Engineering a natural Saccharomyces cerevisiae strain for ethanol production from inulin by consolidated bioprocessing

Abstract

BackgroundThe yeast Saccharomyces cerevisiae is an important eukaryotic workhorse in traditional and modern biotechnology. At present, only a few S. cerevisiae strains have been extensively used as engineering hosts. Recently, an astonishing genotypic and phenotypic diversity of S. cerevisiae was disclosed in natural populations. We suppose that some natural strains can be recruited as superior host candidates in bioengineering. This study engineered a natural S. cerevisiae strain with advantages in inulin utilization to produce ethanol from inulin resources by consolidated bioprocess. Rational engineering strategies were employed, including secretive co-expression of heterologous exo- and endo-inulinases, repression of a protease, and switch between haploid and diploid strains.ResultsResults from co-expressing endo- and exo-inulinase genes showed that the extracellular inulinase activity increased 20 to 30-fold in engineered S. cerevisiae strains. Repression of the protease PEP4 influenced cell physiology in late stationary phase. Comparison between haploid and diploid engineered strains indicated that diploid strains were superior to haploid strains in ethanol production albeit not in production and secretion of inulinases. Ethanol fermentation from both inulin and Jerusalem artichoke tuber powder was dramatically improved in most engineered strains. Ethanol yield achieved in the ultimate diploid strain JZD-InuMKCP was close to the theoretical maximum. Productivity achieved in the strain JZD-InuMKCP reached to 2.44 and 3.13 g/L/h in fermentation from 200 g/L inulin and 250 g/L raw Jerusalem artichoke tuber powder, respectively. To our knowledge, these are the highest productivities reported up to now in ethanol fermentation from inulin resources.ConclusionsAlthough model S. cerevisiae strains are preferentially used as hosts in bioengineering, some natural strains do have specific excellent properties. This study successfully engineered a natural S. cerevisiae strain for efficient ethanol production from inulin resources by consolidated bioprocess, which indicated the feasibility of natural strains used as bioengineering hosts. This study also presented different properties in enzyme secretion and ethanol fermentation between haploid and diploid engineering strains. These findings provided guidelines for host selection in bioengineering.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-016-0511-4) contains supplementary material, which is available to authorized users.

Biofuel production from Jerusalem artichoke tuber inulins: a review

“…With acid or high temperature hydrolysis, a small portion of glucose and fructose are degraded to 5-HMF but it is less inhibitory to yeast than furfural generated by degradation of xylose which lowers yield of ethanol in lignocellulosic biomass based fermentation processes (Sanchez and Bautista, 1988). K. marxianus has lower ethanol yield and tolerance compared with S. cerevisiae (Wang et al, 2016).…”

“…Recent undertakings have successfully engineered inulinase synthesis in S. cerevisiae for CBP. Wang et al (2016) introduced inulinase gene from K. marxianus into S. cerevisiae diploid strain JCD, and repressed vacuolar proteinase gene PEP4 to increase heterologous protein production. This resulting strain JZD-InuMKCP showed highest ethanol productivity of 3.2 g/L/h in 24 h and 2.44 g/L/h in 36 h with 95% theoretical ethanol yield solely fermented on JA tuber flour.…”

Recent advances in bio-based multi-products of agricultural Jerusalem artichoke resources

“…A natural engineering S. cerevisiae engineered with rational strategies such as co-expressing exo- and endo-inulinase gene, inactivated proteases between haploid and diploid was investigated for inulin utilization to produce ethanol. Ethanol fermentation from 200 g/L inulin and 250 g/L raw Jerusalem artichoke tuber powder resulted in productivity of 2.44 and 3.13 g/L/h, respectively [ 97 ]. Actually, in addition to building engineering strains, some yeast genus, such as Kluyveromyces fragilis and Kluyveromyces marxianus can both produce inulinase and ethanol.…”

A one-step bioprocess for production of high-content fructo-oligosaccharides from inulin by yeast

“…The wild type S. cerevisiae haploid strain JZH was used as the initial host (Wang, Li, & Wang, 2016).…”

“…(Wang et al, 2016) pUG6-TSC Ty1-P TEF1 -SP SUC2 -InuC opz -T CYC1 This study pUG6-ΔSUC2 DNA cassette for deletion of SUC2 (Wang & Li, 2013) …”