Enhance  Methanol Tolerability of M. Extorquens AM1 By Adaptive Evolution

Authors: 
Cui, L. Y., Tsinghua University
Liang, W. F., Tsinghua University
Zhu, W. L., Tsinghua University
Zhang, C., Tsinghua University
Xing, X. H., Tsinghua University

Enhance
methanol tolerability of M. extorquens
AM1 by adaptive evolution

M.
extorquens
AM1 is the most extensively studied
methylotroph model strain in methylotrophic biosynthesis. Methylotrophic
biosynthesis using methanol as feedstock is a promising and attractive way in
industrial biotechnology for the large productivity and low price of methanol
produced from coal or bio-waste anaerobic fermentation-based biomethane.
However,  methanol  toxicity  to 
M. extorquens  limits  the substrate concentration in  the 
fermentation  broth,  and 
for  this  reason  the methanol based production  processes  is 
of  low  productivity and long fermentation time.

To obtain the strain with higher methanol
tolerability, atmospheric and room temperature plasma (ARTP) was used in this study
to obtain mutant strains library. By screening mutant strains in generations cultured
with medium containing 5% methanol (v/v), strain CLY-2533 with stable methanol
tolerability was obtained. The tolerance of CLY-2533 was improved more than 2
times than that of the wild-type strain AM1. The final OD600 of
CLY-2533 was 1.83 times higher than that of the wild strain AM1 in 5% (v/v)
methanol. The specific growth rate of CLY-2533 was improved more than 0.37
times. Furthermore, the production of mevalonic acid (MEV) and final OD600 of
CLY-2533-mvt were 496.44
¡À 7.32mg/L
and 10.31 ¡À 0.32, respectively,  which  were  59.7%  and 
40.5%  higher  than  that  of 
the  wild-type strain AM1-mvt.