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Jiang Y.-Z.,National and Local United Engineering Laboratory of Metabolic Control Fermentation Technology | Zhang C.-L.,National and Local United Engineering Laboratory of Metabolic Control Fermentation Technology | Wang Z.-G.,National and Local United Engineering Laboratory of Metabolic Control Fermentation Technology | Xie X.-X.,National and Local United Engineering Laboratory of Metabolic Control Fermentation Technology | And 2 more authors.
Modern Food Science and Technology | Year: 2014

Glutamine has important effects in biological systems and has been widely used in many areas, including in the food and medicine industries. Glutamic acid is the precursor for glutamine biosynthesis, and is the most common by-product in glutamine fermentation. Previous studies have shown that the protein encoded by NCgl1221 is an important glutamic acid exporter and that pyruvate carboxylase is a key enzyme in the feedback pathway of Corynebacterium glutamicum. In order to reduce glutamic acid accumulation during glutamine fermentation and to improve the yield of glutamine, in this study, NCgl1221 of the glutamine-producing strain GM34 was knocked out using homologous recombination technology, resulting in the construction of the mutant strain GM34ΔNCgl1221. Pyc encoding pyruvate carboxylase was also overexpressed in the constructed strain GM34-pXMJ19pyc. Fermentation carried out in 5-L bottles showed that NCgl1221 knockout reduced glutamic acid accumulation by 19.05%. Overexpression of pyc resulted in a promotion of glutamine production and conversion rate by 5.54% and 2.37%, respectively. Taken together, these results demonstrate that NCgl1221 knockout and pyc overexpression can effectively reduce glutamic acid accumulation and improve glutamine production. ©, 2014, South China University of Technology. All right reserved.


Li Z.-H.,Tianjin University of Science and Technology | Li Z.-H.,National and Local United Engineering Laboratory of Metabolic Control Fermentation Technology | Li Z.-H.,Tianjin Engineering Laboratory of Efficient and Green Amino Acid Manufacture | Zhang C.-L.,Tianjin University of Science and Technology | And 5 more authors.
Lecture Notes in Electrical Engineering | Year: 2015

To investigate the production of L-glutamic acid with high yield as well as improved purity, the optimization of crystallization process was conducted. During this study, various physicochemical parameters (e.g., initial temperature, cooling rate, acid adding rate, ultrasonic time, and stirring speed) of concentrated isoelectric crystallization method were evaluated to optimize the yield and purity of L-glutamic acid. The optimum crystallization parameters are as follows: acid adding rate 0.5 mL/min, ultrasonic time 10 min, and stirring speed 200 rpm. The yield of L-glutamic acid at optimal condition was 95.4%, attaining a 6.5% growth. The purity of crystallized product exceeded 99%, giving a rise of 4%. The optimal crystallization process with higher yield and improved purity reduces the energy consumption and thus promotes sustainable development. © Springer-Verlag Berlin Heidelberg 2015.


Wang L.,South China University of Technology | Cao Z.,Tianjin University of Science and Technology | Cao Z.,Key Laboratory of Industrial Fermentation Microbiology | Hou L.,Tianjin University of Science and Technology | And 10 more authors.
Applied Microbiology and Biotechnology | Year: 2016

Citric acid is produced by an industrial-scale process of fermentation using Aspergillus niger as a microbial cell factory. However, citric acid production was hindered by the non-fermentable isomaltose and insufficient saccharification ability in A. niger when liquefied corn starch was used as a raw material. In this study, A. niger TNA 101ΔagdA was constructed by deletion of the α-glucosidase-encoding agdA gene in A. niger CGMCC 10142 genome using Agrobacterium tumefaciens-mediated transformation. The transformants A. niger OG 1, OG 17, and OG 31 then underwent overexpression of glucoamylase in A. niger TNA 101ΔagdA. The results showed that the α-glucosidase activity of TNA 101ΔagdA was decreased by 62.5 % compared with CGMCC 10142, and isomaltose was almost undetectable in the fermentation broth. The glucoamylase activity of the transformants OG 1 and OG 17 increased by 34.5 and 16.89 % compared with that of TNA 101ΔagdA, respectively. In addition, for the recombinants TNA 101ΔagdA, OG 1 and OG 17, there were no apparent defects in the growth development. Consequently, in comparison with CGMCC 10142, TNA 101ΔagdA and OG 1 decreased the residual reducing sugar by 52.95 and 88.24 %, respectively, and correspondingly increased citric acid production at the end of fermentation by 8.68 and 16.87 %. Citric acid production was further improved by decreasing the non-fermentable residual sugar and increasing utilization rate of corn starch material in A. niger. Besides, the successive saccharification and citric acid fermentation processes were successfully integrated into one step. © 2016, Springer-Verlag Berlin Heidelberg.


Zhang D.-L.,Tianjin University of Science and Technology | Zhang D.-L.,Tianjin Engineering Laboratory of Efficient and Green Amino Acid Manufacture | Zhang D.-L.,National and Local United Engineering Laboratory of Metabolic Control Fermentation Technology | Xu Q.-Y.,Tianjin University of Science and Technology | And 11 more authors.
Modern Food Science and Technology | Year: 2013

The ppnk and gdh encoding NAD kinase (NADK) and glutamate dehydrogenase (GDH) were two important enzymes in the glutamate biosynthesis pathway. The two genes were amplified by polymerase chain reaction (PCR) from the glutamate-producing strain CN1021. The specific activity of NAD kinase in extracts was increased by 2.4-fold, and GDH, by 2.1-fold. When both genes were co-expressed in CN1021, the activity of NADK and GDH were increased by 2.0-fold and 1.5-fold, respectively. The flask fermentation results showed that the separate over-expression of ppnk and gdh in CN1021 approximately 7.9% higher and 1.4% more L-glutamate than the original strain, moreover, co-expressing the two genes strain exhibited 13.2% higher L-glutamate. Taken together, the results demonstrated that co-expression of gdh and ppnk genes can significantly improve the production of L-glutamate.


Zhang C.,Tianjin University of Science and Technology | Zhang C.,National and Local United Engineering Laboratory of Metabolic Control Fermentation Technology | Zhang C.,Tianjin Engineering Laboratory of Efficient and Green Amino Acid Manufacture | Du S.,Tianjin University of Science and Technology | And 10 more authors.
Biotechnology Letters | Year: 2015

Objectives: To rationally identify targets for enhancing adenosine production, transcription level of genes involved in adenosine synthesis of Bacillus subtilis XGL was detected during the fermentation process, complemented with metabolite pool analysis. Results: PurR-regulated genes (pur operon and purA) and prs were down-regulated and 5-phosphoribosyl 1-pyrophosphate (PRPP) decreased considerably after 24 h when adenosine significantly accumulated. Since PRPP could strongly antagonize the binding of PurR to its targets, it was inferred that down-regulation of pur operon and purA might be due to a low PRPP pool, which was confirmed by metabolite analysis. So desensitized prs responsible for PRPP synthesis was overexpressed, resulting in increased PRPP concentration and pur operon transcription. To further enhance the adenosine production, desensitized purF and prs were co-overexpressed with integrating additional copy of purA to B. subtilis XGL genome, resulting in 24.3 % (1.29 g/g DCW) higher adenosine production than that by B. subtilis XG. Conclusions: Overexpression of prs, purF and purA under the guidance of transcriptional and metabolite pool analysis significantly increased adenosine production. Strategies used in this study have potential applications for rational modification of industrial microorganisms. © 2015, Springer Science+Business Media Dordrecht.

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