English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Background    Yarrowia lipolytica , one of the most widely studied “nonconventional” oleaginous yeast species, is unable to grow on cellulose. Recently, we identified and overexpressed two endogenous β-glucosidases in  Y. lipolytica , thus enabling this yeast to use cello-oligosaccharides as a carbon source for growth. Using this engineered yeast platform, we have now gone further toward building a fully cellulolytic  Y. lipolytica  for use in consolidated bioprocessing of cellulose.    Results  Initially, different essential enzyme components of a cellulase cocktail (i.e,. cellobiohydrolases and endoglucanases) were individually expressed in  Y. lipolytica  in order to ascertain the viability of the strategy. Accordingly, the  Trichoderma reesei  endoglucanase I ( Tr EG I) and II ( Tr EG II) were secreted as active proteins in  Y. lipolytica , with the secretion yield of EG II being twice that of EG I. Characterization of the purified His-tagged recombinant EG proteins (rh Tr EGs) revealed that rh Tr EG I displayed higher specific activity than rh Tr EG II on both cellotriose and insoluble cellulosic substrates, such as Avicel, β-1, 3 glucan, β-1, 4 glucan, and PASC. Similarly, cellobiohydrolases, such as  T. reesei  CBH I and II ( Tr CBH I and II), and the CBH I from  Neurospora crassa  ( Nc CBH I) were successfully expressed in  Y. lipolytica.  However, the yield of the expressed  Tr CBH I was low, so work on this was not pursued. Contrastingly, rh Nc CBH I was not only well expressed, but also highly active on PASC and more active on Avicel (0.11 U/mg) than wild-type  Tr CBH I (0.065 U/mg). Therefore, work was pursued using a combination of  Nc CBH I and  Tr CBH II. The quantification of enzyme levels in culture supernatants revealed that the use of a hybrid promoter instead of the primarily used TEF promoter procured four and eight times more  Nc CBH I and  Tr CBH II expressions, respectively. Finally, the coexpression of the previously described  Y. lipolytica  β-glucosidases, the CBH II, and EG I and II from  T. reesei , and the  N. crassa  CBH I procured an engineered  Y. lipolytica  strain that was able to grow both on model cellulose substrates, such as highly crystalline Avicel, and on industrial cellulose pulp, such as that obtained using an organosolv process.    Conclusions  A  Y. lipolytica  strain coexpressing six cellulolytic enzyme components has been successfully developed. In addition, the results presented show how the recombinant strain can be optimized, for example, using artificial promoters to tailor expression levels. Most significantly, this study has provided a demonstration of how the strain can grow on a sample of industrial cellulose as sole carbon source, thus revealing the feasibility of  Yarrowia -based consolidated bioprocess for the production of fuel and chemical precursors. Further, enzyme and strain optimization, coupled to appropriate process design, will undoubtedly lead to much better performances in the future.    Electronic supplementary material  The online version of this article (doi:10.1186/s13068-017-0819-8) contains supplementary material, which is available to authorized users.

Conferring cellulose-degrading ability to Yarrowia lipolytica to facilitate a consolidated bioprocessing approach