Global Transcriptome Profile of the Oleaginous Yeast Saitozyma podzolica DSM 27192 Cultivated in Glucose and Xylose

Habibu Aliyu,Katrin Ochsenreither,Anke Neumann,Olga Gorte

doi:10.3390/jof7090758

Habibu Aliyu, Katrin Ochsenreither + Show 2 more

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https://doi.org/10.3390/jof7090758

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Abstract

Unlike conventional yeasts, several oleaginous yeasts, including Saitozyma podzolica DSM 27192, possess the innate ability to grow and produce biochemicals from plant-derived lignocellulosic components such as hexose and pentose sugars. To elucidate the genetic basis of S. podzolica growth and lipid production on glucose and xylose, we performed comparative temporal transcriptome analysis using RNA-seq method. Approximately 3.4 and 22.2% of the 10,670 expressed genes were differentially (FDR < 0.05, and log2FC > 1.5) expressed under batch and fed batch modes, respectively. Our analysis revealed that a higher number of sugar transporter genes were significantly overrepresented in xylose relative to glucose-grown cultures. Given the low homology between proteins encoded by most of these genes and those of the well-characterised transporters, it is plausible to conclude that S. podzolica possesses a cache of putatively novel sugar transporters. The analysis also suggests that S. podzolica potentially channels carbon flux from xylose via both the non-oxidative pentose phosphate and potentially via the first steps of the Weimberg pathways to yield xylonic acid. However, only the ATP citrate lyase (ACL) gene showed significant upregulation among the essential oleaginous pathway genes under nitrogen limitation in xylose compared to glucose cultivation. Combined, these findings pave the way toward the design of strategies or the engineering of efficient biomass hydrolysate utilization in S. podzolica for the production of various biochemicals.

Highlights

According to the forecast of the United Nations, the world’s population is expected to grow by ~20% to 9.7 billion people within the 30 years [1]
The oleaginous yeast Saitozyma podzolica DSM 27192, cultivated on glucose and xylose (Figure 1) was sampled for RNA-sequencing (RNA-seq) at 22, 48, 70 and 120 h with a view to evaluate the transcriptional response of the yeast during growth on the two sugars
The biomass increased steadily to a maximum of 26.78 ± 3.50 (Figure 1a) and 25.38 ± 0.25 g/L (Figure 1b) on glucose and xylose, respectively. The latter phase is characterised by accumulation of singlecell oil (SCO), a process triggered by nitrogen limitation, with the complete depletion of the nitrogen source at 70 h [9]

Summary

Introduction

According to the forecast of the United Nations, the world’s population is expected to grow by ~20% to 9.7 billion people within the 30 years [1]. The demand for energy and material resources will increase. To satisfy these requirements and to circumvent economic and environmental challenges, which are associated with reliance on fossil sources, renewable and sustainable energy sources need to be developed. Microbial lipids produced by oleaginous yeasts could contribute as one of the numerous alternative energy sources. Oleaginous yeasts are able to accumulate up to 70% of their cell dry mass to the storage lipids, mainly triacylglycerols [2]. Yeasts are able to metabolize a large spectrum of cheap and abundant raw materials, such as lignocellulosic plant biomass or waste from the agricultural and food industry, enabling carbon recycling within a biorefinery concept [3,4,5]. Yeast cell propagation proceeds with high duplication rates and the cultivation can be upscaled, in contrast to microalgae

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