A crude transfructosylating enzyme from a new isolate Bacillus marcerans EG-7 required a lag period for catalytic activity during formation of fructooligosaccharides from sucrose. The lag period was markedly reduced by addition of various ammonium ions to the reaction mixture; 100 mM NH4NO3 enhanced the enzyme activity by 15 fold (at 40 h) reducing the lag-time from 25 h to 30 min. In contrast, partially purified enzyme completely removed the lag period while ammonium ions still accelerated the initial reaction rate.