Cellulolytic preparations from micro-organisms of the rumen and from Myrothecium verrucaria.

Abstract

SUMMARY: A study has been made of the degradation of different forms of cellulose (‘eellulolysis’), comprising soluble substituted derivatives (carboxymethyl-cellulose), insoluble cellulose powder, swollen cellulose, hydrocellulose and native cotton fibres, by concentrated suspensions of mixed rumen micro-organisms and by the aerobic fungus Myrothecium verrucaria. Mixed rumen micro-organisms are shown to be one of the most powerful sources of cellulolytic enzyme, in that they produce almost complete solubilization of all the above forms of cellulose in a relatively short period (3 days). Enrichment cultures of rumen micro-organisms were prepared by growing concentrates of mixed micro-organisms on cellulose powder. Cellulolysis was followed by determining the cellulose disappearance, formation of cellulolytic activity and gas evolution. Freeze-dried powders and their derived acetone powders obtained from washed concentrated supensions (non-enrichment cultures) of mixed rumen micro-organisms solubilized up to 80% of insoluble cellulose powder. Cell-free extracts were isolated: (a) from concentrated suspensions and from freeze-dried powders of rumen micro-organisms by extraction with butanol; (b) from concentrated suspensions of enrichment cultures by grinding with alumina at low temperature. The butanol extracts solubilized cellulose powder to a small extent (10% solubilization) and were more effective against the soluble carboxymethyl-cellulose. In contrast, the alumina extracts were more active against insoluble cellulose (30% solubilization) but were only weakly active against carboxymethyl-cellulose. Cell-free filtrates from Myrothecium verrucaria, an aerobic fungus much used in work on cellulose metabolism, were shown to possess cellulolytic properties very similar to those of alumina extracts from enrichment cultures of rumen micro-organisms. The significance of the results is discussed in relation to the mode of breakdown of cellulose.