Mechanism Of The Responses Of Blakeslea Trispora To Ethylene Promoting Carotenoid Biosynthesis

Carotenoids, a group of important natural pigments, are widely used in our daily life. Among many methods to product carotenoids in current, microbial fermentation using Blakeslea trispora is superior to the others for its low-cast and non-toxic and got much attention from scientists. In our study, we found that ethylene, which released by ethephon, can also increase the synthesis of β-carotene in B. trispora. However, little information is known by far about the regulation manner of ethylene on carotene synthesis in B. trispora and we still need further study for it.At first, we investigated the optimization of fermentation conditions for ethephon addition in P-carotene production by B. trispora. In our research, addition of a 50ppm of ethephon to the medium while cultivated for 36 h can obtain a maximum of β-carotene production about 1.869 g·L-1 which have a promotion for 52% to the control groups. The experimental results show that ethephon treated can significantly enhance the production of β-carotene in B. trispora.We surveyed the metabolic responses to ethephon in B. trispora by a GC-MS-based metabolomics approach combined with multivariate analysis and find the differential metabolites discriminating the control groups from the ethephon treated groups by PCA and PLS-DA. The changes of metabolites were clearly observed between control (without ethephon) and ethephon treated groups which were mainly reflected in the metabolism of fatty acids, carbohydrates, and amino acids. In our research, glycolysis and the biosyntheses of carotenoids were promoted and the metabolic flux to TCA cycle, fatty acids and amino acids metabolism was diminished by the addition of ethephon. And the similar results can be also observed in plants when treated by ethylene.The effect of ethylene on p-carotene production in B.trispora and transcriptional levels of genes hmgR, carRA and carB involved in β-carotene biosynthesis pathway were investigated in this study. Experimental results show that the transcriptional levels of genes hmgR, carRA and carB were increased by ethephon treated in B.trispora. This suggests that the ethylene can stimulate the level of gene transcription of the enzymes related to the metabolic pathways of carotenoids to improve the carotenoids biosynthesis in B.trispora...