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Biodegradable organic waste offers significant opportunities for resource recovery within the frame of the circular economy. In this work, the effects of carbon-encapsulated iron nanoparticles and ozone pre-treatments in the mesophilic methanogenic stage of a temperature-phased an-aerobic digestion have been studied using biochemical methanogenic potential (BMP) tests and modeling simulation. To do that, digestates from a pre-treated thermophilic acidogenic reactor that co-digested sludge and wine vinasse were used. The addition of nanoparticles favored the removal of particulate matter, which increased by 9% and 6% in terms of total solids and volatile solids, respectively. When combined with ozone pre-treatment, these increases were 27% and 24%, respectively, demonstrating enhanced AD efficiency. The dose of iron nanoparticles encapsulated in carbon did not result in a statistically significant increase in methane production when sludge and vinasse were used as feedstock. The combination of nanoparticles with the ozone pre-treatment significantly improved the methanogenic phase of the second stage, increasing the methane production yield by 22% and reducing the lag phase from 10 days to 3 days, according to the modified Gompertz model. [ABSTRACT FROM AUTHOR]

This study focused on determining the effect of the inoculum to substrate ratio (ISR) on biogas production efficiency from the anaerobic co-digestion of two substrates: synthetic food waste and common reeds (Phragmites australis) that were ground and pre-treated using sodium hydroxide at a concentration of 2% to increase access to their cellulose. It also studied the role of different mixing ratios of the two substrates in improving the stability of the digestion process and increasing biogas production. A series of batch tests were carried out under mesophilic conditions using three ratios of ISR: 1:4, 1:2, and 1:1, and five substrate mixing ratios (synthetic food waste: pre-treated P. australis): 25:75, 50:50, 75:25, 100:0, and 0:100. The results showed low biogas production at the ISR 1:4 (21.58±0.00–44.46±0.01 mL/g volatile solid (VS) added), and the reactors suffered from acidification at the different substrates mixing ratios, while the biogas production increased at an ISR of 1:2, where the reactors with the substrate mixing ratio of 25:75 presented the highest biogas production (82.17±0.62 mL/g VS added), and the digestion process was stable. However, the reactors with substrate mixing ratios of 50:50, 75:25, and 100:0 suffered from acidification effects at this ISR. In contrast, at ISR of 1:1, the reactors did not expose to acidification inhibition at all the substrates mixing ratios, and the highest biogas production was found at synthetic food waste: pre-treated P. australis mixing ratios of 75:25 and 100:0 (76.15±1.85 and 82.47±1.85 mL/g VS added, respectively). [ABSTRACT FROM AUTHOR]

(1) The study aims to utilize a reported approach for culturing mesophilic bacteria from a plastic waste environment; (2) The work revived mesophilic microbial population from an aged PET recycling site using a culture-based approach, and determined the purified isolates in genus level in 16S identification; (3) A total of 59 bacterial isolates were obtained, in which microbial species, including Pseudomonas spp, Rhodococcus spp, and Burkholderia spp were identified as abundance. It was observed that the surviving microbes favoured sodium propionate as a short-chain carbon source for growth, rather than the intended plastic substrate, PET. The preference of sodium propionate utilization by several bacterial isolates, including 5601W (detected as Rhodococcus spp.), 5601Y, 7801, and 7802 (detected as Burkholderia spp.), was confirmed through growth curve analysis and cell enumeration conducted in a medium where sodium propionate served as the sole carbon source.; (4) The microbial demonstration revealed the metabolic complex of microbial communities in the environment and indicated the challenges associated with bacterial isolation from environments with accumulated plastic waste. [ABSTRACT FROM AUTHOR]

(1) The study aims to utilize a reported approach for culturing mesophilic bacteria from a plastic waste environment; (2) The work revived mesophilic microbial population from an aged PET recycling site using a culture-based approach, and determined the purified isolates in genus level in 16S identification; (3) A total of 59 bacterial isolates were obtained, in which microbial species, including Pseudomonas spp, Rhodococcus spp, and Burkholderia spp were identified as abundance. It was observed that the surviving microbes favoured sodium propionate as a short-chain carbon source for growth, rather than the intended plastic substrate, PET. The preference of sodium propionate utilization by several bacterial isolates, including 5601W (detected as Rhodococcus spp.), 5601Y, 7801, and 7802 (detected as Burkholderia spp.), was confirmed through growth curve analysis and cell enumeration conducted in a medium where sodium propionate served as the sole carbon source.; (4) The microbial demonstration revealed the metabolic complex of microbial communities in the environment and indicated the challenges associated with bacterial isolation from environments with accumulated plastic waste.

[Display omitted] • Temperature had an impact on solubilisation and fermentation yields. • Volatile fatty acids profile was influenced by temperature. • Each temperature studied had its own microbial consortium. • Waste activated sludge microbiota had a key role on the microbial consortium. • Acetoclastic methanogens from WAS could thrive in the fermenters. This work aims to improve the continuous co-fermentation of waste activated sludge (WAS) and food waste (FW) by investigating the long-term impact of temperature on fermentation performance and the underpinning microbial community. Acidogenic co-fermentation of WAS and FW (70:30 % VS-basis) to produce volatile fatty acids (VFA) was studied in continuous fermenters at different temperatures (25, 35, 45, 55 °C) at an organic loading rate of 11 gVS/(L·d) and a hydraulic retention time of 3.5 days. Two batches of WAS (A and B) were collected from the same wastewater treatment plant at different periods to understand the impact of the WAS microbioota on the fermenters' microbial communities. Solubilisation yield was higher at 45 °C (575 ± 68 mgCOD/gVS) followed by 55 °C (508 ± 45 mgCOD/gVS). Fermentation yield was higher at 55 °C (425 ± 28 mgCOD/gVS) followed by 35 °C (327 ± 17 mgCOD/gVS). Temperature also had a noticeable impact on the VFA profile. At 55 °C, acetic (40 %) and butyric (40 %) acid dominated, while acetic (37 %), butyric acid (31 %), and propionic acid (17 %) dominated at 35 °C. At 45 °C, an accumulation of caproic acid was detected which did not occur at other temperatures. Each temperature had a distinct microbial community, where the WAS microbiota played an important role. The biomass mass-balance showed the highest growth of microorganisms (51 %) at 35 °C and WAS_B, where a consumption of acetic acid was observed. Therefore, at 35 °C, there is a higher risk of acetic acid consumption probably due to the proliferation of methanogens imported from WAS. [ABSTRACT FROM AUTHOR]

The possibility of producing hydrogen and methane from sedimented pulp and paper mill waste fibre was explored for the first time in a double-stage process. Hydrogen and methane production was compared in batch experiments under four different conditions: two-stage hydrogen and methane production under (i) mesophilic (37 °C) and (ii) thermophilic (55 °C) and one-stage methane production under (iii) mesophilic and (iv) thermophilic conditions. Among these conditions studied, two-stage thermophilic anaerobic digestion achieved the highest hydrogen yield (42.1 ± 2.91 mL/g VS) and methane yield (334 ± 26.8 mL/g VS) at 55 °C. The experimental results were fitted to modified Gompertz equation, and a strong correlation was built from the overall magnitude of the regression (R2 ranged from 0.996to 0.989) between the experimental data and the applied equation. Total energy yield from the two-stage thermophilic process was higher (3.7 kWh/L) than the one-stage process (1.7 kWh/L). The two-stage treatment also reduced the treatment time by half. Knowledge gained from this study will provide a basis for future investigation of two-stage treatment of sedimented fibres. [ABSTRACT FROM AUTHOR]

This study aims to identify the optimal conditions for generating biogas from poultry manure with respect to pH, C/N ratio, and temperature. The study was conducted in lab batch bioreactor having a working volume of 2 l at different conditions with respect to pH, carbon to nitrogen ratio (C/N), and temperature. A full factorial design is designed to analyze the impact of the three parameters and their interactions. Experiments are replicated four times to ensure the reproducibility of data. Results indicate that temperature is the only influencing parameter on biogas production from poultry manure within a pH range of 6–8 and a C/N ratio range of 10/1 to 40/1. Moreover, there is no interaction between the three parameters, and mesophilic conditions are found to be the optimum conditions for biogas production. The maximum biogas yield of 285 ml/g VS is found in mesophilic conditions at 37 °C with a retention time of 20 days. Biogas production kinetics are similar in mesophilic and thermophilic conditions but vary in psychrophilic conditions.

ABSTRACTFood waste (FW) is high in nutrients and has gained global attention as an ideal substrate for bioenergy recovery through anaerobic digestion (AD). Ambient digesters have been widely used because of their ease of installation, low cost, and low energy input. However, to improve biogas production sustainably, there is a need to consider reactor heating using renewable energy such as solar. This study sought to apply psychrophilic and mesophilic biodigester temperatures for FW treatment. For ambient digestion, a complete-mix flexible biodigester, named STH-1000A, covered in a greenhouse structure was operated between 24 and 32 °C. A prototype complete-mix tank biodigester, named VUT-1000C, was designed and operated at mesophilic conditions of 37 °C through solar geyser heating. VUT-1000C produced 1200 L of biogas per day while STH-1000A 150 L/day. VUT-1000C and STH-1000A generated up to 1.8 and 0.4 kWh of electricity, respectively. The power balance showed that VUT-1000C used 68% of its power production and STH-1000A consumed 398%. Digester heating using solar geyser is a novel and promising technique for achieving mesophilic condition leading to improved biogas production.

Biodegradable organic waste offers significant opportunities for resource recovery within the frame of the circular economy. In this work, the effects of carbon-encapsulated iron nanoparticles and ozone pre-treatments in the mesophilic methanogenic stage of a temperature-phased an-aerobic digestion have been studied using biochemical methanogenic potential (BMP) tests and modeling simulation. To do that, digestates from a pre-treated thermophilic acidogenic reactor that co-digested sludge and wine vinasse were used. The addition of nanoparticles favored the removal of particulate matter, which increased by 9% and 6% in terms of total solids and volatile solids, respectively. When combined with ozone pre-treatment, these increases were 27% and 24%, respectively, demonstrating enhanced AD efficiency. The dose of iron nanoparticles encapsulated in carbon did not result in a statistically significant increase in methane production when sludge and vinasse were used as feedstock. The combination of nanoparticles with the ozone pre-treatment significantly improved the methanogenic phase of the second stage, increasing the methane production yield by 22% and reducing the lag phase from 10 days to 3 days, according to the modified Gompertz model.

The effects of trace metals (iron (Fe), cobalt (Co) + Fe, and Co + nickel (Ni) + Fe) on mesophilic and thermophilic anaerobic digestion of food waste were quantified experimentally. Supplementation with 0 ≤ [Co] ≤ 5 mg/L, 0 ≤ [Ni] ≤ 10 mg/L, or 0 ≤ [Fe] ≤ 200 mg/L can significantly improve the productivity of mesophilic (MD) and thermophilic (TD) digesters. Addition of micronutrients increased biogas production, but excessive addition of trace metals hindered the production. Supplementation with Fe + Co or Fe + Co + Ni increased biogas production more than the addition of only Fe did. Within the design boundaries, the optimal concentrations for supplementation with three trace metals in MD were [Co] = 0.33 mg/L, [Ni] = 0.43 mg/L, and [Fe] = 5.35 mg/L, and in TD were [Co] = 1.41 mg/L, [Ni] = 3.84 mg/L, and [Fe] = 200 mg/L. TD required larger amounts of the trace metals than MD (4.3–37.4 times). The results can give quantitative information on trace metal supplementation for successful anaerobic digestion. [ABSTRACT FROM AUTHOR]

Food waste (FW) is high in nutrients and has gained global attention as an ideal substrate for bioenergy recovery through anaerobic digestion (AD). Ambient digesters have been widely used because of their ease of installation, low cost, and low energy input. However, to improve biogas production sustainably, there is a need to consider reactor heating using renewable energy such as solar. This study sought to apply psychrophilic and mesophilic biodigester temperatures for FW treatment. For ambient digestion, a complete-mix flexible biodigester, named STH-1000A, covered in a greenhouse structure was operated between 24 and 32 °C. A prototype complete-mix tank biodigester, named VUT-1000C, was designed and operated at mesophilic conditions of 37 °C through solar geyser heating. VUT-1000C produced 1200 L of biogas per day while STH-1000A 150 L/day. VUT-1000C and STH-1000A generated up to 1.8 and 0.4 kWh of electricity, respectively. The power balance showed that VUT-1000C used 68% of its power production and STH-1000A consumed 398%. Digester heating using solar geyser is a novel and promising technique for achieving mesophilic condition leading to improved biogas production. [ABSTRACT FROM AUTHOR]

Despite the awareness on the importance of using biogas produced from various biomasses that were previously considered as wastes, the fact remains that its applicability or usage in domestic purposes such as cooking stoves has not really gained attention especially in developing countries. Based on this reason, this research designed a batch system biogas generating facility that will serve the energy needed for cooking meals by a family size of six members, using rumen contents of cattle (Bos indicus) as biomass. The results made known that an anaerobic digester having a capacity of 2.7m³ will perfectly serve for such facility to meet its intended use when fed with 72kg of substrate per batch, while the gas holder volume should be 0.527m³. Necessary appurtenances including water jacket were designed and detailed dimensions, drawings as well as costing of the entire facility were provided to ease fabrication and possibly adjustment in the future if the need arise. [ABSTRACT FROM AUTHOR]

The study presents the results of the laboratory experiment performed on the anaerobic digestion of water hyacinth biomass harvested from the Volta River basin of Ghana and Fruit waste sludge as the inoculum. Batch mode of experiment was performed under mesophilic conditions (29 ± 3 °C) with a hydraulic retention time of 61 days. The experimental setup was made up of three (3) fermenter bottles of 5.0 L capacity namely F1, F2 and F3. F1 served as the control whiles F2 and F3 served as the test fermenter bottles. Each of the fermenter bottles was fitted with BlueSens methane sensor and BlueVcount flowmeter for the measurement of methane composition and biogas volumes, respectively. The Theoretical Biomethane Potential (BMP) of the water hyacinth biomass was estimated to be 422.23 ml/gVS. The experimental BMP was determined to be 402.62 ml CH4/gVS and 356.03 ml CH4/gVS for F2 and F3, respectively. Consequently, a biodegradability value of 95.36 and 84.32 % was obtained from F2 and F3, respectively. Moreover, the F2 fermenter bottle recorded a cumulative net methane and biogas volumes of 5576.3 ml and 12,014 ml, respectively. Likewise, a total net cumulative methane and biogas volumes of 4931.0 ml and 11,384 ml were produced from the F3 fermenter bottle. Using the First order kinetic model, an average value of hydrolysis constant for water hyacinth biomass was determined as 0.051 day−1. Furthermore, the modified Gompertz model, the logistic function model and Transference function models were used to fit the experimental cumulative biogas and methane production data. The outcome of the study shows that, the production of biogas from water hyacinth biomass harvested the Volta River basin of Ghana could offer sustainable control solutions to its invasion on water bodies whiles providing a cheap and reliable means of biofuel to the riparian communities.

Biogas digestates produced from anaerobically processed food or dairy manure have demonstrated some potential to suppress different pathogens and pests. In this study, digestates from these two substrates processed mesophilically (20 to 40°C) or thermophilically (>40°C) were compared for their nematode-suppressive potential. In bioassays, the suppressive potential of Heterodera schachtii or Meloidogyne incognita was tested at different amendment rates. Testing was expanded to field microplot experiments with M. incognita and greenhouse tests with Pratylenchus vulnus. In the bioassay with H. schachtii, fewer nematodes penetrated radish roots after amendment with thermophilic than with mesophilic digestates. Root penetration was lowest after treatment with digestates of food waste and thermophilic dairy manure at the highest rate. In a watermelon bioassay with M. incognita, nematode-induced galling and egg mass production were reduced after amendment with food waste digestates compared with manure digestates and after thermophilic compared with mesophilic digestates in the case of egg masses. In a greenhouse experiment with peach rootstock ‘Nemaguard’, the numbers of P. vulnus in roots were diminished after amendment with digestates at the highest rate. In microplot experiments with bell peppers, plants initially were more vigorous after amendment with thermophilic digestates than after mesophilic digestate additions. This effect was transient and was no longer measurable at harvest. In summary, food waste digestates, especially those that were thermophilically produced, had nematode suppressive and plant growth-improving properties. These effects were not long lasting and probably need additional mitigation for practical utility. [Figure: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Three sequential batch reactors were operated for the enrichment in microbial communities able to store polyhydroxyalkanoates (PHAs) using activated sludge as inoculum. They ran simultaneously under the same operational conditions (organic loading rate, hydraulic and solids retention time, cycle length, C/N ratio) just with the solely difference of the working temperature: psychrophilic (15°C), mesophilic (30°C), and thermophilic (48°C). The microbial communities enriched showed different behaviors in terms of consumption and production rates. In terms of PHA accumulation, the psychrophilic community was able to accumulate an average amount of 17.7 ± 5.7 wt% poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV), the mesophilic 40.3 ± 7.0 wt% PHBV, and the thermophilic 14.8 ± 0.3 wt% PHBV in dry weight over total solids. The average PHBV production yields for each selected community were 0.41 ± 0.12 CmmolPHBV/CmmolVFA at 15°C, 0.64 ± 0.05 CmmolPHBV/CmmolVFA at 30°C, and 0.39 ± 0.14 CmmolPHBV/CmmolVFA at 48°C. The overall performance of the mesophilic reactor was better than the other two, and the copolymers obtained at this temperature contained a higher PHV fraction. The physico‐chemical properties of the obtained biopolymers at each temperature were also measured, and major differences were found in the molecular weight, following an increasing trend with temperature. Practitioner Points: PHBV molecular weight is influenced by the operational temperature increasing with it.Increasing temperatures promote the production of HB over HV.The best accumulation performance was found at 30°C for the tested operational conditions. [ABSTRACT FROM AUTHOR]

Enzyme treatment of plastics at elevated temperatures can catalyze plastic biodegradation by improving enzyme accessibility to the polymer. Comparison of candidate proteins to databases of known plastic degrading proteins offers a streamlined screening approach for thermophilic plastic biodegradation candidates. Key commercial plastics like polypropylene, polystyrene and polyethylene usually require an oxidation event to impact polymer backbone chains. Heat pretreatment could be the key to enhancing polymer oxidation and improving plastic biodegradation by microorganisms/enzymes. Protein engineering is a useful tool which can improve a protein's plastic biodegradation performance by improving thermostability and stabilizing protein tertiary structure. Biological degradation of plastic waste is an environmentally and economically friendlier alternative to current recycling practices and enables the cycling of plastic monomers back into virgin-quality plastics. However, due to slow reaction rates, there is a lack of an industrially viable biodegradation strategy for most plastics. Here, we highlight the applicability of a thermophilic biodegradation strategy over a mesophilic approach, to enhance enzyme accessibility and catalyze plastic biodegradation. Thus, at reactions closer to the melting temperature or glass transition temperature of plastics, thermophilic reactions can offer an alternative direction to conventional plastic biodegradation strategies. [ABSTRACT FROM AUTHOR]

Variation of the digester temperature during the year enables the operation of digesters as seasonal heat storage contributing to a holistic heat management at water resource recovery facilities. Full‐ and lab‐scale process data were conducted to examine the effect of the digester temperature on process stability, sludge liquor quality, and dewaterability. Both full‐ and lab‐scale digesters show a stable anaerobic degradation process with a hydraulic retention time of more than 20 days and organic load rates up to 2.2‐kg COD/(m3·day) at temperatures between 33 and 53°C. The concentrations of soluble COD and ammonium‐nitrogen in the sludge liquor digested at 53°C are 2.6 to 5.8 times and 1.3 times higher, respectively, than in the sludge liquor digested at 37°C. Dewatering tests show an enhancement of the dewaterability but a clear increase in the polymer demand at increased digester temperature. Practitioner Points: Digesters can operate as seasonal heat storage within mesophilic and thermophilic temperaturesStable anaerobic degradation process for HRT above 20 daysMaintenance of process stability as well as quantity and quality of biogasIncrease of soluble COD in sludge liquor at higher temperaturesBetter dewaterability but higher demand for polymers with increasing temperature [ABSTRACT FROM AUTHOR]

This study aimed to investigate biogas production and energy balance in a two-stage anaerobic digestion system of fruit/vegetable waste under thermophilic and mesophilic conditions. Firstly, the feedstock was hydrolyzed and acidified in an acidic reactor at 37 °C with a retention time of 5 d. Then, the liquid hydrolysate was collected and pumped into an up-flow methane reactor under a mesophilic temperature with a retention time of 5 d and a thermophilic condition with a retention time of 3 d. The experimental results showed that in the thermophilic methane reactor, the COD removal, biogas yield, and methane concentration were 96.3%, 492 mL/g-VS, and 70.4%, respectively. These values were 3%, 10%, and 3% higher, respectively, than those obtained in the mesophilic methane reactor. In terms of energy, the mesophilic and thermophilic methane reactors consumed the same thermal energy demand for temperature control. They were much lower than the heat values produced by the power engine. The two-stage anaerobic digestion system using a thermophilic methane reactor obtained a gross energy of 11.20 kJ/g-VS and a net energy of 9.83 kJ/g-VS. These values were 13.2% and 14.8% higher, respectively, than those obtained by the system with a mesophilic condition. Moreover, the use of a thermophilic reactor helped reduce the reactor volume by 40%, leading to significant investment cost savings. [ABSTRACT FROM AUTHOR]

Garbage kitchen waste has been considered as one of the most difficult global issues with negative effect on the environment and health. It contains high amounts of cellulose and other organic waste which become ideal environments for the growth of pathogenic microbes and their toxic products which may reach agricultural land and water system. As a compromise, certain microbes are implemented under certain conditions to reduce and manage food waste. In the present study microorganism isolated from garbage kitchen waste collected in Duhok city. one thermophilic bacterium, two mesophilic bacteria, and fungus. All isolates were identified to the genus level and verified by morphological and biochemical characteristics. The findings show that two mesophilic bacteria were fungus from the genera Mucor and Rhizopus, one was a bacterium from the family Staphylococci, and one was a thermophilic Bacillus species. The enzyme activities of the isolates were estimated and revealed that Bacillus spp. has cellulase, protease and catalase activity while Staphylococcus spp. has only protease and catalase activity. Mucor and Rhizopus spp. have only cellulase and catalase activity. To estimate the level of garbage degradation. The level of garbage degradation was estimated by tacking the weight of the sample before and after degradation as well as detecting the content of protein and carbohydrate by using Folin Lowry and di-nitro salicyclic acid, phenol sulphuric acid method. The comparative study showed that both mesophilic (Mucor) and thermophilic microorganisms (Bacillus) showed the best degrader compared with Staphylococcus and Rhizopus.

Methane potential of three-phase olive mill solid waste (3POMSW) was evaluated by biochemical methane potential (BMP) tests at temperatures of 37.5 °C and 55 °C. The results have shown, that thermophilic processing has a higher methane and biogas yield by 10% and 17.2%, respectively, compared to mesophilic conditions. Concluding thermophilic conditions of 3POMSW results in higher conversion of the feedstock into biogas. The result of addition of enzymes (MethaPlus, Hemicellulase, PectinaseL, Amylase S and Lipase) and their mixtures to 3POMSW at 55 °C has shown that the optimum mixture of enzymes was Metha Plus and Hemicellulase, which resulted in an increase of methane yield by 1.3% compared to the base case without addition of enzymes. Simple model equations were developed based on first-order kinetic in order to calculate the biogas yield versus the time as a function of reaction rate constant (k) and the maximum biogas yield (ymax). In this study, results have shown two different reaction rates obtained for the mixtures of enzymes with 3POMSW of 0.130 d−1 from t = 0…14 days and 0.034 d−1 from t = 28…63 days. The developed simple model equations can be applied for calculating the biogas yield at the time and by optimizing the process improving biological nutrient removal.

Aeromonas salmonicida has long been known as psychrophiles since it is mainly isolated from cold water fish, and recent reports have revealed the existence of mesophilic strains isolated from warm sources. However, the genetic differences between mesophilic and psychrophilic strains remain unclear due to few complete genomes of mesophilic strain are available. In this study, six A. salmonicida (2 mesophilic and 4 psychrophilic) were genome‐sequenced, and comparative analyses of 25 A. salmonicida complete genomes were conducted. The ANI values and phylogenetic analysis revealed that 25 strains formed three independent clades, which were referred as typical psychrophilic, atypical psychrophilic and mesophilic groups. Comparative genomic analysis showed that two chromosomal gene clusters, related to lateral flagella and outer membrane proteins (A‐layer and T2SS proteins), and insertion sequences (ISAs4, ISAs7 and ISAs29) were unique to the psychrophilic groups, while the complete MSH type IV pili were unique to the mesophilic group, all of which may be considered as lifestyle‐related factors. The results of this study not only provide new insights into the classification, lifestyle adaption and pathogenic mechanism of different strains of A. salmonicida, but also contributes to the prevention and control of disease caused by psychrophilic and mesophilic A. salmonicida. [ABSTRACT FROM AUTHOR]

Hot springs are like nature's spas, which include warm and humid aquatic habitats that serve as a sanctuary for a diverse range of microorganisms, including bacteria, archaea, viruses, and eukaryotes fungi. Among these, fungi are one of the most important microorganisms, carrying out essential functions that often go unnoticed but are crucial in accelerating biological processes. These organisms have adapted to survive under a wide range of thermal conditions. While thermophilic fungi can withstand the scorching heat of deserts and hyper-saline conditions, other variants like mesophilic and psychrophilic fungi prefer more moderate and colder temperatures, respectively. The study employs shotgun metagenomic sequencing to obtain a fine-grained taxonomic classification of lesser-known species and microbial eukaryotes. This study aims to explore the relationship between fungal diversity and temperature in three distinct thermal zones; thermophilic (hot spring), mesophilic (plain field), and psychrophilic (semi-frigid zone) zones. The findings of our study demonstrated that there is a notable and positive association between the diversity of fungi and temperature, suggesting that temperature is a key factor in moulding fungal communities. However, it is important to note that further research is necessary to elucidate the underlying causal mechanisms of this relationship. Overall, our study adds to the knowledge of how environmental factors influence microbial diversity and can aid in the development of strategies for the conservation and management of fungal communities. Fungi are essential for many industrial applications, and their role in causing illnesses is also significant, making this research valuable for both scientific and practical purposes. [ABSTRACT FROM AUTHOR]

The rapid growth of the Malaysian poultry and palm oil industries has led biomass waste generation in abundance specifically chicken manure and empty fruit bunch (EFB). Anaerobic digestion (AD) is a circular economy-based approach which converts chicken manure and EFB into biogas which can be utilized for heating and power generation. Operating temperature is an imperative consideration for AD hence the objective of the study is to evaluate the effect of different temperature profiles namely, psychrophilic (20 °C), mesophilic (35 °C) and thermophilic (50 °C) on AD of chicken manure and EFB. The kinetic parameters are also evaluated using five kinetic models to enable readers to comprehend the kinetic behaviours of the systems. The volume and composition of biogas is measured every five days for a 50-day retention time. The findings observed that mesophilic condition is the most favourable with cumulative methane, CH4 composition of up to 17.07%, almost two folds that of thermophilic (9.12%) and five folds that of psychrophilic (3.49%). The CH4 generation rate, Rb based on the modified Gompertz model which is deemed the best fit further supports these findings as the Rb under mesophilic condition is significantly higher (0.330 mL/gvs day) compared to psychrophilic (0.088 mL/gvs day) and thermophilic (0.120 mL/gvs day) conditions. [ABSTRACT FROM AUTHOR]

ABSTRACT Anaerobic digestion (AD) stands out as a degradation pathway for the treatment of agro-industrial waste. This study aimed to evaluate the biogas production (Pb) from the co-digestion of swine (SW) and laying hen waste (LHW) under different temperature conditions (psychrophilic x mesophilic). The studies were carried out on a laboratory scale in anaerobic reactors (1.25 L) in a batch system for 60 days. Three mixtures in volumetric proportions (%) of 25/75 (P1), 50/50 (P2), and 75/25 (P3) (SW/LHW) were studied. The mixtures were characterized before and after AD in terms of TS, VS, and COD under temperatures of 18 and 36 °C, with Pb measured daily. Pb was higher at 36 °C for all mixtures compared to the psychrophilic condition (18 °C). Among the mixtures, the highest Pb value was observed for P3, reaching 0.34 and 0.60 m3 biogas kg−1 CODremoved for 18 and 36 °C, respectively. The digestate showed an increase in the contents of micro-and macronutrients for P1, P2, and P3 after AD, which indicates its use for agricultural purposes. The co-digestion of swine and laying hen waste is a promising proposal in terms of management and energy recovery of biogas, especially for mesophilic conditions in mixtures with a predominance of laying hen waste.

The pre-chilling of rabbit carcasses in an immersion tank directly interferes with microbial control. Therefore, this study was developed to examine the influence of different pre-chill tank water temperatures (4, 7, and 10 °C) on the microbiological quality of rabbit carcasses. Samples of rabbit carcasses and water and ice from the pre-chiller tank were collected; mesophilic aerobic heterotrophic microorganisms (MES), enterobacteria (EC), and coagulase-positive Staphylococcus (CPS) were counted; and the presence of Salmonella spp. was investigated. After the carcasses were immersed in the pre-chiller, there was a significant increase (p < 0.05) in MES (38.69 and 88.06 Log CFU·mL−1 at 4 and 10 °C, respectively) and EC (3.20, 4.15, and 4.84 Log CFU·mL−1 at 4, 7, and 10 °C, respectively). The average EC count tended to increase after the carcasses were immersed in the pre-chiller at different temperatures, but this increase was not significant. Water samples showed MES, EC, and CPS counts only after the immersion of the carcasses; however, the presence of these microorganisms was not detected in any of the ice samples. Salmonella spp. was not identified in the analyzed samples. The microorganisms analyzed at the three pre-chiller water temperatures evaluated did not multiply on the surface of the rabbit carcasses or in the pre-chiller water after carcass immersion. This study showed that none of the three pre-chilling temperatures were able to reduce the count of indicator microorganisms in the carcasses of rabbits. These data provide scientific support to discuss the need for specific norms and guidelines for rabbit meat production. [ABSTRACT FROM AUTHOR]

In this two-phase study, it was shown that a mixture with equal parts of manure and resulting animal blood was the optimal combination for obtaining biogas and biol. A quadratic growth trend in variable gas pressure over time—as well as its behavior—was confirmed for pHs around the neutral value for the substrate used in both the pilot phase and in the microplant, which had a mechanical implementation and mechatronic system for the control of variables that intervene in the anaerobic digestion process; this allowed for the confirmation of the results found in the first phase of research—without concerns that a lack of control over the process variables would cause—in such a way that it constituted a path for the industrialization of the waste treatment process in slaughterhouses that could be optimized by the use of the optimal combination that produces the greatest cm3 amount of gas. Anaerobic digestion in biodigesters is carried out at different constant temperature values within the mesophilic range, with a hydraulic retention time of 25 days. A direct relationship was found between temperature, biogas production and pH behavior in the buffer(s). The pH remained close to neutral and the gas pressure increased from 15 to 20. The findings indicated that the value for the C/N ratio of the blood of four was compensated for by its buffer system, composed of bicarbonate, hemoglobin, proteins and phosphates. [ABSTRACT FROM AUTHOR]

ABSTRACT: Thermoduric bacteria are known to affect the quality of Cheddar cheese, with manifested defects including slits, weak body, and blowing. Thermoduric bacteria are likely to increase in numbers during cheese-making, as in-process conditions are conducive to proliferation. The present study was conducted to track thermoduric bacterial progression during an 18- to 20-h Cheddar cheese production run and during ripening when the pasteurizer was washed at midway through the production day. This study also correlated a broad range of chemical changes to the growth of thermoduric bacteria during ripening. Three independent cheese trials were performed at 3.5- ± 0.5-mo intervals. Samples were drawn in duplicates at 4 different times of the day: at the start of the run (vat 1), prior to a midday wash of the pasteurizer (vat 20), after the midday wash of the pasteurizer (vat 21), and at the end of the run (vat 42) for raw milk, pasteurized milk, and cheese. Cheeses were also tested during ripening for 6 mo. Results showed that raw milk total bacterial counts comprised 0.24% thermoduric mesophiles (TM) and 0.12% thermoduric thermophiles (TT). The thermoduric thermophilic bacterial counts increased by log10 1.23 during the pasteurizer run of 9 to 10 h, indicating a buildup of thermoduric thermophilic bacteria during the pasteurization process itself. Midday washing reduced thermophilic counts by log10 1.36, as evident by pre- and post-midday wash counts. However, a thermophilic buildup during post-midday wash was again noticed near the end of the 20-h run. We found that TT bacteria decreased in the first 60 d of ripening, whereas TM bacteria increased during the same period. However, TT bacteria increased later during 60 to 180 d of ripening. Bacillus licheniformis was the most frequently isolated bacteria in this study and was recovered at all production stages sampled during the cheese-making and ripening. We observed a significant increase in the level of orotic and uric acids in the vat made at the end of the day. No significant difference in the overall chemical composition, proteolysis, sugar, or other organic acids was observed in cheese made at the start versus the end of the production run.

Syngas, a mixture of CO, H 2 , and CO 2 , is produced by waste carbonaceous feedstocks gasification, which plays an important role in renewable energy production. This study investigated the biomethanation of syngas (45% H 2 , 30% CO, 25% CO 2) in a trickle-bed reactor operated under mesophilic (35 °C), hyper-mesophilic (45 °C), and thermophilic conditions (55 °C). The results revealed that CH 4 production increased with increasing temperature. CH 4 production under steady-state conditions at the hyper-mesophilic and thermophilic temperatures were comparable; 92.2 ± 1.7 mmol/(L bed ∙d) and 93.9 ± 0.9 mmol/(L bed ∙d), respectively. On the contrary, electron losses in volatile fatty acids were the highest under mesophilic conditions. Additionally, digestate can be dosed as a nutrient addition and as a continuous inoculum source to ensure the optimal syngas biomethanation performance. The hyper-mesophilic conditions strategy illustrates possible energy savings for bioreactor heating with CH 4 production comparable to thermophilic conditions, thus saving operating costs. [ABSTRACT FROM AUTHOR]

Anaerobic digestion stabilizes municipal sludge through total solids reduction and biogas production. It is generally accepted that hydrolysis accounts for the rate‐limiting step of municipal sludge anaerobic digestion, impacting the overall rates of solids reduction and methane production. Technically, the sludge hydrolysis rate can be enhanced by the application of thermal hydrolysis pretreatment (THP) and is also affected by the total solids concentration, temperature, and solids retention time used in the anaerobic digestion. This study systematically analyzed and compared ways to take these four factors into the consideration of modern anaerobic digestion system for achieving the maximum solid reduction. Results showed that thermophilic anaerobic digestion was superior to mesophilic anaerobic digestion in terms of solids reduction but vice versa in terms of the methane production when integrated with THP. This difference has to do with the intermediate product accumulation and inhibition when hydrolysis outpaced methanogenesis in THP‐enhanced thermophilic anaerobic digestion, which can be mitigated by adjusting the solids retention time. Practitioner points: THP followed by TAD offers the greatest solids reduction rate.THP followed by MAD offered the greatest methane production rate.FAN inhibition appears to be an ultimate limiting factor constraining the methane production rate.In situ ammonia removal technique should be developed to further unblock the rate‐limiting step. [ABSTRACT FROM AUTHOR]

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Large amount of vegetal by-products are generated during production and processing steps. Introducing silage from vegetable by-products into dairy goat feed would be of great interest from the point of view of reducing costs and supporting the circular economy. The aim of this research was to study the effect of 40% inclusion of silage broccoli by-products and artichoke plant by-products in the diet of Murciano-Granadina goats throughout the lactation to establish milk suitability for fermented milks production. The novelty of this study is the use of milk from goats fed for a long term with a high inclusion of silages from artichoke plant and broccoli by-products, being the first one on broccoli inclusion. Two starter cultures thermophilic (YO-MIXTM300), and, mesophilic (MA400) were used and fermented milks were analyzed at two storage times after fermentation. Fermentation enhances antioxidant properties of fermented milks from all diets (p < 0.05), especially when mesophilic starter cultures are used. The main findings are that long term inclusion of 40% silage from broccoli and artichoke plant by-products in balanced diets of dairy goats yields milk suitable for fermentation by yogurt and cheese cultures, the inclusion of broccoli silage enhances antioxidant properties (p < 0.05), and, the inclusion of plant artichoke enhances fatty acids health indexes (p < 0.05). [ABSTRACT FROM AUTHOR]

In Kenya, 57% of the municipal solid waste generated is Food waste (FW) which has high organic content. However, the treatment and bioconversion of FW to biogas have always been challenging due to its rapid biodegradation, resulting from rapid hydrolysis and accumulation of volatile fatty acids and lowering pH in the bioreactor. In this study, the anaerobic digestibility of FW as a mono substrate was compared to co-digestion of FW with water hyacinth (WH) for improved biogas production and organic matter removal efficiency in a laboratory batch reactor. Different mix proportions of FW and WH were co-digested under mesophilic conditions (37 °C) at a dilution of 6% (w/v) Total Solids (TS) content. The TS of the substrates (Food waste and Water Hyacinth) were pre-processed to have a concentration of TS at 6% (60 g/L) to operate a wet AD which requires the substrate to be less than 15% TS. The proportions of WH: FW (v/v) were 100:0, 85:15, 70:30, 55:45, 30:70, 15:85, and 0:100. In the batch rectors the anaerobic co-digestion was conducted with Substrate to Inoculum (S/I) ratio of 1:1. FW is generally considered to have high volatile solids which hydrolyze rapidly lowering pH arising from excess production of Hydrogen which in presence of CO2 and acetogenic bacteria leads to more production of acetate, formate and other long chain fatty acids which inhibits methanogenesis as a result of rapid acidification. The rapid acidification of the bioreactors that are used to treat FW results in the inhibition of the methanogenesis process. The co-digestion of the substrates could have improved the process parameters by reducing acidity caused by the high C/N ratio, reducing the inhibitory range, and increasing the buffer capacity which enhanced the bio-methane potential and the microbial activity. The batch experiments were set in triplicate for both cases of FW, WH, mixtures, and Inoculum. The results showed that the average gas yields after 81 days for the various mix proportions were 256.27and 357.69 ml/g-VS for mono-digestion of WH and FW respectively. For the mixtures of WH: FW the average reported biogas production were 305.01, 280.27, 548.91,616.01 and 270.87 ml/g-VS for mixtures of 15:85, 30:70, 55:45,70:30 and 85:15 respectively. The modified Gompertz model showed that the digesters with WH and FW alone had lag times of 2.599 and 1.052 days respectively. The mix substrates of WH: FW 85:15, 70:30, 55:45, 30:70 and 15:85 shown lag times of 2.456, 3.777, 2.574, 1.956 and 1.75 days respectively. A mix (WH: FW) of 70:30 had the highest maximum specific biogas production Rmax and the maximum biogas production potential of 18.19 mlCH4/gVS per day and 607.7mlCH4/gVS respectively. The R2 and RSME values ranged from 0.9867 to 0.9963 and 2.663 to 9.359 respectively in all the digesters. The study shows that the co-digestion of WH and FW in the mix ratio of 70:30 improved the volume of biogas produced and organic matter removal efficiency reached 79%.

This study aimed to investigate biogas production and energy balance in a two-stage anaerobic digestion system of fruit/vegetable waste under thermophilic and mesophilic conditions. Firstly, the feedstock was hydrolyzed and acidified in an acidic reactor at 37 °C with a retention time of 5 d. Then, the liquid hydrolysate was collected and pumped into an up-flow methane reactor under a mesophilic temperature with a retention time of 5 d and a thermophilic condition with a retention time of 3 d. The experimental results showed that in the thermophilic methane reactor, the COD removal, biogas yield, and methane concentration were 96.3%, 492 mL/g-VS, and 70.4%, respectively. These values were 3%, 10%, and 3% higher, respectively, than those obtained in the mesophilic methane reactor. In terms of energy, the mesophilic and thermophilic methane reactors consumed the same thermal energy demand for temperature control. They were much lower than the heat values produced by the power engine. The two-stage anaerobic digestion system using a thermophilic methane reactor obtained a gross energy of 11.20 kJ/g-VS and a net energy of 9.83 kJ/g-VS. These values were 13.2% and 14.8% higher, respectively, than those obtained by the system with a mesophilic condition. Moreover, the use of a thermophilic reactor helped reduce the reactor volume by 40%, leading to significant investment cost savings.

Aeromonas salmonicida is a typical cold water bacterial pathogen that causes furunculosis in many freshwater and marine fish species worldwide. In our previous study, the pathogenic A. salmonicida (SRW-OG1) was isolated from a warm water fish, Epinephelus coioides was genomics and transcriptomics analyzed. Type II secretion system was found in the genome of A. salmonicida SRW-OG1, while the expressions of tatA, tatB, and tatC were significantly affected by temperature stress. Also, sequence alignment analysis, homology analysis and protein secondary structure function analysis showed that tatA, tatB, and tatC were highly conservative, indicating their biological significance. In this study, by constructing the mutants of tatA, tatB, and tatC, we investigated the mechanisms underlying temperature-dependent virulence regulation in mesophilic A. salmonida SRW-OG1. According to our results, tatA, tatB, and tatC mutants presented a distinct reduction in adhesion, hemolysis, biofilm formation and motility. Compared to wild-type strain, inhibition of the expression of tatA, tatB, and tatC resulted in a decrease in biofilm formation by about 23.66%, 19.63% and 40.13%, and a decrease in adhesion ability by approximately 77.69%, 80.41% and 62.14% compared with that of the wild-type strain. Furthermore, tatA, tatB, and tatC mutants also showed evidently reduced extracellular enzymatic activities, including amylase, protease, lipase, hemolysis and lecithinase. The genes affecting amylase, protease, lipase, hemolysis, and lecithinase of A. salmonicida SRW-OG1 were identified as cyoE, ahhh1, lipA, lipB, pulA, HED66_RS01350, HED66_RS19960, aspA, fabD, and gpsA, which were notably affected by temperature stress and mutant of tatA, tatB, and tatC. All above, tatA, tatB and tatC regulate the virulence of A. salmonicida SRW-OG1 by affecting biofilm formation, adhesion, and enzymatic activity of extracellular products, and are simultaneously engaged in temperature-dependent pathogenicity. [ABSTRACT FROM AUTHOR]

Conventional anaerobic digestion is currently challenged by limited degradability and low methane production. Herein, it is proposed that magnetic nanoparticles (Fe3O4-NPs) and bioelectrochemical systems can be employed for the improvement of organic content degradation. In this study, the effect of electrode configuration was examined through the application of a bioelectrochemical system and Fe3O4-NPs in anaerobic digestion (AD). A microbial electrolysis cell with cylindrical electrodes (MECC) and a microbial electrolysis cell (MEC) with rectangular electrodes were compared against the traditional AD process. Biochemical methane potential (BMP) tests were carried out using digesters with a working volume of 800 mL charged with 300 mL inoculum, 500 mL substrate, and 1 g Fe3O4-NPs. The electrodes (zinc and copper) of both digesters were inserted inside the BMPs and were powered with 0.4 V for 30 days at 40 °C. The MECC performed better, improving degradability, with enhanced methane percentage (by 49% > 39.1% of the control), and reduced water pollutants (chemical-oxygen demand, total organic carbon, total suspended solids, turbidity, and color) by more than 88.6%. The maximum current density was 33.3 mA/m2, and the coulombic efficiency was 54.4%. The MECC showed a remarkable potential to maximize methane enhancement and pollution removal by adjusting the electrode configuration. [ABSTRACT FROM AUTHOR]

[Display omitted] • All the feeding conditions were stable for the sufficient support from mineral alkalinity. • VS and COD removal maintained about 80% all along the experiment. • Prokaryotic community decreased in diversity and shifted greatly for PW = 50 %. • PW contents as 40% is TS (13.1% in total weights) was suggested. • Mesophilic co-digestion of PW with FW recovered biomethane as 445 ∼ 350 NL/kg-VS fed. Biomethane recovery from paper waste (PW) was achieved by mesophilic co-digestion with food waste. The feeding material containing 0%, 20%, 40% and 50% of PW in total solids (TS) were investigated in the long-term continuous operation. The results showed that the biogas production, pH, alkalinity and biodegradation of volatile solids (79.8 ± 3.6%) were stable for PW contents no more than 50%. The PW = 50% condition was considered the critical limit for the reasons of pump clogging, sufficient alkalinity (2.0 ± 0.3 g-CaCO 3 /L) and depletion of ammonia. Prokaryotic diversity indices decreased with the increased PW contents. Great shifts were observed in the prokaryotic communities before and after the PW contents reaches 50% as TS (18.4% as total weights). Biomethane recovery yields were deceasing from 445 to 350 NL-CH 4 /kg-fed-volatile-solids. The PW contents as 40% as TS (13.1% as total weights) obtained the optimal performance among all the feeding conditions. [ABSTRACT FROM AUTHOR]

• Effects of thermo-/mesophilic anaerobic digestion on sludge pyrolysis were studied. • Thermophilic anaerobic digestion removed more organics from sludge than mesophilic. • Thermophilic process retained small molecules but enriched more bio-refractory ones. • Kinetics and thermodynamics showed more favorable changes at lower conversion rates. • Ideal anaerobic digestion extent might maximize the subsequent pyrolytic efficiency. Anaerobic digestion (AD) combined with pyrolysis has been used as an innovative sludge-to-energy process that enhances energy recovery. This study investigated the different impacts of mesophilic and thermophilic AD on subsequent pyrolysis. The pyrolysis characteristics, kinetics, and thermodynamics of raw sludge (RS) and digested sludge (DS) after both mesophilic and thermophilic AD were investigated using thermogravimetric analysis (TGA) and three kinetic models (Starink, Flynn–Wall–Ozawa, Kissinger–Akahira–Sunose). TGA results indicated that thermophilic AD reduced the weight loss from 71.2-75.6 % for RS to 55.0–59.1 % for DS, more considerably than mesophilic AD (reducing from 70.6-75.2 % to 61.3–69.5 %), indicating higher organic matter removal. Kinetic analysis showed that the activation energy (E) of RS and DS pyrolysis ranged from 128.9 to 399.9 kJ/mol and 117.3 to 470.4 kJ/mol, respectively. Mesophilic AD generally increased the E, while thermophilic AD did not markedly alter E at low conversion rates (0.2–0.5) but increased it at high conversion rates (0.6–0.8), changing from 203.7–399.9 kJ/mol for RS to 248.9–470.4 kJ/mol for DS. Thermodynamic analysis showed that mesophilic AD generally enhanced pyrolysis favorability and reactivity but impeded activated complex formation. Thermophilic AD enhanced favorability and favored complex formation at low conversion rates but hindered it at high conversion rates. Reactivity varied with thermophilic AD extent, with excessive AD reducing reactivity. Pyrolysis–gas chromatography/mass spectrometry analysis confirmed that AD, on the one hand, decomposed biodegradable organics into low-molecular-weight organics, retained them in the DS, and facilitated subsequent pyrolysis. On the other hand, AD could accumulate large bio-refractory molecules, rendering DS less prone to pyrolytic decomposition. This effect of thermophilic AD was more significant than that of mesophilic AD. Given more favorable change was observed in kinetics and thermodynamics at lower conversion rates, low-temperature pyrolysis to produce biochar might be a promising strategy for DS treatment. The insights gained in this study may guide the optimization of AD conditions to maximize the efficiency of subsequent pyrolysis, providing more insight into the thermochemical conversion of DS and pyrolysis design. [ABSTRACT FROM AUTHOR]

Reuse of leachates by recycling them for composting is part of the circular economy. However, directly returning compost leachates to the mixture might increase the concentration of contaminants in the stabilized mass. The application of the ultrasonic modification of leachate was aimed at increasing the activity of microorganisms and the availability of nutrients, and reducing the number of pathogenic species. The purpose of the work was to determine the impact of variable ultrasonic (time and amplitude) field parameters on the biochemical properties, and number of selected groups of microorganisms, of leachates from a composting process. The tests used short sonication times of 15, 30, 60, 90, and 120 s and vibration amplitudes of 15.25, 30.5, and 46 µm. The assessment was made on the basis of changes in numbers of microbial communities (mesophilic, thermophilic, Escherichia coli, Salmonella spp. and fungi) and enzymatic activity (dehydrogenases-DHA), as well as respiratory activity (AR). Based on the conducted research, it was found that the leachate sonication time of 60 s and amplitude 30.5 µm were the most effective. The above parameters were considered borderline, above which there were no significant differences in the values of the analyzed indicators. [ABSTRACT FROM AUTHOR]

Prokaryotic Argonautes (pAgos) from mesophilic bacteria are attracting increasing attention for their genome editing potential. So far, it has been reported that KmAgo from Kurthia massiliensis can utilize DNA and RNA guide of any sequence to effectively cleave DNA and RNA targets. Here we find that three active pAgos, which have about 50% sequence identity with KmAgo, possess typical DNA-guided DNA target cleavage ability. Among them, RsuAgo from Rummeliibacillus suwonensis is mainly explored for which can cleave both DNA and RNA targets. Interestingly, RsuAgo-mediated RNA target cleavage occurs only with short guide DNAs in a narrow length range (16–20 nt), and mismatches between the guide and target sequence greatly affect the efficiency of RNA target cleavage. RsuAgo-mediated target cleavage shows a preference for a guide strand with a 5′-terminal A residue. Furthermore, we have found that RsuAgo can cleave double-stranded DNA in a low-salt buffer at 37 °C. These properties of RsuAgo provide a new tool for DNA and RNA manipulation at moderate temperatures. [ABSTRACT FROM AUTHOR]

Anaerobic digestion is applied to recover energy from rice straw (RS) which is a lignocellulosic agricultural residue produced in huge quantities in Asia and Africa. Because of the high solids content of this feedstock, high solids anaerobic co-digestion in batch mode must be further investigated. In this study, optimal operating conditions for the anaerobic co-digestion of RS with cow dung (CD) in batch mode, with and without leachate recirculation, were assessed under mesophilic temperature conditions. Preliminary experiments carried out in 2 L batch reactors confirmed that the concentration of RS in the mixture of substrates S0, in g VSRS/kg of mixture is an important parameter. Only batch reactors with the lowest S0 values (29 g VSRS/kg) produced biogas and rest of the reactors followed a long lag phase. The use of digestate from a previous batch as an inoculum was investigated with S0 values of 29 and 55 g VSRS/kg. Use of the digestate with S0 of 29 g VSRS/kg improved both initial degradation kinetics and the methane yield measured after 60 days. However, at S0 of 55 g VSRS/kg, the degradation kinetics were affected and after two months, 32 % of the biodegradable organic matter could not be eliminated. When leachate recirculation was performed in 6L leach-bed reactors (LBRs) with S0 between 30 and 65 g VSRS/kg, the highest methane yield was recorded at the lowest S0 value. It can be concluded that under batch mode, an RS concentration around 30 g VSRS/kg may be recommended for industrial applications. [ABSTRACT FROM AUTHOR]

Thermoduric bacteria are known to affect the quality of Cheddar cheese, with manifested defects including slits, weak body, and blowing. Thermoduric bacteria are likely to increase in numbers during cheese-making, as in-process conditions are conducive to proliferation. The present study was conducted to track thermoduric bacterial progression during an 18- to 20-h Cheddar cheese production run and during ripening when the pasteurizer was washed at midway through the production day. This study also correlated a broad range of chemical changes to the growth of thermoduric bacteria during ripening. Three independent cheese trials were performed at 3.5- ± 0.5-mo intervals. Samples were drawn in duplicates at 4 different times of the day: at the start of the run (vat 1), prior to a midday wash of the pasteurizer (vat 20), after the midday wash of the pasteurizer (vat 21), and at the end of the run (vat 42) for raw milk, pasteurized milk, and cheese. Cheeses were also tested during ripening for 6 mo. Results showed that raw milk total bacterial counts comprised 0.24% thermoduric mesophiles (TM) and 0.12% thermoduric thermophiles (TT). The thermoduric thermophilic bacterial counts increased by log 10 1.23 during the pasteurizer run of 9 to 10 h, indicating a buildup of thermoduric thermophilic bacteria during the pasteurization process itself. Midday washing reduced thermophilic counts by log 10 1.36, as evident by pre- and post-midday wash counts. However, a thermophilic buildup during post-midday wash was again noticed near the end of the 20-h run. We found that TT bacteria decreased in the first 60 d of ripening, whereas TM bacteria increased during the same period. However, TT bacteria increased later during 60 to 180 d of ripening. Bacillus licheniformis was the most frequently isolated bacteria in this study and was recovered at all production stages sampled during the cheese-making and ripening. We observed a significant increase in the level of orotic and uric acids in the vat made at the end of the day. No significant difference in the overall chemical composition, proteolysis, sugar, or other organic acids was observed in cheese made at the start versus the end of the production run. [ABSTRACT FROM AUTHOR]

• Digestion of the small particle size fraction of municipal waste was investigated. • Non-biodegradable molecules limited methane generation potential of substrate. • The absence of unreacted layer favoured degradation of more organics of waste. • Better mixing of substrate and microorganisms promoted methane generation. • Digestate of pilot reactor presented low stability and high heavy metal content. High-solid anaerobic digestion of the very small particle fraction of mechanically-sorted organic fraction of municipal solid waste (OFMSW) was examined in mesophilic digestion tests in a conventional laboratory (0.013 m3) and a pilot (0.300 m3) reactor. The non-biodegradable and recalcitrant molecules together with the low protein and starch contents of the small-particles of OFMSW limited the methane generation potential of substrate. In the conventional AD system, methane yields remained low at 0.139 m3kg VS -1 due to formation of a non-reacting layer on digestate surface, which restricted utilization of the available in OFMSW digestible organics. The absence of surface solid crust in the pilot unit favoured consumption of a greater proportion of volatile solids of the OFMSW. Dry AD was remarkably stable over the entire period and negligibly effected by the toxic H 2 S yields. Methane generation (0.167 m3kg VS -1) was increased 1.2-fold compared to the conventional system due to a better mixing of substrate and microorganisms achieved inside the pilot reactor, which led to an increase of the digested volatile organics. Digestate presented low stability and high heavy metal content, both of which restrain its implementation as soil conditioner or fertilizer in agriculture. A secondary co-digestion treatment may be required for the neutralization of digestate. [ABSTRACT FROM AUTHOR]

This study aimed to compare the production of hydrogen and 1,3-propanediol from crude glycerol (10 g/L) in mesophilic (30 °C) and thermophilic (55 °C) anaerobic fluidized bed reactors, namely AFBR30 °C and AFBR55 °C, respectively, at hydraulic retention times (HRT) reduced from 8 to 1 h. In AFBR30 °C, the absence or low hydrogen yields can be attributed to the production of 1,3-propanediol (maximum of 651 mmol/mol glycerol), and the formation of caproic acid (maximum of 1097 mg/L) at HRTs between 8 and 2 h. In AFBR55 °C, the hydrogen yield of 1.20 mol H2/mol glycerol consumed was observed at the HRT of 1 h. The maximum yield of 1,3-propanediol in AFBR55 °C was equal to 804 mmol/mol glycerol at the HRT of 6 h and was concomitant with the production of hydrogen (0.87 mol H2/mol glycerol consumed) and butyric acid (1447 mg/L). [ABSTRACT FROM AUTHOR]

Abstract Biogas plants are a widespread renewable energy technology. However, the use of digestate for agronomic purposes has often been a matter of concern. It is controversial whether biogas plants might harbor some pathogenic clostridial species, which represent a biological risk. Moreover, the inhabitance of Clostridium hard-cheese spoiling species in anaerobic digesters can be problematic for hard-cheese manufacturing industries, due to the issue of cheese blowing defects. This study investigated the effect of mesophilic anaerobic digestion processes on the Clostridium consortia distribution over time. Specifically, three lab-scale CSTRs treating agricultural biomass were characterized by considering both the whole microbial community and the cultivable clostridial spores. It is assessed an overall reduction of the Clostridium genus during the anaerobic digestion process. Moreover, it was evidenced a slight, but steady decrease of the cultivable clostridial spores, mainly represented by two pathogenic species, C. perfringens and C. bifermentans, and one hard-cheese spoiling species, C. butyricum. Thus, it is revealed an overall reduction of the clostridial population abundance after the mesophilic anaerobic digestion treatment of agricultural biomass.