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Issue 42, 2020, Issue in Progress
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Transformation of remnant algal biomass to 5-HMF and levulinic acid: influence of a biphasic solvent system

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Abstract

The primary commercial product from the green microalgae Dunaliella salina is β-carotene. After extracting the lipophilic fraction containing this red-orange pigment, an algal residue remains. As the carotenogenesis is induced by light stress with simultaneous nitrogen depletion, the protein content is low and the remnant is comprised largely of storage carbohydrates. In this work, we transformed the defatted remnant directly to the platform chemicals, 5-hydroxy methyl furfural (5-HMF) and levulinic acid (LA), without previous purification or any pretreatment. The batch experiments were carried out in an autoclave under biphasic solvent conditions at 453 K for 1 h using acidic ZSM-5 zeolite as a heterogeneous catalyst. Mixtures of methyl isobutyl ketone (MIBK/H2O) or tetrahydrofuran (THF/H2O/NaCl) with water were used to create the biphasic reactor conditions. The biphasic reaction mixtures helped to increase the 5-HMF yield and simultaneously mitigated the formation of insoluble humins. The carbon yields of 5-HMF and of LA in the MIBK/H2O biphasic system without NaCl were 13.9% and 3.7%, respectively. The highest carbon yield of 5-HMF (34.4%) was achieved by adding NaCl to the reaction mixture containing THF/H2O. The experimentally measured partition ratios of 5-HMF between the two liquid phases were compared to the predictions calculated by the computational method COSMO-RS, which is a quantum chemistry-based method to predict the thermodynamic equilibria of liquid mixtures and the solubilities. The COSMO-RS predicted partition ratios of 5-HMF were in line with the experimentally measured ones.

Graphical abstract: Transformation of remnant algal biomass to 5-HMF and levulinic acid: influence of a biphasic solvent system

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Article information


Submitted
26 Mar 2020
Accepted
14 Jun 2020
First published
29 Jun 2020

This article is Open Access

RSC Adv., 2020,10, 24753-24763
Article type
Paper

Transformation of remnant algal biomass to 5-HMF and levulinic acid: influence of a biphasic solvent system

L. K. Rihko-Struckmann, O. Oluyinka, A. Sahni, K. McBride, M. Fachet, K. Ludwig and K. Sundmacher, RSC Adv., 2020, 10, 24753
DOI: 10.1039/D0RA02784G

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