Elicitation of lignin peroxidase inStreptomyces lividans

Abstract

Using a novel starch-based medium (DJMM) which elicits high expression of lignin peroxidase (ALiP-P3) fromStreptomyces viridosporus T7A, significant levels of ALiP-P3 (between 1135 and 1784 nmol/g cell-min) were excreted byS. lividans TK23, TK24, and TK64 with the supernatants capable of degrading dichlorophenol (these strains were previously reported to produce low levels of LiP). TheS. lividans wildtype strains produced 1/9 to 1/6 the cell-specific LiP activity previously detected inS. viridosporus T7A cultures grown in the same starch-based medium; however, by using DJMM to increase the cell density, the volumetric activity of wild-typeS. lividans TK23, TK24, and TK64 strains was increased 11 to 20-fold compared to cultivations in a yeast-extract-based medium. Consequently, this increase of LiP production allows the direct analysis of LiP activity in the supernatants of these strains without the need for enzyme concentration through ultrafiltration. Immunoblot analysis verified that a single 56.5 kDa band, secreted by all three strains, was extremely similar in size and immunologic reactivity to the 59.5 kDa ALiP-P3 isoform of S.viridosporus T7A. In addition, Western blot analysis was used to show that a previously cloned 4.1 kb chromosomal fragment ofS. viridosporus T7A DNA did not contain the ALiP-P3 structural genes.