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Fermentation 2017, 3(2), 14;

Microbial Production of Malic Acid from Biofuel-Related Coproducts and Biomass

Department of Chemistry, Texas A&M University-Commerce, Commerce, TX 75429, USA
Academic Editor: Gunnar Lidén
Received: 24 February 2017 / Revised: 5 April 2017 / Accepted: 6 April 2017 / Published: 10 April 2017
(This article belongs to the Special Issue Carboxylic Acid Production)
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The dicarboxylic acid malic acid synthesized as part of the tricarboxylic acid cycle can be produced in excess by certain microorganisms. Although malic acid is produced industrially to a lesser extent than citric acid, malic acid has industrial applications in foods and pharmaceuticals as an acidulant among other uses. Only recently has the production of this organic acid from coproducts of industrial bioprocessing been investigated. It has been shown that malic acid can be synthesized by microbes from coproducts generated during biofuel production. More specifically, malic acid has been shown to be synthesized by species of the fungus Aspergillus on thin stillage, a coproduct from corn-based ethanol production, and on crude glycerol, a coproduct from biodiesel production. In addition, the fungus Ustilago trichophora has also been shown to produce malic acid from crude glycerol. With respect to bacteria, a strain of the thermophilic actinobacterium Thermobifida fusca has been shown to produce malic acid from cellulose and treated lignocellulosic biomass. An alternate method of producing malic acid is to use agricultural biomass converted to syngas or biooil as a substrate for fungal bioconversion. Production of poly(β-l-malic acid) by strains of Aureobasidium pullulans from agricultural biomass has been reported where the polymalic acid is subsequently hydrolyzed to malic acid. This review examines applications of malic acid, metabolic pathways that synthesize malic acid and microbial malic acid production from biofuel-related coproducts, lignocellulosic biomass and poly(β-l-malic acid). View Full-Text
Keywords: malic acid; biomass; polymalic acid; plant hydrolysates; Aureobasidium; Aspergillus; Thermobifida; Rhizopus malic acid; biomass; polymalic acid; plant hydrolysates; Aureobasidium; Aspergillus; Thermobifida; Rhizopus

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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West, T.P. Microbial Production of Malic Acid from Biofuel-Related Coproducts and Biomass. Fermentation 2017, 3, 14.

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