A preliminary investigation on lipid accumulation by Metschnikowia pulcherrima

In the context of circular economy, microbial biomasses are promising alternative source for food and feed production, and oleaginous yeasts, producing intracellular lipids for over 20% of dry cell weight, can be key resources. Metschnikowia pulcherrima is a non-conventional yeast increasingly explored for wine-related applications, and it has an industrial potential as an oleaginous species, being able to grow on different agro- food residues, tolerating low pH and temperature. This study aimed to investigate qualitative methods suitable for high- throughput screening of a large collection of M. pulcherrima strains for lipids accumulation. Ten strains of M. pulcherrima clade were used as test collection. Strains were grown at lab scale in a high C/N medium, and lipid droplets were observed under the microscope. The qualitative plate method with Rhodamine B dye was evaluated in both visible and UV light, then compared with lipid extraction and gravimetric quantification. While qualitative protocols did not robustly reveal the oleaginous behaviour, quantitative data showed that one novel strain, VUCC500, could be an interesting single-cell-oil strain, with glucose as a carbon source. Remarkably, its yield increased in preliminary tests with alternative low-cost carbon sources. Further studies are necessary to define reliable protocols for primary screening of M. pulcherrima strains in VUCC collection, with VUCC500 as positive control. However, since VUCC500 genome is sequenced, further analyses will be focused on this strain, targeting safety aspects necessary for this non-QPS species.