2-keto-L-Gulonic acid → L-Ascorbic Acid

Participants

Reaction Steps

Two derivatives of the original strain, Alicyclobacillus sp. NA-21, MA-10, and MB-6 were sequentially obtained by conventional mutagenesis followed by the selection steps described below. From the original strain, MA-10 was selected as a strain having tolerance against a higher 2-keto-L-gulonic acid concentration (about a 1% (w/v) improvement from 10% (w/v), at 60° C. and pH 2.5) after ultraviolet irradiation. Subsequently, from MA-10, MB-6 was selected as a strain having tolerance against a higher temperature (about a 2° C. improvement from 60° C., at 11% (w/v) of 2-keto-L-gulonic acid and pH 2.5) after treatment with N-methyl-N′-nitro-N-nitrosoguanidine. L-Ascorbic acid productivities were compared among the original strain, MA-10 and MB-6 by the same living-cell reaction described above at 62° C. and pH 2.5, using 11% (w/v) of 2-keto-L-gulonic acid and a medium containing ×0.5 conc. of LM101d salt base, 0.25%(w/v) of D-glucose, ×0.1 conc. of MM, ×0.05 conc. of VM and ×0.005 conc. of AM. The original strain, MA-10, and MB-6 produced 2.02, 2.22, and 2.80 g/L of L-ascorbic acid at 23 hours, respectively. The aerobic blank and the anaerobic control produced 1.63 and 1.94 g/L of L-ascorbic acid, respectively.

Provenance & Evidence