Screening and identification of Monacus strain with high TMP production and statistical optimization of its culture medium composition and liquid state fermentation conditions using response surface methodology (RSM)

Teramethylpyrazine (TMP) is a pyrazine alkaloid with a variety of pharmacological effects and widely used in clinical practice. In this study, Monascus strain M-3 with high TMP and low citrinin productions was screened from red yeast rice collected from different areas of Fujian province in China. Monascus strain M-3 was further identified through molecular biological methods based on the sequencing of different gene regions. Results showed that primer set of β-tubulin-F/β-tubulin-R targeting the β-tubulin gene was more suitable for the identification of Monascus strain M-3. Based on comparative analysis of the results obtained by different primer sets, Monacus strain M-3 was finally identified as Monascus purpureus. Then, the composition of culture medium and liquid state fermentation conditions of Monacus strain M-3 were optimized by single-factor experiment and central composite design of response surface methodology, with the purpose of optimizing the TMP productions. The optimum composition of culture medium and liquid state fermentation conditions are as follows: starch 5.1%, peptone 3.51%, Mg₂SO₄ 0.1%, NaNO₃ 0.2%, KH₂PO₄ 0.25%, fermentation temperature of 28.23 °C, fermentation time of 9 d, shaker speed of 180 r/min, inoculum size of 7.21% and loading volume of 100 mL/250 mL triangular flask. Under the optimum composition of culture medium and liquid state fermentation conditions, the TMP production of Monacus strain M-3 can reach 13.49 µg/mL. This study is expected to provide a new approach of TMP production through biosynthesis by Monascus strain, and promote the further development of functional foods or medicines from Monascus fermentation products.