Green Chemistry
Communication
reported in this work and compared it with the fermentative
biosynthesis and the chemical synthesis of this molecule. The
E factor was significantly lower for all biosynthetic processes
compared to the chemical one, although water was the major
contributor in all cases. The green metrics forecast a decrease
in the E factor of our process if the operational stability of the
biocatalyst is maximised according to the weight of the bioca-
talyst mass in the total value of the E factor.
Conflicts of interest
There are no conflicts to declare.
Fig. 4 Weighted E factor values of different serinol production pro-
cesses. Contribution of water (blue), solvents other than water (yellow),
reagents (red) and catalyst (green) to the total E factor were plotted. E
factor values were calculated from the data reported in this work, Luo
et al. (ref. 23), Andreen et al. (ref. 21), and Bhandare et al. (ref. 24).
Acknowledgements
S. Velasco acknowledges CONACyT for the granted postdoc-
toral fellowship. L. Betancor, E. Jackson and M. Ripoll
acknowledge PEDECIBA, National Research and Innovation
Agency of Uruguay (ANII) (POS_NAC_2019_1_158182) and
and glucose-driven fermentative processes with an E factor of Universidad ORT Uruguay. Fernando López acknowledges the
60 due to the high titer of serinol. When the fermentation is funding of IKERBASQUE and Spanish Government (BIO2015-
not optimised and the starting material was glycerol instead of 69887-R). This work was performed under the Maria de
glucose, the E factor increased up to 300, a similar value to the Maeztu Units of Excellence Programme
–
Grant No.
one calculated for the system herein presented and catalysed MDM-2017-0720 Ministry of Science, Innovation and
by the hybrid heterogeneous biocatalyst.
Universities.
Remarkably, the contribution of the catalyst to the total E
factor was notorious in the systems with the G. oxydans resting
cells and the immobilised transaminase co-entrapped into the
alginate pearls. We envision that the weight of the biocatalysts
in the total E-factor will be reduced by improving the re-use of
this hybrid system.
Notes and references
‡Upgrades in price were calculated using the Merck-Sigma-Aldrich catalogue
and the market price from crude glycerol provided by Alcoholes del Uruguay
(ALUR) (Montevideo, Uruguay).
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Conclusions
More sustainable approaches for valorising and up-grading
renewable raw materials and wastes contribute to expand the
concept of biorefinery. In particular, glycerol is one of the
largest surpluses of the biodiesel industry that need to be
transformed into high-added value products. In this work, we
have up-graded glycerol to serinol through a hybrid biocataly-
tic system that co-entraps resting cells and immobilised
enzymes into an alginate matrix. The combination of resting
cells and isolated enzymes is not trivial, so we herein designed
a novel heterogeneous multi-functional biocatalyst able to
oxidise glycerol to DHA, and concurrently aminate the inter-
mediate ketone to serinol. This was possible through the
spatial confinement of resting G. oxydans and an immobilised
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Soc. Rev., 2013, 42, 6346–6377.
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lyse the concurrent oxidation and transamination reactions in Green Sustain. Chem., 2020, 25, 100343.
one-pot. Using this hybrid and heterogeneous biocatalyst, we 11 K. Goldberg, K. Schroer, S. Lütz and A. Liese, Appl.
achieved up to 36 mM of serinol, the highest titer ever reported Microbiol. Biotechnol., 2007, 76, 249–255.
for a non-fermentative serinol biosynthesis. Finally, we ana- 12 L. Lu, L. Wei, K. Zhu, D. Wei and Q. Hua, Bioresour.
lysed the sustainability metrics of the serinol biosynthesis
Technol., 2012, 117, 317–324.
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Green Chem., 2021, 23, 1140–1146 | 1145