Abstract
The yeast strains IPM32-16, ISM28-8sT, and IPM46-17, isolated from plant and soil samples from Iriomote Island, Japan, were explored in terms of lipid production during growth in a mixture of glucose and xylose. Phylogenetically, the strains were most closely related to Cystobasidium slooffiae, based on the sequences of the ITS regions and the D1/D2 domain of the LSU rRNA gene. The strains were oleaginous, accumulating lipids to levels > 20% dry cell weight. Moreover, kinetic analysis of the sugar-to-lipid conversion of a 1:1 glucose/xylose mixture showed that the strains consumed the two sugars simultaneously. IPM46-17 attained the highest lipid content (33%), mostly C16 and C18 fatty acids. Thus, the yeasts efficiently converted lignocellulosic sugars to lipids, aiding in biofuel production (which benefits the environment, promotes rural jobs, and strengthens fuel security). The strains constituted a novel species of Cystobasidium, for which we propose the name Cystobasidium iriomotense (type strain ISM28-8sT = JCM 24594T = CBS 15015T).
Highlights
Chemical and fuel production from lignocellulosic biomass is receiving increasing attention [1, 2]
We focused on oleaginous yeasts that could utilize glucose and xylose simultaneously and selected three strains, IPM3216, ISM28-8sT, and IPM46-17, for evaluation
A phylogenetic tree based on the sequences of the internal transcribed spacer (ITS) regions plus D1/D2 domain of the LSU rRNA genes showed that the three strains clustered with Cystobasidium slooffiae, C. fimetarium, and C. minutum (Fig 1)
Summary
Chemical and fuel production from lignocellulosic biomass is receiving increasing attention [1, 2]. Hydrolysates of such biomasses contain mixtures of sugars, mainly glucose and xylose in various ratios [3, 4]. Complete conversion of sugars in hydrolysates is necessary for efficient utilization of lignocellulosic biomass. The production of microbial lipids via enzymatic degradation of lignocellulosic biomass is currently a subject of intense interest. One major barrier to commercial application is the cost of the enzymes used to degrade cellulose to monosaccharides. The absence of a high-performance microorganism (a strain that can efficiently convert released sugars to lipid) renders practical production difficult
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