Improvement of clavulanic acid production in Streptomyces clavuligerus F613-1 by using a claR-neo reporter strategy

Background: Streptomyces clavuligerus was the producer of clavulanic acid, claR, a pathway-specific transcriptional regulator in S. clavuligerus, positively regulates clavulanic acid biosynthesis. In this study, the promoter-less kanamycin resistance gene neo was fused with claR to obtain strain NEO from S. clavuligerus F613-1. The claR-neo fusion strain NEO was mutated using physical and chemical mutagens and then screened under high concentrations of kanamycin for high-yield producers of clavulanic acid. Results: The reporter gene neo was fused downstream of claR and used as an indicator for expression levels of claR in strain NEO. After three rounds of continuous treatment and screening, the high-yield clavulanic acid-producing strain M3-19 was obtained. In the shaking flask model, the clavulanic acid titer of M3-19 reached 4.33 g/L, which is an increase of 33% over the titer of 3.26 g/L for the starting strains S. clavuligerus F613-1 and NEO. Conclusions: Our results indicate that neo can be effectively used as a reporter for the expression of late-stage biosynthetic genes when screening for high-yield strains and that this approach has strong potential for improving Streptomyces strains of industrial value.

The radiation protection role of heparin-SOD conjugate in irradiated mice

ABSTRACT Heparin-SOD conjugate (Hep-SOD) was prepared by modifying Cu,Zn-SOD with heparin. An acute radiation-induced mouse injury model was constructed to study the radiation protection effects of Hep-SOD conjugate. Fifty-six mice were randomly divided into seven groups: (I) normal control group; (II) irradiated control group; (III) positive control group (amifostine group, 300 mg/kg); (IV) SOD group (35000 U/kg); (V) high dosage of Hep-SOD group (70000 U/kg); (VI) medium dosage of Hep-SOD group (35000 U/kg); (VII) low dosage of Hep-SOD group (17500 U/kg). Drugs were intraperitoneally injected into each mouse 1 h before radiation except for the normal control group. All the irradiated groups were irradiated with 6 Gy. Organ indices, haematopoietic function indices, peripheral blood cells, liver function test, oxidative stress state and pathological observation were detected to study the effects of Hep-SOD on irradiated mice. Results showed that bone marrow suppression of irradiated mice could be reduced when treated by Hep-SOD before radiation. Oxidative stress detection and pathological observation of the liver and intestine showed that the damage caused by radiation was relieved when mice were treated with Hep-SOD before radiation. This study shows a new direction to prevent organisms from the damage caused by radiation.

Studies on the formation and synthetic mechanism of related substance G in potassium clavulanate production

The objective of this study was to investigate the formation and synthetic mechanism of related substance G in potassium clavulanate production. The impurity in the potassium clavulanate final product, with a retention time of 13.5 min, was confirmed as related substance G by high performance liquid chromatography-mass spectrometry/mass spectrometry. Related substance G analysis during the production of clavulanic acid showed that this impurity could be synthesized during fermentation, and the amount increased with the fermentation time. Studies on its synthetic mechanism showed that L-tyrosine and succinic acid were the precursors for biosynthesis of related substance G in vivo. The reaction was deduced to be catalyzed by an enzyme. The enzyme was a type of extracellular enzyme present in the fermentation supernatant.

O objetivo deste estudo foi investigar a formação e o mecanismo sintético da substância G relacionada na produção de clavulanato de potássio. A impureza do produto final clavulanato de potássio, com tempo de retenção de 13,5 min, foi confirmada como substância G relacionada por cromatografia líquida de alta eficiência-espectrometria de massas/espectrometria de massas. A análise da substância G relacionada durante a produção do ácido clavulânico mostrou que essa impureza poderia ser sintetizada durante a fermentação e que a quantidade aumenta com o tempo de fermentação. Estudos do seu mecanismo sintético mostraram que a L-tirosina e o ácido succínico foram os precursores in vivo para a biossíntese da substância G relacionada. Deduziu-se que a reação foi catalisada por uma enzima. A enzima foi do tipo extracelular, presente no sobrenadante da fermentação.

Studies on the formation and forming mechanism of the related substance E in potassium clavulanate production by HPLC-MS/MS

The objective of this study was to investigate the formation and forming mechanism of the related substance E in potassium clavulanate production. The impurity with retention time of 11.1 min in potassium clavulanate final product was confirmed as the related substance E by high performance liquid chromatography with tandem mass spectrometric detection (HPLC-MS/MS).The related substance E analysis during the production of clavulanic acid showed that this impurity could be formed during both the fermentation and purification processes, especially in the later fermentation stage, filtration concentration and back-extraction procedure. Clavulanic acid was the precursor of the related substance E. Studies on its forming mechanism showed that the related substance E was formed by the combination of the imino group of one molecule of clavulanic acid with the carboxyl group of another molecule of clavulanic acid with the opening of β-lactam ring. Results of a multi-factor orthogonal test confirmed that the concentration of clavulanic acid was the dominant factor to accelerate the reaction, while the temperature was another contributing factor. The pH 5.0-6.5 had little impact on the generation of the related substance E.

O objetivo deste estudo foi investigar a formação da substância E e o respectivo mecanismo na produção de clavulanato de potássio. Confirmou-se a impureza com tempo de retenção de 11,1 min no produto final, clavulanato de potássio, como substância E, por meio de cromatografia líquida de alta eficiência, em conjunto com detecção por espectrometria de massas (CLAE-MS-MS). A análise da substância relacionada E durante a produção do ácido clavulânico mostrou que essa impureza pode ser formada tanto durante a fermentação quanto durante os processos de purificação, especialmente no estágio final de fermentação, filtração, concentração e procedimento de extração. O ácido clavulãnico foi o precursor da substância E. Estudos no mecanismo de sua formação mostraram que a substância E formou-se pela combinação do grupo imina da molécula do ácido clavulânico com o grupo carboxílico de outra molécula de ácido clavulânico, com a abertura do anel β-lactâmico. Resultados do teste ortogonal multifatorial confirmaram que a concentração do ácido clavulânico foi o fator dominante para acelerar a reação, enquanto a temperatura foi outro fator que contribuiu. O pH de 5,0 a 6,5 teve pouco impacto na geração da substância E.