Construction of a Compact Array of Microplasma Jet Devices and Its Application for Random Mutagenesis of Rhodosporidium Toruloides.

A small and efficient DNA mutation-inducing machine was constructed with an array of microplasma jet devices (7 x 1) that can be operated at atmospheric pressure for microbial mutagenesis. Using this machine, we report disruption of a plasmid DNA and generation of mutants of an oleaginous yeast Rhodosporidium toruloides. Specifically, a compact-sized microplasma channel (25 x 20 x 2 mm(3)) capable of generating an electron density of greater than 10(13) cm(-3) was constructed to produce reactive species (N-2*, N-2(+), O, OH, and H-alpha) under helium atmospheric conditions to induce DNA mutagenesis. The length of microplasma channels in the device played a critical role in augmenting both the volume of plasma and the concentration of reactive species. First, we confirmed that microplasma treatment can linearize a plasmid by creating nicks in vitro. Second, we treated R. toruloides cells with a jet device containing 7 microchannels for 5 min; 94.8% of the treated cells were killed, and 0.44% of surviving cells showed different colony colors as compared to their parental colony. Microplasma-based DNA mutation is energy-efficient and can be a safe alternative for inducing mutations compared to conventional methods using toxic mutagens. This compact and scalable device is amenable for industrial strain improvement involving large-scale mutagenesis.