Biochar assisted cellulose anaerobic digestion under the inhibition of dodecyl dimethyl benzyl ammonium chloride: Dose-response kinetic assays, performance variation, potential promotion mechanisms.

This study evaluated the inhibitory effect and mitigation strategy of dodecyl dimethyl benzyl ammonium chloride (DDBAC) suppression on anaerobic digestion. With the 12 h-suppression, only 16.64% of anaerobes were alive, and acetotrophic methanogens were significantly inhibited. As for batch test, DDBAC suppression significantly prolonged the start-up of systems and decreased the biogas production. In cellulose semi-continuous digestion process, the DDBAC suppression induced volatile fatty acids accumulation and pH decrease. However, the biochar amended reactor effectively mitigated the DDBAC suppression and achieved 370.5 mL/d·g-chemical-oxygen-demand biogas production. Moreover, 17.8% more protein in extracellular polymeric substances was secreted as the bio-barrier to defense the DDBAC suppression. Furthermore, microbial analysis showed that biochar addition selectively enriched directed interspecies electron transfer (DIET) participant bacteria (Anaerolineaceae and Syntrophomonas) and methanogens (Methanosaeta and Methanobacterium). Meanwhile, the potential metabolic pathway analysis showed that the abundance of amino acids and energy metabolism were increased 28% and 8%, respectively. The abundance of encoding enzyme related to hydrogenotrophic and acetotrophic methanogenesis enriched 1.88 times and 1.48 times, respectively. These results showed the performance and mechanisms involved in DIET establishment with ethanol stimulation biochar addition.

The dosage-effect of biochar on anaerobic digestion under the suppression of oily sludge: Performance variation, microbial community succession and potential detoxification mechanisms.

This study investigated the dosage-effect of biochar on the suppressed mesophilic digestion of oily sludge (OS) containing naphthalene (recalcitrant compound) and starch (easily bioavailable substrate). Methanogenesis was inhibited in control with OS, where biomethane yield (63.33 mL/gVS) was obviously lower than theoretical yield (260.55 mL/gVS). With adding optimal dose of biochar (0.60 g/gVS OS), the highest CH4 yield (138.41 mL/gVS) was 2.19 times of control. Meanwhile, the efficiencies of hydrolysis, acidogenesis and acetogenesis were significantly enhanced. However, excessive biochar (4.80 g/gVS OS) caused negative effects with methanogenic efficiency diminished by 32.5% and lag phase prolonged by 5.72 h. Dissolved organic matter (DOM) analysis showed that humic acid-like and fulvic acid-like components percentages of fluorescence regional integration were decreased because of the adsorption of biochar. In addition, biochar mediating interspecies electron transfer selectively enriched electroactive fermentation bacteria (Clostridium and Bacteroides) and acetoclastic Methanosaeta, which was responsible for promoting mesophilic digestion performance. The functional genes related to metabolism and environmental information processing were potentially activated by biochar. Above results indicate that moderate biochar application may mitigate the bio-toxicity suppression of OS, which help to provide a promising pathway for reinforcing oily wastes bio-treatment.

Toxic effect and mechanism of ultrafine carbon black on mouse primary splenocytes and two digestive enzymes.

This paper investigated the toxic effect and mechanism of ultrafine carbon black (UFCB) on splenocytes and enzymes in the digestive system. It was found that the toxicity of UFCB to splenocytes was dose-dependent. UFCB with a low concentration (<15 µg/mL) had no significant effect on splenocytes while UFCB with high concentration (>15 µg/mL) induced significant oxidative damage with increased content of reactive oxygen species (ROS) (134%) and malonaldehyde (MDA) (222.3%) along with the decreased activity of superoxide dismutase (SOD) (55.63%) and catalase (CAT) (87.73%). Analysis combined cellular and molecular levels indicated that UFCB induced splenocyte toxicity through oxidative stress. The interactions of UFCB with two important digestive enzymes, α-amylase and lipase, were also studied respectively. Results showed that the interaction of UFCB and the two enzymes altered the particle size and fluorescence intensity in both experimental systems. The formation of protein corona also resulted in the contraction of the polypeptide skeleton in both enzymes, which further inhibited their activity. Our work provided basic data on the toxicity of UFCB in the spleen and digestive system and fills the gap in the study of UFPs toxicity. CAPSULE: UFCB induced splenocyte toxicity and enzyme dysfunction through oxidative stress and protein corona formation respectively.

Study of the effects of ultrafine carbon black on the structure and function of trypsin.

Due to the rapid development of industrial society, air pollution is becoming a serious problem which has being a huge threat to human health. Ultrafine particles (UFPs), one of the major air pollutants, are often the culprits of human diseases. At present, most of the toxicological studies of UFPs focus on their biological effects on lung cells and tissues, but there are less researches taking aim at the negative effects on functional proteins within the body. Therefore, we experimentally explored the effects of ultrafine carbon black (UFCB) on the structure and function of trypsin. After a short-term exposure to UFCB, the trypsin aromatic amino acid microenvironment, protein backbone and secondary structure were changed significantly, and the enzyme activity showed a trend that rose at first, then dropped. In addition, UFCB interacts with trypsin in the form of a complex. These studies demonstrated the negative effects of UFCB on trypsin, evidencing potential effects on animals and humans.

Anaerobic co-digestion of chicken manure and cardboard waste: Focusing on methane production, microbial community analysis and energy evaluation.

This study aimed to investigate the synergistic effect and microbial community changes between chicken manure (CM) and cardboard (CB) during anaerobic co-digestion. Meanwhile, the energy balance of biogas engineering was extrapolated based on the batch tests. In batch tests, co-digestion system achieved the highest improvement (14.2%) and produced 319.62 mL CH4/gVS with a 65:35 ratio of CB: CM. More extracellular polymeric substance secretion promoted the electron transfer for acidogenesis and more hydrolase was provided with 31.6% improvement. The microbial analysis illustrated that higher acetoclastic Methanosaeta abundance was achieved, leading to 211% enhancement of acetoclastic pathway. Moreover, associated network illustrated that the higher methane production was mainly achieved through matching of hydrolytic bacteria and acidogenesis bacteria. As for energy balance, the synergistic effect increased the energy output by 38% and energy recovery to 46.4%.

Enhancement methane fermentation of Enteromorpha prolifera waste by Saccharomyces cerevisiae: batch kinetic investigation, dissolved organic matter characterization, and synergistic mechanism.

With the invasion of green tide, there were millions of tons of Enteromorpha prolifera (Enteromorpha) that need to be disposed of. An efficient microecological system for Enteromorpha fermentation was constructed using Saccharomyces cerevisiae (S. cerevisiae) and granular sludge at mesophilic condition (35 °C). In order to investigate the influence of S. cerevisiae dosage on fermentation, biomethane production and variations in dissolved organic matter (DOM) were investigated. The results indicated that the microecosystem with added S. cerevisiae exhibited improved fermentation capacity. Specifically, biomethane production was improved by 18%, with a maximum methane yield of 331 mL/g VS, and the time required to reach 90% methane yield was reduced by 41%. There were positive linear relationships between S. cerevisiae dosage and the efficiency of hydrolysis, acidogenesis, acetogenesis, and methanogenesis (R2 > 0.9). According to theoretical calculations, there was a positive effect of lower S. cerevisiae dosage (less than 0.93 g/g TS) on biomethane production, and excess dosage (more than 0.93 g/g TS) led to a negative effect due to volatile fatty acid (VFA) accumulation. The excitation-emission matrix (EEM) indicated that the humification index (HIX) and fulvic acid (FA) percentage of fluorescence regional integration in the system were decreased because the quinone and ketone groups of the FA accepted electrons from S. cerevisiae. These findings suggested that this microecosystem can accelerate fermentation speed (41%) and increase biomethane output (18.2%). The synergistic effect of Enteromorpha fermentation with Saccharomyces cerevisiae addition.

Enhanced anaerobic performance and SMD process in treatment of sulfate and organic S-rich TMBA manufacturing wastewater by micro-electric field-zero valent iron-UASB.

This study focused on investigating reactor performance, simultaneous methanogeneis and denitrifiction (SMD) process for treatment of a sulfate plus organic sulfur - rich 3,4,5-Triethoxybenzaldehyde (TMBA) manufacturing wastewater with variable COD/TSO42- (total sulfate) ratio by micro-electric field- zero-valent-iron (ZVI) UASB for 390 days. The initial COD/TSO42- was set as 1.42, 0.9 and 0.5, respectively by manually introducing sulfate. The experimental results indicated that micro-electric field- zero-valent-iron UASB was an attractive integrated option for satisfactory COD removal, nitrate reduction and a reasonable methane yield rate even at COD/TSO42- as low as 0.9. Further declining the COD/TSO42- to 0.5 can result in a moderate inhibition of SMD process. The behavior of organic S release was not inhibited over the entire experimental period. Thus, surprisingly, sulfate concentration in the effluent was always higher than that in the influent. In comparison with sludge sample at Day-1, sludge at Day-390 was characterized with high abundant Tissierella Soehngenia, Anaerolinaceae and Brevundimonas diminuta, which played critical role in promising performance in COD abatement. The relatively low abundance of sulfate reducing bacteria (SRB) such as Desulfobulbus and Desulfomicrobium can explain the lower sulfate reduction efficiency in term of high concentration of sulfate plus released from organic S-rich compounds.

Characterization of the interaction between carbon black and three important antioxidant proteins using multi spectroscopy and modeling simulations.

A major user of carbon black is the pigment and dyes industry, where carbon black is incorporated into paints, inks, printers, and plastics. However, little is known about the mechanism underlying the toxicity of carbon black to antioxidant proteins. Carbon black can cause oxidative stress to organisms after they invade into the body. Antioxidant proteins play a key role in keeping the organism from nanoparticle-induced oxidative damage and tend to bind with nanoparticles immediately after their invading into the biological environment, so it is meaningful to elucidate the toxicity of nanoparticles on the antioxidant proteins. In this study, the toxicity of carbon black (SB100) on three different antioxidant proteins (TF (transferrin), SOD (superoxide dismutase), and LYZ (lysozyme)) were investigated. The multi-spectra studies indicated that SB100 interacted with these three proteins and changed their structure in different ways. SB100 changed the microenvironment of fluorophores in SOD and LYZ by quenching the fluorescence spectra of the two enzymes, while changed that of TF by increasing the fluorescence intensity of TF. SB100 changed the secondary structure of these three proteins by decreasing the α-helix content of TF and increasing that of SOD and LYZ. Moreover, SB100 changed the hydrophobicity of the three proteins in different ways as well. And SOD exhibits a more severe activity inhibition than LYZ after exposed to SB100. In summary, SB100 caused different structural and functional changes to these three antioxidant enzymes.

The toxic effects of alizarin red S on catalase at the molecular level.

Alizarin red S (ARS) is a widespread mordant dye derived from alizarin. However, it was reported to be mutagenic and carcinogenic probably because it could induce oxidative damages in organisms. Catalase (CAT) is an important antioxidant enzyme defensing oxidative damages induced by xenobiotics. The underlying mechanisms of ARS interacting with CAT have not been clarified yet. This study is conducted to characterize the functional and conformational changes on CAT by ARS and the binding details to further investigate their interaction mechanisms. Under exposure of ARS at 5 µM, CAT activity was significantly decreased to 76.2%. Inhibition of CAT probably resulted in promotion of intracellular oxidative stress and pro-oxidant property of ARS. The interaction between ARS and CAT was proved to be spontaneous and exothermic. However, limited structural changes were observed according to spectroscopic results. Results showed that ARS prefers to bind with residues buried in the active site and could alter the activity of CAT, which were agree with the molecular docking results. This work proves the adverse effects of ARS on CAT mainly at molecular level and further highlights its potential risks to heath.