Process for the bioconversion of fumarate to L-malate

DETAILED DESCRIPTION What is claimed is: 1.
A process for preparing L-malate from fumarate comprising incubating under bioconversion conditions a proliferated cell mass derived from a microorganism containing fumarase effective to convert exogenous fumarate to L-malate in an aqueous solution of fumarate, said solution containing the cell mass in a concentration of from about 0.
5 to 50 g/l (calculated as dry mass) and an initial fumarate concentration of about 170-400 g per liter of liquid, calculated as fumaric acid and relative to the total volume of the solution, at least half of the fumarate being in the form of ammonium-fumarate, said incubation being maintained until the yield of L-malate, calculated as L-malic acid, reaches at least 0.
9 g per gram of initial fumarate, calculated as fumaric acid.
2.
A process of claim 1, further comprising, prior to said incubating step, proliferating a microbial cell mass, derived from a microorganism containing fumarase effective to convert exogenous fumarate to L-malate, in an aqueous solution containing a source of assimilable carbon and nutrients for said microorganism, and separating the proliferated cell mass from the culture liquid.
3.
A process of claim 2, wherein said nutrient solution contains 1-30 g/l of fumarate; whereby said microorganism is adapted to effect bioconversion of fumarate.
4.
A process of claim 2, wherein said assimilable carbon source is corn meal, glucose, sucrose, glycerol or ethanol.
5.
A process of claim 1, wherein said incubation is maintained for 0.
5-2 days, at 20.
degree.
-50.
degree.
C.
and pH 3-9.
6.
A process of claim 1, which further comprises recovering the freely moving cell mass produced during said bioconversion of fumarate to L-malate and using at least a portion thereof as the inoculum in at least one subsequent incubation for bioconversion of fumarate to L-malate, the initial concentration of fumarate, calculated as fumaric acid, being 170-400 g per liter of the cell-free solution, said subsequent incubation being maintained until the yield of L-malate, calculated as L-malic acid, reaches at least 0