Digestion Of Bacteria Research Articles

Advancing the treatment of low carbon-to-nitrogen ratio municipal wastewater using a novel microaerobic sludge bed approach: Insights into enhanced performance and functional microbial community

Microaerobic sludge bed systems could align with low-energy, reasonable carbon-nitrogen (C/N) ratio, and synchronous removal objectives during wastewater treatment. However, its ability to treat municipal wastewater (MW) with varying low C/N ratio, low NH4+ concentration, along with managing sludge bulking and loss are still unclear. Against this backdrop, this study investigated the performance of an Upflow Microaerobic Sludge Bed Reactor (UMSR) treating MW characterized by varying low C/N ratios and low NH4+ concentrations. The study also thoroughly examined associated sludge bulking and loss, pollutant removal efficiencies, sludge settleability, microbial community structures, functional gene variations, and metabolic pathways. Findings revealed that the effluent NH4+-N concentration gradually decreased to 0 mg/L with a decrease in the C/N ratio, whereas the effluent COD was unaffected by the influent, maintaining a concentration below 50 mg/L. Notably, TN removal efficiency reached 90% when C/N ratio was 3. The decrease in the C/N ratio (C/N ratio was 1) increased microbial community diversity, with abundances of AOB, AnAOB, aerobic denitrifying bacteria, and anaerobic digestion bacteria reaching 8.34%, 0.96%, 5.07%, and 9.01%, respectively. Microorganisms' metabolic pathways significantly shifted, showing increased carbohydrate and cofactor/vitamin metabolism and decreased amino acid metabolism and xenobiotic biodegradation. This study not only provides a solution for the effluent of different pre-capture carbon processes but also demonstrates the UMSR's capability in managing low C/N ratio municipal wastewater and emphasizes the critical role of microbial community adjustments and functional gene variations in enhancing nitrogen removal efficiency.

Effect of biochar addition on the anaerobic digestion of food waste: microbial community structure and methanogenic pathways.

This study assessed the effects of the addition of biochar prepared at 700 °C with different dosages on the anaerobic digestion of food waste. The biochar addition at a concentration of 10.0 g/L increased the cumulative methane yield by 128%, and daily methane production was also significantly promoted. The addition of biochar derived from poplar sawdust significantly increased the relative abundance of dominant bacteria for anaerobic digestion by 85.54-2530% and promoted the degradation of refractory organic matter and the transfer of materials between the hydrolysis and acid production stages. Further analysis has demonstrated that Bathyarchaeia and hydrogenotrophic methanogens were enriched by the biochar addition. Meanwhile, the relative abundances of functional genes, including C5-branched dibasic acid metabolism, and pyruvate metabolism, were increased by 11.38-26.27%. The relative abundances of genes related to major amino acid metabolism, including histidine metabolism, lysine biosynthesis, and phenylalanine, tyrosine, and tryptophan biosynthesis, were increased by 11.96-15.71%. Furthermore, the relative abundances of genes involved in major replication and repair were increased by 14.76-22.76%, and the major folding, sorting, degradation, and translation were increased by 14.47-19.95%, respectively. The relative abundances of genes related to major membrane transport and cell motility were increased by 10.02 and 83.09%, respectively.

Shrimp Digestive Bacteria Performance for Shrimp Waste Chitin Extraction

Generally, chitin is isolated chemically. An environmentally friendly alternative to chitin extraction is enzymatic extraction. The research aims to determine the effectiveness and optimum conditions for enzymatic chitin extraction of shrimp waste (heads, shells, and tails) using lactic acid bacteria (LAB) and proteolytic bacteria from the shrimp's digestive tract (faeces and intestines). The research stages were isolation, enrichment, and determining shrimp digestion's bacterial colonies, microscopic identification of shrimp digestive bacteria, and determining the effectiveness and optimal conditions for shrimp waste's chitin isolation. Aerobic and Anaerobic Total Plate Count (TPC), LAB, and proteolytic bacteria from shrimp's digestive tract per gram of sample were respectively 5.52 and 5.59 log CFU; 4.76 and 4.56 log CFU; 6.46 and 6.20 log CFU. Microscopic morphology shows that LAB and proteolytic bacteria of shrimp digestive are gram-positive as cocci or rods. The deproteinization value of shrimp waste reached 31%, especially for treatment with a pH of 5.0–7.0 (during proteolytic bacteria fermentation) and pre-treatment of boiling, drying and coarse grinding of shrimp waste (PP2) before extraction. However, the demineralization value of shrimp waste is only 4.5% (PP1) and 3% (PP2), with LAB as the primary fermentation agent because proteolytic bacteria have been unable to reduce the mineral content in shrimp waste further.

Malakoplakia of the Endometrium: A Rare Unexpected Disease Raising Clinical Concern for Malignancy.

Malakoplakia is a rare disease that manifests as a histiocytic inflammatory process and most often occurs in the urinary bladder. It is caused by an impaired capacity of histiocytes to kill and digest bacteria. The typical histopathologic findings are sheets of histiocytes with granular eosinophilic cytoplasm and characteristic Michaelis-Gutmann bodies, spherical bodies with a targetoid appearance. Malakoplakia is even rarer in the gynecologic tract, and our literature search found only 21 published patients of malakoplakia involving the endometrium. Here we report a 60-year-old female patient who presented with recurrent pelvic infections and postmenopausal bleeding, which raised concern for an endometrial malignancy. Hysterectomy with salpingo-oophorectomy revealed malakoplakia involving the endometrium and also the right ovary. Michaelis-Gutmann bodies were visible on the intraoperative frozen section that was performed to rule out an endometrial malignancy. We summarize the clinicopathologic findings of the published patients of endometrial malakoplakia.

Unveiling the microbial dynamics in vermicomposting with coir pith as earthworm substrate

This study explored the impact of incorporating coir pith, a byproduct of the coconut industry, into the vermicomposting substrate of Eudrilus eugeniae earthworms. The groups were compared based on their diets: cow manure only or cow manure mixed with varying amounts of coir pith. The aim was to assess the effects of coir pith on earthworm growth, mortality and the microbial community involved in vermicomposting. Earthworms fed with higher proportions of coir pith (70 % w/w) experienced reduced growth (0.81 g/worm) and increased mortality (24.67 %) after 5 weeks of vermicomposting. These effects were attributed to the high level of total phenolic content in the system. Coir pith required specific bacteria for digestion and detoxification, and excessive intake disrupted the earthworms' digestion, thus hindering nutrient absorption. The study also examined the microbial composition of the vermicast samples and identified variations based on the diet. Bacterial taxa involved in lignocellulose degradation, such as Bacteriodota, Azospirillum, Chitinophagaceae, Marinomonas and Pantoea, exhibited decreased abundances in treatments with coir pith. Conversely, the abundances of potentially harmful bacteria, such as Aeromonas, increased with higher coir pith inclusion levels. This pioneering investigation sheds light on the feasibility of coir pith use in vermicomposting and emphasises the importance of optimising earthworm diets to enhance microbial ecological functions and improve vermicompost quality.

Microplastics Enhance the Prevalence of Antibiotic Resistance Genes in Anaerobic Sludge Digestion by Enriching Antibiotic-Resistant Bacteria in Surface Biofilm and Facilitating the Vertical and Horizontal Gene Transfer.

Antibiotic resistance genes (ARGs) and microplastics (MPs) are recognized as emerging contaminants and threats to global human health. Despite both of them being significantly detected in their "hotspots", i.e., waste activated sludge (WAS), rare studies on how MPs affect ARGs and antibiotic-resistant bacteria (ARB) in anaerobic sludge digestion are available. Herein, the fate of ARGs and ARB after exposure to MPs of three dosages (10, 30, and 80 particles/g-TS), three polymer types (LDPE, PET, and PS), and three branching extents (LDPE, LLDPE, and HDPE) in anaerobic sludge digestion was investigated. Metagenomic results indicated that all variants of MPs resulted in an increase of the relative abundance of ARGs in the digester compared to the control. The abundance of ARGs demonstrated a dosage-dependent relationship within the range from 10 to 80 particles/g-TS, resulting in an increase from 4.5 to 27.9% compared to the control. Branching structure and polymer type influence ARG level in the sludge digester as well. Mechanism studies revealed that LDPE selectively enriched potential ARB and ARGs in the surface biofilm, possibly creating a favorable environment for ARB proliferation and ARG exchange. Furthermore, vertical transfer of ARGs was facilitated by LDPE through increasing bacterial cell proliferation accompanied by the enhancement of relevant functional genes. The elevated abundance of mobile genetic elements (MGEs) and ARGs-carrying plasmids also demonstrated that MGE-mediated horizontal transfer was promoted by LDPE at 80 particles/g-TS. This effect was compounded by increased oxidative stress, cell membrane permeability, and cell cohesion, collectively facilitating horizontal ARG transfer. Consequently, both vertical and horizontal transfer of ARGs could be concurrently promoted by LDPE an in anaerobic sludge digester.

Short-Term Alternate Feeding between Terrestrially Sourced Oil- and Fish Oil-Based Diets Modulates the Intestinal Microecology of Juvenile Turbot.

A nine-week feeding trial was conducted to investigate changes in the intestinal microbiota of turbot in response to alternate feeding between terrestrially sourced oil (TSO)- and fish oil (FO)-based diets. The following three feeding strategies were designed: (1) continuous feeding with the FO-based diet (FO group); (2) weekly alternate feeding between soybean oil (SO)- and FO-based diets (SO/FO group); and (3) weekly alternate feeding between beef tallow (BT)- and FO-based diets (BT/FO group). An intestinal bacterial community analysis showed that alternate feeding reshaped the intestinal microbial composition. Higher species richness and diversity of the intestinal microbiota were observed in the alternate-feeding groups. A PCoA analysis showed that the samples clustered separately according to the feeding strategy, and among the three groups, the SO/FO group clustered relatively closer to the BT/FO group. The alternate feeding significantly decreased the abundance of Mycoplasma and selectively enriched specific microorganisms, including short-chain fatty acid (SCFA)-producing bacteria, digestive bacteria (Corynebacterium and Sphingomonas), and several potential pathogens (Desulfovibrio and Mycobacterium). Alternate feeding may maintain the intestinal microbiota balance by improving the connectivity of the ecological network and increasing the competitive interactions within the ecological network. The alternate feeding significantly upregulated the KEGG pathways of fatty acid and lipid metabolism, glycan biosynthesis, and amino acid metabolism in the intestinal microbiota. Meanwhile, the upregulation of the KEGG pathway of lipopolysaccharide biosynthesis indicates a potential risk for intestinal health. In conclusion, short-term alternate feeding between dietary lipid sources reshapes the intestinal microecology of the juvenile turbot, possibly resulting in both positive and negative effects.

Superoxide: The enigmatic chemical chameleon in neutrophil biology.

The burst of superoxide produced when neutrophils phagocytose bacteria is the defining biochemical feature of these abundant immune cells. But 50 years since this discovery, the vital role superoxide plays in host defense has yet to be defined. Superoxide is neither bactericidal nor is it just a source of hydrogen peroxide. This simple free radical does, however, have remarkable chemical dexterity. Depending on its environment and reaction partners, superoxide can act as an oxidant, a reductant, a nucleophile, or an enzyme substrate. We outline the evidence that inside phagosomes where neutrophils trap, kill, and digest bacteria, superoxide will react preferentially with the enzyme myeloperoxidase, not the bacterium. By acting as a cofactor, superoxide will sustain hypochlorous acid production by myeloperoxidase. As a substrate, superoxide may give rise to other forms of reactive oxygen. We contend that these interactions hold the key to understanding the precise role superoxide plays in neutrophil biology. State-of-the-art techniques in mass spectrometry, oxidant-specific fluorescent probes, and microscopy focused on individual phagosomes are needed to identify bactericidal mechanisms driven by superoxide. This work will undoubtably lead to fascinating discoveries in host defense and give a richer understanding of superoxide's varied biology.

The 3-D optimization of an axial mixer propeller through high fidelity simulations

Homogeneous mixing is an important process quality indicator in biogas fermenters for introducing fresh organic feed material to certain bacteria groups such as methanogenic bacteria for anaerobic digestion. Energy consumption for mixing processes is one of the highest operational costs in biogas plants. Thus, it is crucial to carefully consider the energy expenditure per generated thrust (the first performance metric of an axial mixer) for a biogas mixer, since biogas plants are considered as a net carbon zero energy plant. There are several different types of mixers. Axial mixers both high speed and low speed together with paddle mixers are most common among various types of mixers used in fermenter tanks. In this study it is planned to improve conventional axial biogas mixer efficiency using computer aided engineering tools for design and optimization. This goal will be achieved by using a parametric design strategy for blade geometry together with the open source CFD analysis suite OpenFOAM for measuring performance metrics (i.e. power, torque, and thrust). The most efficient design will be chosen from a set of design candidates residing inside a reasonably large parametric state space, via maximizing the thrust to power ratio.

Methods for Intensifying Biogas Production from Waste: A Scientometric Review of Cavitation and Electrolysis Treatments

This article presents future trends in research using microbiological methods to intensify bioprocesses for biogas production. The pretreatment by combinations of physical and chemical methods, such as cavitation and electrolysis, is considered. The approach of the article involved reviewing the residual area on the intensification technologies of anaerobic digestion with current methods to improve the quality and quantity of biogas. The most valuable reported positive results of the pretreatment of biological raw materials in the cavitation process were reviewed and are presented here. A model of the effect of electrolysis on the species diversity of bacteria in anaerobic digestion was developed, and changes in the dominance of the ecological and trophic systems were revealed on the basis of previous studies. The stimulating effect on biogas yield, reduction in the stabilization period of the reactor, and inactivation of microorganisms at lower temperatures is associated with different pretreatment methods that intensify anaerobic digestion. More research is recommended to focus on the electrolysis treatment of different types of waste and their ratios with optimization of regime parameters, as well as in combination with other pretreatments to produce biomethane and biohydrogen in larger quantities and in better qualities.

Prophylactic sequential antibiotic therapy for recurrent liver/biliary sepsis

Background and AimsRecurrent liver/biliary sepsis are rare and can occur in different situations. Curative treatment of acute septic episodes is based on antibiotics. Nevertheless, recurrent sepsis can be life-threatening, and the treatment of the underlying disease could be complex, and eventually not possible. The aim of the present study was to report our experience on prophylactic sequential antibiotic therapy for recurrent liver/biliary sepsis in a large cohort of patients with long follow-up. MethodsAll patients who received a prophylactic sequential antibiotic therapy for recurrent liver/biliary sepsis in our institution from 2005 to 2020 were included. Prophylactic sequential antibiotic therapy was based on per os antibiotics with expected antibacterial activity on digestive bacteria, mainly Gram-negative bacilli. The primary end-point was the reduction of the number of septic episodes to 1 or less episode per year, and not severe (not requiring hospitalization). ResultsWere included 33 adult patients and the main initial disease/condition leading to prophylaxis was history of hepaticojejunostomy (78.8%). The majority of septic episodes required hospitalization (57.6%). First line prophylactic sequential antibiotic therapy was weekly ciprofloxacin in all cases. First line therapy was successful in the long-term in 19 patients (57.6%), with a median follow-up of 92 months (range: 25-206). Global efficacy (first-second-third lines) was 28/33 (84.8%). ConclusionsThe results of the present study with very long follow-up suggest that prophylactic sequential antibiotic therapy can successfully prevent recurrent liver/biliary sepsis with good tolerance.

The dose makes the poison: feeding of antibiotic-treated winter honey bees, Apis mellifera, with probiotics and b-vitamins

Honey stores of Apis mellifera colonies are replaced with sugar water by beekeepers, which may result in malnutrition. Nutritional supplements have been developed, but the importance of bacterial probiotics and vitamins is poorly understood. Given that supplementary feeding with vitamins and probiotics may enhance worker weight and longevity, this might suggest a feasible approach to mitigate winter colony losses. Here, we conducted a laboratory hoarding cage study with freshly emerged winter bees, which were treated with the antibiotic tetracycline to reduce gut bacteria obtained post-emergence and subsequently assigned to feeding regimes: sucrose only, sucrose + pollen, probiotics (low and high dosage), probiotics + pollen (low and high dosage), or b-vitamins (low and high dosage) (N = 8 treatments, 29 workers/cage × 8 replicates). In parallel, another age cohort of bees remained on their frame (= Frame) to establish their gut microbiota and were subsequently fed with sucrose only or sucrose + pollen (N = 2 treatments, 29 workers/cage × 4 replicates). The most beneficial effects on body weights were found in workers given ad libitum access to pollen, notably in the Frame Sucrose + Pollen group, confirming the inherent importance of post-emergent gut flora inoculation and the role of gut bacteria in protein digestion. Furthermore, both Frame groups and the antibiotic-treated workers fed with probiotic low + pollen survived longer than all other groups, highlighting a fundamental host-microbial relationship. On the other hand, our current treatments alone, post-tetracycline, did not yield any positive results. In contrast, high dosages of both probiotic and b-vitamins significantly reduced lifespan compared to their low concentration counterparts, probably due to dysbiosis and toxicity, suggesting that the outcome was dose-dependent. These results highlight that bacterial and b-vitamin supplementation can alter longevity with advisable caution since harmful concentrations appear to exist.

Relationships Between Diurnal Changes of Tongue Coating Microbiota and Intestinal Microbiota.

The oral cavity and the intestine are the main distribution locations of human digestive bacteria. Exploring the relationships between the tongue coating and gut microbiota, the influence of the diurnal variations of the tongue coating microbiota on the intestinal microbiota can provide a reference for the development of the disease diagnosis and monitoring, as well as the medication time. In this work, a total of 39 healthy college students were recruited. We collected their tongue coating microbiota which was collected before and after sleep and fecal microbiota. The diurnal variations of tongue coating microbiota are mainly manifested on the changes in diversity and relative abundance. There are commensal bacteria in the tongue coating and intestines, especially Prevotella which has the higher proportion in both sites. The relative abundance of Prevotella in the tongue coating before sleep has a positive correlation with intestinal Prevotella; the r is 0.322 (p < 0.05). Bacteroides in the intestine had the most bacteria associated with the tongue coating and had the highest correlation coefficient with Veillonella in the oral cavity, which was 0.468 (p < 0.01). These results suggest that the abundance of the same flora in the two sites may have a common change trend. The SourceTracker results show that the proportion of intestinal bacteria sourced from tongue coating is less than 1%. It indicates that oral flora is difficult to colonize in the intestine in healthy people. This will provide a reference for the study on the oral and intestinal microbiota in diseases.

Optimization of Biomethane Production via Fermentation of Chicken Manure Using Marine Sediment: A Modeling Approach Using Response Surface Methodology

In this study, marine sediment (MS) was successfully used as a source of methanogenic bacteria for the anaerobic digestion (AD) of chicken manure (CM). Using MS showed high production in liquid and semi-solid conditions. Even in solid conditions, 169.3 mL/g volatile solids of chicken manure (VS-CM) was produced, despite the accumulation of ammonia (4.2 g NH3-N/kg CM). To the best of our knowledge, this is the highest methane production from CM alone, without pretreatment, in solid conditions (20%). Comparing MS to Ozouh sludge (excess activated sewage sludge) (OS), using OS under semi-solid conditions resulted in higher methane production, while using MS resulted in more ammonia tolerance (301 mL/gVS-CM at 8.58 g NH3-N/kg). Production optimization was carried out via a response surface methodology (RDM) model involving four independent variables (inoculum ratio, total solid content, NaCl concentration, and incubation time). Optimized methane production (324.36 mL/gVS-CM) was at a CM:MS ratio of 1:2.5 with no NaCl supplementation, 10% total solid content, and an incubation time of 45 days.

Effects of different antibiotic operation modes on anaerobic digestion of dairy manure: Focus on microbial population dynamics

The inhibition effect of four antibiotics, i.e. ampicillin (AMP), tylosin (TYL), florfenicol (FLO) and sulfamethazine (SMT), was investigated in dairy manure digesters for both single dosing and semi-continuous dosing operations over a period of 40 days. High throughput 16S rRNA sequence analysis revealed that dosing mode did have significant impact on microbial community, i.e. antibiotics had a notable effect on bacteria in single dosing digesters, while archaea were the major population affected in the semi-continuous dosing operations. FLO shows the most severe inhibition on biogas production and remarkably effected bacterial communities, which led to a complete upset of the whole community. Although the effect of SMT on biogas production was marginal, methanogens populations were notably shifted. A four-stage inhibition process on microbial community was proposed based on the ratio of the affected bacteria to archaea to shed new light on microbial population dynamics during anaerobic digestion. Moreover, we found that the semi-continuous operation mode of antibiotics is more efficient in terms of microbial community changes, which may guide the formulation of veterinary drug doses and cycle intervals.

Xylitol enhances synthesis of propionate in the colon via cross-feeding of gut microbiota

BackgroundXylitol, a white or transparent polyol or sugar alcohol, is digestible by colonic microorganisms and promotes the proliferation of beneficial bacteria and the production of short-chain fatty acids (SCFAs), but the mechanism underlying these effects remains unknown. We studied mice fed with 0%, 2% (2.17 g/kg/day), or 5% (5.42 g/kg/day) (weight/weight) xylitol in their chow for 3 months. In addition to the in vivo digestion experiments in mice, 3% (weight/volume) (0.27 g/kg/day for a human being) xylitol was added to a colon simulation system (CDMN) for 7 days. We performed 16S rRNA sequencing, beneficial metabolism biomarker quantification, metabolome, and metatranscriptome analyses to investigate the prebiotic mechanism of xylitol. The representative bacteria related to xylitol digestion were selected for single cultivation and co-culture of two and three bacteria to explore the microbial digestion and utilization of xylitol in media with glucose, xylitol, mixed carbon sources, or no-carbon sources. Besides, the mechanisms underlying the shift in the microbial composition and SCFAs were explored in molecular contexts.ResultsIn both in vivo and in vitro experiments, we found that xylitol did not significantly influence the structure of the gut microbiome. However, it increased all SCFAs, especially propionate in the lumen and butyrate in the mucosa, with a shift in its corresponding bacteria in vitro. Cross-feeding, a relationship in which one organism consumes metabolites excreted by the other, was observed among Lactobacillus reuteri, Bacteroides fragilis, and Escherichia coli in the utilization of xylitol. At the molecular level, we revealed that xylitol dehydrogenase (EC 1.1.1.14), xylulokinase (EC 2.7.1.17), and xylulose phosphate isomerase (EC 5.1.3.1) were key enzymes in xylitol metabolism and were present in Bacteroides and Lachnospiraceae. Therefore, they are considered keystone bacteria in xylitol digestion. Also, xylitol affected the metabolic pathway of propionate, significantly promoting the transcription of phosphate acetyltransferase (EC 2.3.1.8) in Bifidobacterium and increasing the production of propionate.ConclusionsOur results revealed that those key enzymes for xylitol digestion from different bacteria can together support the growth of micro-ecology, but they also enhanced the concentration of propionate, which lowered pH to restrict relative amounts of Escherichia and Staphylococcus. Based on the cross-feeding and competition among those bacteria, xylitol can dynamically balance proportions of the gut microbiome to promote enzymes related to xylitol metabolism and SCFAs.CGRfu2_UbvGGd6F7x5LTJkVideo

The impact and fate of clarithromycin in anaerobic digestion of waste activated sludge for biogas production

Clarithromycin retained in waste activated sludge (WAS) inevitably enters the anaerobic digestion system. So far, the complex impacts and fate of clarithromycin in continuous operated WAS anaerobic digestion system are still unclear. In this study, two semi-continuous long-term reactors were set up to investigate the effect of clarithromycin on biogas production and antibiotic resistance genes (ARGs) during WAS anaerobic digestion, and a batch test was carried out to explore the potential metabolic mechanism. Experimental results showed that clarithromycin at lower concentrations (i.e., 0.1 and 1.0 mg/L) did not affect biogas production, whereas the decrease in biogas production was observed when the concentration of clarithromycin was further increased to 10 mg/L. Correspondingly, the relative abundance of functional bacteria in WAS anaerobic digestion (i.e., Anaerolineaceae and Microtrichales) was reduced with long-term clarithromycin exposure. The investigation of ARGs suggested that the effect of methylation belonging to the target site modification played a critical role for the anaerobic microorganisms in the expression of antibiotic resistance, and ermF, played dominated ARGs, presented the most remarkable proliferation. In comparison, the role of efflux pump was weakened with a significant decrease of two detected efflux genes. During WAS anaerobic digestion, clarithromycin could be partially degraded into metabolites with lower antimicrobial activity including oleandomycin and 5-O-desosaminyl-6-O-methylerythronolide and other metabolites without antimicrobial activity.

Exploring the functional significance of novel cellulolytic bacteria for the anaerobic digestion of rice straw

The purpose of this study is to evaluate the potential of isolated novel bacterial strains for rice straw (RS) hydrolysis in terms of total sugar and COD (chemical oxygen demand) solubilization to improve overall biomethane yield. Four out of seven pretreatment setup with isolated bacterial strains i.e., Bacillus paralicheniformis VKVVG3 (CDf), Perlucidibaca piscinae VKVVG6 (CDd1), Bacillus clausii VKAK2 (RSa1) and Bacillus mojavensis VKAK1 (CDb1) exhibited higher saccharification compared to untreated RS. The CDf pretreated RS showed highest efficiency with 137% COD solubilization and 320% sugar accumulation at optimal dosage of 109 CFU/mL within 4-day of incubation. The batch reactor (20L) study with CDf pretreated RS produced 476 mL/g VSsubstrate compared to 310 mL/g VSsubstrate for untreated RS which corresponds to 53.6% higher than untreated RS. The FESEM, FTIR, and XRD analysis also support the overall results, indicating excellent degradation of the structural morphology of the RS microcrystalline structure. Furthermore, the fitting error in bio-kinetic parameters using modified Gompertz, Fitzhugh, and Monomolecular models were 5.47, 2.44, and 4.28% respectively, with R2 values above 0.99, also supports the experimental data. The results of this study revealed many positive interpretations concerning the future expansion of the existing system for bacterial pretreatment of RS.

Linking Bacterial Communities Associated with the Environment and the Ecosystem Engineer Orchestia gammarellus at Contrasting Salt Marsh Elevations

The digestive tract of animals harbors microbiota important for the host’s fitness and performance. The interaction between digestive tract bacteria and soil animal hosts is still poorly explored despite the importance of soil fauna for ecosystem processes. In this study, we investigated the interactions between the bacterial communities from the digestive tract of the litter-feeding, semi-terrestrial crustacean Orchestia gammarellus and those obtained from the environment; these organisms thrive in, i.e., soil and plant litter from salt marshes. We hypothesized that elevation is an important driver of soil and litter bacterial communities, which indirectly (via ingested soil and litter bacteria) influences the bacterial communities in the digestive tract of O. gammarellus. Indeed, our results revealed that elevation modulated soil and litter bacterial community composition along with soil organic matter content and the C:N ratio. Soil and plant litter differed in alpha diversity indexes (richness and diversity), and in the case of plant litter, both indexes increased with elevation. In contrast, elevation did not affect the composition of bacterial communities associated with O. gammarellus’ digestive tract, suggesting selection by the host, despite the fact that a large component of the bacterial community was also detected in external sources. Importantly, Ca. Bacilloplasma and Vibrio were highly prevalent and abundant in the host. The taxonomic comparison of Ca. Bacilloplasma amplicon sequence variants across the host at different elevations suggested a phylogenetic divergence due to host habitat (i.e., marine or semi-terrestrial), thus supporting their potential functional role in the animal physiology. Our study sheds light on the influence of the environment on soil animal–bacteria interactions and provides insights into the resilience of the O. gammarellus–associated bacteria to increased flooding frequency.

The synergistic strategy and microbial ecology of the anaerobic co-digestion of food waste under the regulation of domestic garbage classification in China

With the implementation of new domestic garbage classification policy in China, attention is growing to improve the treatment efficiency of municipal ‘wet’ waste. Combing with the new regulation, the synergistic strategy and the microbial ecology of the anaerobic co-digestion (AcoD) of cooked food waste (CFW), uncooked food waste (UCFW) and rice straw (RS) were analyzed in current study. Results showed that the maximum cumulative methane yield (CMY) and synergic index were obtained when CFW and UCFW were mixed at the ratio of 1:1 (based on volatile solid content). The highest CMY 452.94 ± 0.99 mL/g-VS was obtained when the ratio of CFW, UCFW and RS was 0.81:0.09:0.10, which was 16.29%, 36.20% and 121.84% higher than their mono-digestion, respectively. The AcoD promoted the methane potential by prolonging the release time of organic matter and slowing down the hydrolysis rate. Furthermore, the AcoD increased the species diversification and relative abundance of fermentation bacteria in digesters, and Methanosaeta predominated the methanogen communities. This study demonstrated a clean and sustainable AcoD strategy for safe disposal of urban food waste and revealed the variation of microbial community, which can provide a base for efficient bioenergy recovery from urban domestic garbage.