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.