Methanol is a promising alternative substrate with low cost and good availability for chemicals and fuels production. Although methanol can be readily converted into short chain chemicals and fuels such as olefins through traditional catalytic conversions, biological conversion of methanol may provide more economic operating conditions and more extensive product range.

In the last few years, massive efforts have been devoted to enable industrial platform organisms to incorporate methanol for building up cellular constituents and producing chemicals. However, the existing synthetic methylotrophs still utilize sugar as the major carbon source and methanol is only a minor co-substrate, limiting the bioconversion of methanol.

Recently, a research team led by Prof. ZHENG Ping and Prof. SUN Jibin at the Tianjin Institute of Industrial Biotechnology (TIB) of the Chinese Academy of Sciences designed and experimentally engineered the industrial workhorse Corynebacterium glutamicum to serve as a methanol-dependent synthetic methylotroph for methanol bioconversion to amino acids.  

By engineering the pentose phosphate pathway and introducing methanol dehydrogenase and ribulose monophosphate pathway, the researchers constructed a synthetic methylotrophic C. glutamicum. Notably, the synthetic methylotroph requires co-utilization of methanol and xylose for growth and the methanol uptake rate is directly associated with its growth rate.

Therefore, adaptive laboratory evolution could be applied to improving methanol utilization efficiency. After 14 passages of adaptive laboratory evolution, the evolved mutant showed a 20-fold increase in cell growth rate and utilized methanol and xylose with a high mole ratio of 3.83:1. By feeding the evolved mutant with ¹³C-methanol and non-labeled xylose, they found that up to 63% carbons of intracellular metabolites were derived from methanol.

Since C. glutamicum is a native glutamate producer, methanol was further used as a carbon source for glutamate production using the methanol-dependent strain. This study demonstrates the potential application of synthetic methylotrophs in bioconversion of methanol into valuable chemicals, including amino acids.  

The study entitled "Engineering Corynebacterium glutamicum for methanol-dependent growth and glutamate production" was published in Metabolic Engineering.

This work was supported by the National Natural Science Foundation of China, the Key Research Program of Chinese Academy of Sciences, the International Partnership Program of Chinese Academy of Sciences, the Special Program of Talents Development for Excellent Youth Scholars in Tianjin, and the first Special Support Plan for Talents Development and High-level Innovation and Entrepreneurship Team of the Tianjin Municipal City. 

Strategies to construct the methanol-dependent C. glutamicum. (Image by TIB)  

¹³C-labeling in intracellular metabolites from the methanol-dependent C. glutamicum. (Image by TIB)