Screening of medium constituents for clavulanic acid production by Streptomyces clavuligerus

ABSTRACT Clavulanic acid is a β-lactam compound with potent inhibitory activity against β-lactamases. Studies have shown that certain amino acids play essential roles in CA biosynthesis. However, quantitative evaluations of the effects of these amino acids are still needed in order to improve CA production. Here, we report a study of the nutritional requirements of Streptomyces clavuligerus for CA production. Firstly, the influence of the primary nitrogen source and the salts composition was investigated. Subsequently, soybean protein isolate was supplemented with arginine (0.0-3.20 g L-1), threonine (0.0-1.44 g L-1), ornithine (0.0-4.08 g L-1), and glutamate (0.0-8.16 g L-1), according to a two-level central composite rotatable design. A medium containing ferrous sulfate yielded CA production of 437 mg L-1, while a formulation without this salt produced only 41 mg L-1 of CA. This substantial difference suggested that Fe2+ is important for CA biosynthesis. The experimental design showed that glutamate and ornithine negatively influenced CA production while arginine and threonine had no influence. The soybean protein isolate provided sufficient C5 precursor for CA biosynthesis, so that supplementation was unnecessary. Screening of medium components, together with experimental design tools, could be a valuable way of enhancing CA titers and reducing the process costs.

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.

Coordinate production of cephamycin c and clavulanic acid by Streptomyces clavuligerus.

Production of cephamycin c and clavulanic acid by Streptomyces clavuligerus was investigated using different media in shake flask condition. Highest cell growth (3.8 g/L) was observed in glycerol, sucrose, proline and glutamic acid (GSPG) medium. Although, GSPG medium supported maximum growth, it was least effective for the synthesis of both cephamycin and clavulanic acid. Yield of cephamycin and clavulanic acid was maximum in dextrin and K medium, respectively. High and low level of constituents of dextrin medium, affected production of both cephamycin and clavulanic acid. Biosynthesis of clavulanic acid was associated with production of cephamycin c.