The invention relates to a method for producing L-4-hydroxyisoleucine by a microbial
enzyme conversion method. The method comprises the following steps: 1, culturing a mature
bacterial strain; 2,
grafting mature
escherichia coli recombinant
bacteria which are capable of inducing production of L-4-hydroxyisoleucine into a
fermentation tank, and carrying out
fermentation culture, wherein the temperature of the
fermentation process is controlled in two stages, i.e., 4 to 36 DEG C in the earlier stage and 30 to 32 DEG C in the later stage; 3, collecting
thallus after fermentation, adding
phosphate buffer and washing, then adding alpha-oxoglutarate,
isoleucine,
ferrous sulfate,
magnesium sulfate and
ascorbic acid, and carrying out forced ventilation for
catalysis; 4, removing
bacteria from the catalytic liquid with a
ceramic membrane, filtering with an
ultrafiltration membrane, decoloring with
activated carbon, desalting with faintly acid cation exchange resin, adsorbing
effluent with 732 cation exchange resin and eluting with
ammonia water, carrying out
evaporation concentration and recrystallization to obtain the L-4-hydroxyisoleucine. The preparation method disclosed by the invention is simple and efficient in
reaction system and simple and feasible in extraction process. The conversion rate is up to over 95.4 percent, and the purity of the product can reach over 98 percent.