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Amino acids are naturally occurring and structurally diverse metabolites in biological system, whose potentials for chemical expansion, however, have not been fully explored. Here, we devise a metabolic platform capable of producing industrially important C3-C5 diols from amino acids. The presented platform combines the natural catabolism of charged amino acids with a catalytically efficient and thermodynamically favorable diol formation pathway, created by expanding the substrate scope of the carboxylic acid reductase toward noncognate ω-hydroxylic acids. Using the established platform as gateways, seven different diol-convertible amino acids are converted to diols including 1,3-propanediol, 1,4-butanediol, and 1,5- pentanediol. Particularly, we afford to optimize the production of 1,4-butanediol and demonstrate the de novo production of 1,5-pentanediol from glucose, with titers reaching 1.41 and 0.97 g l−1, respectively. Our work presents a metabolic platform that enriches the pathway repertoire for nonnatural diols with feedstock flexibility to both sugar and protein hydrolysates.

3-Hydroxypropionic acid (3HP), an important three carbon (C3) chemical, is designated as one of the top platform chemicals with an urgent need for improved industrial production. Halomonas bluephagenesis shows the potential as a chassis for competitive bioproduction of various chemicals due to its ability to grow under an open, unsterile and continuous process. Here, we report the strategy for producing 3HP and its copolymer poly(3-hydroxybutyrate-co-3-hydroxypropionate) (P3HB3HP) by the development of H. bluephagenesis . The transcriptome analysis reveals its 3HP degradation and synthesis pathways involving endogenous synthetic enzymes from 1,3-propanediol. Combing the optimized expression of aldehyde dehydrogenase (AldD Hb ), an engineered H. bluephagenesis strain of whose 3HP degradation pathway is deleted and that overexpresses alcohol dehydrogenases (AdhP) on its genome under a balanced redox state, is constructed with an enhanced 1.3-propanediol-dependent 3HP biosynthetic pathway to produce 154 g L −1 of 3HP with a yield and productivity of 0.93 g g −1 1,3-propanediol and 2.4 g L −1 h −1 , respectively. Moreover, the strain could also accumulate 60% poly(3-hydroxybutyrate-co-32–45% 3-hydroxypropionate) in the dry cell mass, demonstrating to be a suitable chassis for hyperproduction of 3HP and P3HB3HP. 3-Hydroxypropionic acid (3HP) is an important platform chemical. Here, the authors engineer Halomonas bluephagenesis by deleting newly identified degradation pathway and balancing redox state to achieve high level production of 3HP and its copolymer under open and unsterile conditions.

Microbial fermentations are widely used for the production of chemicals used as pharmaceuticals, food ingredients, materials, solvents, and biofuels.Technoeconomic analysis of a given fermentation process is important to perform before scaling the process to levels that enable commercial production.Titer, rate, and yield (TRY) of the fermentation process are key metrics that are used for technoeconomic analysis.TRY metrics have different impacts on the technoeconomic analysis, and it is important to be aware of these differences. Microbial fermentations offer the opportunity to produce a wide range of chemicals in a sustainable fashion, but it is important to carefully evaluate the production costs. This can be done on the basis of evaluation of the titer, rate, and yield (TRY) of the fermentation process. Here we describe how the three TRY metrics impact the technoeconomics of a microbial fermentation process, and we illustrate the use of these for evaluation of different processes in the production of two commodity chemicals, 1,3-propanediol (PDO) and ethanol, as well as for the fine chemical penicillin. On the basis of our discussions, we provide some recommendations on how the TRY metrics should be reported when new processes are described. Microbial fermentations offer the opportunity to produce a wide range of chemicals in a sustainable fashion, but it is important to carefully evaluate the production costs. This can be done on the basis of evaluation of the titer, rate, and yield (TRY) of the fermentation process. Here we describe how the three TRY metrics impact the technoeconomics of a microbial fermentation process, and we illustrate the use of these for evaluation of different processes in the production of two commodity chemicals, 1,3-propanediol (PDO) and ethanol, as well as for the fine chemical penicillin. On the basis of our discussions, we provide some recommendations on how the TRY metrics should be reported when new processes are described.

A competitive colorimetric assay has been established to detect chloramphenicol (CAP). It is based on the use of colloidal and electrostatically stabilized aptamer-modified gold nanoparticles (GNPs). The CAP aptamer is modified by a sequence of 5 adenosine groups to anchor it on the surface of GNPs. It can competitively capture two compounds, viz. D-(-)-threo-2-amino-1-(4-nitrophenyl)-1,3-propanediol (CAP-base, with a positive charge) and CAP (which is uncharged). The capture of the positively charged CAP-base triggers the aggregation of modified GNPs in salt-containing solution, and this causes a color change from red to purple. However, in the presence of CAP and CAP-base, the capture of the uncharged CAP weakens this color change by a competing process for capture. Thus, the concentration of CAP is associated with the degree of deaggregation of GNPs and can be quantified by the ratio of absorbances at 620 nm and 520 nm. The assay has a 22 nM limit of detection in acidic solution, and the response is linear in the range of 0.20 to 3.20 μM CAP concentration. This assay was successfully applied to the determination of CAP in spiked environmental water samples. Conceivably, this method has a wide scope in that it may be applied to a wide range of analytes if respective aptamers are available. Graphical abstract Schematic presentation of a competitive non-cross linking deaggregating method for detecting chloramphenicol. The surface charge of polyA-Apt@GNPs and its aggregation degree (purple) are determined by the charge of target. (CAP-base: precursor of CAP; PolyA-Apt@GNPs: 5′-polyA-modified DNA aptamer functionalized gold nanoparticles.)

The demand for 1,3-propanediol (1,3-PDO) has increased sharply due to its role as a monomer for the synthesis of polytrimethylene terephthalate (PTT). Although Clostridium butyricum is considered to be one of the most promising bioproducers for 1,3-PDO, its low productivity hinders its application on industrial scale because of the longer time needed for anaerobic cultivation. In this study, an excellent C. butyricum (DL07) strain was obtained with high-level titer and productivity of 1,3-PDO, i.e., 104.8 g/L and 3.38 g/(L•h) vs. 94.2 g/L and 3.04 g/(L•h) using pure or crude glycerol as substrate in fed-batch fermentation, respectively. Furthermore, a novel sequential fed-batch fermentation was investigated, in which the next bioreactor was inoculated by C. butyricum DL07 cells growing at exponential phase in the prior bioreactor. It could run steadily for at least eight cycles. The average concentration of 1,3-PDO in eight cycles was 85 g/L with the average productivity of 3.1 g/(L•h). The sequential fed-batch fermentation could achieve semi-continuous production of 1,3-PDO with higher productivity than repeated fed-batch fermentation and would greatly contribute to the industrial production of 1,3-PDO by C. butyricum.Key points• A novel C. butyricum strain was screened to produce 104.8 g/L 1,3-PDO from glycerol.• Corn steep liquor powder was used as a cheap nitrogen source for 1,3-PDO production.• A sequential fed-batch fermentation process was established for 1,3-PDO production.• An automatic glycerol feeding strategy was applied in the production of 1,3-PDO.

Optically pure 1,2-diols and 1,3-diols are the most privileged structural motifs, widely present in natural products, pharmaceuticals and chiral auxiliaries or ligands. However, their synthesis relies on the use of toxic or expensive metal catalysts or suffer from low regioselectivity. Catalytic asymmetric synthesis of optically pure 1,n-diols from bulk chemicals in a highly stereoselective and atom-economical manner remains a formidable challenge. Here, we disclose a versatile and modular method for the synthesis of enantioenriched 1,2-diols and 1,3-diols from the high-production-volume chemicals ethane-1,2-diol (MEG) and 1,3-propanediol (PDO), respectively. The key to success is to temporarily mask the diol group as an acetonide, which imparts selectivity to the key step of C(sp 3 )-H functionalization. Additionally, 1,n-diols containing two stereogenic centers are also prepared through diastereoselective C(sp 3 )-H functionalization. The late-stage functionalization of biological active compounds and the expedient synthesis of chiral ligands and pharmaceutically relevant molecules further highlight the synthetic potential of this protocol. Catalytic asymmetric synthesis of optically pure 1,n-diols from bulk chemicals in a stereoselective and atom-economical manner remains a challenge. Here, the authors report a modular method for the synthesis of enantioenriched 1,2-diols and 1,3-diols from the high-production-volume chemicals ethylene glycol and 1,3-propanediol, respectively.

1,3-Propanediol (1,3-PDO) has numerous industrial applications in the synthesis of the monomer of the widely used fiber polytrimethylene terephthalate. In this work, the production of 1,3-PDO by Klebsiella pneumoniae is increased by dual-substrate cultivation and fed-batch fermentation. Experimental results indicate that the production of 1,3-PDO can be elevated to 16.09 g/L using a dual substrate ratio (of glucose to crude glycerol) of 1/30 and to 20.73 g/L using an optimized dual-substrate ratio of 1/20. Ultimately, the optimal dual-substrate feeding for a 5 L scale fed-batch fermenter that maximizes 1,3-PDO production (29.69 g/L) is determined. This production yield is better than that reported in most related studies. Eventually, the molecular weight and chemical structure of 1,3-PDO were obtained by FAB-MS, 1H-NMR, and 13C-NMR. Also, in demonstrating the effectiveness of the fermentation strategy in increasing the production and production yield of 1,3-PDO, experimental results indicate that the fermentation of 1,3-PDO is highly promising for commercialization.

Here we demonstrate that Tris (2-amino-2-(hydroxymethyl)-1,3-propanediol), largely used as a buffering agent, is a linear mixed inhibitor ( K i = 12 ± 2 mM and α = 3 ± 1) of the GH1 β-glucosidase from the insect Spodoptera frugiperda (Sfβgly). Such an inhibition mechanism implies the formation of a non-productive ESI complex involving Sfβgly, substrate, and Tris. In addition, Tris binding reduces by 3 fold the enzyme affinity for the substrate. Hence, at concentrations higher than the K i , Tris can completely abolish Sfβgly activity, whereas even at lower concentrations the presence of Tris causes underestimation of β-glucosidase kinetic parameters ( K m and k cat ). In agreement with the inhibition mechanism, computational docking showed that Tris could bind to a pocket placed at the lateral of the active site opening in the Sfβgly-substrate complex, hence leading to the formation of an ESI complex. In agreement with the crystallographic data available, computational docking also showed that Tris may find binding spots in the interior of the active site of the Sfβgly and several GH1 β-glucosidases. Moreover, the variety of their active site shapes results in a multiplicity of binding profiles, foreseeing different inhibition mechanisms. Thus, Tris inhibition may affect other GH1 β-glucosidases. This remark should be taken into account in their study, highlighting the importance of the appropriate buffer for accurate enzyme characterization.

Pressurized liquid extraction (PLE) is considered an advanced extraction technique developed in the mid-1990s with the aim of saving time and reducing solvent with respect to traditional extraction processes. It is commonly used with solid and semi-solid samples and employs solvent extraction at elevated temperatures and pressures, always below the respective critical points, to maintain the solvent in a liquid state throughout the extraction procedure. The use of these particular pressure and temperature conditions changes the physicochemical properties of the extraction solvent, allowing easier and deeper penetration into the matrix to be extracted. Furthermore, the possibility to combine the extraction and clean-up steps by including a layer of an adsorbent retaining interfering compounds directly in the PLE extraction cells makes this technique extremely versatile and selective. After providing a background on the PLE technique and parameters to be optimized, the present review focuses on recent applications (published in the past 10 years) in the field of food contaminants. In particular, applications related to the extraction of environmental and processing contaminants, pesticides, residues of veterinary drugs, mycotoxins, parabens, ethyl carbamate, and fatty acid esters of 3-monochloro-1,2-propanediol and 2-monochloro-1,3-propanediol from different food matrices were considered.

Diols encompass important bulk and fine chemicals for the chemical, pharmaceutical and cosmetic industries. During the past decades, biological production of C3-C5 diols from renewable feedstocks has received great interest. Here, we elaborate a general principle for effectively synthesizing structurally diverse diols by expanding amino acid metabolism. Specifically, we propose to combine oxidative and reductive formations of hydroxyl groups from amino acids in a thermodynamically favorable order of four reactions catalyzed by amino acid hydroxylase, L-amino acid deaminase, α-keto acid decarboxylase and aldehyde reductase consecutively. The oxidative formation of hydroxyl group from an alkyl group is energetically more attractive than the reductive pathway, which is exclusively used in the synthetic pathways of diols reported so far. We demonstrate this general route for microbial production of branched-chain diols in E. coli . Ten C3-C5 diols are synthesized. Six of them, namely isopentyldiol (IPDO), 2-methyl-1,3-butanediol (2-M-1,3-BDO), 2-methyl-1,4-butanediol (2-M-1,4-BDO), 2-methyl-1,3-propanediol (MPO), 2-ethyl-1,3-propanediol (2-E-1,3-PDO), 1,4-pentanediol (1,4-PTD), have not been biologically synthesized before. This work opens up opportunities for synthesizing structurally diverse diols and triols, especially by genome mining, rational design or directed evolution of proper enzymes. Diols are important bulk and fine chemicals, but bioproduciton of branch-chain diols is hampered by the unknown biological route. Here, the authors report the expanding of amino acid metabolism for biosynthesis of branch-chain diols via a general route of combined oxidative and reductive formations of hydroxyl groups.