A microalgal-based preparation with synergistic cellulolytic and detoxifying action towards chemical-treated lignocellulose

Manuel Benedetti, Simone Barera, Paolo Longoni, Zeno Guardini, Natalia Herrero Garcia, David Bolzonella, Damar Lopez-Arredondo, Luis Herrera-Estrella, Michel Goldschmidt-Clermont, Roberto Bassi, Luca Dall’Osto

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

High-temperature bioconversion of lignocellulose into fermentable sugars has drawn attention for efficient production of renewable chemicals and biofuels, because competing microbial activities are inhibited at elevated temperatures and thermostable cell wall degrading enzymes are superior to mesophilic enzymes. Here, we report on the development of a platform to produce four different thermostable cell wall degrading enzymes in the chloroplast of Chlamydomonas reinhardtii. The enzyme blend was composed of the cellobiohydrolase CBM3GH5 from C. saccharolyticus, the β-glucosidase celB from P. furiosus, the endoglucanase B and the endoxylanase XynA from T. neapolitana. In addition, transplastomic microalgae were engineered for the expression of phosphite dehydrogenase D from Pseudomonas stutzeri, allowing for growth in non-axenic media by selective phosphite nutrition. The cellulolytic blend composed of the glycoside hydrolase (GH) domain GH12/GH5/GH1 allowed the conversion of alkaline-treated lignocellulose into glucose with efficiencies ranging from 14% to 17% upon 48h of reaction and an enzyme loading of 0.05% (w/w). Hydrolysates from treated cellulosic materials with extracts of transgenic microalgae boosted both the biogas production by methanogenic bacteria and the mixotrophic growth of the oleaginous microalga Chlorella vulgaris. Notably, microalgal treatment suppressed the detrimental effect of inhibitory by-products released from the alkaline treatment of biomass, thus allowing for efficient assimilation of lignocellulose-derived sugars by C. vulgaris under mixotrophic growth.

Original languageEnglish
Pages (from-to)124-137
Number of pages14
JournalPlant Biotechnology Journal
Volume19
Issue number1
DOIs
StatePublished - Jan 2021

Keywords

  • Chlamydomonas
  • Chlorella
  • biofuel
  • biogas
  • cell wall degrading enzymes
  • glycoside hydrolases
  • phosphite
  • plant cell wall
  • transplastomic microalgae

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