Improvement of R-2-(4-hydroxyphenoxy) propionic acid biosynthesis of Beauveria bassiana by combined mutagenesis.

R-2-(4-hydroxyphenoxy)propionicacid (HPOPA) is a valuable intermediate for the synthesis of enantiomerically pure aryloxyphenoxypropionic acid herbicides. In this work, to improve the HPOPA biosynthesis by Beauveria bassiana ZJB16002 from the substrate R-2-phenoxypropionic acid (POPA), the original HPOPA producer B. bassiana ZJB16002 was subjected to physical mutagenesis with 137 Cs-γ irradiation and chemical mutagen N-methyl-N'-nitro-N-nitrasoguanidine (NTG) induced mutagenesis. The effects of different treatment doses of the mutagens on the lethal rate and positive mutation rate were investigated, and the results showed that the optimal 137 Cs-γirradiation dose and NTG concentration was 850 Gy and 500 µg/mL, respectively. Under these conditions, a mutant strain CCN-7 with the highest HPOPA production capacity was obtained through two rounds of 137 Cs-γ irradiation treatment followed by one round of NTG mutagenesis. At the substrate (POPA) concentration of 50 g/L, HPOPA titer of CCN-7 reached 36.88 g/L, which was 9.73-fold higher than the parental strain. The morphology of the wild-type and mutant strain was compared and the results might provide helpful information in exploration of the correlation of morphology and biochemical features of B. bassiana.