Evidence that beneficial microbial inoculation enhances heavy metal-contaminated soil remediation: Variations in plant endophyte communities.

Microbial remediation of heavy metal (HM)-contaminated soil is a sustainable approach; however, the impact of microbial inoculation on the internal environment of plants remains understudied. Thus, Enterobacter sp. FM-1 (Enterobacter sp.) and the hyperaccumulator Bidens pilosa L. (B. pilosa L.) were used to study these effects. Through analyses of plant physiological and biochemical characteristics, the endophytic microbial community composition, microbial co-occurrence networks and functional predictions, the potential mechanisms by which Enterobacter sp. benefits the phytoremediation of HM-contaminated soil by B. pilosa L. were elucidated. Inoculation with Enterobacter sp. promoted the growth of B. pilosa L. and influenced the endophytic microbial community diversity in B. pilosa L. Interactions among endophytes facilitated the formation of microbial networks, with endophytic fungi playing a more prominent role than endophytic bacteria as the level of HM contamination increased. Functional predictions via PICRUSt2 revealed that endophytic bacteria are involved primarily in processes related to carbohydrate metabolism, ABC transporters, and amino acid metabolism. In conclusion, this study provides evidence for the beneficial role of microbes in improving the plant endosphere environment.

High-solid co-digestion performance of lipids and food waste by mesophilic hollow fiber anaerobic membrane bioreactor.

The co-digestion performance of mesophilic (37℃) hollow fiber anaerobic membrane bioreactor (HF-AnMBR) in treating high-solid lipids and food waste (FW) for 180 days was investigated. The organic loading rate (OLR) was increased from 2.33 to 14.64 g-chemical oxygen demand (COD) /L/d by increasing the lipids/FW from 10%, 30%, and 50% on dry based. The COD conversion efficiency for methane was 83.13%, 84.85%, 82.63%, and 84.30%, and the sludge growth rate was 0.001, 0.097, 0.065, 0.016 g TS/g COD at OLR of 2.33, 9.36, 12.76 and 14.64 g-COD/L/d, respectively. The COD, proteins, and carbohydrates concentrations in permeate were stable, with an average of 2.25, 0.50, and 0.18 g/L, respectively. The long-term stable performance of the HF-AnMBR indicated that this study will help guide application of the co-digestion of lipids and food waste.

Biogas production performance and system stability monitoring in thermophilic anaerobic co-digestion of lipids and food waste.

A thermophilic anaerobic co-digestion system treating lipids and food waste was demonstrated by a long-term operation (over 600 days) with different lipid/TS ratios (from 10 % to 80 %). The lipids degradation efficiency achieved 90 % in the system when the lipid/TS ratio was less than 70 %. Addition of lipids significantly enhanced methane production, as the lipid/TS ratio increased from 10% to 70 %, the biogas production rate increased from 2.36 g/L/d to 3.42 g/L/d with 59.7 % to 67.7 % of methane. From the view of system stability, the increase of lipid/TS ratio reduced the alkalinity of the system and eventually caused the system collapse. In order to avoid losses due to overload, the results suggested that the ratio of total ammonia nitrogen to alklinity-6.5 could be used as a monitoring indicator. And the system could maintain efficient operation when the indicator was less than 0.6.

Enhanced biomethanation of lipids by high-solid co-digestion with food waste: Biogas production and lipids degradation demonstrated by long-term continuous operation.

Biomethanation of lipids by high-solid co-digestion with food waste (FW) was investigated with a long-term operation under the mesophilic condition. The experiment was conducted with a continuous stirred-tank reactor (CSTR) at a hydraulic retention time (HRT) of 30 days and an influent TS concentration of 10% by varying influent lipid/TS ratio from 10% to 60%. As lipid/TS ratio increased from10% to 50%, it was found that the biogas production rate improved by 30% and the content of CH4 in the biogas increased by up to 67%. When the lipid/TS ratio reached 60%, the whole system collapsed. It was inferred that when the lipid/TS ratio was less than 50%, sufficiently high concentration of microorganisms ensured by high-solid co-digestion maintained relatively high average reaction rates for hydrolysis, acidogenesis, acetogenesis and methanogenesis. The rapid degradation of lipid reduced the adsorption to the surface of microbes, thereby ensuring the stability of the system.

Simultaneous detection of the distance and direction for a noncooperative target based on the microwave photonic radar.

For a noncooperative target, multiple-dimension detection is required to determine its spatial location. A microwave photonic radar is proposed for simultaneous detection of the distance and direction of targets. At the transmitter, a linear frequency modulation (LFM) signal with a large instantaneous bandwidth was obtained by frequency doubling. Meanwhile, the optical reference signal was supplied. At the receiver, two antennas with a certain baseline length were used to receive the echo signal. The dechirp process and fixed-length cable are combined to decouple the distance and direction and distinguish between the positive and negative directions of a target. Theoretical derivation has already verified that the distance and direction can be resolved simultaneously by dechirping of the echo modulation signal and reference signal. In experiments, an LFM signal with an instantaneous bandwidth of 2 GHz (2-4 GHz) was generated and launched as the detection signal. Targets at different distances with positive and negative angles were detected. The results show that the directional measurement ranges from -72.5° to 72.5°, and the error is less than 1.6°. The measured distance was found to be quite similar to the actual distance. The proposed approach can confirm the spatial location of a noncooperative target by combining the detection of both distance and direction. Furthermore, the baseline length need not be less than half the wavelength of the echo signal, and large antennas can be chosen to improve the detection distance and range accuracy.