关键词: 普鲁兰酶产生菌；筛选；普鲁兰酶；鉴定；发酵条件

Abstract:

Pullulanase is considered as a starch debranching enzyme, and is very useful in starch industry. The present study aims at the isolation and identification of bacteria producing pullulanase from the environmental samples, and studies on the optimum growth conditions in fermentative medium. The strains producing pullulanase were obtained by using spread-plate method. A strain with the highest pullulanase activity was identified according to its morphological, physiological, biochemical and 16S rDNA sequence. A series of experiments were conducted for the optimization of fermentative medium and growth conditions. Among the isolated strain, strain H4 showed the highest pullulanse activity from the soil close to a starch processing plants. Strain H4 was identified as Exiguobacterium sp.. The optimum medium for pullulanase was consisted of 2% potato starch, 1% peptone, 0.5% yeast extract, 0.1% KH2PO4, 0.05% MgSO4·7H2O and 0.0001% FeSO4. Under the condition of initial pH 7.0, 37℃ and 200 r/min for 72 h, the yield of pullulanase could reach to 6.35 U/mL, which was 110.2% higher than the control (3.02 U/mL).

Key words: bacteria producing pullulanase, screen, pullulanase, identification, fermentation condition