Production of galactitol from galactose by the oleaginous yeast Rhodosporidium toruloides IFO0880

Christopher V Rao,Yong-Su Jin,Sujit Sadashiv Jagtap,Ashwini Ashok Bedekar,Jing-Jing Liu

doi:10.1186/s13068-019-1586-5

Christopher V Rao, Yong-Su Jin + Show 3 more

Open Access

https://doi.org/10.1186/s13068-019-1586-5

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Abstract

BackgroundSugar alcohols are commonly used as low-calorie sweeteners and can serve as potential building blocks for bio-based chemicals. Previous work has shown that the oleaginous yeast Rhodosporidium toruloides IFO0880 can natively produce arabitol from xylose at relatively high titers, suggesting that it may be a useful host for sugar alcohol production. In this work, we explored whether R. toruloides can produce additional sugar alcohols.ResultsRhodosporidium toruloides is able to produce galactitol from galactose. During growth in nitrogen-rich medium, R. toruloides produced 3.2 ± 0.6 g/L, and 8.4 ± 0.8 g/L galactitol from 20 to 40 g/L galactose, respectively. In addition, R. toruloides was able to produce galactitol from galactose at reduced titers during growth in nitrogen-poor medium, which also induces lipid production. These results suggest that R. toruloides can potentially be used for the co-production of lipids and galactitol from galactose. We further characterized the mechanism for galactitol production, including identifying and biochemically characterizing the critical aldose reductase. Intracellular metabolite analysis was also performed to further understand galactose metabolism.ConclusionsRhodosporidium toruloides has traditionally been used for the production of lipids and lipid-based chemicals. Our work demonstrates that R. toruloides can also produce galactitol, which can be used to produce polymers with applications in medicine and as a precursor for anti-cancer drugs. Collectively, our results further establish that R. toruloides can produce multiple value-added chemicals from a wide range of sugars.

Highlights

Sugar alcohols are commonly used as low-calorie sweeteners and can serve as potential build‐ ing blocks for bio-based chemicals
Rhodosporidium toruloides produce galactitol during growth on galactose in nitrogen‐rich medium To determine whether R. toruloides IFO0880 produces any sugar alcohols in addition to arabitol, we measured growth on arabinose, cellobiose, fructose, galactose, glucose, glycerol, mannose, and sucrose in nitrogen-rich medium, the same based medium that induces arabitol production during growth on xylose (Fig. 1)
This metabolite was identified as d-galactitol by gas chromatography–mass spectrometry (GC–MS) and proton nuclear magnetic resonance spectroscopy (1H-NMR) (Additional file 2: Figure S2 and Additional file 3: Figure S3)

Summary

Introduction

Sugar alcohols are commonly used as low-calorie sweeteners and can serve as potential build‐ ing blocks for bio-based chemicals. Sugar alcohols are commonly used as low-calorie, natural sweeteners [1] They have been proposed by the Department of Energy as potential building blocks for bio-based chemicals [2]. Sugar alcohols are naturally found in fruits, vegetables, and mushrooms [3] They can be produced from sugars using yeast. Erythritol, mannitol, ribitol, and xylitol [4,5,6,7,8,9,10] Production of these sugar alcohols by yeast often results, though not always, from redox imbalances associated with growth on different sugars [4, 5]. A number of sugar alcohols are industrially produced using yeast fermentations [12,13,14,15]

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