Biochar leachate reduces primary nitrogen assimilation by inhibiting nitrogen fixation and microbial nitrate assimilation.

Biochar contains biotoxic aromatic compounds, and their influence on nitrogen-fixing cyanobacteria, the critical nitrogen fixer in paddy soil, has never been tested. Here, the physiological, metabolomic, and transcriptomic analyses of Nostoc sp. PCC7120 in response to biochar leachate were performed. The results suggested that biochar leachate inhibited the efficiency of photosynthesis, nitrogen fixation, and nitrate assimilation activities of nitrogen-fixing cyanobacteria. Biochar leachate containing aromatic compounds and odd- and long-chain saturated fatty acids impaired the membrane structure and antenna pigments, damaged the D1 protein of the oxygen evolution complex, and eventually decreased the electron transfer chain activity of photosystem II. Moreover, the nitrogen fixation and nitrate assimilation abilities of nitrogen-fixing cyanobacteria were inhibited by a decrease in photosynthetic productivity. A decrease in iron absorption was another factor limiting nitrogen fixation efficiency. Our study highlights that biochar with relatively high contents of dissolved organic matter poses a risk to primary nitrogen assimilation reduction and ecosystem nitrogen loss. Further evidence of the potential negative effects of biochar leachates on the fixation and assimilation capacity of nitrogen by soil microbes is needed to evaluate the impact of biochar on soil multifunctionality prior to large-scale application.

Mechanisms of total phosphorus removal and reduction of ß-lactam antibiotic resistance genes by exogenous fungal combination activated sludge.

This study utilized Trichoderma and activated sludge to construct combined activated sludge (TAS). The metagenomic approach was employed to examine the shifts in microbial community structure and function of TAS under amoxicillin stress and investigate the mechanism underlying the reduction of ß-lactam antibiotic resistance genes (ß-ARGs). The findings demonstrated that the elevated aundance of glpa, glpd, ugpq, glpq, and glpb were primarily responsible for the reduction in total phosphorus (TP) removal by TAS. The increased abundance of Proteobacteria and Verrucomicrobia led to enhanced expression of ugpb, phnd, and phne, thereby improving the TP removal of TAS. Furthermore, antibiotic inactivation has gradually become the primary antibiotic resistance mechanism in TAS. Specifically, an increase in the abundance of OXA-309 in TAS will decrease the probability of amoxicillin accumulation in TAS. A decrease in ß-ARGs diversity confirmed this. This study presents a novel approach to reducing antibiotic and ARG accumulation in sludge.

Biochar amendment reduces biological nitrogen fixation and nitrogen use efficiency in cadmium-contaminated paddy fields.

Cadmium (Cd) contamination poses a considerable threat to human health through grain enrichment and limits biological nitrogen fixation (BNF) in paddy fields. Biochar has shown great potential for agricultural soil remediation because it inactivates Cd, but uncertainties remain as to how biochar amendments affect BNF and grain N use efficiency in paddies. To elucidate these issues, we investigated the effects of biochar amendment on the structure and function of diazotrophic bacterial communities in different rice growth stages in Cd-contaminated paddy fields, and evaluated the contribution of BNF to grain N use efficiency under biochar amendment. The results showed that biochar amendment significantly increased the abundance of diazotrophic bacteria in the tillering and jointing stages. Furthermore, the community structure of soil diazotrophic bacteria markedly changed with biochar amendment, with a significant reduction in the abundances of Euryarchaeota, Desulfobacterales (Proteobacteria), and Sphingomonadales (Bacteroidetes) in the tillering stage. Changes in the soil carbon/nitrogen (C/N) ratio was the main factor driving diazotrophic microbial community characteristics caused by the release of available C from biochar at the tillering stage, rather than the Cd. Moreover, biochar amendment increased the efficiency of BNF (especially for autotrophic N2 fixation) in the vegetative phase of rice growth. Notably, biochar amendment significantly decreased BNF efficiency during the filling stage and reduced grain N use efficiency. The limited available nutrients in biochar and the toxicity of polycyclic aromatics and phenols in biochar-derived dissolved organic matter were responsible for the varied impacts of biochar on BNF in different rice growth stages. For the first time, we report that biochar amendment in paddy soils reduces Cd toxicity but also inhibits BNF and thereby decreases N use efficiency. Therefore, before applying biochar to inactivate Cd in paddy fields, there should be a trade-off between agricultural production and ecological safety to achieve sustainable agriculture.

Treatment of amoxicillin-containing wastewater by Trichoderma strains selected from activated sludge.

This study screened a Trichoderma strain (Trichoderma pubescens DAOM 166162) from activated sludge to solve the limitation of traditional biological processes in the treatment of amoxicillin (AMO) containing wastewater. The mechanism of the removal of AMO wastewater by T. pubescens DAOM 166162 (TPC) was studied. AMO resulted in a higher protein percentage in the extracellular polymeric substances (EPS) secreted by TPC, which facilitated the removal of AMO from the wastewater. Fourier transform infrared spectroscopy and excitation-emission matrix were used to characterize EPS produced by metabolizing different carbon sources. It was found that the hydroxyl group was the primary functional group in EPS. The life activity of TPC was the cause of the pH rise. The main pathway of degradation of AMO by TPC was the hydroxyl group uncoupling the lactam ring and the hydrolysis of AMO in an alkaline environment. The removal efficiency of AMO in wastewater by TPC was >98 % (24 h), of which the biodegradation efficiency was 70.01 ± 1.48 %, and the biosorption efficiency was 28.44 ± 2.97 %. In general, TPC is an effective strain for treating wastewater containing AMO. This research provides a new idea for AMO wastewater treatment.

Enantioselective toxicity, degradation and transformation of the chiral insecticide fipronil in two algae culture.

The occurrence of pesticides and their metabolites in the environment can alter the ecological relationships between aquatic food chains. Fipronil is a broad-spectrum insecticide which release in the environment may harm the non-target organisms. However, the toxicity and biotransformation of its two enantiomers are far from fully understood. The present study aimed to investigate the aquatic toxicity and environmental behavior of fipronil at enantiomeric level using two freshwater algae, Scenedesmus quaclricauda (S. quaclricauda), and Chlorella vulgaris (C. vulgaris) through an integrative approach the transformation process of the individual enantiomer isolated and in racemic form. The 72 h-EC50 values of rac-, R-, S-fipronil varied from 3.27 to 7.24 mg L-1 with R-fipronil posing a more significant effect on algal growth inhibition. Chlorophyll a was more susceptible to fipronil exposure than chlorophyll b and carotenoids. Enantioselective alterations on physiological and biochemical parameters (chlorophyll a, chlorophyll b, carotenoids, and the activities of antioxidant enzyme catalase (CAT) and superoxide dismutase (SOD)) were also observed. The half-lives (T1/2) of R-fipronil and S-fipronil in algae culture were 3.4-3.5 d and 4.0-4.9 d, respectively. By the end of the 17-d exposure, the enantiomer fractions (EFs) increased to 0.59, indicating a preferential depuration of R-fipronil. The metabolites monitoring showed the fipronil sulfide was the main metabolite followed by fipronil sulfone. The results revealed that the enantiomers of fipronil pose enantiospecific behaviors induced by these two algae, with the R-enantiomer more toxic to algal growth and favorable in degradation. These analyses are beneficial for understanding the ecological effect of chiral pesticide in aquatic environment, and the enantiomeric differences of the toxicity, degradation and the formation of toxic metabolites could be helpful for the eco-environmental risk evaluation.

Effects of different carbon sources on the removal of ciprofloxacin and pollutants by activated sludge: Mechanism and biodegradation.

This research investigated the effects of ciprofloxacin (CIP) (0.5, 5, and 20 mg/L) on SBR systems under different carbon source conditions. Microbial community abundance and structure were determined by quantitative PCR and high-throughput sequencing, respectively. The biodegradation production of CIP and possible degradation mechanism were also studied. Results showed that CIP had adverse effects on the nutrient removal from wastewater. Compared with sodium acetate, glucose could be more effectively used by microorganisms, thus eliminating the negative effects of CIP. Glucose stimulated the microbial abundance and increased the removal rate of CIP by 18%-24%. The mechanism research indicated that Proteobacteria and Acidobacteria had a high tolerance for CIP. With sodium acetate as a carbon source, the abundance of nitrite-oxidizing bacterial communities decreased under CIP, resulting in the accumulation of nitrite and nitrate. Rhodanobacter and Microbacterium played a major role in nitrification and denitrification when using sodium acetate and glucose as carbon sources. Dyella and Microbacterium played positive roles in the degradation process of CIP and eliminated the negative effect of CIP on SBR, which was consistent with the improved removal efficiency of pollutants.

TRAF3IP3 mediates the recruitment of TRAF3 to MAVS for antiviral innate immunity.

RIG-I-MAVS antiviral signaling represents an important pathway to stimulate interferon production and confer innate immunity to the host. Upon binding to viral RNA and Riplet-mediated polyubiquitination, RIG-I promotes prion-like aggregation and activation of MAVS. MAVS subsequently induces interferon production by activating two signaling pathways mediated by TBK1-IRF3 and IKK-NF-κB respectively. However, the mechanism underlying the activation of MAVS downstream pathways remains elusive. Here, we demonstrated that activation of TBK1-IRF3 by MAVS-Region III depends on its multimerization state and identified TRAF3IP3 as a critical regulator for the downstream signaling. In response to virus infection, TRAF3IP3 is accumulated on mitochondria and thereby facilitates the recruitment of TRAF3 to MAVS for TBK1-IRF3 activation. Traf3ip3-deficient mice demonstrated a severely compromised potential to induce interferon production and were vulnerable to RNA virus infection. Our findings uncover that TRAF3IP3 is an important regulator for RIG-I-MAVS signaling, which bridges MAVS and TRAF3 for an effective antiviral innate immune response.

Anti-tyrosinase kinetics and antibacterial process of caffeic acid N-nonyl ester in Chinese Olive (Canarium album) postharvest.

Enzymatic browning and bacterial putrefaction are mainly responsible for quality losses of Chinese Olive (Canarium album) postharvest and lead to very short shelf life on average. Screening anti-browning and anti-bacterial agents is important for preservation of Chinese Olive. Caffeic acid N-nonyl ester (C-9) and caffeic acid N- Heptyl ester (C-7) was synthesized as inhibitors of tyrosinase, which is a key enzyme in browning process. The compound of C-9 could inhibit the activity of tyrosinase strongly and its IC50 value was determined to be 37.5µM, while the compound of C-7 had no inhibitory ability. Kinetic analyses showed that compound of C-9 has been a reversible inhibitory mechanism below 50µM and been irreversible mechanisms above 50µM. For the reversible inhibitory mechanism, the values of inhibitory constants (KI and KIS) were determined to be 24.6 and 37.4µM, respectively. The results of Chinese Olive fruit postharvest showed that the compound of C-9 could effectively anti-browning and anti-bacterial putrefaction. In addition, this compound had strong antibacterial activities against Staphylococcus aureus, Escherichia coli, Bacillus subtilis and Salmonella. Therefore, C-9 could be a potential anti-browning and anti-bacterial reagent.

Alpha-substituted derivatives of cinnamaldehyde as tyrosinase inhibitors: inhibitory mechanism and molecular analysis.

Alpha-substituted derivatives of cinnamaldehyde (alpha-bromocinnamaldehyde, alpha-chlorocinnamaldehyde, and alpha-methylcinnamaldehyde) were used as inhibitors on mushroom tyrosinase. The result showed that three compounds can reduce both monophenolase and diphenolase activity on tyrosinase, and the inhibition was reversible. The IC50 values of alpha-bromocinnamaldehyde, alpha-chlorocinnamaldehyde, and alpha-methylcinnamaldehyde were 0.075, 0.140, and 0.440 mM on monophenolase and 0.049, 0.110, and 0.450 mM on diphenolase, respectively. The inhibition types and constants on diphenolase for these inhibitors were further studied. The molecular inhibition mechanisms of tyrosinase by the derivatives were investigated by UV-scanning study, fluorescence quenching, and molecular docking. These assays demonstrated that the derivatives could decrease the formation of o-quinones, and all derivatives were static quenchers of mushroom tyrosinase. Docking results implied that they could not form metal interactions with the copper ions of the enzyme, whereas they could interact with the amino acid residues of active site center. This research on alpha-substituted derivatives of cinnamaldehyde as tyrosinase inhibitors would lead to advances in the field of antityrosinase.

Enzymatic saccharification of cassava residues and glucose inhibitory kinetics on ß-glucosidase from Hypocrea orientalis.

Cassava residues are byproducts of the starch industry containing abundant cellulose for bioproduction of green fuel. To obtain maximum sugar yields from cassava residues, the optimal conditions for hydrolyzing the residues were determined using cellulase prepared from a novel Hypocrea orientalis strain. The optimal pH value and optimal temperature for the cellulase hydrolysis were 5.0 and 50 °C, respectively. The concentration of NaOH was determined to be 1% for pretreatment of cassava residues to gain enough soluble sugars suitably. The yield of released sugars was 10 mg/mL in the optimal conditions after 24 h of reaction, which was similar to that of bagasse and wheat grass. Inhibition kinetics of H. orientalis ß-glucosidase (BG) by glucose was first studied using the progress-of-substrate-reaction method as described by Tsou (Tsou, C. L. Adv. Enzymol. Related Areas Mol. Biol. 1988, 61, 381-436), and the microscopic inhibition rate constants of glucose were determined. The results showed that glucose could inhibit BG reversibly and competitively. The rate constants of forward (k(+0)) and reverse (k(-0)) reaction were measured to be 4.88 × 10(-4) (mM·s)(-1) and 2.7 × 10(-4) s(-1), respectively. Meanwhile, the inhibition was more significant than that of L-glucose, D-mannose, D-galactose, D-aminoglucose, acetyl-D-glucose, and D-fructose. This work reveals how to increase sugar yields and reduce product inhibition during enzymatic saccharification of cellulose.