Genome structure of a Saccharomyces cerevisiae strain widely used in bioethanol production

Abstract

Bioethanol is a biofuel produced mainly from the fermentation of carbohydrates derived from agricultural feedstocks by the yeast Saccharomyces cerevisiae. One of the most widely adopted strains is PE-2, a heterothallic diploid naturally adapted to the sugar cane fermentation process used in Brazil. Here we report the molecular genetic analysis of a PE-2 derived diploid (JAY270), and the complete genome sequence of a haploid derivative (JAY291). The JAY270 genome is highly heterozygous (;2 SNPs/kb) and has several structural polymorphisms between homologous chromosomes. These chromosomal rearrangements are confined to the peripheral regions of the chromosomes, with breakpoints within repetitive DNA sequences. Despite its complex karyotype, this diploid, when sporulated, had a high frequency of viable spores. Hybrid diploids formed by outcrossing with the laboratory strain S288c also displayed good spore viability. Thus, the rearrangements that exist near the ends of chromosomes do not impair meiosis, as they do not span regions that contain essential genes. This observation is consistent with a model in which the peripheral regions of chromosomes represent plastic domains of the genome that are free to recombine ectopically and experiment with alternative structures. We also explored features of the JAY270 and JAY291 genomes that help explain their high adaptation to industrial environments, exhibiting desirable phenotypes such as high ethanol and cell mass production and high temperature and oxidative stress tolerance. The genomic manipulation of such strains could enable the creation of a new generation of industrial organisms, ideally suited for use as delivery vehicles for future bioenergy technologies.

Morphophysiological and molecular characterization of wild yeast isolates from industrial ethanol process

“…This can be observed in the results obtained by the analysis of 26S rDNA sequencing (Figure 1), where isolates presented distinct banding patterns when compared to the reference strains. This can be caused by the emergence of a native strain in the process, or due to adaptive evolution, as mentioned by Argueso et al (2009), Burke (2012) and Xufre et al (2011). The results made it possible to identify groups of wild strains that are probably of a common origin, most likely like the local microbiota, as similarly observed by Kishkovskaia et al (2017).…”

“…Yeast isolates subjected to harsh conditions tend to develop genetic-induced physiological traits that make them more resistant, including the activation of genes responsible for cell wall integrity and oxidative stress response (Elsztein et al, 2011). Chromosomal rearrangements referred to as adaptive evolution were reported for the industrial PE-2 strain, under industrial-related environments and extended laboratory storage conditions (Argueso et al, 2009). This can be observed in the results obtained by the analysis of 26S rDNA sequencing (Figure 1), where isolates presented distinct banding patterns when compared to the reference strains.…”

Innovative Biological Solutions to Challenges in Sustainable Biofuels Production

“…Yeast is a well-established fermenting microorganism in existing commercial-scale ethanol industries. PE-2 is one of the most widely adopted yeast strains for the sugarcane fermentation process, used in about 30% of Brazilian distilleries, generating roughly 10% of the world's bioethanol supply (Argueso et al, 2009). The generation and conversion of fermentable sugars from lignocellulosic materials to ethanol is strongly dependent on the feedstock pretreatment and strain selection (Lau & Dale, 2009).…”

“…In 1996, the S. cerevisiae laboratory strain S288c became the first eukaryote to have its genome completely sequenced (Bayer et al, 2007;Argueso et al, 2009). Since then, other haploid strains from diverse backgrounds have been sequenced (RM11-1a, YJM789, M22, YPS163, and AWRI1631; http://www.broad.mit.edu/), followed by a large-scale effort to determine the genome sequences of many others (Bayer et al, 2007;Wei et al, 2007;Doniger et al, 2008;Argueso et al, 2009). Extensive analyses have been conducted to examine the nucleotide sequence diversity between these strains and the results from these studies provide valuable insights for synthetic biology and artificial biology to create efficient and robust yeast strains.…”

“…The Brazilian system is based on sucrose obtained from sugarcane, which can be converted to bioethanol directly by yeast species without enzymatic pre-treatment, allowing this system to produce an energy surplus estimated at about eightfold (Goldemberg, 2007;Robertson et al, 2008;Argueso et al, 2009). Yeast is a well-established fermenting microorganism in existing commercial-scale ethanol industries.…”