SOLUBILIZATION AND MINERALIZATION OF [C-14]LIGNOCELLULOSE FROM WHEAT-STRAW BY STREPTOMYCES-CYANEUS CECT-3335 DURING GROWTH IN SOLID-STATE FERMENTATION

Nine Streptomyces strains were screened for their ability to solubilis e and mineralise C-14-labelled lignin during growth in solid-state fer mentation. Streptomyces viridosporus was confirmed as an active lignin -degrading organism along with a new isolate, Streptomyces sp. UAH 15, further classified as Streptomyces cyaneus CECT 3335. This organism w as able to solubilise and mineralise the [C-14]lignin fraction of lign ocellulose (44.96 +/- 1.77% and 3.41 +/- 0.48% respectively) after 21 days of incubation. Cell-free filtrates from Streptomyces sp. grown in solid-state fermentation were capable of solubilising up to 20% of th e [C-14]lignin after 2 days incubation, with most of the product detec ted in the acid-soluble rather than in the water-soluble fraction. Ide ntification of the extracellular enzymes produced during growth of S. cyaneus CECT 3335 revealed that extracellular peroxidase and phenol ox idase activities were present, with the activity of phenol oxidase bei ng 100 times greater than peroxidase activity. The activity of these t wo enzymes was found to correlate with both solubilisation and mineral isation rates. This is the first report of phenol oxidase activity pro duced by a Streptomyces strain during growth in solid-state fermentati on. A role for the enzyme in the solubilisation and mineralisation of lignocellulose by S. cyaneus is suggested.