Production of extracellular enzymes by Thermomonospora curvata during growth on protein‐extracted lucerne fibres

Abstract

After extraction of food protein from lucerne, the residual fibre was used as a carbon and energy source by the thermophilic actinomycete, Thermomonospora curvata. Induction of catabolic exoenzymes during growth for 7 d on the fibre at 53°C in a mineral salts minimal medium was compared with that on a variety of other inductive substrates. A fibre concentration of 1.5% (w/v) was optimal for total protein secretion. The fibre was a poor substrate for amylase production due to lack of inducer rather than to catabolite repression by soluble sugars released during degradation. β‐Glucosidase release during growth on the fibre was about 10 times that observed in cultures grown on cellobiose or cellulose, but production of other cellulolytic enzymes was about one‐half that produced on cellulose. Pectinolytic activity (measured as polygalacturonate lyase) was equal to that produced on pectin. Cells grown on the fibre released about eight times as much proteinase as those grown on cellulose, but proteolytic activity was transient and decreased rapidly during later growth. Xylanase appeared to be co‐ordinately induced with cellulolytic enzymes; comparable maximal activities, observed during growth on either the fibre or cellulose, were three times that produced on xylan or xylose.

Purification and characterization of the major β‐1,4‐endoglucanase from Thermomonospora curvata

“…Thermomonospora curvata is a thermophilic actinomycete which establishes itself as the dominant bacterial population in a variety of aerated composts (Niese 1959;Fergus 1964;Stutzenberger 1971) and secretes a variety of thermostable extracellular enzymes during growth on either complex plant materials or on purified polymeric substrates (Bernier et al 1988;Stutzenberger 1994). This paper describes the purification and characterization of the major endoglucanase (EG) from T. curaala and comparison of its characteristics to those of the EG produced by Thermomonospora /;sea.…”