Response mechanisms of different Saccharomyces cerevisiae strains to succinic acid.

BACKGROUND: The production of succinic acid (SA) from biomass has attracted worldwide interest. Saccharomyces cerevisiae is preferred for SA production due to its strong tolerance to low pH conditions, ease of genetic manipulation, and extensive application in industrial processes. However, when compared with bacterial producers, the SA titers and productivities achieved by engineered S. cerevisiae strains were relatively low. To develop efficient SA-producing strains, it's necessary to clearly understand how S. cerevisiae cells respond to SA. RESULTS: In this study, we cultivated five S. cerevisiae strains with different genetic backgrounds under different concentrations of SA. Among them, KF7 and NBRC1958 demonstrated high tolerance to SA, whereas NBRC2018 displayed the least tolerance. Therefore, these three strains were chosen to study how S. cerevisiae responds to SA. Under a concentration of 20 g/L SA, only a few differentially expressed genes were observed in three strains. At the higher concentration of 60 g/L SA, the response mechanisms of the three strains diverged notably. For KF7, genes involved in the glyoxylate cycle were significantly downregulated, whereas genes involved in gluconeogenesis, the pentose phosphate pathway, protein folding, and meiosis were significantly upregulated. For NBRC1958, genes related to the biosynthesis of vitamin B6, thiamin, and purine were significantly downregulated, whereas genes related to protein folding, toxin efflux, and cell wall remodeling were significantly upregulated. For NBRC2018, there was a significant upregulation of genes connected to the pentose phosphate pathway, gluconeogenesis, fatty acid utilization, and protein folding, except for the small heat shock protein gene HSP26. Overexpression of HSP26 and HSP42 notably enhanced the cell growth of NBRC1958 both in the presence and absence of SA. CONCLUSIONS: The inherent activities of small heat shock proteins, the levels of acetyl-CoA and the strains' potential capacity to consume SA all seem to affect the responses and tolerances of S. cerevisiae strains to SA. These factors should be taken into consideration when choosing host strains for SA production. This study provides a theoretical basis and identifies potential host strains for the development of robust and efficient SA-producing strains.

Anaerobic digestion integrated with microbial electrolysis cell to enhance biogas production and upgrading in situ.

Anaerobic digestion (AD) is an effective and applicable technology for treating organic wastes to recover bioenergy, but it is limited by various drawbacks, such as long start-up time for establishing a stable process, the toxicity of accumulated volatile fatty acids and ammonia nitrogen to methanogens resulting in extremely low biogas productivities, and a large amount of impurities in biogas for upgrading thereafter with high cost. Microbial electrolysis cell (MEC) is a device developed for electrosynthesis from organic wastes by electroactive microorganisms, but MEC alone is not practical for production at large scales. When AD is integrated with MEC, not only can biogas production be enhanced substantially, but also upgrading of the biogas product performed in situ. In this critical review, the state-of-the-art progress in developing AD-MEC systems is commented, and fundamentals underlying methanogenesis and bioelectrochemical reactions, technological innovations with electrode materials and configurations, designs and applications of AD-MEC systems, and strategies for their enhancement, such as driving the MEC device by electricity that is generated by burning the biogas to improve their energy efficiencies, are specifically addressed. Moreover, perspectives and challenges for the scale up of AD-MEC systems are highlighted for in-depth studies in the future to further improve their performance.

Continuous thermophilic composting of distilled grain waste improved organic matter stability and succession of bacterial community.

Continuous thermophilic composting (CTC) is potentially helpful in shortening the composting cycle. However, its universal effectiveness and the microbiological mechanisms involved are unclear. Here, the physicochemical properties and bacterial community dynamics during composting of distilled grain waste in conventional and CTC models were compared. CTC accelerated the organic matter degradation rate (0.2 vs. 0.1 d-1) and shortened the composting cycle (24 vs. 65 d), mainly driven by the synergism of bacterial genera. Microbial analysis revealed that the abundance of Firmicutes was remarkably improved compared to that in conventional composting, and Firmicutes became the primary bacterial phylum (relative abundance >70 %) during the entire CTC process. Moreover, correlation analysis demonstrated that bacterial composition had a remarkable effect on the seed germination index. Therefore, controlling the composting process under continuous thermophilic conditions is beneficial for enhancing composting efficiency and strengthening the cooperation between bacterial genera.

Autoimmune Pancreatitis Surveillance: A Simplified MRI Protocol Versus a Comprehensive Pancreatic MRI Protocol.

RATIONALE AND OBJECTIVES: Magnetic resonance imaging (MRI) has good diagnostic performance and causes no radiation damage, making it an ideal tool for the autoimmune pancreatitis (AIP) surveillance. However, its time cost is high. This study aimed to evaluate (1) whether a simplified protocol (SP) of MRI for AIP surveillance provides information equivalent to the comprehensive protocol (CP) and (2) the time cost reductions associated with using an SP. MATERIALS AND METHODS: This retrospective single-institutional study included 40 patients with AIP with at least two contrast-enhanced MRI/magnetic resonance cholangiopancreatography studies. Two radiologists evaluated two imaging sets (CP/SP) per patient, independently. Intra- and inter-observer agreement in the evaluation of the pancreas and extrapancreatic organs involvement using the SP/CP in addition to the time cost differences between the SP and CP were assessed. Intra- and inter-rater reliability were assessed using Cohen's kappa test, intraclass correlations, or the weighted kappa test. The differences in time costs between the CP and SP were compared using the Mann-Whitney U test or Wilcoxon signed-rank test. RESULTS: The SP had strong intra- and inter-observer agreement with the CP in evaluating MRI parameters (κ ï¼ž 0.60, moderate to excellent) and disease activity status (κ ï¼ž 0.80, all excellent). The overall image acquisition time cost for the SP was 49.2% of the CP. For the two radiologists, the image interpretation time cost of the SP was reduced by approximately 35% and 27% compared to the CP. CONCLUSION: For AIP surveillance, SP MRI provides information consistent with the CP and is less time-consuming.

Different responses of mesophilic and thermophilic anaerobic digestion of waste activated sludge to PVC microplastics.

The effect of microplastics (MPs) retained in waste activated sludge (WAS) on anaerobic digestion (AD) performance has attracted more and more attention. However, their effect on thermophilic AD remains unclear. Here, the influence of polyvinyl chloride (PVC) MPs on methanogenesis and active microbial communities in mesophilic (37 °C) and thermophilic (55 °C) AD was investigated. The results showed that 1, 5, and 10 mg/L PVC MPs significantly promoted the cumulative methane yield in mesophilic AD by 5.62%, 7.36%, and 8.87%, respectively, while PVC MPs reduced that in thermophilic AD by 13.30%, 18.82%, and 19.99%, respectively. Moreover, propionate accumulation was only detected at the end of thermophilic AD with PVC MPs. Microbial community analysis indicated that PVC MPs in mesophilic AD enriched hydrolytic and acidifying bacteria (Candidatus Competibacter, Lentimicrobium, Romboutsia, etc.) together with acetoclastic methanogens (Methanosarcina, Methanosaeta). By contrast, most carbohydrate-hydrolyzing bacteria, propionate-oxidizing bacterium (Pelotomaculum), and Methanosarcina were inhibited by PVC MPs in thermophilic AD. Network analysis further suggested that PVC MPs significantly changed the relationship of key microorganisms in the AD process. A stronger correlation among the above genera occurred in mesophilic AD, which may promote the methanogenic performance. These results suggested that PVC MPs affected mesophilic and thermophilic AD of WAS via changing microbial activities and interaction.

Valorizing kitchen waste to produce value-added fertilizer by thermophilic semi-continuous composting followed by static stacking: Performance and bacterial community succession analysis.

To explore an effective decentralized kitchen waste (KW) treatment system, the performance and bacterial community succession of thermophilic semi-continuous composting (TSC) of KW followed by static stacking (SS) was studied. A daily feeding ratio of 10% ensured stable performance of TSC using an integrated automatic reactor; the efficiencies of organic matter degradation and seed germination index (GI) reached 80.88% and 78.51%, respectively. SS for seven days further promoted the quality of the compost by improving the GI to 91.58%. Alpha- and beta-diversity analyses revealed significant differences between the bacterial communities of TSC and SS. Firmicutes, Actinobacteria, Chloroflexi, Gemmatimonadetes, and Myxococcota were dominant during the TSC of KW, whereas the members of Proteobacteria and Bacteroidetes responsible for product maturity rapidly proliferated during the subsequent SS and ultimately dominated the compost with Firmicutes and Actinobacteria. These results provide new perspectives for decentralized KW treatment using TSC for practical applications.

Evaluation of physicochemical properties, bacterial community, and product fertility during rice straw composting supplemented with different nitrogen-rich wastes.

This study evaluated the compostability of rice straw as the main feedstock (75 % in dry weight), supplemented with three different nitrogen-rich wastes, namely food waste (FW), dairy manure (DM), and sewage sludge (SS). Organic matter (OM) degradation, maturity and fertility of the end-product, and bacterial community structure during the composting processes were compared. All composting processes generated mature end-product within 51 days. Notably, FW addition was more effective to accelerate rice straw OM degradation and significantly improved end-product fertility with a high yield of Chinese cabbage. The succession of the bacterial community was accelerated with FW supplementation. Genera Geobacillus, Chryseolinea, and Blastocatella were significantly enriched during the composting of rice straw with FW supplementation. Finally, temperature, total nitrogen, moisture, pH, and total carbon were the key factors affecting microorganisms. This study provides a promising alternative method to enhance the disposal of larger amounts of rice straw in a shorter time.

The responses of mesophilic and thermophilic anaerobic digestion of municipal sludge to periodic fluctuation disturbance of organic loading rate.

Fluctuation disturbance of organic loading rate (OLR) is common in actual anaerobic digestion (AD), but its effects on AD of municipal sludge gets little attention. This study investigated the responses of reactor performance and active microbial community in mesophilic and thermophilic AD of municipal sludge before, during and after OLR periodic fluctuation disturbance. The performance of both reactors were similar before and after disturbance although some parameter values changed during the disturbance, which indicated their enough buffer capacity to OLR periodic fluctuation. Different microbial community at RNA level was observed in the two reactors. When the OLR disturbance commenced, the microbial community changed greatly in thermophilic AD. Error and attack tolerance of the microbial network was analyzed in order to learn the response mechanisms to OLR disturbance. The results assisted that the thermophilic microbial community was more vulnerable, but the reactor performance of which could be maintained using the functional redundancy strategy under OLR fluctuation disturbance.

Thermophilic semi-continuous composting of kitchen waste: Performance evaluation and microbial community characteristics.

This study evaluated the feasibility, system stability, and microbial community succession of thermophilic semi-continuous composting of kitchen waste (KW). The results revealed that treatment performance was stable at a 10 % feeding ratio, with an organic matter (OM) degradation efficiency of 81.5 % and seed germination index (GI) of 50.0 %. Moreover, the OM degradation efficiency and GI were improved to 83.4 % and 70.0 %, respectively, by maintaining an optimal compost moisture content (50-60 %). However, feeding ratios of ≥ 20 % caused deterioration of the composter system owing to OM overloading. Microbial community analysis revealed that Firmicutes, Actinobacteria, Chloroflexi, Proteobacteria, and Gemmatimonadetes were dominant. Additionally, moisture regulation significantly increased the Proteobacteria abundance by 57.1 % and reduced the Actinobacteria abundance by 57.8 %. Moreover, network analysis indicated that the bacterial community stability and positive interactions between genera were enhanced by moisture regulation. This information provides a useful reference for practical KW composting treatment in the semi-continuous mode.

Microbial communities in crude oil phase and filter-graded aqueous phase from a Daqing oilfield after polymer flooding.

AIMS: The aim was to characterize indigenous micro-organisms in oil reservoirs after polymer flooding (RAPF). METHODS: The microbial communities in the crude oil phase (Oil) and in the filter-graded aqueous phases Aqu0.22 (>0.22 µm) and Aqu0.1 (0.1-0.22 µm) were investigated by 16S rRNA gene high-throughput sequencing. RESULTS: Indigenous micro-organisms related to hydrocarbon degradation prevailed in the three phases of each well. However, obvious differences in bacterial compositions were observed amongst the three phases of the same well and amongst the same phase of different wells. The crude oil and Aqu0.22 shared many dominant bacteria. Aqu0.1 contained a unique bacterial community in each well. Most bacteria in Aqu0.1 were affiliated to culturable genera, suggesting that they may adapt to the oil reservoir environment by reduction of cell size. Contrary to the bacterial genera, archaeal genera were similar in the three phases but varied in relative abundances. The observed microbial differences may be driven by specific environmental factors in each oil well. CONCLUSIONS: The results suggest an application potential of microbial enhanced oil recovery (MEOR) technology in RAPF. The crude oil and Aqu0.1 contain many different functional micro-organisms related to hydrocarbon degradation. Both should not be overlooked when investing and exploring the indigenous micro-organisms for MEOR. SIGNIFICANCE AND IMPACT OF THE STUDY: This work facilitates the understanding of microbial community structures in RAPF and provides information for microbial control in oil fields.

The impacts of carbon emissions and voluntary carbon disclosure on firm value.

Investors and other stakeholders are starting to pay attention to firms' carbon emissions and carbon disclosure. This study investigated the effects of voluntary carbon disclosure information and carbon emissions on firm value from listed companies in the Shanghai and Shenzhen 300 (CSI 300) Index. We also apply the Probit model to predict the probability of voluntary carbon disclosure information. The results indicate that the increase in carbon emissions has a negative impact on firm value. The action that companies select to disclose carbon emissions has a positive impact on firm value. The effect of leverage ratio on VCDI is increasing year by year. What is more, the probability of the average size firm carbon disclosure was 30.73% in 2020. Company management needs to pay attention to the risks caused by carbon emissions and ensure the quality of carbon disclosure information, especially the authenticity and reliability of the information.

Production of volatile fatty acid from fruit waste by anaerobic digestion at high organic loading rates: Performance and microbial community characteristics.

This study examined the performance and microbial community dynamics of an anaerobic volatile fatty acid (VFA) production reactor for treating fruit waste by stepwise increasing organic loading rates (OLRs) from 8 to 24 g volatile total solids (VTS)/(L·d). Results showed that higher VFA concentrations of 52.25-61.90 g chemical oxygen demand (COD)/L can be maintained at each OLR, thereby resulting to a production of 0.70-0.76 g chemical oxygen demand (COD)VFA/g VTS. Notably, an increase in OLR from 8 to 14 g VTS/(L·d) was beneficial for achieving higher VFA concentrations and yields. Moreover, an increase in OLR affected the VFA distribution significantly; acetate and butyrate became dominant in the fermentation liquid at OLRs ≥ 14 g VTS/(L·d). Microbial community dynamics analysis revealed that phyla Firmicutes and Actinobacteriota were predominant at each OLR, and the genera Lactobacillus, Clostridium_sensu_stricto_12, and Caproiciproducens were closely related to anaerobic VFA production.

Effect of distillery sewage sludge addition on performance and bacterial community dynamics during distilled grain waste composting.

This study evaluated the dynamics of physicochemical characteristics and bacterial communities during the co-composting of distilled grain waste (DGW) and distillery sewage sludge (SS), with DGW mono-composting as a control. Results showed that co-composting with SS significantly improved DGW degradation efficiency (61.38% vs. 54.13%) and end-product quality (seed germination index: 129.82% vs. 113.61%; N + P2O5 + K2O: 9.08% vs. 5.28%), compared to DGW mono-composting. Microbial community analysis revealed that co-composting accelerated the bacterial community succession rate and enhanced the abundance of the phyla Proteobacteria, Firmicutes, Chloroflexi, and Deinococcota by 45.86%, 4.38%, 37.49%, and 15.29%, respectively. Network analysis showed that DGW-SS co-composting altered the interactions among the bacterial genera and improved bacterial community stability. Spearman correlation analysis indicated that the correlation between bacterial genera and environmental factors was more significant in DGW-SS co-composting. Therefore, co-composting of DGW and SS is a suitable strategy for the treatment of solid byproducts from spirit distilleries.

Bacterial Community Structure and Metabolic Function Succession During the Composting of Distilled Grain Waste.

Distilled grain waste (DGW) can be converted to organic fertilizer via aerobic composting process without inoculating exogenous microorganisms. To illustrate the material conversion mechanism, this study investigated the dynamic changes of bacterial community structure and metabolic function involved in DGW composting. Results showed that a significant increase in microbial community alpha diversity was observed during DGW composting. Moreover, unique community structures occurred at each composting stage. The dominant phyla were Firmicutes, Proteobacteria, Actinobacteriota, Bacteroidota, Myxococcota, and Chloroflexi, whose abundance varied according to different composting stages. Keystone microbes can be selected as biomarkers for each stage, and Microbispora, Chryseolinea, Steroidobacter, Truepera, and Luteimonas indicating compost maturity. Co-occurrence network analysis revealed a significant relationship between keystone microbes and environmental factors. The carbohydrate and amino acid metabolism were confirmed as the primary metabolic pathways by metabolic function profiles. Furthermore, nitrogen metabolism pathway analysis indicated that denitrification and NH3 volatilization induced higher nitrogen loss during DGW composting. This study can provide new understanding of the microbiota for organic matter and nitrogen conversion in the composting process of DGW.

Bioaugmentation with syntrophic volatile fatty acids-oxidizing consortia to alleviate the ammonia inhibition in continuously anaerobic digestion of municipal sludge.

Ammonia inhibition easily affects the performance of anaerobic digestion (AD) for municipal sludge and the oxidization of volatile fatty acids (VFAs) is the rate-limiting step of this process. Bioaugmentation is considered to be an effective method to alleviate ammonia inhibition of AD, but most study used the hydrogenotrophic methanogens as the bioaugmentation culture. In this study, bioaugmentation of mesophilic AD (MAD) and thermophilic AD (TAD) under ammonia inhibition with syntrophic acetate and propionate oxidizing consortia was investigated. The results showed that the bioaugmented reactors recovered earlier than control reactors with 20 (MAD) and 8 (TAD) days, respectively. The high-throughput 16S rRNA gene sequencing indicated that the relative abundance of carbohydrates fermenter (Lentimicrobium), syntrophic VFAs-oxidizing bacteria (Rikenellaceae_DMER64, Smithella and Syntrophobacter) and acetoclastic and hydrogenotrophic methanogens (Methanosaeta, Methanolinea and Methanospirillum) increased in MAD after bioaugmentation. However, part of the bioaugmentation culture could not adapt to the high free ammonia (FAN) concentration in MAD and the effect was weakened. In TAD, proteolytic bacteria (Keratinibaculum and Tepidimicrobium), syntrophic VFAs-oxidizing bacteria (Syntrophomonas) and hydrogenotrophic methanogen (Methanosarcina) were strengthened. The effect of bioaugmentation in TAD was durable even at higher organic loading rate (OLR), due to its positive influence on microbial community. These results suggested that the different bioaugmentation mechanism occurred in MAD and TAD, which are derived from the synergetic effects of ammonia tolerance and microbial interactions. Our study revealed the VFAs-oxidizing consortia as bioaugmented culture could be the potential strategy to alleviate the ammonia stress of AD.

Performance and microbial community dynamics during rice straw composting using urea or protein hydrolysate as a nitrogen source: A comparative study.

Aerobic composting is a promising alternative for the recycling of rice straw (RS), and an applicable nitrogen source is necessary to improve the process. The aim of this study was to compare the performance and microbial community dynamics of RS composting using urea or protein hydrolysate from leather waste (PHL) as a nitrogen source. Results showed that PHL addition achieved a faster temperature increase rate at start-up (1.85 ℃·h-1 vs 1.07 ℃·h-1), higher volatile solid degradation efficiency (48.04% vs 46.98%), and greater germination indices (111.72% vs 89.87%) in the end products, as compared to urea. The major bacterial phyla included Proteobacteria, Firmicutes, Bacteroidetes, and Actinobacteria in both composting processes. Although the bacterial communities in both processes succeeded in a similar pattern according to different composting phases, PHL addition accelerated the succession rate of the microbial community. Co-occurrence network analysis revealed that bacterial community composition was strongly correlated with physicochemical properties such as dissolved organic carbon (DOC), NH4+, pH, temperature, and total nitrogen (TN) content. These results proved the potential of using PHL as a nitrogen source to improve the RS composting process.

Biochar addition reduces nitrogen loss and accelerates composting process by affecting the core microbial community during distilled grain waste composting.

This study evaluated the impact of biochar addition on nitrogen (N) loss and the process period during distilled grain waste (DGW) composting. Results from the five treatments (0, 5, 10, 15, and 20% biochar addition) indicated that 10% biochar addition (DB10) was optimal, resulting in the lowest N loss, 25.69% vs. 40.01% in the control treatment. Moreover, the DGW composting period was shortened by approximately 14 days by biochar addition. The composition of the microbial community was not significantly altered with biochar addition in each phase, however, it did accelerate the microbial succession during DGW composting. N metabolism pathway prediction revealed that biochar addition enhanced nitrification and inhibited denitrification, and the latter phenomenon was the main reason for reducing N loss during DGW composting. Based on the above results, a potential mechanism model for biochar addition to reduce N loss during the DGW composting process was established.

Potential for reduced water consumption in biorefining of lignocellulosic biomass to bioethanol and biogas.

Increasing ethanol demand and public concerns about environmental protection promote the production of lignocellulosic bioethanol. Compared to that of starch- and sugar-based bioethanol production, the production of lignocellulosic bioethanol is water-intensive. A large amount of water is consumed during pretreatment, detoxification, saccharification, and fermentation. Water is a limited resource, and very high water consumption limits the industrial production of lignocellulosic bioethanol and decreases its environmental feasibility. In this review, we focused on the potential for reducing water consumption during the production of lignocellulosic bioethanol by performing pretreatment and fermentation at high solid loading, omitting water washing after pretreatment, and recycling wastewater by integrating bioethanol production and anaerobic digestion. In addition, the feasibility of these approaches and their research progress were discussed. This comprehensive review is expected to draw attention to water competition between bioethanol production and human use.

[Correlation of Intravoxel Incoherent Motion-derived Parameters with Computer Tomography Perfusion Parameters in Insulinoma].

Objective To prospectively evaluate the correlation between intravoxel incoherent motion (IVIM)-derived parameters and CT perfusion parameters as well as the pathological grade in insulinoma. Methods A total of 55 patients with suspected insulinoma undergoing IVIM and CT perfusion scans were prospectively enrolled. The images were post-processed to obtain IVIM parameters including apparent diffusion coefficient (ADC),diffusion (D),perfusion correlated diffusion (D*),and f,and CT perfusion parameters including blood flow (BF),blood volume (BV),and permeability (PM). The pathological specimens were stained to obtain pathological parameters including the grading,ki-67 index,and the mitotic count. The IVIM derived parameters of normal pancreas including head,body,and tail as well as that of the pancreatic insulinoma were compared. The correlation between IVIM parameters and CT perfusion parameters as well as the pathological parameters was analyzed. Results ADC and D values of pancreatic tail were significantly lower than those of the pancreatic head and neck (all P<0.001). There were significant differences in all IVIM parameters between insulinoma and normal pancreas (all P<0.001). The ADC and f value of the normal pancreas was positively correlated with BF (r=0.437,P=0.003;r=0.357,P=0.010). There is no correlation between the remaining IVIM parameters and the CT perfusion parameters as well as between IVIM parameters and pathological parameters (all P>0.05). Conclusions IVIM parameters differ at different anatomical parts of normal pancreas. IVIM parameters can distinguish normal pancreatic parenchyma from insulinoma. The ADC value is weakly correlated with BF.

Dynamic change of bacterial community during dairy manure composting process revealed by high-throughput sequencing and advanced bioinformatics tools.

The aim of this work was to study the dynamic change in structure and potential function of bacterial community during dairy manure composting process using high-throughput sequencing and advanced bioinformatics tools. Alpha diversity of microbial community significantly decreased during the thermophilic phase and then recovered gradually. Beta diversity analysis showed unique community structures in different composting phases. Keystone microbes such as genus Corynebacterium, Bacillus, Luteimonas and Nonomuraea were identified for different composting phases. Six functional modules were identified for bacterial community during the composting process using co-occurrence analysis. These modules were significantly associated with temperature, pH, degradation of organic matter and maturation of compost. Predicted metagenomics analysis showed that the relative abundance of amino acid, lipid, energy and xenobiotics metabolism increased during the composting process. These results provide valuable insights into the microbiota during dairy manure composting and how the structures and metabolic functions changed in response to composting phases.