Addition of biotin and thiamine hydrochloride accelerates the synthesis of L-ornithine

In addition to the modification of key enzymes in metabolic pathways, the addition of key coenzymes is also an important method to promote the synthesis of products (Y. Cao, Duan, & Shi, 2014). Biotin and thiamine hydrochloride are the coenzymes of carboxylase in the metabolic process. Biotin plays an important role in the metabolism of bacterial proteins, which could change the content of cell membrane components and permeability. Different concentrations of biotin affect the transcription levels of enzymes and promote the synthesis of glutamate (Y. Cao et al., 2014; Yan Cao, Mpofu, Jian, & Zuoying, 2012). In order to further optimize the fermentation process, we attempted to adding the coenzyme during the L-ornithine production. The concentration of biotin and thiamine hydrochloride in the fermentation medium was 0.9 μM and 15 μM (Hyun Jin, Myung Cho, & Hoon Park, 2007), and the L-ornithine production increased to 33.4 g/L compared with no adding coenzyme fermentation (27.1 g/L) (Fig.5). During the 0-48 h fermentation period in shake flasks, the strain XAB03 grows with abundant nutrients, the energy distribution mainly focuses on the growth of the bacteria while the production of L-ornithine is weak. From 48-72 h, the growth tends to be stable and the L-ornithine is synthesized rapidly. The results provide a research direction for the promotion of certain target products through the addition of coenzymes and some small molecules.