Enhanced O-succinyl-l-homoserine production by recombinant Escherichia coli ΔIJBB*TrcmetL/pTrc-metAfbr -Trc-thrAfbr -yjeH via multilevel fermentation optimization.

AIMS: Constructing a strain with high yield of O-succinyl-l-homoserine (OSH) and improving the titre through multilevel fermentation optimization. METHODS AND RESULTS: OSH high-yielding strain was first constructed by deleting the thrB gene to block the threonine biosynthesis. Single-factor experiment was carried out, where a Plackett-Burman design was used to screen out three factors (glucose, yeast and threonine) from the original 11 factors that affected the titre of OSH. The Box-Behnken response surface method was used to optimize the fermentation conditions. Through gene editing and medium optimization, the titre of OSH increased from 7·20 to 8·70 g l-1 in 500 ml flask. Furthermore, the fermentation process and fed-batch fermentation conditions including pH, temperature, feeding strategy and feeding medium were investigated and optimized. Under the optimal conditions, the titre of OSH reached 102·5 g l-1 , which is 5·6 times higher than before (15·6 g l-1 ). CONCLUSIONS: O-succinyl-l-homoserine fermentation process was established and the combination of response surface methodology and metabolic pathway analysis effectively improved the titre of OSH. SIGNIFICANCE AND IMPACT OF THE STUDY: In this study, the titre of OSH reached the needs for industrial production and the metabolic pathway of OSH was demonstrated for further optimization.

Effects of lipids and surfactants on the fermentation production of echinocandin B by Aspergillus nidulans.

AIMS: Echinocandin B (ECB) is a kind of lipopeptide antifungal antibiotic, as well as the key precursor of antifungal drug Anidulafungin. Its efficient bioproduction plays an important role in promoting the industrial production of Anidulafungin. METHODS AND RESULTS: In this study, methyl oleate and Tween 80 were firstly used to enhance the ECB fermentation by Aspergillus nidulans, the results showed that the ECB titre was significantly enhanced with the addition of methyl oleate and Tween 80. Among the lipids, methyl oleate was found to play a pivotal role in increasing the ECB titre to 2123 mg l-1 , which was more than five times higher than that of the control. The addition of Tween 80 in the medium resulted in ECB titre increased to 2584 mg l-1 . The scanning electron microscope (SEM) and N-phenyl-1-naphthylamine (NPN) assay indicated that Tween 80 could influence the cell membrane permeability of A. nidulans, and enhance the intracellular and extracellular substance exchange, therefore lead to the increasing of ECB titre. CONCLUSIONS: Methyl oleate and Tween 80 are optimal carbon sources and surfactants for efficient ECB biosynthesis respectively. SIGNIFICANCE AND IMPACT OF THE STUDY: Surfactant was used in ECB fermentation for the first time, which provided feasible ideas for optimizing the fermentation process of other fungi.

Improvement of gibberellin production by a newly isolated Fusarium fujikuroi mutant.

AIMS: To obtain and investigate the potential mechanism for GA3 production in Fusarium fujikuroi GA-251, a high GA3 producer. METHODS AND RESULTS: Fusarium fujikuroi IMI 58289 was bred with Cobalt-60 (60 Co) radiation and lithium chloride treatment. The best mutant strain GA-251 was obtained for the subsequent optimization of fermentation conditions. The yield of GA3 by GA-251 was 2100 mg l-1 , while the wild-type strain was 100 mg l-1 , which is a 21-fold increase in the yield. To elucidate the mechanism of high GA3 yield of GA-251, the genome was sequenced and compared with wild-type strain IMI 58289. The results showed 2295 single nucleotide polymorphisms, 1242 small indels and 30 structural variants. These mutations were analysed and enriched in the MAPK signalling pathway, the mRNA surveillance pathway and endocytosis. The potential reasons for the improved GA3 biosynthesis were investigated. CONCLUSIONS: The potential mechanism of high GA3 yield was attributed to endocytosis pathway and histone modification proteins family. SIGNIFICANCE AND IMPACT OF THE STUDY: A mutant strain GA-251 in this work that could potentially be utilized in the industrial yield of GA3 . The comparative genome analysis would shed light onto the mechanism of yield improvement and be a theoretical guide for further metabolic engineering.

Network-scale effect on synchronizability of fully coupled network with connection delay.

Network-scale effect on synchronizability of fully coupled network with connection delay is investigated in this paper. The master stability function, which governs the stability of synchronization manifold, is first obtained by separating the synchronization manifold direction from other transverse directions. Then, by introducing a new time variable in the master stability function, it is shown the effect of connection delay can be weakened with the increase of network scale, and thus, in contrast to the situation without connection delay, large network scale is more positive to the synchronizability of fully coupled network with connection delay. Those findings are confirmed by the studies on two specific networks with nodes of typical nonlinear dynamical systems.

Size-dependent elastic moduli and vibrational properties of fivefold twinned copper nanowires.

Based on atomistic simulations, the elastic moduli and vibration behaviors of fivefold twinned copper nanowires are investigated in this paper. Simulation results show that the elastic (i.e., Young's and shear) moduli exhibit size dependence due to the surface effect. The effective Young's modulus is found to decrease slightly whereas the effective shear modulus increases slightly with the increase in the wire radius. Both moduli tend to approach certain values at a larger radius and can be suitably described by core-shell composite structure models. Furthermore, we show by comparing simulation results and continuum predictions that, provided the effective Young's and shear moduli are used, classic elastic theory can be applied to describe the small-amplitude vibration of fivefold twinned copper nanowires. Moreover, for the transverse vibration, the Timoshenko beam model is more suitable because shear deformation becomes apparent.

Expression of ERCC1 and BRCA1 predict the clinical outcome of non-small cell lung cancer in patients receiving platinum-based chemotherapy.

We examined mRNA expression levels of ERCC1, BRCA1, RRM1, and human ß-tubulin-III (TUBB3) in non-small-cell lung carcinoma (NSCLC) patients and investigated the association between expression of these genes and the clinical outcome of NSCLC treatment. A total of 366 patients who underwent surgery for NSCLC were included in this study. All patients received third-generation platinum-based chemotherapy as first-line treatment. The relative cDNA quantification for ERCC1, RRM1, BRCA1, and TUBB3 was determined using a fluorescence-based, real-time detection method. We found that low expression of ERCC1 and BRCA1 was associated with a good response to platinum-based chemotherapy, with an odds ratio [95% confidence interval (CI)] of 2.09 (1.33-3.27) and 2.92 (1.85-4.62), respectively. Multivariate Cox regression analysis indicated that patients with low expression of ERCC1 and BRCA1 attained a longer overall survival time than those with high expression, with a hazard ratio (95%CI) of 0.42 (0.23-0.77) and 0.39 (0.21-0.71), respectively. However, RMM1 and TUBB2 expressions were not correlated with clinical outcome of NSCLC. In conclusion, we found that low expression of ERCC1 and BRCA1 can be useful for selecting NSCLC patients who would benefit from chemotherapy and warrants further investigation in prospective studies.

Time-delay effect on the bursting of the synchronized state of coupled Hindmarsh-Rose neurons.

The time-delay effect on the bursting of the synchronized state of coupled Hindmarsh-Rose neurons is investigated in this paper. The time-delay influence on the structure of the slow manifold is first studied by using the method of stability switch. And then on the basis of the geometric singular perturbation theory, case studies are given to show that the time delay can suppress the bursting oscillation or lead to more complex dynamics. In particular, the mechanism of the transition from bursting oscillation to relaxation oscillation and to chaotic bursting is stated. Numerical results are given to demonstrate the validity of the analytical results.

R-enantioselective hydrolysis of 2,2-dimethylcyclopropanecarboxamide by amidase from a newly isolated strain Brevibacterium epidermidis ZJB-07021.

AIMS: To isolate new micro-organisms with R-stereospecific amidase activity and to examine their potential as biocatalysts in enantioselective hydrolysis of 2,2-dimethylcyclopropanecarboxamide (1). METHODS AND RESULTS: A novel R-stereospecific amidase-producing strain ZJB-07021 was isolated through a sophisticated colorimetric screening method. Based on morphology, physiological tests, Biolog system (GP2) and 16S rRNA sequence, the new isolate was identified as Brevibacterium epidermidis. After 70 min of bioconversion at 35 degrees C, kinetic resolution of (R,S)-1 by the amidase afforded (S)-1 in 41.1% yield (>99% ee) and (R)-2 in 49.9% yield (69.7% ee) with an average E-value of 23. The enantioselectivity was found to be temperature dependent and enhanced from 12.6 at 45 degrees C to 65.9 at 14 degrees C. CONCLUSIONS: A novel bacterial strain of B. epidermidis ZJB-07021 producing R-stereospecific amidase was isolated and characterized. The isolate exhibited high E values for kinetic resolution of racemic-1 to (S)-1. SIGNIFICANCE AND IMPACT OF THE STUDY: To our knowledge, this was the first report on the species B. epidermidis that harboured R-stereospecific amidase. Strain ZJB-07021 could be further improved as a suitable biocatalyst for the stereoselective bioconversion of racemic-1 after optimization of culture and biotransformation process.

Improvement of astaxanthin production by a newly isolated Phaffia rhodozyma mutant with low-energy ion beam implantation.

AIMS: Isolation, characterization and identification of Phaffia sp. ZJB 00010, and improvement of astaxanthin production with low-energy ion beam implantation. METHODS AND RESULTS: A strain of ZJB 00010, capable of producing astaxanthin, was isolated and identified as Phaffia rhodozyma, based on its physiological and biochemical characteristics as well as its internal transcribed spacer (ITS) rDNA gene sequence analysis. With low-energy ion beam implantation, this wild-type strain was bred for improving the yield of astaxanthin. After ion beam implantation, the best mutant, E5042, was obtained. The production of astaxanthin in E5042 was 2512 microg g(-1) (dry cell weight, DCW), while the wild-type strain was about 1114 microg g(-1) (DCW), an increase of 125.5%. Moreover, the fermentation conditions of mutant E5042 for producing astaxanthin were optimized. The astaxanthin production under the optimized conditions was upscaled and studied in a 50-l fermentor. CONCLUSIONS: A genetically stable mutant strain with high yield of astaxanthin was obtained using low-energy ion beam implantation. This mutant may be a suitable candidate for the industrial-scale production of astaxanthin. SIGNIFICANCE AND IMPACT OF THE STUDY: Astaxanthin production in Phaffia rhodozyma could be efficiently improved by low-energy ion beam implantation, which is a new technology in the mutant breeding of micro-organisms. The mutant obtained in this work could potentially be utilized in industrial production of astaxanthin.

Increased expression of long noncoding RNA LINC00961 suppresses glioma metastasis and correlates with favorable prognosis.

OBJECTIVE: Long non-coding RNA LINC00961 (LINC00961) has been reported to play an important role in tumor development and metastasis of lung cancer. However, the expression and role of LINC00961 in glioma remains unclear. The present study aimed to investigate the expression of LINC00961 in patients with glioma and to investigate its effect on glioma cells. PATIENTS AND METHODS: Quantitative Real-Time PCR (qRT-PCR) was performed to detect the expression of LINC00961 in glioma tissues and cell lines. Then, the association between LINC00961 expression and clinical pathological parameters and prognosis of glioma patients were further evaluated. Gain of function studies were performed to determine the effects of LINC00961 on proliferation and metastasis of glioma cells. Western blotting assay was used to explore the regulation mechanism. RESULTS: We found that LINC00961 was significantly downregulated in glioma tissues and cell lines compared with that of adjacent normal brain tissues and normal human astrocytes. Low expression of LINC00961 was significantly correlated with WHO grade and KPS score. Clinical analysis indicated that patients with low LINC00961 expression had a shorter overall survival than those with high expression. Univariate and multivariable Cox regression analyses further identified that down-regulated LINC00961 might act as an independent prognostic factor for glioma patients. Functionally, overexpression of LINC00961 significantly suppressed glioma cells proliferation, migration, and invasion. Mechanistically, we found that overexpression of LINC00961 inhibited glioma cell EMT. CONCLUSIONS: LINC00961 might be considered as a novel molecule involved in glioma development, which provides an independent prognostic indicator and a potential therapeutic target for glioma patients.