PROTEASE AND LIPASE PRODUCTION BY A STRAIN OF SERRATIA-MARCESCENS (532-S)

Production of both exolipase and exoprotease activities by Serratia ma rcescens 532 S isolated from an aerobic fixed-biomass reactor were str ongly influenced by nutritional factors which acted as inducers or rep ressors. In batch culture, protease and lipase activities were produce d after the exponential phase. NH4Cl, amino acids and simple carbon so urces caused repression of protease activity. At a concentration of 1. 5 g L-1, the individual addition of maltose, mannitol, acetate, fructo se or glucose, repressed exoprotease production, with the greatest eff ect by glucose. An inverse relationship existed between exoprotease sy nthesis and increasing glucose concentrations. Lipids activated lipase production, the most significant increase occurred when Tween 80 was added in the medium. Thus, glucidolytic, proteolytic and lipolytic act ivities could be efficiently expressed in batch cultures only successi vely. At low dilution rate of chemostat cultures with a constant gluco se input concentration of 2 g L-1, glucidolytic, proteolytic and lipol ytic activities were produced, but did not have the same regulation: a t D values < 0.08 h-1, the level of protease activity dropped while th at of lipase showed a corresponding increase. Above these values, incr easing D led to a decrease of the two hydrolase activities, at the lev el of the specific activities as well as in the specific rate of biosy nthesis of each enzyme. Similar results were obtained in chemostat cul ture with a constant specific growth rate of 0.04 h-1 with increasing glucose input concentrations, i.e. protease and lipase activities decr eased when the specific glucose uptake rates were enhanced.