Nuclease P1 can hydrolyze nucleic acid into four 5'-mononucleotides, which are widely used as food additives and pharmaceutical intermediates. Nuclease P1 is mainly obtained by microbial fermentation and the low fermentation efficiency of microorganisms for enzyme production is the limit of its application. In order to improve the productivity of nuclease P1, a semi-continuous fermentation of Penicillium citrinum TKZY02 using free-cell was established and the residual sugar, retention volume and air–liquid ratio were optimized. The results indicated that at least 6 fermentation times was performed under the optimum semi-continuous fermentation condition, and the average enzyme activity was up to 518.2 U/mL, which were 16.5% and 9.7% higher than those of batch fermentation and original semi-continuous fermentation, respectively. The average productivity reached 20.9 U/mL/h, which was 42.4% and 21.5% higher than those of batch fermentation and original semi-continuous fermentation, respectively. These findings indicated that Penicillium citrinum TKZY02 was suitable for the production of commercially acceptable levels of nuclease P1 in semi-continuous culture.

核酸酶P1可以将核酸水解成四个5'-单核苷酸，广泛用作食品添加剂和医药中间体。核酸酶P1主要通过微生物发酵获得，微生物发酵产酶效率低限制了其应用。为了提高核酸酶P1的产率，建立了柑橘青霉TKZY02游离细胞半连续发酵工艺，并对残糖、保留体积和气液比进行了优化。结果表明，在最佳半连续发酵条件下进行至少6次发酵，平均酶活力高达518.2 U/mL，比分批发酵和原始半连续发酵分别提高了16.5%和9.7%。分别连续发酵。平均产率达到20.9 U/mL/h，比分批发酵和原始半连续发酵分别提高42.4%和21.5%。这些发现表明，柠檬青霉TKZY02 适合在半连续培养中生产商业上可接受水平的核酸酶 P1。