Optimization And Whole Genome Sequencing Analysis For Beta-Carotene Production In Rhodotorula SP

Abstract

A potential and plentiful source for the creation of natural products is yeast. However, yeast which can produce carotenoids, a group of pigments widely used in various industries is rare. Rhodotorula sp. is well-known in beta-carotene production. Therefore, characterization of whole genome of this yeast and optimization of conditions for carotenoid producing ability in Rhodotorula sp. are interesting. In the study, Rhodotorula sp. was cultivated on suitable culture media to screen pigment production under light intensity, temperature and time. Total carotenoids, especially beta-carotene were extracted completely from the yeast cells by using an optimal method by combination of acetone and ultrasound. The concentration of total carotenoids and beta-carotene extracted from Rhodotorula sp. was determined using spectrophotometry. To optimize the multi-factors for beta-carotene production, response surface methodology (RSM) and Box-Behnken design (BBD) were employed. A total of 15 experiments from designed matrix were conducted in triplicate, and the extracted beta-carotene content was evaluated along with the interaction between incubation conditions. The best optimal conditions for beta carotene extraction in this yeast was Luria-Bertani medium (pH 7.0), incubation time of 120 hours at 25°C under white light intensity (500 lux). Under these conditions, the average cell biomass was 0.0046g dry weight/mL culture and beta-carotene content was 138.88±0.41 μg/g dry weight. These results highlighted the potential of Rhodotorula sp. as a valuable source of carotenoids for industrial applications. Furthermore, whole genome sequencing analysis identified Rhodotorula sp. as Rhodotorula mucilaginosa. The yeast had 8 gene clusters responsible for secondary synthesis and 176 genes involved in carbohydrate, glycoconjugate metabolism, especially terpenoid synthase, isopentenyl pyrophosphatase (IPP) with isomerase genes to form general carotenoids such as beta-carotene. Additionally, by comparing some hypothetical protein of this yeast to the reference strains in data bank, it was discovered that these proteins had a low identity to the proteins of reference strains leading to the variation of beta-carotene production in yeasts. The study contributes a beta-carotene source, a method for beta-carotene extraction from the yeast, and the information of secondary metabolites in yeast for pharmaceutical science.