Conversion of Fumaric Acid to l‐Malic by Sol‐Gel Immobilized Saccharomyces cerevisiae in a Supported Liquid Membrane Bioreactor

Abstract

Conversion of fumaric acid (FA) to L-malic acid (LMA) was carried out in a bioreactor divided by two supported liquid membranes (SLMs) into three compartments: Feed, Reaction, and Product. The Feed/Reaction SLM, made of tri-n-octylphosphine oxide (vol 10%) in ethyl acetate, was selective toward the substrate, fumaric acid (S(FA/LMA) = 10). The Reaction/Product SLM, made of di(2-ethylhexyl) phosphate (vol 10%) in dichloromethane, was selective toward the product, L-malic acid (S(LMA/FA) = 680). Immobilized yeast engineered to overproduce the enzyme fumarase [E.C. 4.2.1.2] was placed in the Reaction compartment and served as the catalyst. The yeast was immobilized in small glasslike beads of alginate-silicate sol-gel matrix. The construction of the bioreactor ensured unidirectional flow of the substrate from the Feed to the Reaction and of the product from the Reaction to the Product compartments, with the inorganic counterion traveling in the opposite direction. The conversion of almost 100%, above the equilibrium value of ca. 84% and higher than that for the industrial process, 70%, was achieved. In contrast to the existing industrial biocatalytic process resulting in L-malic acid salts, direct production of the free acid is described.

Organic acids: old metabolites, new themes

“…Good results for fumaric acid conversion to L ‐malic acid were obtained with agarose‐immobilized cells, although the bioconversion rates decreased in a linear fashion with the diameter of the agarose beads, demonstrating mass transfer limitations controlling bioconversion rates 65. More recently, a conversion value of almost 100%, above the equilibrium value of ca 84% and higher than that for the industrial process (70%), was achieved with the above mentioned S. cerevisiae in a bioreactor which was divided into three compartments by two supported liquid membranes 67. The construction of the bioreactor ensured a unidirectional flow of the substrate from the Feed to the Reaction (middle) compartments and of the product from the Reaction to the Product compartments, with the inorganic counter‐ion moving in the opposite direction.…”

l -Malate Production by Metabolically Engineered Escherichia coli

“…Presently, malic acid usage is limited to pharmaceuticals, cosmetics, and acidulants in the food industry (3,33). It is produced as a racemic mixture by chemical synthesis (hydration of maleic or fumaric acid) or as enantiomerically pure L-malate by the enzymatic hydration of fumarate (immobilized cells or fumarase) (3,9,30). Substrates for the synthesis of malic acid (maleic acid, fumaric acids, maleic anhydride) are derived from petroleum (32).…”

Encapsulation of cells within silica matrixes: Towards a new advance in the conception of living hybrid materials

“…These hybrid materials, synthesized in the right conditions, can improve the overall hazardous metal uptake [49] and allow the design of continuous bioreactor able to degrade toxic compounds (e.g. phenol) or used in the bioconversion [50,51].…”