ABSTRACT
The fermentation system with high solid materials for food waste (FW) is uneven in nutrition and easy to produce volatile acid accumulation, which causes the reaction system to acidify and affects the normal operation of fermentation. This study evaluated the effect of the co-substrate percentages (FW:CB = 9:1, FW:CB = 8:2, FW:CB = 7:3) and the initial total solid contents (12%, 15%, 18%) on the co-fermentation acidification performance of FW and cardboard waste (CB). The maximum methane production was obtained when mono-fermenting FW had high solids contents (1.4 L/kg). The methane production increased and then decreased with the increasing percentages of CB. Under the conditions of FW:CB = 8:2, the maximum methane production could reach 3.4 L/kg. The lower methane production (1.8 - 2.5 L/kg) with high percentages of CB (FW:CB = 7:3) was translated into higher yields of caproic acid (up to 26%), which indicated that lower percentages of CB had a stabilization effect due to the higher buffering capacities in co-fermentation. As a result, this study demonstrated new possibilities for using CB percentages to control the production of high added-value biogas in dry co-fermentation of FW.
Subject(s)
Food , Refuse Disposal , Anaerobiosis , Bioreactors , Fermentation , Hydrogen-Ion Concentration , MethaneABSTRACT
OBJECTIVE: To explore the role of N~6-methyladenosine(m~6A) catalytic enzymes(methyltransferases and demethylases) in cadmium-induced oxidative damage in human renal epithelial cells(HK-2 cells), and to analyze the correlation between nuclear factor-erythroid 2-related factor 2(NRF2) and m~6A catalytic enzymes. METHODS: i) HK-2 cells in logarithmic growth phase were randomly divided into control group and 6 cadmium sulfate treatment groups, then treated with 0, 2, 4, 8, 16, 32 and 64 μmol/L cadmium sulfate solution for 24 hours. The cell survival rates were detected by CCK-8 assay, and the appropriate doses of cadmium sulfate were selected for subsequent experiments. ii) HK-2 cells in logarithmic growth phase were randomly divided into control group and low-, medium-, and high-dose groups, and treated with 0, 4, 8, and 16 μmol/L cadmium sulfate solution respectively for 24 hours. Subsequently, the levels of reactive oxygen species(ROS) were detected by fluorescence probe. The mRNA expression of NRF2, the m~6A methyltransferases such as methyltransferase like proteins(METTL) 3, METTL14, METTL16 and the m~6A demethylases such as fat mass and obesity associated protein(FTO), AlkB family of nonheme Fe(Ⅱ)/α-ketoglutarate(α-KG)-dependent dioxygenases 5(ALKBH5) were determined by real-time polymerase chain reaction. RESULTS: i) The survival rate of HK-2 cells was more than 60.00% and lower than that of the control group(P<0.05) after the cells were stimulated with 16 μmol/L of cadmium sulfate. Therefore, 4, 8 and 16 μmol/L of cadmium sulfate were selected as the stimulation concentrations in the follow-up experiments. ii) The relative expression of NRF2, METTL3, METTL14 and METTL16 in HK-2 cells in low-dose group increased(all P<0.05), while the levels of ROS and the relative mRNA expression of NRF2, METTL3, METTL14, METTL16 and FTO in HK-2 cells in medium and high-dose groups increased(all P<0.05) when compared with the control group. There was no significant difference in the expression of ALKBH5 mRNA among these 4 groups(P>0.05). In the correlation analysis, NRF2 mRNA expression was positively correlated with the mRNA expression of METTL3 and METTL16 [Pearson correlation coefficient(r) = 0.61 and 0.66, respectively, all P<0.05]. There was no correlation between NRF2 mRNA expression and METTL14, FTO and ALKBH5(r=0.53, 0.48, and 0.01 respectively, all P>0.05). CONCLUSION: Cadmium sulfate may increase intracellular ROS level, up-regulate NRF2 expression and activate NRF2 signaling pathway as well as enhance the expression of METTL3 and METTL16 in HK-2 cells, thus increasing intracellular oxidative damage and decreasing the cell survival rate.
ABSTRACT
Objective To explore the clinical application of treponema pallidum enzyme-linked immunosorbent assay (TP-ELISA),syphilis toluidine red unheated serum regain test (TRUST) and treponema pallidum particle agglutination assay (TPPA) for the diagnosis of syphilis,improvement of the process of sequence syphilis screening program and thus assisting clinical diagnosis and treatment of syphilis.Methods The serum samples were both screened by TP-ELISA and TRUST simultaneously.The positive was confirmed by TPPA test.Syphilis serological test results of patients were collected and retrospectively analyzed.Results The 3 618 cases out of total 82 026 serum samples were reactive by TP-ELISA,453 were reactive to TRUST,and 1 684 were confirmed positive on TPPA;thepositive rate were 4.41%,0.55%and 2.05%;The TP-ELISA,TRUST and TPPA positive conformity rate or titer were rising with the TP-ELISA S/CO and TRUST titer increasing.Conclusion There is a positive correlation of TP-ELISA S/CO among the TPPA,TRUST of positive conformity rate and titer.Using TP-ELISA and TRUST as screening,TPPA as confirmed test,the diagnostic efficiency of the process of sequence syphilis screening program can be improved.