The invention discloses a method for preparing the product of active
lactic acid galactococcus, which comprises the technical processes of constructing strains (constructing, connecting, transforming and selecting plasmids), preparing a
fermentation culture medium, activating the strains, inoculating, fermentaing and
drying. The strains with high expression and an optimized medium formulation are used in the method, the methods of
pH control and the like are adopted for prolonging the logarithmic phase of the thalli, the density of the thalli in a fermenting
system is increased by 100 times, the yield of living thalli is larger than 10 CFU / ml, and the expressing quantity of a
PAL protein is larger than 12 percent. The obtained thalli have the ability for efficiently transforming phenyl
alanine into cinnamylate, and the
specific enzyme activity of the
PAL is larger than 50U / g. The stability of the obtained thalli
powder is good and can be kept for six months under 4 DEG C, the number of the living thalli can reach more then 10 CFU / g, and the
specific enzyme activity of the
PAL is not obviously reduced. The fermenting cost is reduced by 2 / 3. The PAL with low cost can be conveniently and largely provided for PKU treatment by using the invention.