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Bioethanol production from date palm fibers: Effect of alkaline hydrogen peroxide pretreatment and fermentation conditions

I. Ben Atitallah 1,2 ,  I. Ntaikou 3 , G. Antonopoulou 3 , C. Bredai 4 , G. Lyberatos 3,5 , T.  Mechichi 2   1 Laboratory of Enzyme Engineering and Microbiology, National  School of Engineers of  Sfax , University of  Sfax , BP 1173, 3038  Sfax , Tunisia.  2 Laboratory of Biochemistry and Enzyme Engineering of Lipases, National School of Engineers of  Sfax , University of  Sfax , BP 1173, 3038  Sfax , Tunisia.  3 Institute of Chemical Engineering Sciences, 11  Stadiou   st. ,  Platani ,  Patras , GR 26504, Greece  4 Electromechanical Systems Laboratory LASEM, National Engineering School of  Sfax , University of  Sfax ,  Soukra  km 4, 3038  Sfax , Tunisia  5 School of Chemical Engineering, National Technical University of Athens, GR 15780 Athens, Greece.  ntaikou@iceht.forth.gr

8 th  International Conference on Sustainable Solid Waste Management 23-26 June 2021, Thessaloniki, Greece

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Exploitation of date palm  fibers   for the production of second generation bioethanol  via yeast by exploring the: fractionation and saccharification of lignocellulose via novel thermochemical pretreatment maximisation of ethanol yields via yeast mono- and co-cultures

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Date palm lignocellulose l eaves trunk Trunk Leaves 50% 50% (w/w) 5  % TS (w/v) SSF SHF Solids Hydrolysate Enzymatic hydrolysis Bioethanol Fermentation Fermentation Enzymatic hydrolysis Fermentation + Bioethanol SSF Pretreatment Slurry Enzymatic hydrolysis Fermentation + Bioethanol

NaOH, 0.5% (w/v) H 2 O 2,  0.5%  (v/v) H 2 O 2,  1 %  (v/v )  +   NaOH,  1% (w/v) NaOH ,  0.5% (w/v)  →   H 2 O 2 ,  30%  (v/v ) H 2 O 2,  30%  (v/v )  →   NaOH, 0.5 %  (w/v)  80 ° C, 24 h

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NaOH, 0.5% (w/v) H 2 O 2,  0.5%  (v/v) H 2 O 2,  1 %  (v/v )  +   NaOH,  1% (w/v) NaOH ,  0.5% (w/v)  →   H 2 O 2 ,  30%  (v/v ) H 2 O 2,  30%  (v/v )  →   NaOH, 0.5 %  (w/v)

The material recovery (MR) was high in all cases (67-78%) Single step H 2 O 2  treatment led to the highest MR and lowest yield of free sugars Reducing to free sugars ratio was approximately 20% in all cases  2 step treatments were more effective on Hemicellulose solubilisation Lignin removal Cellulose removal ranged from 52%-59%, with H 2 O 2  treatments either in single step or two steps process leading to higher solubilisation

Cellulose : 42.30 ± 0.25 Hemicellulose : 23.82 ± 1.11 Lignin : 27.17 ± 0.79

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Enzyme Conditions  Cellulase  blend pH=4.8, 50 o C,   30  FPU  Cellic / gTS

X19 0 5 10 24 30 48 0.34976798143851512 1.3139211136891 2.9897911832947002 5.5339907192575399 5.7761020881671001 6.0347215777262102 P. stipitis 0 5 10 24 30 48 0.13410672853828301 0.48587354988399001 1.6542923433875001 3.5823665893270999 3.9118329466357311 4.8069605568445501 X19+P. stip 0 5 10 24 30 48 0.40197215777262185 2.1925754060324829 4.4245939675199999 6.6473317865429236 6.8300464037122977 7.12

Co-cultures resulted to higher ethanol production in all cases  Fermentation of pretreated DPF using co-cultures of  Wickerchamomyces   anomalus   and  Pichia   stipitis    leaded to  the highest  ethanol titters  of 7.12  g/L ( 6.70  g/L at SHF).  The fermentation mode did not seem to affect much the fermentation efficiency.  The direct fermentation of slurry led to higher yields.

Strain   Slurry Hydrolysate Solid SSF SHF SSF SHF W.  anomalus 0.38  ± 0.01 128.01  ± 3.12 0.38  ± 0.01 142.40  ± 4.44 - - 0.36  ± 0.01 52.45 ± 3.01 0.30 ± 0.00 50.24 ± 3.01 P.  stipitis 0.37  ± 0.01 101.82  ± 1.99 0.37  ± 0.01 118.05  ± 2.65 0.16 ± 0.01 30.83  ± 1.82 0.37  ± 0.00 48.29 ± 2.18 0.31 ± 0.01 45.77 ± 3.01 Co-cultures 0.41  ± 0.01 151.07  ± 2.47 0.40  ± 0.01 158.26  ± 3.52 - - 0.38  ± 0.02 66.12 ± 3.31 0.36  ± 0.01 61.44 ± 3.01

Two step pretreatment : NaOH , 0.5% (w/v)  →   H 2 O 2,  30%  (v/v)

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We acknowledge financial support of this work by the project “Research infrastructure for Waste Valorization and Sustainable Management of Resources, INVALOR” (MIS 5002495) which is implemented under the “Action for the Strategic Development on the Research and Technological Sector”, funded by the Operational  Programme  "Competitiveness, Entrepreneurship and Innovation" (NSRF 2014-2020) and co-financed by Greece and the European Union (European Regional Development Fund).

Co-financed by Greece and the European Union

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