Isolation of inulinase production strain and optimization of its fermentation condition

46 strains capable of producing inulinase were isolated from rhizosphere soil of Jerusalem artichoke(Helianthus tuberosus L.)in the salt-affected lands of Laizhou,Shandong Province.Of all,a strain with high inulinase productivity was obtained through further screening.This strain was identified as Penicillium sp.B01 primarily.After studying on its fermentation condition,the optimum condition for higher inulinase production by Penicillium sp.B01 was determined as shown below(g·L-1):extract of Jerusalem artichoke 120,yeast extract 25,NH4H2PO4 2.5,NaCl 5.0,FeSO4·7H2O 0.1,ZnSO4·7H2O 0.1;pH 7,inoculated with 3.75% of spore suspensions(2.5×106 mL-1).Maximal inulinase activity of Penicillium sp.B01 was 25.78 U·mL-1 and obtained after 72 h of growth in shake cultures(40 mL of medium in 250 mL flasks).This inulinase was mostly exo-inulinase.