Consolidated bioprocessing of starch based on a bilayer cell factory without genetic modification of yeast

Athanasios Drosos, Konstantina Boura, Agapi Dima, Ioannis K. Karabagias, Poonam Singh - Nee Nigam, Maria Kanellaki, A.A. Koutinas

Research output: Contribution to journalArticlepeer-review

Abstract

The exploitation of starchy wastes for the production of value-added products and
the consolidated bioprocessing (CBP) have a positive environmental and cost-effective
impact. For this reason, a cell factory (CF) was employed to perform three bioprocesses
in one step (CBP) for alcoholic fermentation of starch without genetic modification. CF is
a bilayer biocatalyst consisting of an inner layer of immobilized Saccharomyces cerevisiae
on tubular cellulose (TC) and an external layer of immobilized Aspergillus awamori on
alginates (ALG). In first, the suggested CF was proved to be more effective compared
with co-immobilized S. cerevisiae and A. awamori on ALG beads for starch fermentation.
Subsequently, the effect of the (i) S. cerevisiae concentration (g S. cerevisiae/g TC) during
its immobilization, (ii) CaCl2 concentration (% w/v), (iii) form of bilayer CF (wet or
freeze-dried) and (iv) freeze-dried CF concentration on 5% (w/v) starch fermentation was
examined. It was found that the higher ethanol production (32.17 mL/L), productivity
(4.60 mL/L/d) and yield (0.51 g ethanol/g starch) reaching the theoretical one were
obtained when the CF in freeze dried form fermented 100 mL of 5% (w/v) starch solution.
Finally, two repeated fermentation batches were performed using the best CF. The
ethanol yield was decreased during the repeated fermentation batches, but remained in
acceptable levels. The successful preparation of CF was verified with FTIR spectroscopy,
SEM and TEM analysis. The results indicated that the objective of designing CF was
successfully achieved, and the results are promising to be the base for the exploitation of
starchy wastes and the development of an innovation in brewing industry by eliminating
the malting stage. This CF can be applied as model for different bioprocesses of White
Biotechnology, e.g. substituting S. cerevisiae with the appropriate microorganism to
produce other metabolites of added value.
Original languageEnglish
Article number 101844
Pages (from-to)1-11
Number of pages11
JournalEnvironmental Technology & Innovation
Volume24
Early online date4 Aug 2021
DOIs
Publication statusE-pub ahead of print - 4 Aug 2021

Keywords

  • Starch
  • Consolidated bioprocessing (CBP)
  • Alcoholic fermentation
  • Cell factory
  • Tubular cellulose

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