Expanding the Toolbox of R-Selective Amine Transaminases by Identification and Characterization of New Members

Amine transaminases (ATAs) are used to synthesize enantiomerically pure amines, which are building blocks for pharmaceuticals and agrochemicals. R-selective ATAs belong to the fold type IV PLP-dependent enzymes, and different sequence-, structure- and substrate scope-based features have been identified in the past decade. However, our knowledge is still restricted due to the limited number of characterized (R)-ATAs, with additional bias towards fungal origin. We aimed to expand the toolbox of (R)-ATAs and contribute to the understanding of this enzyme subfamily. We identified and characterized four new (R)-ATAs. The ATA from Exophiala sideris contains a motif characteristic for d -ATAs, which was previously believed to be a disqualifying factor for (R)-ATA activity. The crystal structure of the ATA from Shinella is the first from a Gram-negative bacterium. The ATAs from Pseudonocardia acaciae and Tetrasphaera japonica are the first characterized (R)-ATAs with a shortened/missing N-terminal helix. The active-site charges vary significantly between the new and known ATAs, correlating with their diverging substrate scope.     

A combination of near-infrared hyperspectral imaging with two-dimensional correlation analysis for monitoring the content of biogenic amines in mutton

The study investigated the feasibility of using a combination of near-infrared hyperspectral imaging (NIR-HSI) with two-dimensional correlation (2DCOS) analysis for rapid and non-destructive determination of the content of biogenic amines in mutton during refrigerated storage. Total contents of biogenic amines (TBA) were used as the perturbation. By analysing the synchronous and asynchronous two-dimensional correlation spectra, sensitive variables that were closely related to TBA contents were obtained. The results showed that the wavelengths in the spectra range of 1002–1335 nm were the research area for the detection of TBA contents in mutton. The least-squares support vector machines (LSSVM) model based on effective wavelengths selected by competitive adaptive reweighted sampling (CARS) from 2DCOS analysis showed excellent results, with correlation coefficient in prediction (Rp) of 0.91, root mean square error in prediction (RMSEP) of 1.67 mg kg⁻¹ and the ratio of performance deviation (RPD) of 2.76. The research demonstrated that the combination of NIR-HSI and 2DCOS could be used as an effective method for monitoring the content of biogenic amines in mutton.     

Crude Oil Production

Current data on crude oil, field/lease condensate, and natural gas liquids produced from NGL plants. Updated on a monthly basis.     

Hop bitter acids inhibit carbohydrate metabolism,enhance biogenic amine metabolism and alter L-malic acid,glutamic acid and arginine metabolism of Lactobacillus brevis 49

Beer contains only limited amounts of readily fermentable carbohydrates and amino acids. Beer spoilage lactic acid bacteria have to come up with metabolic strategies in order to deal with selective nutrient content. The research was performed to investigate the influence of iso-α-acids on the metabolism of organic acids, biogenic amines (BAs), off-flavour compounds, carbohydrates and amino acids of Lactobacillus brevis 49. Only glyoxylic acid and ethyl formate in de man, rogosa, sharpe broth was consumed, and multiple organic acids, BAs and off-flavour compounds were produced. By supplementing a series of concentrations of hop iso-α-acids, consumption of L-malic acid, glutamic acid and arginine and generation of BAs were found benefit for bacteria to develop hop-resistance. In the metabolism of carbohydrates, glucose was preferred over maltose and maltriose, and hops significantly inhibited the utilisation of carbohydrates. The results provide comprehensive information of metabolites of L. brevis 49 under various concentrations of hop stress.     

Crude Oil Production

Current data on crude oil, field/lease condensate, and natural gas liquids produced from NGL plants. Updated on a monthly basis.     

变质胺液净化复活技术进展

用于脱硫及脱碳的胺液在长期使用中因降解或杂质混入发生变质，导致脱硫脱碳效率下降、胺液发泡、装置腐蚀及能耗增大等系列问题，而胺液净化复活技术是解决胺液系统问题的有效手段。本文从变质胺液中污染物出发，分别总结了固体颗粒物、烃类及表面活性物质、胺变质产物及热稳定盐的成因、危害及其控制手段。针对热稳定盐等重点难处理污染物，主要介绍了蒸馏回收、离子交换以及电渗析等净化技术的技术原理及国内外研究与应用概况，并对技术特点进行总结分析。最后通过技术对比指出，电渗析因具备胺液回收率高、热稳定盐净化深度高、能耗适中、产生少量易处理污染物等特点，是我国在胺液净化复活技术领域最具潜力的发展方向。     

NMR Profiling of Exhaled Breath Condensate Defines Different Metabolic Phenotypes of Non-Cystic Fibrosis Bronchiectasis

Nuclear-magnetic-resonance (NMR) profiling of exhaled breath condensate (EBC) provides insights into the pathophysiology of bronchiectasis by identifying specific biomarkers. We evaluated whether NMR-based metabolomics discriminates the EBC-derived metabolic phenotypes (“metabotypes”) of 41 patients with non-cystic fibrosis (nCF) bronchiectasis of various etiology [24 subjects with Primary Ciliary Dyskinesia (PCD); 17 patients with bronchiectasis not associated with PCD (nCF/nPCD)], who were compared to 17 healthy subjects (HS). NMR was used for EBC profiling, and Orthogonal Projections to Latent Structures with partial least-squares discriminant analysis (OPLS-DA) was used as a classifier. The results were validated by using the EBC from 17 PCD patients not included in the primary analysis. Different statistical models were built, which compared nCF/nPCD and HS, PCD and HS, all classes (nCF/nPCD-PCD-HS), and, finally, PCD and nCF/nPCD. In the PCD-nCF/nPCD model, four statistically significant metabolites were able to discriminate between the two groups, with only a minor reduction of the quality parameters. In particular, for nCF/nPCD, acetone/acetoin and methanol increased by 21% and 18%, respectively. In PCD patients, ethanol and lactate increased by 25% and 28%, respectively. They are all related to lung inflammation as methanol is found in the exhaled breath of lung cancer patients, acetone/acetoin produce toxic ROS that damage lung tissue in CF, and lactate is observed in acute inflammation. Interestingly, a high concentration of ethanol hampers cilia beating and can be associated with the genetic defect of PCD. Model validation with 17 PCD samples not included in the primary analysis correctly predicted all samples. Our results indicate that NMR of EBC discriminates nCF/nPCD and PCD bronchiectasis patients from HS, and patients with nCF/nPCD from those with PCD. The metabolites responsible for between-group separation identified specific metabotypes, which characterize bronchiectasis of a different etiology.     

The assessment of commercial beef and chicken bouillons in terms of heterocyclic aromatic amines and some of their precursors

Herein, the assessment of commercial beef and chicken bouillons in terms of heterocyclic aromatic amines (HAAs) and some of their precursors was evaluated. Creatine and creatinine levels were ranged between 0.57–0.80 and 0.28–0.94 mg g⁻¹, respectively. Glutamic acid was found to be the most abundant amino acid in both bouillons. 2-amino-3,7,8-trimethylimidazo[4,5-ƒ]quinoxaline (7,8-DiMeIQx, up to 0.03 ng g⁻¹) was the only quantified analyte in beef bouillons, whereas it (up to 0.08 ng g⁻¹) was determined in addition to 2-amino-3-methylimidazo[4,5-ƒ]quinoxaline (IQx, up to 0.08 ng g⁻¹) in chicken bouillons. Creatine, creatinine and free amino acid composition did not have the capacity to initiate the formation of HAAs. Therefore, bouillons do not pose risk in terms of HAAs. However, it should be noted that multiple factors, such as the substrate amount and production conditions, may affect the results. Glutamic acid content is remarkable in commercial bouillons sold in Turkey.     

贮藏温度对青方腐乳生物胺和理化性质的影响

以市售的青方腐乳为原料，研究了开盖后贮藏在不同温度下其生物胺含量、水分活度（Aw）、pH值、氨基酸态氮的动态变化，探讨了生物胺与理化指标之间的相关性。结果显示，青方腐乳在不同温度下贮藏至15 d时总生物胺含量＞1 000 mg/kg，且组胺含量＞100 mg/kg，酪胺含量在贮藏至30 d时（除25 ℃第30天）＞100 mg/kg，均超过了相关标准推荐的限量值；在不同贮藏温度下，青方腐乳水分活度＞0.8，pH变化规律基本一致，在第15天达到最大，4 ℃贮藏时，氨基酸态氮含量随贮藏时间的延长而增大。相关性分析结果表明，理化指标的变化与生物胺存在一定的关系，pH与苯乙胺、尸胺、组胺和亚精胺呈极显著正相关（P＜0.01）。结果表明，为了食用安全，腐乳开盖后应尽量在15 d内食用完。