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Visual and Microscopic Evaluation of Streptomyces Developmental Mutants
Published on: September 12, 2018
Development of Monascus purpureus monacolin K-hyperproducing mutant strains by synchrotron light irradiation and
Sittichoke Ketkaeo1, Yukio Nagano2, Shuichiro Baba1
1United Graduate School of Agriculture Sciences, Kagoshima University, 1-21-24 Korimoto, Kagoshima 890-0065, Japan; Department of Applied Biochemistry and Food Science, Faculty of Agriculture, Saga University, 1 Honjyo-machi, Saga 840-8502, Japan.
Abstract:
Monascus purpureus have been used for making koji and other fermented foods and supplements. M. purpureus characteristically produces monacolin K (MK), a secondary metabolite that competitively inhibits cholesterol synthesis. Synchrotron light irradiation was applied to induce mutation in the strain KUPM5 to improve the MK-producing ability of M. purpureus strain KUPM5. Screening by a bioassay utilizing sensitivities to yeast Saccharomyces cerevisiae from 936 colonies allows isolating three mutant strains: SC01, SC02, and SC03. These mutant strains and the parental strain KUPM5 were subjected to make koji using rice, and their metabolites were compared. All strains SC01, SC02, and SC03 in koji showed higher production of MK than the strain KUPM5. Particularly, the SC02 strain produced MK threefold higher than KUPM5 and maintained the production capabilities of other metabolites, including red, yellow, and orange pigments, mycelial contents, and α-amylase activity comparable to those of the strain KUPM5. Comparative genome analysis among strain KUPM5 and the mutants revealed that synchrotron light irradiation introduced mutations in approximately 90% of the total genes, including SNV, MNV, and indel mutations. The frequencies of SNV substitution in the whole genome occupied 68.96% of all mutations, of which 92.38% were transversions and 7.62% were transitions. This study, therefore, proved the synchrotron light irradiation was highly efficient for the strain improvement of a filamentous fungus, M. purpureus, and provided insights into the properties of mutation in the fungus by this mutagen.
Insights
Synchrotron light irradiation effectively improved Monascus purpureus for higher monacolin K production. Mutant strain SC02 yielded threefold more monacolin K while maintaining other beneficial metabolite production.
Area of Science:
- Microbiology
- Biotechnology
- Food Science
Background:
- Monascus purpureus is utilized in fermented foods and produces monacolin K (MK), a cholesterol-lowering compound.
- Improving MK production in M. purpureus is crucial for its application in functional foods and supplements.
- Strain KUPM5 of M. purpureus was used as the parental strain for mutation induction.
Purpose of the Study:
- To enhance the monacolin K (MK) producing ability of Monascus purpureus strain KUPM5.
- To isolate and characterize mutant strains with improved MK yields.
- To investigate the mutational effects of synchrotron light irradiation on M. purpureus.
Main Methods:
- Synchrotron light irradiation was used to induce mutations in M. purpureus strain KUPM5.
- A bioassay involving Saccharomyces cerevisiae was employed to screen 936 colonies for improved MK production.
- Mutant strains were cultured on rice to produce koji, and their metabolites were analyzed and compared to the parental strain.
Main Results:
- Three mutant strains (SC01, SC02, SC03) were isolated, all showing higher MK production than the parental strain KUPM5.
- Mutant strain SC02 exhibited a threefold increase in MK production compared to KUPM5.
- SC02 maintained comparable levels of pigments, mycelial content, and alpha-amylase activity to the parental strain.
- Comparative genome analysis revealed extensive mutations (SNV, MNV, indel) induced by synchrotron light irradiation.
Conclusions:
- Synchrotron light irradiation is a highly efficient method for strain improvement in filamentous fungi like M. purpureus.
- Mutant strain SC02 represents a significant advancement in MK production for potential industrial applications.
- The study provides valuable insights into the nature and frequency of mutations induced by synchrotron light in M. purpureus.
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