To determine the effective-ness and stability of immobilized cells, productive medium was changed for every production cycle while the immobilized cellswere maintained in the fermenter. Results demonstrate that bothwaste glycerol and palm oil were reduced at the beginning of eachcycle due to the absorption of substrate by chitosan (Fig. 5a). How-ever, the sorbed oil could enhance its bioavailability to the attachedBacillus sp. GY19 and thereby increase lipopeptide production. Thefirst cycle was examined longer than other cycles in order to esti-mate the shortest production time. Lipopeptide yield increasedsteadily until the fourth day of production. The concentration oflipopeptide decreased afterwards probably due to the consump-tion of lipopeptide by the bacterium under starvation conditions.Thus, the following cycles were operated for 4 days in order to avoidlipopeptide consumption.