Digestion Process Research Articles

Identification, screening and molecular mechanisms of natural stable angiotensin-converting enzyme (ACE) inhibitory peptides from foxtail millet protein hydrolysates: a combined in silico and in vitro study.

The stability of bioactive peptides under various food processing conditions is the basis for their use in industrial manufacturing. This study aimed to identify natural ACE inhibitors with excellent stability and investigate their physicochemical properties and putative molecular mechanisms. Five novel ACE inhibitory peptides (QDPLFPL, FPGVSPF, SPAQLLPF, LVPYRP, and WYWPQ) were isolated and identified using RP-HPLC and Nano LC-MS/MS with foxtail millet protein hydrolysates as the raw material. These peptides are non-toxic and exhibit strong ACE inhibitory activity in vitro (IC50 values between 0.13 mg mL-1 and 0.56 mg mL-1). In addition to QDPLFPL, FPGVSPF, SPAQLLPF, LVPYRP, and WYWPQ have excellent human intestinal absorption. Compared to FPGVSPF and SPAQLLPF, the stable helical structure of LVPYRP and WYWPQ allows them to maintain high stability under conditions that mimic gastrointestinal digestion and various food processing (temperatures, pH, sucrose, NaCl, citric acid, sodium benzoate, Cu2+, Zn2+, K+, Mg2+, Ca2+). The results of molecular docking and molecular dynamics simulation suggest that LVPYRP has greater stability and binding capacity to ACE than WYWPQ. LVPYRP might attach to the active pockets (S1, S2, and S1') of ACE via hydrogen bonds and hydrophobic interactions, then compete with Zn2+ in ACE to demonstrate its ACE inhibitory activity. The binding of LVPYRP to ACE enhances the rearrangement of ACE's active structural domains, with electrostatic and polar solvation energy contributing the most energy to the binding. Our findings suggested that LVPYRP derived from foxtail millet protein hydrolysates has the potential to be incorporated into functional foods to provide antihypertensive benefits.

One-year old European perch (Perca fluviatilis)-specific in vitro digestion studies in special regard to feed optimization

The aim was to investigate the effect of water temperature on digestive enzyme activities of perch, to determine at which temperature their digestion process is more suitable. European perch (Perca fluviatilis) (1 year old, 50–60 g, 10 cm) were kept in recirculation system with the stocking density of 9 kg/m3 in 150 litre-sized-tanks, at 16°C, 18°C, 20°C, 22°C. Fish were kept for 1 week acclimatization, starved for 72 hours before feeding (crude protein: 45 %, crude fat: 16 %, crude fiber: 2.6 %; digestible energy: 18.5 MJ). Feeding was twice, with a 6 hours interval. There were 3 tanks for each proper temperature treatment; every tank contained 100 fish. 10 fish were moved out from all the tanks (30 fish per treatments). Stomach, intestine of fish was separated and their walls were washed with 1 ml of distilled water (pH 2.5), with 1 ml of 50 mM Tris-HCl, containing 0.5 M NaCl, 20 mM CaCl2 (pH 7.8), respectively, to retrieve gastric and intestinal digestive extracts. Extracts were used for pepsin, trypsin. total alkaline proteolytic, lipase, α-amylase activity tests. We have succeeded in developing protocol for gaining enzyme-containing extracts to monitor the realistic physiological conditions of perch based on enzyme activity measurements. The protocol was considered to be easy to implement and to provide sufficient enzyme extract to simulate subsequent in vitro digestion. The ambient temperature affected enzyme activities significantly: pepsin (40480.14; 69245.91; 79305.86; 40236.32 U/mg protein), trypsin – (7.77; 9.88; 11.12; 5.42 U/mg protein), total alkaline proteolytic - (1.47; 1.14; 1.25; 0.84 U/mg protein), lipase – (0.40; 1.16; 0.72; 0.76 U/mg protein) and α-amylase (0.29; 0.395; 0.98; 1.17 U/mg protein) activities, respectively at 16, 18, 20 and 22°C. Based on protease activities, 18–20°C was chosen to be the most appropriate rearing temperature, which contributes the most to the proper growth of the fish.

A new green protocol for the identification of microplastics and microfibers in marine sediments, a case study from the Vesuvian Coast, Southern Italy

Microplastics (MP; 1 µm–5 mm) and microfibers (MF; thin, elongated particles with a high-length-to-width ratio) have become a major global environmental issue due to their ubiquity in the oceans and possess complex physicochemical properties that vary their mobility, bioavailability, and toxicity toward organisms and interactions with their surrounding pollutants. Nonetheless, a reliable methodology that would facilitate and automate the monitoring of MP is still lacking. Intending to select practical and standardized methods and considering the challenges in MPs detection, a new analysis protocol based on optical microscopy for the counting and morphological analysis of the particles has been developed. This method overcomes some issues related to the lack of practicality and standardization of the others currently applied, and does not involve sieving, washing, heating, or density separation and digestion processes. Our method is green and requires a minimum quantity of sediment, i.e., 1.5 g, and shortened timeframes. Future research efforts may need to develop and implement new analytical tools and combinations of technologies to complement respective detection limitations and yield reliable characterization of both MFs and MPs. We tested our protocol to study, for the first time, both marine and land sediment in the Vesuvian area of the Gulf of Naples (Italy).

Biology of Black Soldier Fly (Hermetia illucens) and Utilization of its Waste (Maggot Frass) for Plant Growth: A Literature Review

The utilization of maggot frass from Black Soldier Fly (BSF) larvae (Hermetia illucens Linneus, 1875) has garnered attention in the context of organic farming as a promising alternative to enhance plant growth and development. Maggot frass, a byproduct of the larval digestion process, is rich in essential nutrients such as nitrogen, phosphorus, potassium, and contains beneficial microorganisms for the soil. This study employs a literature review method. Literature sources were obtained from the Google Scholar database using keywords such as "maggot frass", "kasgot", "Black Soldier Fly", and "Hermetia illucens". The articles obtained were then analyzed to gather secondary data. The aim of this research is to explore the potential utilization of maggot frass from BSF larvae in enhancing plant growth and development in the context of organic farming. Research on the utilization of maggot frass has shown significant potential in improving soil fertility and increasing crop productivity. Furthermore, the use of BSF larvae in organic waste management can also significantly reduce waste volume while creating valuable resources for agriculture. By integrating the utilization of maggot frass into organic farming practices, it is hoped that a more sustainable and environmentally friendly agricultural system can be created in the future.

Experimental Protocols Used to Mimic Gastrointestinal Protein Digestion: A Systematic Review.

Bioactive peptides derived from native proteins modulate physiological processes in the metabolic pathways. Given that multiple protocols in the literature mimic the digestion of dietary components, gathering studies that use such models directed at protein digestion processes is critical. This systematic review aimed to gather evidence that adopted adequate experimental models to simulate human protein digestion. The databases searched were PubMed, Web of Science, ScienceDirect, Embase, Virtual Health Library, and Scopus. A total of 1985 articles were found, resulting in 20 eligible in vitro studies. The Office of Health Assessment and Translation was used to evaluate methodological quality. Seven studies used plant-based protein sources, twelve used animal protein sources, and one used both. The duration of the oral phase varied, although 60% of the studies employed a protein digestion period of 120 min. Amylase, pepsin, and pancreatin enzymes were utilized in 40% of the studies, with pH levels of 7, 3, and 7, respectively, during the oral, gastric, and intestinal phases. The INFOGEST harmonized static model was adopted by 65% of the studies; INFOGEST is the most effective model for simulating gastrointestinal protein processes in humans and can be used to answer several research questions because it describes experimental conditions close to the human physiological situation.

Crow Search Algorithm for Modelling an Anaerobic Digestion Process: Algorithm Parameter Influence

Corn steep liquor is a waste product from the process of treating corn grain for starch extraction. It is used as a substrate in anaerobic digestion with simultaneous hydrogen and methane production in a cascade of two anaerobic bioreactors. For process research and optimisation, adequate mathematical models are required. So, the authors aim to present a high-quality model of the corn steep liquor process for the sequential production of H2 and CH4. This paper proposes a technique for identifying the best mathematical model of the process using the metaheuristics crow search algorithm (CSA). The CSA was applied for the first time to mathematical modelling of the considered two-stage anaerobic digestion process, using real experimental data. Based on the analysis of the numerical data from the model parameter identification procedures, the influence of the main CSA parameters—the flight length, fl, and the awareness probability, AP—was investigated. Applying classical statistical tests and an innovative approach, InterCriteria Analysis, recommendations about the optimal CSA parameter tuning were proposed. The best CSA algorithm performance was achieved for the AP = 0.05, fl = 3.0, followed by AP = 0.10, fl = 2.5, and AP = 0.15, fl = 3.0. The optimal tuning of the CSA parameters resulted in a 29% improvement in solution accuracy. As a result, a mathematical model of the considered two-stage anaerobic digestion process with a high degree of accuracy was developed.

H2S mitigation for biogas upgrading in a full-scale anaerobic digestion process by using artificial neural network modeling

Biogas production by anaerobic digestion (AD) has emerged as a prominent bio-renewable energy source in recent years. However, the process also produces undesirable by-products, including H2S, thereby negatively impacting the biogas quality. This study focused on mitigating H2S in a full-scale AD located at a wastewater treatment plant (WWTP) by controlling the internal operational parameters by using an artificial neural network (ANN) model. Data from 54 days of AD operation were used to train and validate a structured ANN with a 5-3-1 topology. To minimize the H2S content, optimum values for dry solid (DS), volatile solid (VS), pH, temperature, and primary sludge fraction (PS) were determined to be 6.2 %, 63 %, 7.7, 35.6 °C, and 67.6 %, respectively, using the particle swarm optimization (PSO) algorithm. This optimization indicated a 49 % reduction in the average H2S concentration, from 6117 ppm to 3107 ppm. The analysis of relative importance (RI) showed that the pH (RI = −29.5) and PS (RI = −28.7) were the most critical factors affecting biogas quality. Additionally, several solutions derived from the optimization results were practically implemented in the Qom WWTP to achieve optimal conditions, and the outcomes were discussed.

Destructuration of Canola Protein Gels during In Situ Gastrointestinal Digestion Studied by X-ray Scattering.

We are studying the destructuration of canola protein gels, as a solid food model, during in situ gastrointestinal digestion using synchrotron small-angle X-ray scattering (SAXS). Digestion of two gels, prepared by heating pH 8 and pH 11 solutions, was carried out by diffusion of enzymatic juices into the gel from the top of the capillary and monitored for several tens of hours. Very similar time evolutions of SAXS curves occur at different positions of the gel in the capillary, with a delay determined by the distance from the surface initially in contact with the digestive juice. The main phenomena observed are (i) at the scale of the protein conformation (1-5 nm). The scattering curve is a power law, the exponent of which measures the compactness (related to the degree of unfolding). It can be plotted as a function of the characteristic size of proteins/and interprotein distances and as a function of the scattering intensity. Such diagrams clearly show successive digestion processes. For the pH 11 gel, in which proteins are initially hardly unfolded, the digestive processes are unfolding (1st step), recompaction-aggregation phenomena (2nd step) due to gastrointestinal pH conditions and enzymatic cleavage, further unfolding-disaggregation (3rd step), and final protein cleavage (4th step) down to small peptides. For the pH 8 gel, proteins are initially unfolded, and only the last three steps are observed, showing the influence of easier access for the enzymes. (ii) At the scale of large aggregates (10-50 nm), we observe for both gels a decrease in the size and/or number of these aggregates during digestion and alteration of their interfaces. (iii) At the scale of the secondary protein structure, wide-angle X-ray scattering is very useful for detecting the degradation of the secondary protein structure at different steps of digestion.

A new concept for bioenergy yield in anaerobic digestion process: Highlighting current yield challenges

The development of sustainable energy sources including biogas produced from urban and industrial wastes has received much attention over the past few years. Given that biogas can be an alternative to fossil fuels before long, its yield, representing the value of energy production from the substrate, has been of utmost importance. With reference to the current definition, biogas yield simply depends on the maximum biogas produced per unit mass of the substrate. In this line, anaerobic digestion (AD) is a time-consuming process, whose duration affects the biogas production yield as well as the maximum biogas production rate. Against this background, the present study dedicated focus on the time factor to present a new definition of biogas/methane (CH4) production yield in AD. In light of this, the time entailed for the AD process (T95%), including the lag phase time (Tlag), the time in proportion to the logarithmic production of biogas (Tlog), and the biogas stabilization time (reaching 95 % of the maximum biogas production rate, T→95%) were taken into account. In accordance with previous research, four modes, viz., (i) equal maximum biogas-different time, (ii) different maximum biogas-equal time, (iii) different maximum biogas-different time (receding yield) and (iv) different biogas maximum-different time (approaching yield) were assessed. For this purpose, the kinetic models, namely, modified Gompertz (MG) and logistic function (LF), were recruited to determine the maximum biogas production rate (Rm) and the lag phase time (λ). Among the mentioned modes, the yield difference between the samples investigated according to the current and time-based yields was 24 % on average, and reached 85 % in the first and third modes. Evaluating the data from 32 studies, using the Python programming language, correspondingly revealed that the correlation coefficient between the AD process time (T95%) and the current and time-based yields augmented from 7 % to 51 %. This demonstrated the impact of the time factor on the biogas yield. Based on the MG model, the significance level of the Rm parameter increased from 52 % to 94 %, highlighting the value of the logarithmic phase time of biogas in the AD reactor.

Bioaccumulation and dietary bioaccessibility of microplastics composition and cocontaminants in Mediterranean mussels

Microplastics (MPLs) are contaminants of emerging concern (CECs) ubiquitous in aquatic environments, which can be bioaccumulated along the food chain.In this study, the accumulation of polyethylene (PE), polystyrene (PS) and polyethylene terephthalate (PET) microplastics (MPLs) of sizes below 63 μm was assessed in Mediterranean mussels (Mytilus galloprovincialis spp). Moreover, the potential of mussels to uptake and bioaccumulate other organic contaminants, such as triclosan (TCS) and per- and polyfluoroalkyl substances (PFASs), was evaluated with and without the presence of MPLs. Then, the modulation of MPLs in the human bioaccessibility of co-contaminants was assessed by in vitro assays that simulated the human digestion process. Exposure experiments were carried out in 15 L marine microcosms. The bioaccumulation and bioaccessibility of PE, PS, PET, and co-contaminants were assessed by means of liquid chromatography -size exclusion chromatography-coupled to high-resolution mass spectrometry (LC(SEC)-HRMS).Our outcomes confirm that MPL bioaccumulation in filter-feeding organisms is a function of MPL chemical composition and particle sizes. Finally, despite the lower accumulation and bioaccumulation of PFASs in the presence of MPLs, the bioaccessibility assays revealed that PFASs bioaccessibility was favoured in the presence of MPLs. Since part of the bioaccumulated PFASs are adsorbed onto MPL surfaces by hydrophobic and electrostatic interactions, these interactions easily change with the pH during digestion, and the PFASs bioaccessibility increases.

Optimization of microwave intensified slaughterhouse sludge pretreatment method to enhance anaerobic digestion process by response surface methodology

Optimization of microwave intensified slaughterhouse sludge pretreatment method to enhance anaerobic digestion process by response surface methodology

Influence of probiotic and vitamin C on productivity, digestibility and accessibility of nutrients in the diet of meat quails while reducing the risk of aflatoxicosis

Of all known aflatoxicones, the most dangerous is afl atoxin B1, produced by mold of the genus Aspergillus. It destroys the liver parenchyma, very often leading to cirrhosis of this gland. In addition, aflatoxin B1 suppresses the vital activity of beneficial microfl ora of the digestive tract and the processes of digestion and absorption of nutrients in compound feed. The purpose of the research was to study the effect of vitamin C and the probiotic Bioxymin Chicken on the livability, growth rate, digestibility and accessibility of nutrients in compound feed for meat quails with a tolerant level of aflatoxin B1. The studies have shown that in order to improve the survival rate of livestock, growth rate, increase digestibility and accessibility of nutrients in the diet, vitamin C at a dose of 500 g/t and probiotic Bioxymin Chicken at a dose of 1500 g/t of the compound feed should be included in the composition of complete compound feeds (barley-sorghum-soy type) at a tolerant level of afl atoxin B1. This resulted in a significant (p < 0.05) superiority of the quails of the 3rd experimental group over the control analogues in terms of digestibility coefficients of dry matter, organic matter, crude protein, crude fi ber and nitrogen-free extractive substances. The results of the studies have shown that the activity indices of proteinases, cellulases, lipases, amylases in the chyme of the small intestine are completely consistent with the indices of digestibility and assimilation of nutrients in quail diets. In addition, in comparison with the quails of the control group, the meat quails of the 3rd experimental group showed a higher digestibility of feed nitrogen by 7.10 % (p < 0.05), with an increase in the level of use of this element from the amount taken per day with feed by 3.69 abs.%.

In-situ biomethanation of high CO content syngas in agricultural biogas digesters

To meet global energy demands, syngas with high CO content (>50 %) generated from hydrothermal gasification of agricultural residues or wood, could be utilized as a co-substrate in anaerobic digestion (AD) processes for conversion into CH4. This study investigated in-situ biomethanation using synthetic gas (55 % CO, 35 % H2, and 15 % CO2), mimicking wood gasification syngas, during AD of cow manure, the most abundant agricultural waste. A continuously stirred tank reactor (CSTR) served as a control and was fed only cow manure, while the other two reactors were fed syngas with or without gas recirculation at different gas loading rates (GLRs).In-situ syngas injection in AD of cow manure at GLRs ≤0.3 L LRV−1 d−1 improved overall CH4 productivity compared to the control (0.35 ± 0.1 vs. 0.29 ± 0.1 L LRV−1 d−1), though the CH4 content (45 ± 5 %) was lower than the control reactor (62 ± 3 %), indicating a need for biogas upgrading. Gas recirculation enabled higher CO and H2 conversion efficiencies of 99–100 % but considerably decreased CH4 productivity from cow manure. In-situ biomethanation enhanced the relative abundance of hydrogenotrophic methanogens, highlighting their role in syngas conversion to CH4.

Influence of enzyme drug and adsorbent on digestive metabolism processes of steers fattening in technogenic zone

In the practice of feeding of young ruminants for fattening, feed drugs of new generation adsorbents are increasingly and widely introduced. They often exhibit synergistic eff ects on metabolic processes with a large set of biologically active additives including enzyme drugs. The purpose of the research was to study the infl uence of the adsorbent drugs toxfi n and MEC celloviridin G20x on the state of rumen metabolism in fattening steers in whose diets there was an excess content of lead, zinc and cadmium salts. It was found that in order to activate the processes of digestive metabolism due to better elimination of heavy metal salts, it is advisable to jointly introduce the adsorbent toxfi n in the amount of 1 kg/t of compound feed and MEC celloviridin G20x in the amount of 70 g/t of compound feed into the composition of the rations of fattening steers. The results of the conducted studies showed that by the end of fattening at the age of 18 months the animals of the 4th experimental group had the highest body weight, which surpassed the steers of the 1st control group by 29.20 kg (p < 0.05) or 6.86 %. Relative to the control analogues the steers of the 4th experimental group showed an activation of growth in the forestomachs of ciliates (producers of cellulases and amylases) by 54.26 % (p < 0.05) and bacteria of the Flavobacterium vitarumen group (producers of proteinases) by 29.36 % (p < 0.05). Due to the combined feeding of the adsorbent drugs toxfi n and MEC celloviridin G20x, the processes of detoxifi cation of heavy metal salts were more effective. Therefore, the fattening steers of the 4th experimental group more actively accumulated volatile fatty acids in the rumen fl uid, significantly (p < 0.05) outperforming the animals of the 1st control group in this indicator by 1.68 mmol/100 ml or by 20.71 %.

Thermal pretreatment of swine waste to improve biodegradability in the anaerobic digestion process. Effect on the physicochemical characteristics of the substrate

In anaerobic digestion (AD) processes, hydrolysis is considered the limiting stage in the degradation of solid wastes. Such is the case of swine manure digestion, which due to the complex physical and chemical structure of the lignocellulosic material that composes it, an energy wastage has been observed in terms of methane production. Among the strategies used to improve the hydrolysis stage, it is possible to mention the thermal pretreatment of the substrate, which can significantly improve the biodegradability of the material used as raw material in AD. In this study, the effect of temperature (60–177 °C) and exposure time (30–60 min) on the physicochemical properties of the substrate such as pH, volatile organic acids (VOAs), total inorganic carbonates (TIC), volatile solids (SV), total solids (ST), soluble chemical oxygen demand (CODs) and biochemical methane potential (BMP) were determined. The temperature factor had a higher level of significance compared to the exposure time on the parameters of pH, VOAs, and TIC before and after the biogas generation process. However, the effect was different for CODs, where time was more significant than treatment temperature. As for the parameters of total and volatile solids content (ST and SV), the factors evaluated (temperature and exposure time) did not show significant effect. Also, the pretreatments showed an increase in biochemical methane potential, outperforming the untreated substrate by up to 70.4 % (121.74vs.71.44 mLCH4 gVS-1). The best combination of heating temperature and operating time was 120 °C and 45 min, which promoted the hydrolysis step that was reflected in an increase in CODs and improvement in methane production by 42 % over the untreated substrate

Shell-Core Microbeads Loaded with Probiotics: Influence of Lipid Melting Point on Probiotic Activity.

Probiotics have many beneficial physiological activities, but the poor stability during storage and gastrointestinal digestion limits their application. Therefore, in this study, a novel type of shell-core microbead for loading probiotics was prepared through high-precision concentric drop formation technology using gelatin as the shell material and lipids as the core material. The microbeads have a regular spherical structure, uniform size, low moisture content (<4%) and high probiotic activity (>9.0 log CFU/g). Textural testing showed that the hardness of the medium-chain triglyceride microbeads (MCTBs), cocoa butter replacer microbeads (CBRBs) and hydrogenated palm oil microbeads (HPOBs) increased gradually (319.65, 623.54, 711.41 g), but their springiness decreased (67.7, 43.3, 34.0%). Importantly, lipids with higher melting points contributed to the enhanced stability of probiotics during simulated digestion and storage. The viable probiotic counts of the HCTBs, CBRBs and HPOBs after being stored at 25 °C for 12 months were 8.01, 8.44, and 8.51 log CFU/g, respectively. In the simulated in vitro digestion process, the HPOBs resisted the destructive effects of digestive enzymes and gastric acid on probiotics, with a reduction in the probiotic viability of less than 1.5 log CFU/g. This study can provide new ideas for the preparation of intestinal delivery probiotic foods.

Integration of Digestate-Derived Biochar into the Anaerobic Digestion Process through Circular Economic and Environmental Approaches-A Review.

The growing energy consumption and the need for a circular economy have driven considerable interest in the anaerobic digestion (AD) of organic waste, offering potential solutions through biogas and digestate production. AD processes not only have the capability to reduce greenhouse gas emissions but also contribute to the production of renewable methane. This comprehensive review aims to consolidate prior research on AD involving different feedstocks. The principles of AD are explored and discussed, including both chemical and biological pathways and the microorganisms involved at each stage. Additionally, key variables influencing system performance, such as temperature, pH, and C/N ratio are also discussed. Various pretreatment strategies applied to enhance biogas generation from organic waste in AD are also reviewed. Furthermore, this review examines the conversion of generated digestate into biochar through pyrolysis and its utilization to improve AD performance. The addition of biochar has demonstrated its efficacy in enhancing metabolic processes, microorganisms (activity and community), and buffering capacity, facilitating Direct Interspecies Electron Transfer (DIET), and boosting CH4 production. Biochar also exhibits the ability to capture undesirable components, including CO2, H2S, NH3, and siloxanes. The integration of digestate-derived biochar into the circular economy framework emerges as a vital role in closing the material flow loop. Additionally, the review discusses the environmental benefits derived from coupling AD with pyrolysis processes, drawing on life cycle assessment investigations. Techno-economic assessment (TEA) studies of the integrated processes are also discussed, with an acknowledgment of the need for further TEA to validate the viability of integrating the biochar industry. Furthermore, this survey examines the techno-economic and environmental impacts of biochar production itself and its potential application in AD for biogas generation, aiming to establish a more cost-effective and sustainable integrated system.

Anaerobic digestion of municipal solid waste produced by the city of Algiers using life cycle assessment

This study analyses the life cycle assessment of anaerobic digestion process of municipal solid waste management (MSWM) produced by Algiers city. Some keys parameters of the processes are then modified to analyze the "hot spots" and perform a sensitivity analysis to identify their influence on the results. Data for the inventory came from actual city facilities, and background process information came from Eco invent version 3.1 of SimaPro 8.1 software. The analyzed process contribution indicates that the global warming potential is affected by the anaerobic digestion because of the NOx and CO emissions from the thermal processes of biogas burning and fuel oil combustion for digesters heating. Furthermore, plastics recycling is environmentally beneficial because of net savings. The energy valorization of biogas produces the least amount of environmental damage, eliminating 403.06 kg CO2 eq/ton of waste, saving 18.2 E+09 MJ/ton of fossil fuels, and producing 2.8 E+08 kWhel/year, or 6% of the city's annual electricity consumption.

Influence of inoculum on process parameters and microbial communities during anaerobic digestion of cattle manure: Insights from metabarcoding analysis

Linking the variety of microbial ecology attributes to system functioning is critical to improve operational strategies and to support microbial pathways, in order to conceive efficient and reliable anaerobic digestion process. In the present study, we conducted a direct comparison between two digesters regarding the process parameters and microbial community dynamics between two digesters: one containing only the substrate (cattle manure) (Digester S), and the other (Digester F) enriched with an inoculum. This study aimed to investigate taxonomic and functional changes in the digester microbiome using a 16S rRNA sequencing approach. Results exhibit that the bacterial richness, diversity, and regularity were higher in Digester F. This later showed also a higher biogas yields (BY) and the process performance indicators compared to Digester S. The BY obtained in digester F was 2.17 times higher than that obtained in digester S. Furthermore, significant correlations were obtained between biogas yields (BY) and microbial communities with Firmicutes/Bacillota (Clostridium, Enterococcus, Streptococcus, Ruminococcaceae, Mogibacterium, and Turicibacter), Actinobacteria (Corynebacterium), and Bacteroidetes (Bacteroides, Paludibacter) in the AD systems. Conversely, in Digester S, biogas yield (BY) was highly significant and positively correlated with the abundance of Actinobacteria (Rhodococcus) and Proteobacteria (Moraxella, Oxalobacter). Moreover, the inoculum in digester F resulted in the enrichment of main bacterial functions involved in biogas production. This study provides results that justify the changes in the structure of the microbial community and the functional strategy used by the most representative micro-organisms in the consortia that carried out this process.

Optimization of Liquid-State Anaerobic Digestion by Defining the Optimal Composition of a Complex Mixture of Substrates Using a Simplex Centroid Design

This study aimed to define the optimal composition of three heterogeneous substrates of the anaerobic digestion process to maximize methane production. The investigated substrates were sewage sludge (SS), the organic fraction of municipal solid waste (OFMSW), and horse waste (HW). The optimal composition of these substrates was defined using the mixture design and, more specifically, the simplex–centroid mixture design. Customized methods and materials were employed to study the complex mixture design of these substrates. The findings revealed that the optimal mixture involved all three substrates with the composition 0.17 HW, 0.66 SS, and 0.17 OFMSW, which demonstrated the highest methane yield at 269 NmL·gVS−1. In addition, a mathematical model was developed to predict methane production based on a specific composition of co-substrates. The results were validated at the small pilot scale.