Abstract
To develop a direct microbial sugar conversion platform for the production of lipids, drop-in fuels and chemicals from cellulosic biomass substrate, we chose Yarrowia lipolytica as a viable demonstration strain. Y. lipolytica is known to accumulate lipids intracellularly and is capable of metabolizing sugars to produce lipids; however, it lacks the lignocellulose-degrading enzymes needed to break down biomass directly. While research is continuing on the development of a Y. lipolytica strain able to degrade cellulose, in this study, we present successful expression of several xylanases in Y. lipolytica. The XynII and XlnD expressing Yarrowia strains exhibited an ability to grow on xylan mineral plates. This was shown by Congo Red staining of halo zones on xylan mineral plates. Enzymatic activity tests further demonstrated active expression of XynII and XlnD in Y. lipolytica. Furthermore, synergistic action in converting xylan to xylose was observed when XlnD acted in concert with XynII. The successful expression of these xylanases in Yarrowia further advances us toward our goal to develop a direct microbial conversion process using this organism.
Highlights
Yeasts are employed as the hosts of choices for the heterologous expression of proteins
We successfully demonstrated the heterologous expression of xylanases in Y. lipolytica
The obtained XynII and XlnD transformants showed the ability grow on xylan mineral plates, and form halo zones on xylan mineral plates visualized by Congo Red staining
Summary
Yeasts are employed as the hosts of choices for the heterologous expression of proteins. The ‘‘non-conventional’’ yeasts other than Saccharomyces cerevisiae have been receiving more attention in microbiological research. Among the ‘‘non-conventional’’ yeasts, Y. lipolytica is one of the most attractive and PLOS ONE | DOI:10.1371/journal.pone.0111443. Heterologous Expression of Xylanases in Yarrowia lipolytica extensively studied model organisms for its genetic and physiological research [1, 2]. For its ability to secrete native and heterologous proteins at high levels [3,4,5], for example, wild type strains can secrete 1–2 g/l of alkaline extracellular protease (XPR2) [6], it has been extensively used in a broad range of industrial applications. The availability of genome sequence of Y. lipolytica strain E150 (CLIB99) [7, 8] and the development of genetic tools such as transformation methods [9], and integrative expression cassettes [10,11,12] increase its suitability to be metabolically engineered
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