Factors affecting the formation of polysaccharide depolymerase and glycoside hydrolyase enzymes by Butyrivibrio fibrisolvens NCDO 2249

Abstract

Specific activities of hemicellulose‐degrading polysaccharide depolymerase and glycoside hydrolase enzymes were measured in batch and continuous cultures of Butyrivibrio fibrisolvens NCDO 2249 grown on cellobiose or a hemicellulosic carbohydrate. Enzyme activities were influenced by the growth substrate and by the rate and stage of growth of the micro‐organism. In cellobiose batch cultures specific activities were maximal as the growth rate declined and in the initial stages of the stationary phase. The growth substrate did not affect the range of glycoside hydrolases formed, although specific activities were substrate‐dependent, with activity increases (up to 200‐fold) occurring in enzymes essential for effective substrate utilization. Appreciable xylanase activity was present only in xylan‐grown cultures. The substrate effects were also evident in chemostat cultures. The activity response of the nine enzymes monitored to growth rate changes differed in that while the activity of some enzymes, including xylanase, declined at high dilution rates the activities of others were not growth rate‐dependent and were maintained over the range of dilution rates examined. Exocellular activities were detected only in spent media from cultures grown with a polymeric (hemicellulosic) carbohydrate.