Optimization of extracellular lignocellulolytic enzyme production by a thermophilic actinomycete Thermomonospora fusca BD25

The production of extracellular lignocellulose-degrading enzymes, endo-1,4-beta-xylanase, endo-1,4-beta-glucanase and peroxidase during the growth of Thermomonospora fusca BD25 in basal salts-yeast extract medium containing different carbon sources was studied. The effect of a number of environmental parameters (e.g. dissolved oxygen concentration, pH and temperature) was also investigated using batch and automated bioreactor conditions. The highest enzyme activities were generally obtained after 48-96 h of incubation at 50 degrees C in a basal salts medium containing either 0.6% or 0.8% (w/v) oat spelt xylan and 0.6% (w/v) yeast extract corresponding to C:N ratios of 4 to 1 and 5.3 to 1, respectively. A comparison of enzyme activities revealed that the activity of endo-1,4-beta-xylanase (2.68 U ml(-1)) was greater than those of the other enzyme activities (0.24 U ml(-1); 12.08 mU ml(-1); 19.62 mU ml(-1) and 2 mU ml(-1)) for endo-1,4-beta-glucanase, peroxidase, beta-xylosidase and alpha-L-arabinofuranosidase, respectively. The high levels of enzyme production achieved under bioreactor conditions, coupled with the temperature stability and the activity over a broad pH range of these enzymes signify the suitability for industrial applications such as pulp and paper production. Cell-free enzyme preparations from T. fusca BD25 were capable of releasing both sugar and aromatic compounds during incubation with both ball-milled wheat straw and eucalyptus paper pulp. (C) 1999 Elsevier Science Inc. All rights reserved.