Microbiology and physiology of anaerobic fermentation of cellulose. Progress report (4/30/91--4/30/92) and outline of work for the period 9/1/92--9/1/93

The authors are continuing their efforts to partly dissociate the cellulolytic enzyme complex of C. thermocellum. This complex named cellulosome (also existing as polycellulosome) consists of perhaps as many as 26 different subunits. It is extremely resistant to dissociation and denaturation. Treatments with urea and SDS have little effect unless the latter treatment is at high temperature. Significantly, some of the subunits after SDS dissociation have CMCase (endoglucanase) activity but no activity toward crystalline cellulose. The only reported success of hydrolysis of crystalline cellulose by cellulosomal subunits is by Wu et al. who isolated two protein fractions labeled SL and SS which when combined exhibit a low (about 1% of the original cellulosome) activity toward crystalline cellulose. The long standing goal is still to determine the activities of the individual subunits, to characterize them, to find out how they are associated in the cellulosome, and to establish the minimum number of subunits needed for efficient hydrolysis of crystalline cellulose. This report also presents the results of experiments on cellulose hydrolysis in aerobic fungi, as well as other anaerobic bacteria