[Optimized nutrients management improved citrus yield and fruit quality in China: A meta-analysis]. / å »åˆ†ä¼˜åŒ–ç®¡ç†æé«˜æˆ‘å›½æŸ‘æ©˜äº§é‡å’Œå“è´¨çš„æ•´åˆåˆ†æž.

Clarifying current situation of farmers' fertilization and yield in citrus producing areas and the effects of different fertilization measures can provide a scientific basis for improving the yield and quality of citrus in China. We retrieved 92 literatures on citrus fertilization from the CNKI and Web of Science to examine the impacts of nitrogen (N), phosphorus (P or P2O5), and potassium (K or K2O) fertilizer dosage and partial productivity under farmers' conventional fertilization and experts' optimized fertilization, as well as the effects of optimized fertilization measures on citrus yield and quality by using meta-analysis approach. The average conventional application rates of N, P2O5, and K2O were 507.3, 262.2, and 369.3 kg·hm-2 in citrus production in China. Compared with conventional fertilization, optimized fertilization resulted in a reduction of N and P2O5 by 14.7% and 8.3%, an increase in K2O application by 6.6%, which promoted partial productivity of N, P2O5, and K2O fertilizers by 7.8%, 18.4%, and 14.7%, correspondingly. The optimized fertilization resulted in 11.9% and 2.8% increase in fruit yield and single fruit weight, while improved vitamin C content (Vc, 3.1%), total soluble solids (TSS, 5.9%) and total sugar content (TSC, 8.6%). Additionally, it also led to a reduction in titratable acid (TA, -3.4%) and total acid content (TAC, -3.6%), and consequently elevated the TSS/TA (14.0%) and TSC/TAC (9.5%). Among different optimized fertilization methods, the effect of optimized NPK + medium and/or micro element fertilizer on citrus yield and fruit quality was the best, especially NPK decrement ≤25% between optimized NPK measures. The effect of conventional NPK + organic fertilizer was higher than conventional NPK + medium and/or micro element fertilizer. However, different citrus varieties, including mandarins, pomelos, and oranges, showed different responses to optimized fertilization. Optimized fertilization management could synergistically improve citrus yield, fertilizer use efficiency, and fruit quality. Therefore, the strategy of integrated nutrient management1 with reducing NPK fertilizer, balancing medium and/or micro nutrient fertilizer and improving soil fertility by organic fertilizer should be adopted according to local conditions in citrus producing areas of China.

Improved terephthalic acid production from p-xylene using metabolically engineered Pseudomonas putida.

Terephthalic acid (TPA) is an important commodity chemical used as a monomer of polyethylene terephthalate (PET). Since a large quantity of PET is routinely manufactured and consumed worldwide, the development of sustainable biomanufacturing processes for its monomers (i.e. TPA and ethylene glycol) has recently gained much attention. In a previous study, we reported the development of a metabolically engineered Escherichia coli strain producing 6.7 g/L of TPA from p-xylene (pX) with a productivity and molar conversion yield of 0.278 g/L/h and 96.7 mol%, respectively. Here, we report metabolic engineering of Pseudomonas putida KT2440, a microbial chassis particularly suitable for the synthesis of aromatic compounds, for improved biocatalytic conversion of pX to TPA. To develop a plasmid-free, antibiotic-free, and inducer-free biocatalytic process for cost-competitive TPA production, all heterologous genes required for the synthetic pX-to-TPA bioconversion pathway were integrated into the chromosome of P. putida KT2440 by RecET-based markerless recombineering and overexpressed under the control of constitutive promoters. Next, TPA production was enhanced by integrating multiple copies of the heterologous genes to the ribosomal RNA genes through iteration of recombineering-based random integration and subsequent screening of high-performance strains. Finally, fed-batch fermentation process was optimized to further improve the performance of the engineered P. putida strain. As a result, 38.25 ± 0.11 g/L of TPA was produced from pX with a molar conversion yield of 99.6 ± 0.6%, which is equivalent to conversion of 99.3 ± 0.8 g pX to 154.6 ± 0.5 g TPA. This superior pX-to-TPA biotransformation process based on the engineered P. putida strain will pave the way to the commercial biomanufacturing of TPA in an industrial scale.

Workplace ostracism and employee wellbeing: A conservation of resource perspective.

Introduction: As a common phenomenon of workplace ostracism in corporate management, it is urgent to clarify how it affects employee well-being. Methods: Based on Conservation of Resource Theory, this study investigates the mechanisms of workplace ostracism on employee well-being and examines the mediating role of emotional exhaustion and the moderating role of team forgiveness climate by surveying 282 employees from 68 companies in mainland China. Results: The results show that (1) workplace ostracism negatively affects employee well-being; (2) emotional exhaustion plays a mediating role between workplace ostracism and employee well-being; (3) team forgiveness climate weakens the negative effect of workplace ostracism on emotional exhaustion and negatively moderates the indirect effect of workplace ostracism on employee well-being through emotional exhaustion. Discussion: It tries to provide theoretical basis and practical guidance for eliminating the negative effects of workplace ostracism and focusing on employee well-being.

[Characteristics of soil animal community with different garden plants and various planting periods in Wenjiang District, Chengdu, China]. / æˆéƒ½å¸‚æ¸©æ±ŸåŒºä¸åŒæ ½æ¤å¹´é™å›­æž—æ¤ç‰©åœŸå£¤åŠ¨ç‰©ç¾¤è½ç‰¹å¾.

In order to provide scientific guidance for soil quality evaluation and optimum management of flower and seedling industry, we investigated the characteristics of soil animal community with different garden plants and various planting periods in Wenjiang District, Chengdu. A total of 10258 soil animals belonging to 26 orders and 78 families were captured in four sampling times. There were significant differences in the taxonomic richness in the plots with different garden plants, generally highest in plots with Loropetalum chinense var. rubrum or Ginkgo biloba and lowest in plot with Zoysia japonica. The taxonomic richness was lower in the plots with different garden plants than the control. Taxonomic richness and abundance of soil fauna in Osmanthus fragrans plot did not change across sampling seasons. The abundance but not taxonomic richness of soil fauna in other plots had obvious seasonal variations. Different garden plants and various planting periods significantly influenced soil faunal diversity indices. Density-group index (DG) and Margalef richness index (D) in G. biloba plot, as well as Shannon diversity index (H) and D index in Z. japonica plot decreased significantly with the increases of planting period. The DG and D indices of soil animals in O. fragrans plot increased significantly with increasing planting period. The indices of soil animal diversity in L. chinense var. rubrum plot did not change regularly with planting period. The DG, D, and H indices were lowest in O. fragrans plot with different planting periods. Results of hierarchical clustering and canonical correlation analyse (CCA) indicated that garden plant species had stronger effects on the habitat than planting period. Responses of soil fauna to various habitats were different, with available P and soil pH having stronger effects on soil fauna. Our results indicated that soil animal community shifted with the changes of garden plant and planting period as well as management and cultivation methods. Excessive human interference and monoculture had negative effects on soil animal community and caused soil degradation.

Metabolic engineering of Escherichia coli for the production of benzoic acid from glucose.

Benzoic acid (BA) is an important platform aromatic compound in chemical industry and is widely used as food preservatives in its salt forms. Yet, current manufacture of BA is dependent on petrochemical processes under harsh conditions. Here we report the de novo production of BA from glucose using metabolically engineered Escherichia coli strains harboring a plant-like ß-oxidation pathway or a newly designed synthetic pathway. First, three different natural BA biosynthetic pathways originated from plants and one synthetically designed pathway were systemically assessed for BA production from glucose by in silico flux response analyses. The selected plant-like ß-oxidation pathway and the synthetic pathway were separately established in E. coli by expressing the genes encoding the necessary enzymes and screened heterologous enzymes under optimal plasmid configurations. BA production was further optimized by applying several metabolic engineering strategies to the engineered E. coli strains harboring each metabolic pathway, which included enhancement of the precursor availability, removal of competitive reactions, transporter engineering, and reduction of byproduct formation. Lastly, fed-batch fermentations of the final engineered strain harboring the ß-oxidation pathway and the strain harboring the synthetic pathway were conducted, which resulted in the production of 2.37 ± 0.02 g/L and 181.0 ± 5.8 mg/L of BA from glucose, respectively; the former being the highest titer reported by microbial fermentation. The metabolic engineering strategies developed here will be useful for the production of related aromatics of high industrial interest.

Microbial production of methyl anthranilate, a grape flavor compound.

Methyl anthranilate (MANT) is a widely used compound to give grape scent and flavor, but is currently produced by petroleum-based processes. Here, we report the direct fermentative production of MANT from glucose by metabolically engineered Escherichia coli and Corynebacterium glutamicum strains harboring a synthetic plant-derived metabolic pathway. Optimizing the key enzyme anthranilic acid (ANT) methyltransferase1 (AAMT1) expression, increasing the direct precursor ANT supply, and enhancing the intracellular availability and salvage of the cofactor S-adenosyl-l-methionine required by AAMT1, results in improved MANT production in both engineered microorganisms. Furthermore, in situ two-phase extractive fermentation using tributyrin as an extractant is developed to overcome MANT toxicity. Fed-batch cultures of the final engineered E. coli and C. glutamicum strains in two-phase cultivation mode led to the production of 4.47 and 5.74 g/L MANT, respectively, in minimal media containing glucose. The metabolic engineering strategies developed here will be useful for the production of volatile aromatic esters including MANT.

Metabolic engineering of microorganisms for production of aromatic compounds.

Metabolic engineering has been enabling development of high performance microbial strains for the efficient production of natural and non-natural compounds from renewable non-food biomass. Even though microbial production of various chemicals has successfully been conducted and commercialized, there are still numerous chemicals and materials that await their efficient bio-based production. Aromatic chemicals, which are typically derived from benzene, toluene and xylene in petroleum industry, have been used in large amounts in various industries. Over the last three decades, many metabolically engineered microorganisms have been developed for the bio-based production of aromatic chemicals, many of which are derived from aromatic amino acid pathways. This review highlights the latest metabolic engineering strategies and tools applied to the biosynthesis of aromatic chemicals, many derived from shikimate and aromatic amino acids, including L-phenylalanine, L-tyrosine and L-tryptophan. It is expected that more and more engineered microorganisms capable of efficiently producing aromatic chemicals will be developed toward their industrial-scale production from renewable biomass.

Metabolic Engineering of Escherichia coli for Efficient Production of 2-Pyrone-4,6-dicarboxylic Acid from Glucose.

2-Pyrone-4,6-dicarboxylic acid (PDC) is a pseudoaromatic dicarboxylic acid and is a promising biobased building block chemical that can be used to make diverse polyesters with novel functionalities. In this study, Escherichia coli was metabolically engineered to produce PDC from glucose. First, an efficient biosynthetic pathway for PDC production from glucose was suggested by in silico metabolic flux simulation. This best pathway employs a single-step biosynthetic route to protocatechuic acid (PCA), a metabolic precursor for PDC biosynthesis. On the basis of the selected PDC biosynthetic pathway, a shikimate dehydrogenase (encoded by aroE)-deficient E. coli strain was engineered by introducing heterologous genes of different microbial origin encoding enzymes responsible for converting 3-dehydroshikimate (DHS) to PDC, which allowed de novo biosynthesis of PDC from glucose. Next, production of PDC was further improved by applying stepwise rational metabolic engineering strategies. These include elimination of feedback inhibition on 3-deoxy-d-arabino-heptulosonate-7-phosphate synthase (encoded by aroG) by overexpressing a feedback-resistant variant, enhancement of the precursor phosphoenolpyruvate supply by changing the native promoter of the ppsA gene with the strong trc promoter, and reducing accumulation of the major byproduct DHS by overexpression of a DHS importer (encoded by shiA). Furthermore, cofactor (NADP+/NADPH) utilization was manipulated through genetic modifications of the E. coli soluble pyridine nucleotide transhydrogenase (encoded by sthA), and the resultant impact on PDC production was investigated. Fed-batch fermentation of the final engineered E. coli strain allowed production of 16.72 g/L of PDC from glucose with the yield and productivity of 0.201 g/g and 0.172 g/L/h, respectively, representing the highest PDC production performance indices reported to date.

Metabolic engineering of Escherichia coli for the production of indirubin from glucose.

Indirubin is an indole alkaloid that can be used to treat various diseases including granulocytic leukemia, cancer, and Alzheimer's disease. Microbial production of indirubin has so far been achieved by supplementation of rather expensive substrates such as indole or tryptophan. Here, we report the development of metabolically engineered Escherichia coli strain capable of producing indirubin directly from glucose. First, the Methylophaga aminisulfidivorans flavin-containing monooxygenase (FMO) and E. coli tryptophanase (TnaA) were introduced into E. coli in order to complete the biosynthetic pathway from tryptophan to indirubin. Further engineering was performed through rational strategies including disruption of the regulatory repressor gene trpR and removal of feedback inhibitions on AroG and TrpE. Then, combinatorial approach was employed by systematically screening eight genes involved in the common aromatic amino acid pathway. Moreover, availability of the aromatic precursor substrates, phosphoenolpyruvate and erythrose-4-phosphate, was enhanced by inactivating the pykF (pyruvate kinase I) and pykA (pyruvate kinase II) genes, and by overexpressing the tktA gene (encoding transketolase), respectively. Fed-batch fermentation of the final engineered strain led to production of 0.056 g/L of indirubin directly from glucose. The metabolic engineering and synthetic biology strategies reported here thus allows microbial fermentative production of indirubin from glucose.

Biotransformation of p-xylene into terephthalic acid by engineered Escherichia coli.

Terephthalic acid (TPA) is an important industrial chemical currently produced by energy intensive and potentially hazardous p-xylene (pX) oxidation process. Here we report the development of metabolically engineered Escherichia coli system for biological transformation of pX into TPA. The engineered E. coli strain harbours a synthetic TPA pathway optimized through manipulation of expression levels of upstream and downstream modules. The upstream pathway converts pX to p-toluic acid (pTA) and the downstream pathway transforms pTA to TPA. In a two-phase partitioning fermentation, the engineered strain converts 8.8 g pX into 13.3 g TPA, which corresponds to a conversion yield of 96.7 mol%. These results suggest that the E. coli system presented here might be a promising alternative for the large-scale biotechnological production of TPA and lays the foundations for the future development of sustainable approaches for TPA production.

Recent advances in microbial production of fuels and chemicals using tools and strategies of systems metabolic engineering.

The advent of various systems metabolic engineering tools and strategies has enabled more sophisticated engineering of microorganisms for the production of industrially useful fuels and chemicals. Advances in systems metabolic engineering have been made in overproducing natural chemicals and producing novel non-natural chemicals. In this paper, we review the tools and strategies of systems metabolic engineering employed for the development of microorganisms for the production of various industrially useful chemicals belonging to fuels, building block chemicals, and specialty chemicals, in particular focusing on those reported in the last three years. It was aimed at providing the current landscape of systems metabolic engineering and suggesting directions to address future challenges towards successfully establishing processes for the bio-based production of fuels and chemicals from renewable resources.