Novel mutagenesis and screening technologies for food microorganisms: advances and prospects

Microorganisms are indispensable in the food industry, but wild-type strains hardly meet the current industrial demands due to several undesirable traits. Therefore, microbial strain improvement offers a critical solution to enhance the food industry. Traditional techniques for food microbial improvement, such as the use of chemical mutagens and manual isolation/purification, are inefficient, time-consuming, and laborious, restricting further progress in the area of food fermentation. In this review, the applications of novel mutagenesis and screening technologies used for the improvement of food microbes were summarized, including random mutagenesis based on physical irradiation, microbial screening facilitated by a microtiter plate, fluorescence-activated cell or droplet sorting, and microscaled fermentation in a microtiter plate or microbioreactor. In comparison with conventional methods, these new tools have the potential in accelerating microbial strain improvement and their combined applications could create a new trend for strain development. However, several problems that could affect its potential application may include the following: the lack of specific mutagenesis devices and biosensing systems, the insufficient improvement of the mixed culture system, the low efficiency when using filamentous fungi and flocculating bacteria, and the insufficient safety assessment on harnessing genome-editing technology. Therefore, future works on strain improvement remain challenging for the food industry.