Cellulose degradation and monitoring of viscosity decrease in cultures of Cellulomonas uda grown on printed newspaper

The rheological behavior of cultures of Cellulomonas uda with shredded printed newspaper as the carbon source was studied. The initial substrate concentrations ranged from 23 to 60 g/L. The changes in apparent viscosity were followed on-line by applying a commercially available process viscometer and discretely using a rotational viscometer with an anchor impeller. During the time of highest cellulose degradation, the broths exhibited a pseudoplastic behavior which could be explained satisfactorily by the power-law model. At the end of cultivation when cellulose degradation slowed down, the broths became Newtonian in behavior. Endo-1,4-beta-glucanase, 1,4-beta-xylanase, beta-glucosidase, and beta-xylosidase activities were also determined during cultivation as well as cellulose degradation and cell mass production. The beginning of endoglucanase formation and the start of the final viscosity decrease of the bacterial paper pulp suspensions could be correlated.