Effect of low-level ultrasound treatment on the production of L-leucine by
            <i>Corynebacterium glutamicum</i>
            in fed-batch culture

Zhang, Yufu; Chen, Zhichao; Sun, Pengjie; Xu, Qingyang; Chen, Ning

doi:10.1080/21655979.2021.1906028

Cited by 7 publications

(2 citation statements)

References 44 publications

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“…Under low power sonication, the activity of crude enzyme solution increased with increasing sonication power; the highest activity of 107 U/mL was achieved under the treatment condition of 150 W. However, with further increases in power, the activity showed a trend of weakening. Analysis showed that low-power ultrasound could induce stable cavitation in the surrounding liquid, and the generation and extinction of cavitation bubbles can cause oscillations in the liquid ( Rao and Rathod, 2014 ; Gonçalves et al, 2015 ), which in turn causes changes in the structure of the cell membrane, increasing its permeability to some extent and even disrupting it, causing enzyme molecules to flow from inside the cell to outside the cell ( Zhang et al, 2021 ), and ultrasound produces benign changes in the structure of enzyme molecules ( Wang et al, 2012 ), leading to further increases in enzyme activity. As a result, enzyme activity tends to increase.…”

Section: Resultsmentioning

confidence: 99%

Process study of ceramic membrane-coupled mixed-cell fermentation for the production of adenine

Sun

Gong

et al. 2022

Front. Bioeng. Biotechnol.

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In order to solve the problems of high complexity, many by-products, high pollution and difficult extraction of the existing adenine production process, in this study, ceramic membrane-coupled mixed cell fermentation was used to produce adenine while reducing the synthesis of by-products and simplifying the production process of adenine. Nucleoside hydrolase (encoded by the rihC gene) was used to produce adenine by coordinated fermentation with the adenosine-producing bacterium Bacillus Subtilis XGL. The adenosine hydrolase (AdHy)-expressing strain Escherichia coli BL21-AdHy was successfully employed and the highest activity of the crude enzyme solution was found by orthogonal experiments at 170 W power, 42% duty cycle, and 8 min of sonication. The highest AdHy activity was found after 18 h of induction incubation. E. coli BL21-AdHy was induced for 18 h and sonicated under the above ultrasonic conditions and the resulting crude enzyme solution was used for co-fermentation of the strain and enzyme. Moreover, 15% (v/v) of the AdHy crude enzyme solution was added to fermentation of B. subtilis XGL after 35 h. Finally, the whole fermentation system was dialyzed using coupled ceramic membranes for 45 and 75 h, followed by the addition of fresh medium. In contrast, the AdHy crude enzyme solution was added after 35, 65, and 90 h of B. subtilis fermentation, with three additions of 15, 15, and 10% of the B. subtilis XGL fermentation system. The process was validated in a 5 L fermenter and 14 ± 0.25 g/L of adenine was obtained, with no accumulation of adenosine and d-ribose as by-products. The enzymatic activity of the AdHy crude solution treated with ultrasound was greatly improved. It also reduced the cellular activity of E. coli BL21-AdHy and reduced effects on bacterial co-fermentation. Membrane-coupled dialysis solved the problem of decreased yield due to poor bacterial survival and decreased viability, and eliminated inhibition of the product synthesis pathway by adenosine. The batch addition of crude enzyme broth allowed the continuous conversion of adenosine to adenine. This production method provides the highest yield of biologically produced adenine reported to date, reduces the cost of adenine production, and has positive implications for the industrial production of adenine by fermentation. And it provides a reference for producing other high-value-added products made by fermentation.

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Section: Resultsmentioning

confidence: 99%

Process study of ceramic membrane-coupled mixed-cell fermentation for the production of adenine

Sun

Gong

et al. 2022

Front. Bioeng. Biotechnol.

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“…The metabolic functions of l -leucine in regulating muscle protein synthesis and insulin release have high commercial value in the feed industry [ 3 , 4 ]. Therefore, the increasing market demand for this amino acid has stimulated interest in the development of cost-effective approach for its production on an industrial scale [ 5 ]. Currently, mutagenesis and metabolic engineering strategies are the common methods used to engineer cellular factories for l -leucine production [ 6 ].…”

Section: Introductionmentioning

confidence: 99%

Construction of a plasmid-free l-leucine overproducing Escherichia coli strain through reprogramming of the metabolic flux

Hao,

Pan,

et al. 2023

Biotechnol Biofuels

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Background l-Leucine is a high-value amino acid with promising applications in the medicine and feed industries. However, the complex metabolic network and intracellular redox imbalance in fermentative microbes limit their efficient biosynthesis of l-leucine. Results In this study, we applied rational metabolic engineering and a dynamic regulation strategy to construct a plasmid-free, non-auxotrophic Escherichia coli strain that overproduces l-leucine. First, the l-leucine biosynthesis pathway was strengthened through multi-step rational metabolic engineering. Then, a cooperative cofactor utilization strategy was designed to ensure redox balance for l-leucine production. Finally, to further improve the l-leucine yield, a toggle switch for dynamically controlling sucAB expression was applied to accurately regulate the tricarboxylic acid cycle and the carbon flux toward l-leucine biosynthesis. Strain LEU27 produced up to 55 g/L of l-leucine, with a yield of 0.23 g/g glucose. Conclusions The combination of strategies can be applied to the development of microbial platforms that produce l-leucine and its derivatives.

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An NADPH-auxotrophic Corynebacterium glutamicum recombinant strain and used it to construct L-leucine high-yielding strain

Chen

Liu²,

Zhang³

et al. 2022

Int Microbiol

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The NADPH-regeneration enzymes in Corynebacterium glutamicum were inactivated to construct an NADPH-auxotrophic C. glutamicum strain by gene knockout and gene replacement. The resultant NADPH-auxotrophic C. glutamicum XL-1 ΔZMI Cg ::I Sm (i.e., strain Leu-1) grew well in the basic medium only with gluconate as carbon source. Replacement of the native glyceraldehyde 3-phosphate dehydrogenase (NAD-GapDH Cg ) by NADP-GapDH Ca from Clostridium acetobutylicum is an effective strategy for producing L-leucine in NADPH-prototrophic strain XL-1 and NADPH-auxotrophic strain Leu-1, whereas the L-leucine yield did not differ signi cantly between these strains (14.1 ± 1.8 g/L v.s. 16.2 ± 1.1 g/L). Enhancing the carbon ux in biosynthetic pathway by recombinant expression plasmid pEC-ABNCE promoted L-leucine production, but the shortage NADPH supply limited the L-leucine yield. The mutated promoters of zwf and icd Cg were introduced into C. glutamicum with NADP-GapDH Ca and pEC-ABNCE increased L-leucine yield (32.8 ± 1.7 g/L) and improved cell growth (OD 562 = 41.3 ± 4.2) because the resultant strain C. glutamicum XL-1 ΔMI Cg ::I Sm G Cg ::G Ca P zwf -D1 P icd -D2/pEC-ABNCE (i.e., strain Leu-9) exhibited the proper intracellular NADPH and NADH level. This is the rst report of constructing an L-leucine high-yielding strain that reasonably supplies NADPH by optimizing the biosynthetic pathway of NADPH from an NADPH-auxotrophic strain.

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Effect of low-level ultrasound treatment on the production of L-leucine by Corynebacterium glutamicum in fed-batch culture

Cited by 7 publications

References 44 publications

Process study of ceramic membrane-coupled mixed-cell fermentation for the production of adenine

Process study of ceramic membrane-coupled mixed-cell fermentation for the production of adenine

Construction of a plasmid-free l-leucine overproducing Escherichia coli strain through reprogramming of the metabolic flux

An NADPH-auxotrophic Corynebacterium glutamicum recombinant strain and used it to construct L-leucine high-yielding strain

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