Enhancement of ascomycin production via a combination of atmospheric and room temperature plasma mutagenesis in Streptomyces hygroscopicus and medium optimization

Abstract

Ascomycin, a key intermediate for chemical synthesis of immunosuppressive drug pimecrolimus, is produced by Streptomyces hygroscopicus var. ascomyceticus . In order to improve the strain production, the original S. hygroscopicus ATCC 14891 strain was treated here with atmospheric and room temperature plasma to obtain a stable high-producing S. hygroscopicus SFK-36 strain which produced 495.3 mg/L ascomycin, a 32.5% increase in ascomycin compared to the ATCC 14891. Then, fermentation medium was optimized using response surface methodology to further enhance ascomycin production. In the optimized medium containing 81.0 g/L soluble starch, 57.4 g/L peanut meal, and 15.8 g/L soybean oil, the ascomycin yield reached 1466.3 mg/L in flask culture. Furthermore, the fermentation process was carried out in a 5 L fermenter, and the ascomycin yield reached 1476.9 mg/L, which is the highest ascomycin yield reported so far. Therefore, traditional mutagenesis breeding combined with medium optimization is an effective approach for the enhancement of ascomycin production. Electronic supplementary material The online version of this article (10.1186/s13568-019-0749-x) contains supplementary material, which is available to authorized users.

Generation of Streptomyces hygroscopicus cell factories with enhanced ascomycin production by combined elicitation and pathway‐engineering strategies

“…Meanwhile, the dynamic profiles of ascomycin biosynthesis after 96 hr differed at various DMSO concentrations (0.2%, and 0.6%; Figure d). In addition, according to the result of Figure d, the time course of ascomycin production clearly revealed that ascomycin yield continuously increased and reached the highest at 168 hr, which is in agreement with a previous report (Yu et al, ). In summary, these results suggest that the regulation of intracellular metabolic events involved in ascomycin biosynthesis could be disturbed by DMSO treatment.…”

Bioprocess and genetic engineering aspects of ascomycin production: a review

“…It was due to the high effectiveness of an orally used cyclosporin A that is a cyclic peptide accompanying 11 amino acids [ 23 , 24 ], which led to the discovery of this novel class of compounds [ 7 ]. Tacrolimus (FK506), the analog of ascomycin [ 9 , 11 ] was first produced by S. tsukubaensis in 1984 [ 25 ]. After its discovery, another macrolactam was discovered similarly as ascomycin and cyclosporin A in an antifungal screening method of fermentation broths [ 7 , 26 ] named rapamycin (sirolimus) which is also an immunosuppressant, antifungal, antitumor, and anti-aging drug [ 7 , 27 ].…”

“…Yu et al studied S. hygroscopicus ATCC 14891 for the production of ascomycin and identified seven co-transcription units in the ascomycin biosynthetic gene cluster, including fkbW , fkbU , fkbR1/R2 , fkbE/F/G , fkbB/C/L/K/J/I/H , fkbO/P/A/D/M , and fkbS/Q/N which were responsible for the synthesis of ascomycin with yield improvement. To determine the expression level, one gene in each of the seven co-transcription units ( fkbW , fkbU , fkbR1 , fkbE, fkbB , fkbO , fkbS ) was selected and results revealed that the expression of four co-transcription units ( fkbW , fkbU , fkbB/C/L/K/J/I/H , and fkbO/P/A/D/M ) were responsible for twofold higher improved yield of ascomycin in S. hygroscopicus SFK-36 in comparison to strain ATCC 14891 [ 11 ]. Another study was conducted by Wang et al where three pathways (aminoacyl-tRNA biosynthesis; phenylalanine, tyrosine, and tryptophan biosynthesis; and pentose phosphate pathways) were studied, from which aromatic amino acid and pentose phosphate biosynthesis pathway were seen to be responsible for the synthesis of precursor molecule involved in ascomycin biosynthesis.…”

“…This derivative can be an advantageous alternate of ascomycin with enhanced activity due to changes in the side-chain group [ 4 , 10 ]. It is presently used for first-line treatment of atopic dermatitis (mild-to-moderate) [ 11 ]. Psoriasis, seborrheic dermatitis, and vitiligo are some of the skin inflammatory diseases that can also be treated by the therapeutic effects of the derivatives of ascomycin [ 12 – 14 ].…”

“…This antibiotic has gained sustained attraction from research laboratories and pharmaceutical industries owing to its multifunctional biological properties as well as market prospects [ 9 ]. Recently, many efforts have been made to utilize the therapeutic effects of ascomycin and its derivatives in the medical field for the sake of humans [ 11 , 14 ]. Therefore, the demands also escalate, and to fulfill them, some considerable efforts such as genetic manipulations via strain engineering and fermentation process optimization are done in the past few years.…”