Enhancing Astaxanthin Biosynthesis by Rhodosporidium toruloides Mutants and Optimization of Medium Compositions Using Response Surface Methodology

Tuyet Nhung Tran,Dai-Hung Ngo,Dai-Nghiep Ngo,Hoang Chinh Nguyen,Chia-Hung Su,Quoc Tuan Tran

doi:10.3390/pr8040497

Abstract

Astaxanthin is a valuable carotenoid, which has been approved as a food coloring by the US Food and Drug Administration and is considered as a food dye by the European Union (European Commission). This work aimed to attain Rhodosporidium toruloides mutants for enhanced astaxanthin accumulation using ultraviolet (UV) and gamma irradiation mutagenesis. Gamma irradiation was shown to be more efficient than UV for producing astaxanthin-overproducer. Among the screened mutants, G17, a gamma-induced mutant, exhibited the highest astaxanthin production, which was significantly higher than that of the wild strain. Response surface methodology was then applied to optimize the medium compositions for maximizing astaxanthin production by the mutant G17. The optimal medium compositions for the cultivation of G17 were determined as a peptone concentration of 19.75 g/L, malt extract concentration of 13.56 g/L, and glucose concentration of 19.92 g/L, with the maximum astaxanthin yield of 3021.34 µg/L ± 16.49 µg/L. This study suggests that the R. toruloides mutant (G17) is a potential candidate for astaxanthin production.

Highlights

Astaxanthin (3,30 -dihydroxy-β-carotene-4,40 -dione) is a keto-carotenoid with extensive use as a feed supplement in aquaculture industry due to its contributions to the attractive coloration, growth, and survival of marine animals such as shrimps, salmon, and trout [1,2]
The wild-type R. toruloides was mutated by using UV and screened for astaxanthin overproducers
After being treated with UV for different exposure times (0–30 s) and cultivated on the solid medium for 7 d, the R. toruloides cells were efficiently induced with a rapid color change from slightly pink to red and orange, indicating that UV acts as an inducer for carotenogenesis in R. toruloides

Summary

Introduction

Astaxanthin (3,30 -dihydroxy-β-carotene-4,40 -dione) is a keto-carotenoid with extensive use as a feed supplement in aquaculture industry due to its contributions to the attractive coloration, growth, and survival of marine animals such as shrimps, salmon, and trout [1,2]. Astaxanthin has been approved as a color additive for specific uses in fish and animal foods by the Food and Drug. The European Union considers astaxanthin as a food dye within the E number system (E161j) [3]. Astaxanthin has various applications in pharmaceutical, nutraceutical, and cosmetic industries [3,6]. Because of such benefits, there is an Processes 2020, 8, 497; doi:10.3390/pr8040497 www.mdpi.com/journal/processes

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Results