Characteristics of Enzymes Produced by Ruminococcus flavefaciens which Degrade Plant Cell Walls

Abstract

Enzyme preparations active against crystalline cellulose, marble-milled filter paper, carboxymethylcellulose (CM-cellulose), hemicellulose and xylan were obtained from cultures of Ruminococcus jlavefaciens. These preparations also contained swelling factor, pectin methylesterase, pectin lyase and low levels of aryl P-glucosidase and aryl P-xylosidase. CM-cellulase and xylanase activities were present in a high molecular weight complex, but substrate competition studies showed that different active sites were probably responsible for each activity. Analysis of products and viscosity changes during enzymic hydrolysis of CM-cellulose and xylan indicated that the most active enzymes were of the exo-1,4-Pglycosidase type. A variety of reducing sugars were released from cell walls of Lolium perenne (perennial ryegrass) by enzyme preparations.

Characterization of the extracellular cellulase from a mesophilic clostridium (strain C7)

“…This finding is in agreement with results of previous studies, which indicated that, in other cellulolytic bacteria, the above-mentioned activities are present within a single protein complex (9,20,23). The different temperature and pH optima for Avicelase, CMCase, and xylanase activities in the 700,000-Mr protein complex of strain C7 suggest that different enzymatically active components within the complex are responsible for the hydrolysis of these substrates.…”

Production of Enzymes Degrading Plant Cell Walls and Fermentation of Cellobiose by Ruminococcus flavefaciens in Batch and Continuous Culture

“…The nature and Sources of the celluloses, hemicelluloses and pectin are listed by Pettipher & Latham (1979). Growth on larchwood xylan and oak sapwood hemicellulose was assessed by measuring the disappearance of carbohydrate (Dubois et al, 1956) and by the increase in total cell numbers.…”

“…Ruminococcus flavefaciens strains 67 and 66 (Latham et al, 1978) and the type strain c94 (from Dr M. P, Bryant, Department of Dairy Science, University of Illinois, U.S.A.) were cultivated in basal medium. BMlO containing 0.1 yo (w/v) cellobiose (Pettipher & Latham, 1979). Methods of strict anaerobic culture (Bryant, 1972) were used throughout and all cultures were incubated at 39 "C.…”

“…Cells were harvested from these samples by centrifugation, resuspended in Oxoid phosphate-buffered saline (PBS) and, together with the culture supernatants, stored frozen. The enzyme activities and reducingsugars were assayed using the methods of Pettipher & Latham (1979).…”

“…In addition to being cellulolytic, most strains of R.Jlavefaciens can also degrade hemicellulose and pectin and we have described some characteristics of the enzymes responsible for these activities in the preceding paper (Pettipher & Latham, 1979).…”