EFFECTS OF GLUCOSE, GLUTAMINE, AND MALATE ON THE METABOLISM OF SPODOPTERA-FRUGIPERDA CLONE-9 (SF9) CELLS - AN INITIAL RATE STUDY

Optimal design and operation of bioreactors for insect cell culture is facilitated by functional relations providing quantitative informatio n on cellular metabolite consumption kinetics, as well as on the speci fic cell growth rates (mu(G)). Initial specific consumption rates of g lucose, malate, and oxygen, and associated changes in mu(G). Were meas ured for Spodoptera frugiperda clone 9 (Sf9) cells grown in batch susp ension culture in medium containing 7-35 mM glucose, 0-16 mM malate, a nd 4-16 mM glutamine. The initial specific glucose consumption rate (q (G)) could be described by a modified Michaelis-Menten equation treati ng malate as a ''competitive'' inhibitor (K-I = 6.5 mM) and glutamine as a ''noncompetitive'' inhibitor (K-I = 14 mM) of q(G), with a K-m of 7.1 mM for glucose. All three carbon sources were found to increase m u(G) in a saturable manner, and a modified Monod equation was employed to describe this relationship (mu(Gmax) = 0.047 h(-1)). The initial s pecific oxygen consumption rate (q(O2)) in Sf9 cells could be related to mu(G) by the maintenance energy model, and it was calculated that, under typical culture conditions, about 15-20% of the cellular energy demand comes from functions not related to growth. Fitted parameters i n mathematical expression for mu(G): K-4, Monod constant for glucose ( mM); K-5, modified Monod constant for malate (mM); K-6, Monod constant for glutamine (mM); m(O2), specific consumption rate of oxygen by the cells under zero-growth conditions (nmol/cell/h); q(F), initial speci fic fumarate production rate (nmol/cell/h); q(G), initial specific glu cose consumption rate (nmol/cell/h); q(Gmax), maximum initial specific glucose consumption rate (nmol/cell/h); q(M), initial specific malate consumption rate (nmol/cell/h); q(O2) initial specific oxygen consump tion rate (nmol/cell/h); Y-O2, cell yield on oxygen (cells/nmol); mu, initial specific cell growth rate (h(-1)); mu(G), initial specific cel l growth rate (h(-1)); mu(Gmax), maximum initial specific cell growth rate (h(-1)).