Novel precipitated fluorescent substrates for the screening of cellulolytic microorganisms

New substrates, 2-(2′-benzothiazolyl)-phenyl (BTP) cellooligosaccharides with degree of polymerization (d.p.) 2–4 (BTPG2–4) were synthesized for the screening of microbial cellulolytic activity in plate assays. The substrates were very efficient that was shown for several cellulolytic bacteria, including yeast-like isolates from Kamchatka hot springs. Three tested bacterial strains and eighteen of 30 of the yeast isolates showed ability to degrade cellulose with cellobiohydrolase, β-glucosidase and endo-cellulase activities measured with standard substrates. The structures of 2-(2′-benzothiazolyl)-phenyl oligosaccharides were solved by NMR- and mass-spectrometry. The usefulness of the 2-(2′-benzothiazolyl)-phenyl substrates were also shown during purification of the B. polymyxa cellulolytic complex, which consists of at least three types of the enzymes: cellobiohydrolase, endo-β-d-glucanase and β-glucosidase.