Using gel microdroplets to develop a simple high-throughput screening platform for oleaginous microorganisms

The oleaginous yeast Lipomyces starkeyi is expected to be a new lipid source since this microorganism is capable of accumulating more than 85% lipid per dry cell weight. For effective utilization of oleaginous yeast, mutants with improved lipid production compared to the wild-type have been screened by methods such as single-cell sorting and Percoll density gradient centrifugation. Because these methods need to reculture all mutated oleaginous yeasts together in a flask, it is difficult to evaluate the growth of each individual mutant. Thus, screening for the slow-growing mutants with high-throughput has never been performed by conventional methods. In this study, we developed a high-throughput method using gel microdroplets (GMD). With this method, the growth and lipid production of L. starkeyi can be evaluated simultaneously. L. starkeyi grew in GMD and the size of these microcolonies was evaluated by scattered light. Finally, a mutant with a 10-fold delay in growth compared to the wild-type was obtained. Analysis of genetic information in this mutant could reveal valuable information about critical genes involved in the growth of these microorganisms, which could then be utilized further.