Dissolved organic matter (DOM) has an important effect on soil fertility, activity of microorganisms and transport of contaminants. In this study, DOM released by the hydrochar and biochar prepared ...under various conditions from pig manure, was assessed using a combination of UV–Visible spectroscopy, fluorescence excitation-emission (EEM) spectrophotometry and 1H-nuclear magnetic resonance (1H NMR). The dissolved organic carbon (DOC) extracted from the hydrochar and biochar ranged from 3.34–11.96% and 0.38–0.48%, respectively, and the highest DOM was released by HCK0.5 (180 °C and 0.5% KOH). The aliphatic compounds were most common in DOM which mainly included three humic acid-like and one protein-like substance. The hydrochar-DOM had a larger molecular weight and lower aromaticity than biochar-DOM, but the effect of temperature on the DOM characteristics of hydrochar and biochar was opposite. The acidic treatment increased the content of functional groups containing oxygen and nitrogen in hydrochar-DOM, and alkaline treatment increased the content of aliphatic compounds. The results obtained are beneficial to select carbonation process and guide the rational application of hydrochar and biochar from pig manure in soil remediation field.
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•The higher concentration of DOM in hydrochar than biochar•The hydrochar-DOM had a larger molecular weight and lower aromaticity.•There are mainly three humic acid-like and one protein-like substance in DOM.•The relative proportion of aliphatic compounds in DOM was the highest.•The dilute alkali treatment increased the content and instability of hydrochar-DOM.
Pretreatments such as dilute acid at elevated temperature are effective for the hydrolysis of pentose polymers in hemicellulose and also increase the access of enzymes to cellulose fibers. However, ...the fermentation of resulting syrups is hindered by minor reaction products such as furfural from pentose dehydration. To mitigate this problem, four genetic traits have been identified that increase furfural tolerance in ethanol-producing Escherichia coli LY180 (strain W derivative): increased expression of fucO , ucpA , or pntAB and deletion of yqhD . Plasmids and integrated strains were used to characterize epistatic interactions among traits and to identify the most effective combinations. Furfural resistance traits were subsequently integrated into the chromosome of LY180 to construct strain XW129 (LY180 Δ yqhD ackA:: P yₐdC′fucO-ucpA) for ethanol. This same combination of traits was also constructed in succinate biocatalysts (Escherichia coli strain C derivatives) and found to increase furfural tolerance. Strains engineered for resistance to furfural were also more resistant to the mixture of inhibitors in hemicellulose hydrolysates, confirming the importance of furfural as an inhibitory component. With resistant biocatalysts, product yields (ethanol and succinate) from hemicellulose syrups were equal to control fermentations in laboratory media without inhibitors. The combination of genetic traits identified for the production of ethanol (strain W derivative) and succinate (strain C derivative) may prove useful for other renewable chemicals from lignocellulosic sugars.
Food waste (FW) from large dining facility has been a pressing environmental challenge in China recently. This study developed an innovative species-specific feeding strategy for producing pigeon ...meat and excellent manure from FW. Adding FW to the feed of pigeons significantly increased their feed intake and promoted their growth although the pigeons showed a strong aversion to the FW. We produced a “super manure” with exceptionally high nitrogen (N) content (mean = 10.77 % on a dry basis, 8.04–12.57 %, n = 264) by feeding slowly-growing pigeon species (Columba livia vs. and Caoge Huzhou 11) with protein-high commercial feed and FW. A significant negative relationship between the N and carbon (C) contents in the pigeon manure was found, with C depletion higher than N depletion. Furthermore, the N content in the anaerobic composting (AnC) manure was 29.16 % higher than that in the FW. Fourier transform infrared (FT-IR) analysis and stable isotopes δ13C and δ15N in the manure clearly identified the transformations of nutrients during pigeon feeding and the AnC process. This study opens a path for producing N-high manure using protein-high food waste.
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•Food waste from the large dining room was nutrient-rich.•The pigeons that grew at a low rate produced manure with exceptionally high N content.•Anaerobic composting-produced manure from food waste contained 29.16 % more N than that of food waste.
Straw returning has been shown to improve farmland soil, increase crop yield, and reduce global warming. This study investigated the models of six rice straw-returning techniques based on the life ...cycle assessment method. Compared to the direct modes, the indirect ones showed a greater environmental impact; up to 20.56 times in acidification and emission potentials. There was no significant difference in climate change among the six types. Except for the burning effect, all other modes showed improvement in soil fertility; phosphorus and organic matter content increased by 66.66% and 30.85%, respectively, microbial biomass carbon content doubled (105%), the four organic carbon components increased by >50%, crop morbidity was reduced, and diversity of soil fungus was improved. Feeding, as an indirect method for enhancing soil fertility and economic benefits, is set to emerge as a leading practice in China’s straw management. However, straw-returning technology is limited by cost, greenhouse gases, and increased risk of diseases and pests. There is an urgent need for further improvement and development of carbon sequestration and emission reduction in China’s agriculture.
The present study deals with the degradation of bensulfuron-methyl by microorganisms cultured with different sources of carbon, nitrogen and phosphorus. Addition of carbon source accelerated the ...degradation of bensulfuron-methyl under co-metabolism process. Sodium lactate was the best carbon source for the degradation of bensulfuron-methyl, compared to other carbon sources studied, and the degradation ratio of bensulfuron-methyl reached 79.5%, whereas only 34.6 and 29.7% were removed in the presence of glucose and sucrose, respectively. Supplement of nitrogen source also enhanced degradation of bensulfuron-methyl. However, no significant differences were observed in the loss of bensulfuron-methyl between organic nitrogen and inorganic source. Phosphate buffer was supplemented into the media to maintain neutral conditions for the advantage of the strain growth since increase in pH value was observed. An orthogonal array design was applied to arrange main factors singled out for investigating the influence of factor and interaction between them on the degradation of bensulfuron-methyl. Statistical analysis showed that the concentration of sodium lactate, bensulfuron-methyl and inoculum size were the main effects, and the interaction of sodium lactate and bensulfuron-methyl was of statistical significance.
l
-2-Aminobutyric acid can be synthesized in a transamination reaction from
l
-threonine and
l
-aspartic acid as substrates by the action of threonine deaminase and aromatic aminotransferase, but the ...by-product
l
-alanine was produced simultaneously. A small amount of
l
-alanine increased the complexity of the
l
-2-aminobutyric acid recovery process because of their extreme similarity in physical and chemical properties. Acetolactate synthase has been introduced to remove the pyruvate intermediate for reducing the
l
-alanine concentration partially. To eliminate the remnant
l
-alanine, alanine racemase of
Bacillus subtilis
in combination with
d
-amino acid oxidase of
Rhodotorula gracilis
or
Trigonopsis variabilis
respectively was introduced into the reaction system for the
l
-2-aminobutyric acid synthesis.
l
-Alanine could be completely removed by the action of alanine racemase of
B. subtilis
and
d
-amino acid oxidase of
R. gracilis
; thereby, high-purity
l
-2-aminobutyric acid was achieved. The results revealed that alanine racemase could discriminate effectively between
l
-alanine and
l
-2-aminobutyric acid, and selectively catalyzed
l
-alanine to
d
-alanine reversibly.
d
-Amino acid oxidase then catalyzed
d
-alanine to pyruvate stereoselectively. Furthermore, this method was also successfully used to remove the by-product
l
-alanine in the production of other neutral amino acids such as
l
-tertiary leucine and
l
-valine, suggesting that multienzymatic whole-cell catalysis can be employed to provide high purity products.
Microbial degradation is an important option for combating antibiotic pollution. Arthrobacter nicotianae OTC-16 was isolated as a novel tetracycline-degrading bacterium, which could degrade ...oxytetracycline/tetracycline (OTC/TET). Toxicity assessment indicated that this bacterium effectively converted OTC into byproducts with less toxicity to bacterial and algal indicators. Six degradation products of OTC were tentatively identified, and a potential biotransformation pathway was proposed that includes decarbonylation, reduction, and dehydration. Bioaugmentation of TC removal with this bacterium was further studied in various matrices. In aqueous media, strain OTC-16 accelerated OTC removal over a temperature range of 20–35 ℃, pH range of 6.0–9.0, and OTC concentration range of 25–150 mg L−1. The strain also facilitated the decrease of OTC and TET concentrations in both swine and chicken manures, with a maximum decrease of 91.54%, and increased the degradation of OTC in soils by 8.22–45.45%. A unique advantage of this bacterium in promoting OTC degradation in alkaline environments was demonstrated, where it successfully competed with the indigenous microbiota and largely decreased the relative abundances of the studied tetracycline resistance genes (tetB and tetW) in soil. This work offers a better understanding of the antibiotic bioaugmentation and new microbial sources.
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•An Arthrobacter nicotianae strain is isolated to degrade tetracyclines.
•The bacterium transforms oxytetracycline into nontoxic or low-toxic metabolites.
•Possible degradation pathways and products of oxytetracycline were proposed.
•Successful bioaugmentation of tetracyclines removal in water, manure, and soil.
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