Production of gamma-aminobutyric acid by Lactobacillus brevis NCL912 using fed-batch fermentation

<p>Abstract</p> <p>Background</p> <p>Gamma-aminobutyric acid is a major inhibitory neurotransmitter in mammalian brains, and has several well-known physiological functions. Lactic acid bacteria possess special physiological activities and are generally regarded as safe. Therefore, using lactic acid bacteria as cell factories for gamma-aminobutyric acid production is a fascinating project and opens up a vast range of prospects for making use of GABA and LAB. We previously screened a high GABA-producer <it>Lactobacillus brevis </it>NCL912 and optimized its fermentation medium composition. The results indicated that the strain showed potential in large-scale fermentation for the production of gamma-aminobutyric acid. To increase the yielding of GABA, further study on the fermentation process is needed before the industrial application in the future. In this article we investigated the impacts of pyridoxal-5'-phosphate, pH, temperature and initial glutamate concentration on gamma-aminobutyric acid production by <it>Lactobacillus brevis </it>NCL912 in flask cultures. According to the data obtained in the above, a simple and effective fed-batch fermentation method was developed to highly efficiently convert glutamate to gamma-aminobutyric acid.</p> <p>Results</p> <p>Pyridoxal-5'-phosphate did not affect the cell growth and gamma-aminobutyric acid production of <it>Lb. brevis </it>NCL912. Temperature, pH and initial glutamate concentration had significant effects on the cell growth and gamma-aminobutyric acid production of <it>Lb. brevis </it>NCL912. The optimal temperature, pH and initial glutamate concentration were 30-35°C, 5.0 and 250-500 mM. In the following fed-batch fermentations, temperature, pH and initial glutamate concentration were fixed as 32°C, 5.0 and 400 mM. 280.70 g (1.5 mol) and 224.56 g (1.2 mol) glutamate were supplemented into the bioreactor at 12 h and 24 h, respectively. Under the selected fermentation conditions, gamma-aminobutyric acid was rapidly produced at the first 36 h and almost not produced after then. The gamma-aminobutyric acid concentration reached 1005.81 ± 47.88 mM, and the residual glucose and glutamate were 15.28 ± 0.51 g L^-1and 134.45 ± 24.22 mM at 48 h.</p> <p>Conclusions</p> <p>A simple and effective fed-batch fermentation method was developed for <it>Lb. brevis </it>NCL912 to produce gamma-aminobutyric acid. The results reveal that <it>Lb. brevis </it>NCL912 exhibits a great application potential in large-scale fermentation for the production of gamma-aminobutyric acid.</p

6-Gingerol Activates PI3K/Akt and Inhibits Apoptosis to Attenuate Myocardial Ischemia/Reperfusion Injury

6-Gingerol (6-G) is known to alleviate myocardial ischemia/reperfusion injury. However, the underlying molecular mechanisms of 6-G myocardial protection are not known. In this study, the protective effect of 6-G on ischemia/reperfusion (I/R) damage and whether such a mechanism was related to apoptosis inhibition and activation of phosphoinositide 3-kinases (PI3K)/serine/threonine kinase (Akt) signaling pathway were investigated. Rats were subjected to I/R in the presence or absence of 6-G and the changes of cardiac function, infarct size and histopathological changes, and the levels of cardiac troponin T, creatine kinase-MB, and myocardial apoptosis were examined. The expression of caspase-3, PI3K, p-Akt, and Akt was also determined. We found that 6-G (6 mg/kg) pretreatment significantly improved heart function and ameliorated infarct size and histopathological changes and cardiac troponin T and creatine kinase-MB levels induced by I/R. Moreover, pretreatment with 6-G significantly inhibited myocardial apoptosis and caspase-3 activation induced by I/R. 6-G also upregulated expression of PI3K, p-Akt, and Akt in myocardial tissues. Taken together, these findings suggest that 6-G inhibits apoptosis and activates PI3K/Akt signaling in response to myocardial I/R injury as a possible mechanism to attenuate I/R-induced injury in heart. These results might be important for developing novel strategies for preventing myocardial I/R injury

Stochastic Responses of Lightly Nonlinear Vibroimpact System with Inelastic Impact Subjected to External Poisson White Noise Excitation

A procedure for analyzing stationary responses of lightly nonlinear vibroimpact system with inelastic impact subjected to external Poisson white noise excitation is proposed. First, the original vibroimpact system is transformed to a new system without velocity jump in terms of the Zhuravlev nonsmooth coordinate transformation and the Dirac delta function. Second, the averaged generalized Fokker-Planck-Kolmogorov (FPK) equation for transformed system under parametric excitation of Poisson white noise is derived by stochastic averaging method. Third, the averaged generalized FPK equation is solved by using the perturbation technique and inverse transformation of the Zhuravlev nonsmooth coordinate transformation to obtain the approximately stationary solutions for response probability density functions of original vibroimpact system. Last, analytical and numerical results for two typical lightly nonlinear vibroimpact systems are presented to assess the effectiveness of the proposed method. It is found that they are in good agreement and the proposed method is quite effective

Steady-State Dynamical Response of a Strongly Nonlinear System with Impact and Coulomb Friction Subjected to Gaussian White Noise Excitation

The paper is devoted to the steady-state dynamical response analysis of a strongly nonlinear system with impact and Coulomb friction subjected to Gaussian white noise excitation. The Zhuravlev nonsmooth transformation of the state variables combined with the Dirac delta function is utilized to simplify the original system to one without velocity jump. Then, the steady-state probability density functions of the transformed system are derived in terms of the stochastic averaging method of energy envelope. The effectiveness of the presented analytical procedure is verified by those from the Monte Carlo simulation based on the original system. Effects of different restitution coefficients, amplitudes of friction, and noise intensities on the steady-state dynamical responses are investigated in detail. Results show different intensities of Gaussian white noise can affect the peaks value of the probability density functions, whereas the variations of restitution coefficients and amplitudes of friction can induce the occurrence of stochastic P-bifurcation

Construction of a High-Density Genetic Map for Pitaya Using the Whole Genome Resequencing Approach

Pitaya (Hylocereus undatus) is one of the most economic fleshy fruit tree crops. This study aimed at producing a high-density linkage genetic map of pitaya based on the whole genome resequencing (WGrS) approach. For this purpose, a bi-parental F1 population of 198 individuals was generated and genotyped by WGrS. High-quality polymorphic 6434 single polymorphism nucleotide (SNP) markers were extracted and used to construct a high-density linkage map. A total of 11 linkage groups were resolved as expected in accordance with the chromosome number. The map length was 14,128.7 cM with an average SNP interval of 2.2 cM. Homology with the sequenced reference genome was described, and the physical and genetic maps were compared with collinearity analysis. This linkage map in addition to the available genomic resources will help for quantitative trait mapping, evolutionary studies and marker-assisted selection in the important Hylocereus species

Stochastic and deterministic responses of an asymmetric quad-stable energy harvester

In this paper, stochastic and deterministic dynamical properties of an asymmetric quad-stable energy harvester are explored for improving the energy harvesting performance. Firstly, the harmonic balance method is utilized to explicitly derive the coupled relationship of the displacement amplitude, the constant term, and the output voltage amplitude. By means of direct numerical results, the existence of the multi-valued phenomenon of the asymmetric quad-stable energy harvester is found. Especially, the constant term is asymmetric due to the asymmetric characteristics. In addition, the influence of the depth of different potential wells on the highest orbit of inter-well oscillations is discussed. Finally, it is found that the symbol change of the largest Lyapunov exponent (LLE) of the harvester is consistent with the results derived by bifurcation diagrams, which verify the effectiveness of the LLE. The existence of noise can induce the harvester to transform from period motions to chaotic motions. The transition of the probability density function (PDF) of the harvester is influenced by the potential distribution and depth

Hypolipidemic effects of chitosan and its derivatives in hyperlipidemic rats induced by a high-fat diet

Background: Hyperlipidemia (HLP) is the primary risk factor of cardiovascular disease (CVD). Various factors, including genetics, physical inactivity, and daily nutritional habits, affect the prevalence of HLP. Recently, it was revealed that dietary fibers, such as pectin, psyllium, and especially chitosan (CTS), may play important roles in hypolipidemic management. Thus, this study aims to determine the hypolipidemic effect and mechanism of CTS and its water-soluble derivatives, chitosan oligosaccharides (MN≤1,000 Da (COSI) and MN≤3,000 Da (COSIII)), in male hyperlipidemic rats induced by a high-fat diet (HFD). Design: After the model creation, 120 Sprague-Dawley (SD) rats were equally assigned to 12 groups fed various diets as follows: the normal group with basic diet, an HFD group, an HFD group supplemented with three doses of CTS, COSI and COSIII groups, and an HFD group treated with simvastatin (7 mg/kg·d). After 6 weeks, body weight, fat/body ratio, and the relevant biomarkers of serum, liver, and feces were measured. Additionally, the histological analysis of liver and adipose tissue was performed, and the mRNA expressions of liver peroxisome proliferator-activated receptor-α (PPARα) and hepatic lipase (HL) were examined. Results: Compared with HFD group, rats fed CTS, COSI, and COSIII showed a better ability to regulate their body weight, liver and cardiac indices, fat/body ratio, as well as serum, liver, and fecal lipids, and simultaneously to maintain the appropriate activity of liver and serum superoxide dismutase (SOD), alanine aminotransferase (ALT), aspartate aminotransferase (AST), as well as liver and fecal total bile acids (TBA). Simultaneously, there had been a higher mRNA expression of PPARα and HL in the treatment groups. Conclusion: The obtained results suggested that these three function foods can effectively improve liver lipid metabolism by normalizing the expressions of PPARα and HL, and protect liver from the oxidized trauma by enhancing hepatic function, which could be potentially used to remedy hyperlipidemia

Novel diagnostic biomarkers related to necroptosis and immune infiltration landscape in acute myocardial infarction

Background Acute myocardial infarction (AMI) can occur suddenly, which may induce deadly outcomes, and the population suffering from AMI presents a younger trend. Necroptosis, the new cell necrosis type, is associated with the pathogenic mechanisms of diverse cardiovascular diseases (CVDs). Its diagnostic value and molecular mechanisms in AMI are still unclear. Objective: This study focused on determining key necroptosis-related genes as well as immune infiltration in AMI. Methods We first examined the GSE66360 dataset for identifying necroptosis-related differentially expressed genes (NRDEGs). Thereafter, GO and functional annotation were performed, then a PPI network was built. In addition, “CIBERSORT” in R was applied in comparing different immune infiltration degrees in AMI compared with control groups. The receiver operating characteristic (ROC) curve was plotted to evaluate whether hub NRDEGs could be used in AMI diagnosis. Associations of immune cells with candidate NRDEGs biomarkers were examined by Spearman analysis. Finally, hub NRDEGs were validated by cell qPCR assays and another two datasets. Results A total of 15 NRDEGs were identified and multiple enrichment terms associated with necroptosis were discovered through GO and KEGG analysis. Upon module analysis, 10 hub NRDEGs were filtered out, and the top six hub NRDEGs were identified after ROC analysis. These top six NRDEGs might have a certain effect on modulating immune infiltrating cells, especially for mast cells activated, NK cells activated and neutrophils. Finally, two AMI datasets and qPCR assay came to identical findings. Conclusion Our results offer the reliable molecular biomarkers and new perspectives for necroptosis in AMI, which lay a certain foundation for developing novel anti-AMI therapeutic targets