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

Abstract

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).

Optimized pH and Its Control Strategy Lead to Enhanced Itaconic Acid Fermentation by Aspergillus terreus on Glucose Substrate

“…Based on these process factors, a ranking was performed, considering that the shorter λ, higher P and R m are preferred. Bearing this in mind, points (1)(2)(3)(4)(5) were assigned in a parameter (λ, P, R m )-wise manner to demonstrate how they were affected by the 5 different fermentation conditions ( Table 5). The final assessment was made by summarizing the given scores.…”

“…Microbial fermentation has been demonstrated as an efficient technology to produce a variety of organic acids such as malic acid, succinic acid, propionic acid, itaconic acid, etc. [1][2][3][4]. The latter, itaconic acid, is taken into account as an important compound since it can serve as a platform molecule for the synthesis of industrially-relevant chemicals, such as plastics, etc.…”

Characterization and Optimization of L-Malic Acid Production by Some Clinical Isolates of Aureobasidium pullulans

“…Fungal microorganisms are among the notable sources of green production of MA [25,26]. Considering some of the previous studies, which had highlighted the effect of incubation temperature and CaCO 3 concentration in MA production by fungal microorganisms such as Zygosaccharomyces [26], we decided to investigate these factors effects in the case of A. pullulans var. melanigenum.…”

Malic acid production from renewables: a review

“…The amount of thin stillage produced during dry‐milling can amount to volumes 15‐fold higher than the produced volume of ethanol, making it a low‐cost waste substrate . With thin stillage, the highest malic acid concentration reached was 16.9 g L –1 with a yield of 0.79 g g –1 . These results were obtained with a small‐scale batch process performed in 125‐mL shake flasks, possibly having the potential to obtain higher l‐ malic acid concentrations in the controlled environment of a bioreactor.…”