Residual Organic Material Research Articles

Landfill mining: A step forward to reducing CH4 emissions and enhancing CO2 sequestration from landfill

Landfill management is a major challenge for sustainable development in terms of climate change and resource scarcity. Landfill leachate contains high concentrations of nitrogen (N) and phosphorus (P), which cause eutrophication if discharged improperly. However, the nutrients can be recovered and reused as fertilizers for agriculture, contributing to resource recovery, circular economy, food security, and net zero emissions. Recent advances in landfill management have transformed landfills into resource recovery facilities that can produce nutrient-energy-material (NEM) products for applications through biological or physico-chemical process. Through a literature survey, this article reviews NEM recovery from landfills such as biogas production and composting. This work also discusses the benefits and challenges of NEM recovery for sustainability transition towards net zero emissions, while analyzes knowledge gaps and future research directions for landfill management and NEM recovery. It was conclusive from 193 articles published between 1993 and 2024 that landfill mining presents a promising solution for mitigating CH4 emissions and enhancing CO2 sequestration, both critical in reducing the overall greenhouse gas footprint of waste management. From landfill leachate and/or landfill gas, engineers can recover and recycle nutrients (for fertilizer), materials (for chemistry), and biogas (for electricity). Through landfill management, roadmaps towards decarbonization can be cost-effective and sustainable so that a maximum value of the waste can be extracted before it is discarded. Key findings reveal that CH4 emissions can be reduced by uncovering buried waste, while soil and residual organic material enhance CO2 sequestration through microbial activity. Additionally, this review highlights the economic and environmental benefits of material recovery from landfills, including metals and plastics. Overall, this work emphasizes landfill mining as a sustainable strategy for improving waste management practices, while contributing to climate change mitigation.

Site properties, environmental factors, and crop identify influence soil bacterial communities more than municipal biosolid application

Reducing the environmental impact of Canadian field crop agriculture, including the reliance on conventional synthesised fertilisers, are key societal targets for establishing long-term sustainable practices. Municipal biosolids (MSB) are an abundant, residual organic material, rich in phosphate, nitrogen and other oligo-nutrients, that could be used in conjunction with conventional fertilisers to decrease their use. Though MBS have previously been shown to be an effective fertiliser substitute for different crops, including corn and soybean, there remain key knowledge gaps concerning the impact of MBS on the resident soil bacterial communities in agro-ecosystems. We hypothesised that the MBS fertiliser amendment would not significantly impact the structure or function of the soil bacterial communities, nor contribute to the spread of human pathogenic bacteria, in corn or soybean agricultural systems. In field experiments, fertiliser regimes for both crops were amended with MBS, and compared to corn and soybean plots with standard fertiliser treatments. We repeated this across four different agricultural sites in Quebec, over 2021 and 2022. We sampled MBS-treated, and untreated soils, and identified the composition of the soil bacterial communities via 16S rRNA metabarcoding. We found no indication that the MBS fertiliser amendment altered the structure of the soil bacterial communities, but rather that the soil type and crop identities were the most significant factors in structuring the bacterial communities. Moreover, there was no evidence that the MBS-treated soils were enriched in potential human bacterial pathogens over the two years of our study. Our analysis indicates that not only can MBS function as substitutes for conventional, synthesised fertilisers, but that they also do not disrupt the structure of the resident soil bacterial communities in the short term. Finally, we suggest that the use of MBS in agro-ecosystems poses no greater concern to the public than existing soil bacterial communities. This highlights the significant role MBS could potentially have in reducing the use of conventional industrial fertilisers and improving agricultural production, without risking environmental contamination.

Removal of Microcystis aeruginosa and its extracellular organic matters by using covalently bonded coagulant: An alternative choice in enhanced coagulation for algae-polluted water treatment

High coagulants dosage, Al or Fe residual, unstable flocs, and extracellular organic materials (EOM) released from cells cannot be avoided by using traditional Al or Fe based coagulants in algae removal. Thus, a novel covalently bonded coagulant poly aluminum ferrous chloride/cationic polyacrylamide (CAFM) was developed. The algae and EOM removal performance and mechanisms were investigated in current research. Al and Fe residual, cell integrity, and compactness of flocs were analyzed after coagulation. Furthermore, the disinfection by-products formation potential (DBPFP) and economics was also figured out to confirm the advantage of using CAFM. Results showed that 95.01% of turbidity and 99.3% of OD686 were effectively removed by using CAFM at 6 mg/L. Moreover, lower breakage probability of algae cells and denser flocs were realized by using CAFM compared to common used Al or Fe coagulants. In addition, lower Al and Fe residual and lower DBPFP were confimed in CAFM coagulation. DFT (Density functional theory) and ESP (Electrostatic Potential) results showed CAFM could combine bEOM (bonded extracellular organic matter) and dEOM (dissolved extracellular organic matter) through H-bond from Al atom in the covalent bond. Due to the introduction of various functional groups of different coagulants, charge neutralization and adsorption ability contributed to treating algae-containing water.

Experimental investigations of the preservation/degradation of microbial signatures in the presence of clay minerals under Martian subsurface conditions

The astrobiological exploration of Mars is ongoing. Ancient Martian terrains covered by clay minerals are seen as the most promising targets to search for biosignatures as clay minerals are believed to have a high potential for biopreservation. Here, we experimentally investigate the biopreservation potential of saponite, a Mg-rich smectite, relying on series of experiments conducted with mixtures of E. coli cells and saponite exposed to thermal conditions (up to 200 °C) for different durations (up to 100 days) under a Martian atmosphere (CO2) in the presence of water, thereby simulating episodes of fluid circulation typical of those periodically occurring on Mars. Residues were characterized using elemental analyses, mid-infrared (Mid-IR) spectroscopy and X-ray diffraction (XRD) to document the chemistry of the residual organic materials as well as the nature and crystallinity of the residual mineral materials. Results show that saponite may delay the chemical degradation of some organic materials by selectively trapping N-rich organic compounds within its interlayer space. However, such trapping of N-rich organic compounds does not completely protect them from degradation with increasing temperature and experimental duration, as shown by the N/C atomic ratios, δ13C values, Mid-IR spectra and XRD patterns of the residues of experiments conducted at 200 °C or at 150 °C for 100 days. This suggests that saponite is not that efficient in protecting biogenic organic compounds from thermal degradation over long periods of time. Altogether, the present study provides information on what can be found (and thus pinpointing what should be searched for) in the ancient Martian geological record.

Life cycle assessment of the supply chain processes for the valorisation of corn cob

The circular economy can find a wide range of application in the agricultural sector given the countless possibilities of transforming crop residues and recycling precious resources, playing a strategic role in increasing the sustainability of the agriculture. Under this perspective, crop production provides several residues and waste along the production chain. In the maize cultivation process, a significant amount of residual organic materials is produced and commonly left on the field as soil conditioner and source of nutrients. However, some parts of these residues, such as corn cob, could be considered for valorization processes.Focusing on corn cob as a valuable raw material, the sustainable solutions for its valorization depend on economic and environmental factors. The main aims and novelty of the work is the evaluation of the environmental performance of alternative supply chain in a life-cycle perspective in order to compare the overall sustainability of this valorization alternative, maximizing its environmental added value. The paper reports the results of a Life Cycle Analysis, from cradle-to-gate, of corn cob valorized as a raw material for corn cob pellet. A comparison with wood pellet available on the market and with analogous function has been performed. The results show that cob-based product has environmental impact lower than wood-based products currently used. Finally, the work provides indication for evaluating the benefits of turning an agricultural waste in natural-based material and paves the way of promoting circular economy processes in agriculture production.

Tellurium biogeochemical transformation and cycling in a metalliferous semi-arid environment

Tellurium (Te) is a Critical Mineral and its biogeochemical behaviour has mostly been interpreted from laboratory-based studies rather than direct field observations, due to the scarcity of Te in the environment. The historic mining district of Moctezuma, Sonora, Mexico, hosts the only Au mine worldwide where native tellurium is the main ore mineral (Bambolla mine). In contrast to Bambolla, the nearby San Miguel mine features a typical epithermal-style assemblage of silver sulfides, selenides, and tellurides; this dichotomy provides comparative sites to study environmental Te mobility during weathering as a function of source composition (same host rock and climate). This study characterised the regolith geochemistry, mineralogy and microbial diversity around these two Te-enriched sites. Scanning electron microscopy of fresh mineral surfaces from the weathering zone suggests that Te was released to the environment through oxidative dissolution of primary Te minerals, especially native tellurium at Bambolla. Micron-scale gold grains (<100 μm) in regolith samples have morphologies consistent with the dealloying of the gold telluride calaverite (AuTe2). Secondary Te minerals observed in situ include abundant tellurite (TeO2) and highly Te-enriched Fe (hydr)oxides, which may contain up to 20mole% Te substitution for Fe. The presence of residual organic material in association with embedded secondary nano-minerals suggests that Te (bio)transformation processes were likely associated with weathering. In particular, carbon-rich globules on the surface of millimetre-sized grains of native tellurium contain abundant Te nanoparticles, suggestive of bioreduction. DNA extraction and sequencing of the bacterial 16S rRNA gene revealed that the Te-enriched (up to 1750 ppm) regolith proximal to the Te-rich veins hosted microbial communities with varying composition but similar overall diversity compared to regolith collected from distal locations (more than 50 m from the mineralised veins). Of the detected bacterial Amplicon Sequence Variants (ASVs) from Te-rich regolith which could play an active role in Te (bio)transformation processes, representatives from the phyla Proteobacteria, Actinobacteria and Acidobacteria were the most abundant, followed by Firmicutes, candidate phylum WPS-2, Chloroflexi, Planctomycetes and Patescibacteria. This study provides the first evidence that Te undergoes dynamic cycling in the environment, with nanoscale chemical and structural changes governing the biogeochemical behaviour of Te on the macroscale. In doing so, this work provides important information on the underlying controls for Te mobility in both environmental settings, such as Te-rich rock outcrops and anthropogenic settings, such as Te-containing solar panel stockpiles.

Assessing the microbiota of recycled bedding sand on a Wisconsin dairy farm

BackgroundSand is often considered the preferred bedding material for dairy cows as it is thought to have lower bacterial counts than organic bedding materials and cows bedded on sand experience fewer cases of lameness and disease. Sand can also be efficiently recycled and reused, making it cost-effective. However, some studies have suggested that the residual organic material present in recycled sand can serve as a reservoir for commensal and pathogenic bacteria, although no studies have yet characterized the total bacterial community composition. Here we sought to characterize the bacterial community composition of a Wisconsin dairy farm bedding sand recycling system and its dynamics across several stages of the recycling process during both summer and winter using 16S rRNA gene amplicon sequencing.ResultsBacterial community compositions of the sand recycling system differed by both seasons and stage. Summer samples had higher richness and distinct community compositions, relative to winter samples. In both summer and winter samples, the diversity of recycled sand decreased with time drying in the recycling room. Compositionally, summer sand 14 d post-recycling was enriched in operational taxonomic units (OTUs) belonging to the genera Acinetobacter and Pseudomonas, relative to freshly washed sand and sand from cow pens. In contrast, no OTUs were found to be enriched in winter sand. The sand recycling system contained an overall core microbiota of 141 OTUs representing 68.45% ± 10.33% SD of the total bacterial relative abundance at each sampled stage. The 4 most abundant genera in this core microbiota included Acinetobacter, Psychrobacter, Corynebacterium, and Pseudomonas. Acinetobacter was present in greater abundance in summer samples, whereas Psychrobacter and Corynebacterium had higher relative abundances in winter samples. Pseudomonas had consistent relative abundances across both seasons.ConclusionsThese findings highlight the potential of recycled bedding sand as a bacterial reservoir that warrants further study.

Turning Agricultural Wastes into Biomaterials: Assessing the Sustainability of Scenarios of Circular Valorization of Corn Cob in a Life-Cycle Perspective

Circular economy plays a key role in increasing the sustainability of the agricultural sector, given the countless possibilities of transforming crop residues and recycling precious resources. The maize cultivation process produces a significant amount of residual organic materials, commonly left on the field, as a soil conditioner and source of nutrients even if some parts, such as the cob, play a minor role in these actions. The solutions for the valorization of this remnant depend on economic and environmental factors and the evaluation of the environmental performances of the processes in a life-cycle perspective is important to compare the overall sustainability of the valorization alternatives, maximizing their environmental added value. This work reports the results of Life Cycle Analysis, from cradle-to-gate of corn cob valorized as a raw material in two scenarios: corn cob pellet and corn cob abrasive grits to use as blasting or finishing media. A comparative study has been performed with two products available on the market and with the same functions. The results show that cob-based products have lower impact than those currently used. The work provides indication for evaluating the benefits of turning agricultural wastes in natural-based materials and intends to promote circular economy processes in agriculture production.

Evaluation of the Use of Fiberoptic Bronchoscopy Following Rigid Bronchoscopy in Foreign Body Aspiration

Background: Foreign body aspiration (FBA) is a life-threatening problem that can be lethal in some cases. It usually occurs in children between 1–3 years old. Bronchoscopy is the best way for recognition, treatment and management of this problem. We aimed to evaluate the use of fiberoptic bronchoscopy after rigid bronchoscopy in foreign body aspiration in pediatric population. Materials and Methods: 275 pediatric patients with a history of choking were entered to this cross-sectional study, from August 2015 to September 2018. The study was done in a Dr. Sheikh hospital, Mashhad, Iran. The age and gender of the patients were recorded individually. Rigid bronchoscopy was done for all patients. After that, fiberoptic bronchoscopy was performed immediately or 72 hours after the first procedure based on the patients' symptoms, time and personnel conditions. Data were analyzed by the SPSS software version 16.0. Results: Among 275 patients, 175 cases (63.6%) were male. The patients' age was 3 months to 15 years old. In rigid bronchoscopy, 85 cases had no foreign body and in 190 cases, foreign body was found. In 43 cases fiberoptic bronchoscopy found a residual organic material in spite of negative rigid bronchoscopy.The most residual organic material pertained to 0-3 year age group and the cases with residue in males were more than females. There was a significant difference between FBA and age and gender (p <0.001). Conclusion: FBA in airway branches may not be seen by rigid bronchoscope due to the limited access to the distal branches. We suggest fiberoptic bronchoscopy as a complementary management along with rigid bronchoscopy to investigate distal branches, especially if the foreign body is soft in material.

Preparation of a Rice Husk Composite and Effects of Cold Pressing on the Flexural Strength Properties

The study of composites made from residual organic materials and polymeric resins, has a great projection due to the use of new raw materials and the good physical, mechanical and aesthetic characteristics these materials present in the construction industry. The manufacturing processes of these composites include the necessary pressure application to generate an efficiently compact material, where matrix and reinforcement bonding are efficient. This study defines how the compaction force influences the flexural strength of composites made from polyester resin as polymer matrix, and rice husk as reinforcement material. This is achieved by testing different series of specimens, made by applying different compaction forces in a cold process, to analyse the relationship between compaction and flexural strength. Specimens are made varying only the compaction force, from 2, 5, 8, 11, 14, and 17 tons. The results show that, when the compaction force increases, the flexural strength in the composites also increases, however, there is a pressure range where the flexural strength values are very close, conditioning the use of pressure in relation to the decrease in the specimen section.

Organic agriculture effect on water use, tile flow, and crop yield

AbstractLong‐term crop rotations in organic agricultural systems provide N additions through legumes and residual organic materials to improve soil properties. In addition, enhanced pest management and more efficient water use in the spring and fall may result from the plant biodiversity in organic rotations. The purpose of this study was to compare organic and conventional systems in terms of tile flow or water use, and to determine if corn (Zea mays L.) or soybean [Glycine max (L.) Merr.] yields differed between systems. The experimental plots were in central Iowa and consisted of three treatments: 2‐yr conventional rotation (both crops each year in split plot), 4‐yr organic rotation (all crops present each year), and organic grass–legume forage. In the fall of 2017, 2018, and 2019, organic forage used more water than the mean of the 4‐yr organic rotation, which used more water than the 2‐yr conventional rotation. The same trend was shown for the spring of 2017 and 2019. Conventional corn had higher yield than organic for 3 of 8 yr, with 5 yr not significant. Conventional soybean had higher yield than organic for 2 of 8 yr and lower for 1 yr, with 5 yr not significant. Grass weeds were inversely correlated with leaf area index of corn on 3 of 10 measurement dates and for soybean on 5 of 10 measurement dates, but broadleaf weeds only on one date for soybean. Organic agricultural systems had positive benefits for timing of water use in the spring or fall by forage, alfalfa (Medicago sativa L.), or oat (Avena sativa L.). Some years had comparable yields to conventional corn and soybean.

Hydrothermal Carbonization as a Valuable Tool for Energy and Environmental Applications: A Review

Hydrothermal carbonization (HTC) represents an efficient and valuable pre-treatment technology to convert waste biomass into highly dense carbonaceous materials that could be used in a wide range of applications between energy, environment, soil improvement and nutrients recovery fields. HTC converts residual organic materials into a solid high energy dense material (hydrochar) and a liquid residue where the most volatile and oxygenated compounds (mainly furans and organic acids) concentrate during reaction. Pristine hydrochar is mainly used for direct combustion, to generate heat or electricity, but highly porous carbonaceous media for energy storage or for adsorption of pollutants applications can be also obtained through a further activation stage. HTC process can be used to enhance recovery of nutrients as nitrogen and phosphorous in particular and can be used as soil conditioner, to favor plant growth and mitigate desertification of soils. The present review proposes an outlook of the several possible applications of hydrochar produced from any sort of waste biomass sources. For each of the applications proposed, the main operative parameters that mostly affect the hydrochar properties and characteristics are highlighted, in order to match the needs for the specific application.

Simultaneous Enhancement of Electrical and Optical Properties of Transparent Conducting RuO2 Nanosheet films by Facile Ultraviolet-Ozone Irradiation

The enhancement of electrical and optical properties in transparent conducting electrodes has attracted significant interest for their application in flexible electronic devices. Herein, a method for the fabrication of transparent conducting films is proposed. In this approach, RuO2 nanosheets are synthesized by a simple chemical exfoliation method and deposited as conducting films by repeated Langmuir–Blodgett coating. For enhancing the electrical and optical properties of the films, ultraviolet-ozone irradiation is applied between the repeated coatings for the removal of residual organic materials from the chemically exfoliated nanosheets. We observe that by applying ultraviolet-ozone irradiation for 30 min, the sheet resistance of the films decreases by 10% and the optical transmittance is simultaneously enhanced. Facile ultraviolet-ozone irradiation is shown to be an effective and industrially friendly method for enhancing the electrical and optical properties of oxide nanosheets for their application as transparent conduction electrodes.

1166 A NEW DESIGNED DUODENOSCOPE WITH DETACHABLE DISTAL CAP CAN SIGNIFICANTLY REDUCE ORGANIC RESIDUE CONTAMINATION AFTER REPROCESSING EVALUATED BY ADENOSINE TRIPHOSPHATE TEST

Because of its complex structures with an elevator mechanism, cleaning and disinfection of the duodenoscope are more difficult than other endoscopes. Despite high level disinfection (HLD) protocol, several outbreaks of multidrug resistance bacterial contamination (BC) of the duodenoscope with fixed distal cap were reported. A new designed duodenoscope with detachable distal cap (ED 580XT, Fujifilm, Tokyo, Japan) may have advantage over the conventional duodenoscope with fixed distal cap by allowing the brush to access the backside of the elevator. However, comparative data on BC and organic residue of the conventional duodenoscope vs. the duodenoscope with detachable distal cap after HLD is lacking. During December 2018-April 2019, 108 used duodenoscopes with detachable distal cap underwent HLD and were enrolled 1:1 into group A and group B. In group A (n=54), the distal cap of duodenoscope was detached before manual cleaning (figure 1A and 1B). Whereas in group B (n=54), the distal cap was not detached before manual cleaning (figure 1C and 1D) in order to imitate the conventional duodenoscope with fixed distal cap. After single round of HLD, sample was collected from the elevator site (ES) with swab rotation and submitted for culture and then rapid BC and organic residue evaluation were done by analyzing for Relative Light Units (RLU) that read by adenosine triphosphate (ATP) test (Clean-Trace Surface ATP, 3M, MN, USA). Based on our previous data that demonstrated 100% sensitivity and 100% negative predictive value for BC, the ATP threshold at 40 RLU was used in this study. We compared the proportion of potential BC and organic residue evaluated by rapid ATP test and confirmed BC evaluated by bacterial culture in group A vs. group B after HLD. After HLD, using the ATP threshold at 40 RLU as the cut-off value, the proportion of potential BC and organic residue in group A was significantly lower than that of in group B [20/54 (37%) vs. 41/54 (75.9%); p<0.001] (Table 1). Mean ATP value in group A was also significantly lower than that of in group B [45.2 RLU (range 9-209) vs. 151.9 RLU (range 19-653); p<0.001). In group B, one culture sample was found to have non-pathogenic BC (coagulase negative Staphylococcus). Pathogenic BC confirmed by culture was not documented in the both groups. Since a new design, detachable duodenoscope allows brushing the backside of elevator, it can reduce residual organic material confirmed by the ATP test. Although no pathological organism was found after HLD in both groups, BC from skin and membrane flora was still detected in duodenoscope with fixed distal cap.Table 1Comparison of ATP testing and culture results between the duodenoscope with detachable distal cap vs. the duodenoscope with fixed distal cap after HLDView Large Image Figure ViewerDownload Hi-res image Download (PPT)

Short-interval wildfire and drought overwhelm boreal forest resilience

The size and frequency of large wildfires in western North America have increased in recent years, a trend climate change is likely to exacerbate. Due to fuel limitations, recently burned forests resist burning for upwards of 30 years; however, extreme fire-conducive weather enables reburning at shorter fire-free intervals than expected. This research quantifies the outcomes of short-interval reburns in upland and wetland environments of northwestern Canadian boreal forests and identifies an interactive effect of post-fire drought. Despite adaptations to wildfire amongst boreal plants, post-fire forests at paired short- and long-interval sites were significantly different, with short-interval sites having lower stem densities of trees due to reduced conifer recruitment, a higher proportion of broadleaf trees, less residual organic material, and reduced herbaceous vegetation cover. Drought reinforced changes in proportions of tree species and decreases in tree recruitment, reinforcing non-resilient responses to short-interval reburning. Drier and warmer weather will increase the incidence of short-interval reburning and amplify the ecological changes such events cause, as wildfire activity and post-fire drought increase synergistically. These interacting disturbances will accelerate climate-driven changes in boreal forest structure and composition. Our findings identify processes of ongoing and future change in a climate-sensitive biome.

Understanding the Dynamics of Fluorescence Emission during Zeolite Detemplation Using Time Resolved Photoluminescence Spectroscopy

Time resolved photoluminescence spectroscopy (TRPS) shows potential as a sensitive, nondestructive, high throughput, label-free laser-based spectroscopy technique capable of analyzing low concentrations of organic species adsorbed on and within zeolite pores. Here we report the results from a study that uses TRPS to characterize photoluminescence (PL) arising from synthesized chabazite framework zeolites at three different stages of the detemplation process (from uncalcined, partially calcined, and calcined zeolites). Temporal resolution was used to demonstrate the steric confinement effects of organic structure directing agents (OSDAs) within a zeolite framework and therefore to establish a signature region for determining the presence of the template. Gated spectra comparisons between an uncalcined zeolite and a partially calcined zeolite demonstrated the presence of template alongside the proliferation of template-derived combustion products. An analysis of lifetime values demonstrated the ability for TRPS to track depletion of OSDA and establish a characteristic PL spectrum for a clean zeolite. The sensitivity of the technique is high enough to reveal that there is still residual organic material remaining in a zeolite even after an extended thermal detemplation process.

Effect of triethanolamine on the pyrolysis of metal-propionate-based solutions

The effect of triethanolamine (TEA) on single-salt propionate-based solutions used to prepare YBa2Cu3O7-∂ (YBCO) has been studied through thermal analysis, for film and powder samples. Decomposition has been followed by thermogravimetry (TG) coupled to differential scanning calorimetry (DSC) and evolved gas analysis (EGA-MS and TG-FTIR), while chemical characterization has been carried out by FTIR, XRD and EA. The addition of TEA has little effect on the decomposition of the barium salt. Conversely, the thermal behavior of the copper and yttrium propionate salt with TEA becomes more gradual and less affected by a change of atmosphere than the TEA-free case. This is explained by the fact that the decomposition mechanism is driven by the formation of an ester between the propionate groups and the TEA’s OH groups, which is promoted by inert atmospheres and temperatures above 200 °C. Just like the single salt precursors, the films of the barium and yttrium salts show residual organic material at 500 °C in thick films decomposed in O2.

Production of plant growth-promoting bacteria inoculants from composting leachate to develop durable agricultural ecosystems.

Composting process of residual organic material generates considerable amounts of liquid leachate which contains high organic load. This waste stream can be considered as potential nutrient source to support microbial growth. In the present work, the utilization of compost leachate as fermentation substrate for Bacillus species production was studied. The physicochemical properties of the leachate and two co-substrates (residual yeast and whey permeate) were determined. The characterization of leachate showed that it is a potential source of carbon, but its nitrogen content may limit the bacterial growth. In order to determine a good recipe of culture medium for fermentation of individual strains of Bacillus species, leachate was added with yeast and whey permeate. Raw and diluted leachates with and without amendments were tested in shake-flask fermentation assays. Results showed that Bacillus sp. grew better in diluted leachate than in raw leachate. When co-substrates were added, the growth was improved and the sporulation rate also increased. Since the aim was to produce plant growth-promoting bacteria, one of the objectives of fermentation assays was the production of viable bacteria when Bacillus sp. arrives to soil as component of a fertilizer. For this reason, the obtention of sporulated Bacillus cells was desired. The highest sporulation rate was obtained with co-substrates, inducing more than 89% of vegetative cells to develop spores. This approach of leachate valorization will produce economical benefits reducing the volume of leachate waste to be treated, as well as contribute in a cost-effective production of biological amendments in a circular economy mode.

The detection and quantification of food components on stainless steel surfaces following use in an operational bakery

Food preparation areas in commercial bakeries present surfaces for continual organic fouling. The detection of retained food components and microorganisms on stainless steel surfaces situated for one month in the weighing in area, pastry and confectionary production areas of a bakery were investigated using different methods. Scanning electron microscopy demonstrated the morphology of the material on the surfaces from all three areas, with the weighing in area demonstrating a more even coverage of material. Differential staining assays demonstrated a high percentage coverage of organic material heterogeneously distributed across the surfaces. Differential staining also demonstrated that the amount of organic material on the surface from the confectionary area was significantly greater than from both the pastry and weighing in areas. Although, UV at 353nm did not detect residual surface fouling, performance of the UV detection was optimised and demonstrated that the residual organic material on the weighing in area and the pastry samples was best illuminated at 510–560nm, and from the confectionary area of the bakery at 590–650nm. ATP bioluminescence revealed the confectionary production area contained the highest level of biofouling. Contact plates determined that only low microbial counts (≤2CFU/cm2) were recovered from the surfaces. Changes in the physicochemistry (increased hydrophobicity) demonstrated that all the surfaces were fouled (ΔGiwi −26.8mJ/m2 to −45.4mJ/m2). Fourier Transform Infra-Red Spectroscopy (FTIR) demonstrated that all the surfaces had retained fats, carbohydrates and proteins. This work suggests that a range of methods may be needed to fully detect organic and microbial fouling.

Synthesis of NiAl layered double hydroxides intercalated with aliphatic dibasic anions and their exchange with heptamolybdate

Layered double hydroxides (LDH) of general formula Ni1-x Alx(OH)2(A)x/2. mH2O were obtained by a co-precipitation method at constant pH, using succinate (C4H4O42−), adipate (C6H8O42−) and sebacate (C10H16O42−) as compensation anions and two x values, 0.3 and 0.5. The formation of NiAl LDH was evidenced, although in the Al-richer samples carbon analysis and solid-state 27Al NMR spectroscopy indicated the segregation of a small amount of an aluminum-containing phase. To prepare NiAlMo LDH, the original compensation anions were replaced by heptamolybdate ion using an anion exchange method. The results showed almost complete anion exchange in most samples, with small amounts of residual organic material, evidencing easy removal of the aliphatic dibasic anions as compared with terephthalate. The samples were characterized by FTIR, XRD, ICP-OES, CHN and Raman and 27Al MAS solid-state NMR spectroscopies.