroflexi) showed that they were more abundant in organic soils, whereas g_11-24 (Acidobacteriota), g__Subgroup_7 (Acidobacteriota), and g_Bacillus (Firmicutes) showed differential abundance in nonorganic paddy soils. Functional prediction of microbial communities in paddy soils showed that functions related to carbohydrate metabolism could be the major metabolic activities. Our work indicates that organic farming differs from nonorganic farming in terms of microbial composition in paddy soils and provides specific microbes that might be helpful for understanding soil fertility.

Contaminants of emerging concern reduction and microbial community characterization across a three-barrier advanced water treatment system.

This research investigated the removal of contaminants of emerging concern (CECs) and characterized the microbial community across an advanced water treatment (AWT) train consisting of Coagulation/Flocculation/Clarification/Granular Media Filtration (CFCGMF), Ozone-Biological Activated Carbon Filtration (O3/BAC), Granular Activated Carbon filtration, Ultraviolet Disinfection, and Cartridge Filtration (GAC/UV/CF). The AWT train successfully met the goals of CECs and bulk organics removal. The microbial community at each treatment step of the AWT train was characterized using 16S rRNA sequencing on the Illumina MiSeq platform generated from DNA extracted from liquid and solid (treatment media) samples taken along the treatment train. Differences in the microbial community structure were observed. The dominant operational taxonomic units (OTU) decreased along the treatment train, but the treatment steps did impact the microbial community composition downstream of each unit process. These results provide insights into microbial ecology in advanced water treatment systems, which are influenced and shaped by each treatment step, the microbial community interactions, and their potential metabolic contribution to CECs degradation.

Topsoil and subsoil bacterial community assemblies across different drainage conditions in a mountain environment.

BACKGROUND: High mountainous environments are of particular interest as they play an essential role for life and human societies, while being environments which are highly vulnerable to climate change and land use intensification. Despite this, our knowledge of high mountain soils in South America and their microbial community structure is strikingly scarce, which is of more concern considering the large population that depends on the ecosystem services provided by these areas. Conversely, the Central Andes, located in the Mediterranean region of Chile, has long been studied for its singular flora, whose diversity and endemism has been attributed to the particular geological history and pronounced environmental gradients in short distances. Here, we explore soil properties and microbial community structure depending on drainage class in a well-preserved Andean valley on the lower alpine vegetation belt (~2500 m a.s.l.) at 33.5˚S. This presents an opportunity to determine changes in the overall bacterial community structure across different types of soils and their distinct layers in a soil depth profile of a highly heterogeneous environment. METHODS: Five sites closely located (<1.5 km) and distributed in a well preserved Andean valley on the lower alpine vegetation belt (~2500 m a.s.l.) at 33.5˚S were selected based on a pedological approach taking into account soil types, drainage classes and horizons. We analyzed 113 soil samples using high-throughput sequencing of the 16S rRNA gene to describe bacterial abundance, taxonomic composition, and co-occurrence networks. RESULTS: Almost 18,427 Amplicon Sequence Variant (ASVs) affiliated to 55 phyla were detected. The bacterial community structure within the same horizons were very similar validating the pedological sampling approach. Bray-Curtis dissimilarity analysis revealed that the structure of bacterial communities in superficial horizons (topsoil) differed from those found in deep horizons (subsoil) in a site-specific manner. However, an overall closer relationship was observed between topsoil as opposed to between subsoil microbial communities. Alpha diversity of soil bacterial communities was higher in topsoil, which also showed more bacterial members interacting and with higher average connectivity compared to subsoils. Finally, abundances of specific taxa could be considered as biological markers in the transition from topsoil to subsoil horizons, like Fibrobacterota, Proteobacteria, Bacteroidota for shallower soils and Chloroflexi, Latescibacterota and Nitrospirota for deeper soils. CONCLUSIONS: The results indicate the importance of the soil drainage conditions for the bacterial community composition, suggesting that information of both structure and their possible ecological relationships, might be useful in clarifying the location of the edge of the topsoil-subsoil transition in mountainous environments.

Linking the shifts in the metabolically active microbiota in a UASB and hybrid anaerobic-aerobic bioreactor for swine wastewater treatment.

Due to the high concentration of pollutants, swine wastewater needs to be treated prior to disposal. The combination of anaerobic and aerobic technologies in one hybrid system allows to obtain higher removal efficiencies compared to those achieved via conventional biological treatment, and the performance of a hybrid system depends on the microbial community in the bioreactor. Here, we evaluated the community assembly of an anaerobic-aerobic hybrid reactor for swine wastewater treatment. Sequencing of partial 16S rRNA coding genes was performed using Illumina from DNA and retrotranscribed RNA templates (cDNA) extracted from samples from both sections of the hybrid system and from a UASB bioreactor fed with the same swine wastewater influent. Proteobacteria and Firmicutes were the dominant phyla and play a key role in anaerobic fermentation, followed by Methanosaeta and Methanobacterium. Several differences were found in the relative abundances of some genera between the DNA and cDNA samples, indicating an increase in the diversity of the metabolically active community, highlighting Chlorobaculum, Cladimonas, Turicibacter and Clostridium senso stricto. Nitrifying bacteria were more abundant in the hybrid bioreactor. Beta diversity analysis revealed that the microbial community structure significantly differed among the samples (p < 0.05) and between both anaerobic treatments. The main predicted metabolic pathways were the biosynthesis of amino acids and the formation of antibiotics. Also, the metabolism of C5-branched dibasic acid, Vit B5 and CoA, exhibited an important relationship with the main nitrogen-removing microorganisms. The anaerobic-aerobic hybrid bioreactor showed a higher ammonia removal rate compared to the conventional UASB system. However, further research and adjustments are needed to completely remove nitrogen from wastewater.

Genetic basis for the biodegradation of a polyether-polyurethane-acrylic copolymer by a landfill microbial community inferred by metagenomic deconvolution analysis.

Plastic accumulation in the world amounts to approximately 8300 million tons. Polyurethanes (PU) account for 7.7 % of total plastics production worldwide, and their diverse chemical composition makes them highly recalcitrant to biodegradation. Several works have reported polyurethane-degrading microbial communities. However, it is still necessary to learn more about the chemical, biochemical, and genetic bases linked to the polyurethanolytic phenotype and the microbial taxonomic determinants responsible for metabolizing the PU polymer and its associated chemical additives. To shed light on this problem, we applied physical, chemical, biochemical, metagenomic, and bioinformatic analyses to explore the biodegradation capability and related biochemical and genetic determinants of the BP6 microbial community that can grow in PolyLack, a commercial coating containing a polyether polyurethane acrylate (PE-PU-A) copolymer and several additives, as sole carbon source. We observed complete additives (isopropanol, N-methyl-2-pyrrolidone, 2-butoxyethanol, alkyl glycol ethers) biodegradation and the appearance of released polymer components (toluene diisocyanate (TDI) and methylene diphenyl diisocyanate (MDI) derivatives), and multiple degradation products since early cultivation times. The Hi-C metagenomic analysis identified a complex microbiome with 35 deconvolved Metagenome-Assembled Genomes (MAGs) - several new species - and biodegradation markers that suggest the coexistence of hydrolytic, oxidative, and reductive metabolic strategies for degrading the additives and the PU copolymer. This work also provides evidence of the metabolic capability the BP6 community has for biodegrading polyether polyurethane foams. Based on these analyses, we propose a novel metabolic pathway for 4,4'-methylenedianiline (MDA), an initial biodegradation intermediate of MDI-based PU, encoded in the complex BP6 community metagenome and suggest that this community is a potential biotechnological tool for PU bio-recycling.

Fine cassava fibre utilization as a dietary fibre source for dogs: Effects on kibble characteristics, diet digestibility and palatability, faecal metabolites and microbiota.

The objective was to evaluate through three experiments the effects of a fine cassava fibre (CA: 106 µm) on kibble characteristics, coefficients of total tract apparent digestibility (CTTAD) of macronutrients, diet palatability and faecal metabolites and microbiota of dogs. Dietary treatments consisted of a control diet (CO), without an added fibre source and with 4.3% total dietary fibre (TDF), and a diet with 9.6% CA (106 µm), with 8.4% TDF. Experiment I evaluated the physical characteristics of the kibbles. The palatability test was evaluated in experiment II, which compared the diets CO versus CA. In experiment III, 12 adult dogs were randomly assigned to one of the two dietary treatments for 15 days, totalling six replicates/treatment, to assess the CTTAD of macronutrients; faecal characteristics, faecal metabolites and microbiota. The expansion index, kibble size and friability of diets with CA were higher than the CO (p < 0.05). Additionally, the CA diet presented higher palatability than the CO (p < 0.05) but did not affect CTTAD except for those of fibre (p > 0.05). Moreover, a greater faecal concentration of acetate, butyrate and total short-chain fatty acids (SCFA) and a lower faecal concentration of phenol, indole and isobutyrate were observed in dogs fed the CA diet (p < 0.05). Dogs fed with the CA diet presented a greater bacterial diversity and richness and a greater abundance of genera considered to be beneficial for gut health, such as Blautia, Faecalibacterium and Fusobacterium when compared to the CO group (p < 0.05). The inclusion of 9.6% of a fine CA improves the expansion of kibbles and diet palatability without affecting most of the CTTAD of nutrients. Besides, it improves the production of some SCFA and modulates the faecal microbiota of dogs.

Metabarcoding of Soil Fungal Communities in Rupestrian Grassland Areas Preserved and Degraded by Mining: Implications for Restoration.

Rupestrian grasslands are vegetation complexes of the Cerrado biome (Brazilian savanna), exhibiting simultaneously great biodiversity and important open-pit mining areas. There is a strong demand for the conservation of remaining areas and restoration of degraded. This study evaluated, using next-generation sequencing, the diversity and ecological aspects of soil fungal communities in ferruginous rupestrian grassland areas preserved and degraded by bauxite mining in Brazil. In the preserved and degraded area, respectively, 565 and 478 amplicon sequence variants (ASVs) were detected. Basidiomycota and Ascomycota comprised nearly 72% of the DNA, but Ascomycota showed greater abundance than Basidiomycota in the degraded area (64% and 10%, respectively). In the preserved area, taxa of different hierarchical levels (Agaromycetes, Agaricales, Mortierelaceae, and Mortierella) associated with symbiosis and decomposition were predominant. However, taxa that colonize environments under extreme conditions and pathogens (Dothideomycetes, Pleoporales, Pleosporaceae, and Curvularia) prevailed in the degraded area. The degradation reduced the diversity, and modified the composition of taxa and predominant ecological functions in the community. The lack of fungi that facilitate plant establishment and development in the degraded area suggests the importance of seeking the restoration of this community to ensure the success of the ecological restoration of the environment. The topsoil of preserved area can be a source of inocula of several groups of fungi important for the restoration process but which occur in low abundance or are absent in the degraded area.

Seasonal characterization of the prokaryotic microbiota of full-scale anaerobic UASB reactors treating domestic sewage in southern Brazil.

Upflow Anaerobic Sludge Blanket (UASB) reactors are alternatives in the anaerobic treatment of sanitary sewage in different parts of the world; however, in temperate environments, they are subject to strong seasonal influence. Understanding the dynamics of the microbial community in these systems is essential to propose operational alternatives, improve projects and increase the quality of treated effluents. In this study, for one year, high-performance sequencing, associated with bioinformatics tools for taxonomic annotation and functional prediction was used to characterize the microbial community present in the sludge of biodigesters on full-scale, treating domestic sewage at ambient temperature. Among the most representative phyla stood out Desulfobacterota (20.21-28.64%), Proteobacteria (7.48-24.90%), Bacteroidota (10.05-18.37%), Caldisericota (9.49-17.20%), and Halobacterota (3.23-6.55%). By performing a Canonical Correspondence Analysis (CCA), Methanolinea was correlated to the efficiency in removing Chemical Oxygen Demand (COD), Bacteroidetes_VadinHA17 to the production of volatile fatty acids (VFAs), and CI75cm.2.12 at temperature. On the other hand, Desulfovibrio, Spirochaetaceae_uncultured, Methanosaeta, Lentimicrobiaceae_unclassified, and ADurb.Bin063-1 were relevant in shaping the microbial community in a co-occurrence network. Diversity analyses showed greater richness and evenness for the colder seasons, possibly, due to the lesser influence of dominant taxa. Among the principal metabolic functions associated with the community, the metabolism of proteins and amino acids stood out (7.74-8.00%), and the genes related to the synthesis of VFAs presented higher relative abundance for the autumn and winter. Despite the differences in diversity and taxonomic composition, no significant changes were observed in the efficiency of the biodigesters.

Biomethane recovery through co-digestion of cheese whey and glycerol in a two-stage anaerobic fluidized bed reactor: Effect of temperature and organic loading rate on methanogenesis.

Anaerobic digestion for CH4 recovery in wastewater treatment has been carried out with different strategies to increase process efficiency, among which co-digestion and the two-stage process can be highlighted. In this context, this study aimed at evaluating the co-digestion of cheese whey and glycerol in a two-stage process using fluidized bed reactors, verifying the effect of increasing the organic loading rate (OLR) (2-20 g-COD.L-1.d-1) and temperature (thermophilic and mesophilic) in the second stage methanogenic reactor. The mesophilic methanogenic reactor (R-Meso) (mean temperature of 22 °C) was more tolerant to high OLR and its best performance was at 20 g-COD.L-1.d-1, resulting in methane yield (MY) and methane production (MPR) of 273 mL-CH4.g-COD-1 and 5.8 L-CH4.L-1.d-1 (with 67% of CH4), respectively. Through 16S rRNA gene massive sequencing analysis, a greater diversity of microorganisms was identified in R-Meso than in R-Thermo (second stage methanogenic reactor, 55 °C). Firmicutes was the phyla with higher relative abundance in R-Thermo, while in R-Meso the most abundant ones were Proteobacteria and Bacteroidetes. Regarding the Archaea domain, a predominance of hydrogenotrophic microorganisms could be observed, being the genera Methanothermobacter and Methanobacterium the most abundant in R-Thermo and R-Meso, respectively. The two-stage system composed with a thermophilic acidogenic reactor + R-Meso was more adequate for the co-digestion of cheese whey and glycerol than the single-stage process, promoting increases of up to 47% in the energetic yield (10.3 kJ.kg-COD-1) and 14% in organic matter removal (90.5%).

Characterization and algicidal activity of bacteria from the phycosphere of the harmful alga Karenia mikimotoi.

Harmful algal blooms (HABs) are detrimental to aquatic ecosystems; thus, economical and practical HAB control methods are needed. We analyzed a microbial community closely related to the alga Karenia mikimotoi, which has HABs that can be toxic to aquatic environments. We studied the relationship between algicidal bacteria and the microbial community of K. mikimotoi culture using culture-dependent and culture-independent methods. Bacterial strains Marinobacter sp. (O-7) and Pseudomonas sp. (D-2) were isolated from a K. mikimotoi seawater culture containing a mixed microbial community and determined to have algicidal activity. Both strains produced alga-lysing substances that were toxic to K. mikimotoi. The algicidal extracellular substances produced by D-2 were stable at temperatures ranging from - 80 to 120 °C but sensitive to strong acidic/alkaline conditions. The substances produced by O-7 were inactivated at high temperatures and strong alkaline conditions. Extracellular substances produced by O-7 and D-2 caused K. mikimotoi and Prorocentrum donghaiense cell lysis, but no changes or inhibitory effects occurred in two other chlorophyta groups. O-7 and D-2 exhibited significantly greater algicidal activity during the logarithmic growth phase of K. mikimotoi growth compared to the stationary phase. Culture-independent analysis of the microbial community in association with K. mikimotoi was made using Illumina MiSeq sequencing. Phylogenetic analysis showed that Proteobacteria was the dominant bacterial population in the phycosphere of K. mikimotoi, containing Marinobacter sp. and Pseudomonas sp.. The Marinobacter was abundant and accounted for 5.3% of the total. Our results indicate that certain bacterial species from K. mikimotoi culture might be effective for removal of HABs.

Evaluación del desempeño de una celda de combustible microbiana con electrodo de grafito modificado para el tratamiento de agua residual del procesamiento del café / Evaluation of the performance of a microbial fuel cell with modified graphite electrode for the treatment of wastewater from coffee processing / Avaliação do desempenho de uma célula combustível microbial com eletrodo de grafite modificado para o tratamento de águas residuais do processamento de café

Resumen La actividad cafetalera en Costa Rica procesa aproximadamente 69.000 toneladas de café mediante la técnica de beneficiado húmedo. Esta actividad conlleva un alto impacto ambiental debido a la generación de8Lde agua residual/kg de café oro producido. El presente trabajo tiene como objetivo utilizar el agua residual del procesamiento de café como sustrato en celdas combustibles microbianas (CCM), con el propósito de generar energía eléctrica a través de su uso y, a la vez, disminuir la carga orgánica del residuo. La CCM empleó un cátodo modificado con ftalocianinas de hierro (FePc), generó una eficiencia coulómbica de 0,7% y una densidad de potencia de 89 UW/ cm2 en un ciclo de operación de cinco días. Además, se determinó que la CCM disminuye la demanda química de oxígeno (DQO) del residuo hasta en 27% bajo las condiciones de operación nativas del sustrato, a temperatura ambiente, sin mediadores químicos para la reacción anódica y con el uso de electrodos de platino para el cátodo. El estudio confirma la oportunidad de emplear el sustrato con una flora microbiana nativa apta para la operación de la tecnología de la CCM, y así perfilar el dispositivo como una opción novedosa para el tratamiento de este residuo en Costa Rica.

Abstract In Costa Rica coffee production is the most traditional agroindustrial activity, each year approximately 69,000 tons of coffee are processed through the technique of wet processing. The process has a high environmental impact since it generates eight liters of wastewater/kg of produced coffee. Consequently, the main goal of this research was to evaluate the electric generation of a Microbial Fuel Cell (MFC) with two chambers, using coffee wastewater as a substrate, which would generate a sustainable solution with an added economic value to this waste in Costa Rica. The MFC with a cathode modified with iron phthalocyanines (FePc) generated a coulombic efficiency of 0.7% and a power density of 89 -uW/cm2 in a 5-day operation cycle. In addition, it was determined that the MFC decreases the COD of the waste by up to 27% under native substrate conditions, without the use of high temperatures, or chemical mediators for the anodic reaction and platinum electrodes for the cathode chamber. The efficiency of the device can be improved with changes at design level that reduce the ohmic internal resistance and improve electrical generation, the study confirms the potential of the substrate with a native microorganism suitable for the use of MFC technology, shaping the device as a novelty option for the treatment of the waste in Costa Rica.

Resumo A indústria do café na Costa Rica processa cerca de 69 000 toneladas de café por meio da técnica de moagem úmida, o que acarreta um alto impacto ambiental devido à geração de 8 L de água residual / kg de café dourado. O objetivo deste trabalho era usar águas residuais do processamento do café como substrato em Células de Combustível Microbianas (CCM) a fim de gerar energia elétrica por meio do seu aproveitamento e ao mesmo tempo reduzir a carga orgânica do resíduo. CCM usando cátodo modificado com ftalocianinas de ferro (FePc) gerou uma eficiência coulômbica de 0,7% e uma densidade de potência de 89 uW/cm2 em um ciclo operacional de cinco dias. Além disso, foi determinado que o CCM reduz a Demanda Química de Oxigénio (DQO) do resíduo em até 27% nas condições nativas de operação do substrato, à temperatura ambiente, sem mediadores químicos para a reação anódica e com a utilização de eletrodos de platina para o cátodo. O estudo confirma a oportunidade de utilizar o substrato com flora microbiana nativa adequada para o funcionamento da tecnologia CCM e, assim, delinear o dispositivo como uma nova opção para o tratamento desses resíduos na Costa Rica.