A. Carnicero

Isolation of microorganisms with lignin transformation potential from soil of Tenerife island

Abstract A total of 44 fungi, 15 actinomycetes and 23 bacteria, isolated from ferrallitic and fersiallitic types of soil of Tenerife (Canary Islands) were capable of abundant growth on solid media supplemented with the polymeric fraction of industrial lignin as a single C source. Of 44 fungal strains grown on the media with lignin, 22 showed a positive Sundmans test and decolorization of polymeric dye Poly R-478. However, from the above 22 fungal strains, only Penicillium chrysogenum, Fusarium oxysporum, Pestalotia oxyanthi, Fusarium solani and a strain of basidiomycete fungus gave positive results for peroxidase, Bavendamm, Nobles, and laccase plate tests. Each of these 5 fungi metabolized hydroxylated and non-hydroxylated lignin-related phenylpropanoid acids, either as a single C source or in the presence of carbohydrate. These fungi were also capable of catabolizing lignin-model dehydrogenative polymerizate of coniferyl alcohol (DHP), 14 CO 2 evolving both from 14 C-labelled ring- and 14 C-β-side-chain labelled-DHP. The maximum rate of 14 CO 2 release by fungi imperfecti appeared to be during the initial stages of the metabolism of these fungi.

Laccase activities of Penicillium chrysogenum in relation to lignin degradation

Abstract An extracellular laccase capable of oxidizing ABTS (the diammonium salt of 2,2′-azinobis-3-ethylbenzothiazoline-6-sulfonic acid) was detected in ligninolytic cultures of Penicillium chrysogenum. By contrast, no lignin peroxidase, manganese-dependent peroxidase or aryl-alcohol oxidase was detected at any time during culturing. Both ABTS laccase activity and mineralization of dehydrogenative polymerizate of coniferyl alcohol were regulated by the C/N ratio in the medium and partially inhibited in the presence of thioglycolic acid, suggesting that both events are associated. In the presence of several known laccase inducers neither ABTS laccase activity nor mineralization rates were enhanced. However, a new laccase was detected in P. chrysogenum, able to oxidize 2,6-dimethoxyphenol but not involved in lignin mineralization. Studies with the known ligninolytic basidiomycete Trametes villosa suggest that lignin degradation by this fungus also involves the action of laccase.

Activated oxygen species and two extracellular enzymes : laccase and aryl-alcohol oxidase, novel for the lignin-degrading fungus Fusarium proliferatum

Abstract Laccase, aryl-alcohol oxidase and superoxide radicals were detected in ligninolytic cultures of Fusarium proliferatum. Enzyme activities were present during the secondary metabolism and seen as single protein bands after non-denaturing electrophoresis. In contrast, superoxide radicals were detected during primary growth, correlating with maximal lignin mineralization. Moreover, ligninolysis decreased when scavengers of both superoxide and hydroxyl radicals were added to cultures, indicating that activated oxygen species are involved in lignin degradation.

Limited degradation of industrial, synthetic and natural lignins by Serratia marcescens

SummarySerratia marcescens was found to degrade kraft lignin by only 15%. When 14C-radiolabelled lignocelluloses and DHP lignins were used as substrates the bacterium mineralized to 14CO2 only 1.1–1.9% and 0.4–0.8% of the lignins respectively. However, some 44.4% of the 14C-β-DHP lignin was recovered as soluble radiolabelled products.

Purification and peptidase activity of a bacteriolytic extracellular enzyme from Pseudomonas aeruginosa

A bacteriolytic enzyme excreted by Pseudomonas aeruginosa Paks I was purified: samples were found to be homogeneous by gel filtration chromatography, ion exchange chromatography using CM-cellulose, immunoelectrophoresis, PAGE and SDS-PAGE. The molecular weight of the lytic enzyme was estimated to be 15,000-19,000. The enzyme was active on Gram-positive bacteria with glycine-containing interpeptide bridges in their murein layers. In addition, this lytic enzyme showed peptidase activity catalysing the hydrolysis of pentaglycine peptides into tri- and diglycine peptides.

Short communication: Isolation of a bacterium capable of limited degradation of industrial and labelled, natural and synthetic lignins

Pseudomonas putida, isolated from decomposing plant materials, degraded several lignin-related aromatic compounds. After 30 days of incubation in media containing polymeric Kraft-lignin (PKL), the amount of Klason lignin had decreased by about 13%. When 14C-labelled dehydropolymers of coniferyl alcohol (DHP) lignins and 14C-lignin-lignocelluloses were used as substrates, mineralization to 14CO2 by the P. putida strain ranged from 1.4% to 2.1%.

Relationship between mineralization of synthetic lignins and the generation of hydroxyl radicals by laccase and a low molecular weight substance produced by Petriellidium fusoideum

Abstract A new ligninolytic fungal strain was isolated from the Peruvian Amazon forest. Its enzymatic profile revealed a laccase as the only enzyme related to lignin metabolism. Its partial inhibition with thioglycolate also reduces mineralization. Production of hydroxyl radicals was detected from the first day of incubation. Their inhibition involves a substantial decrease in the mineralization of synthetic lignins. Besides this, the fungus produced a protein-free low molecular weight substance “LMW-S” (about 1.6 kDa) containing 0.1% Fe2+. To elucidate the cooperation between laccase and the LMW-S in producing the hydroxyl radicals ( OH) excreted by this fungus in lignin degradation, different systems composed of partially purified enzyme, LMW-S, and some substrates recognised by the laccase were assayed. A hypothetical mechanism is proposed for the generation of OH radical in this system, in an attempt to explain its participation in the mineralization produced by the fungus.

Staphylolytic enzyme from Pseudomonas aeruginosa: characterization and immunocytochemical localization

Staphylolytic enzyme, a specific peptidase produced by Pseudomonas aeruginosa, has been characterized by using immunochemical procedures. Lytic activity was detected in the extracellular medium of Pseudomonas cultures at the beginning of the stationary growth phase. No activity was detected in bacterial cells. However, lytic protein antigen was present in periplasmic and cytoplasmic fractions, suggesting that staphylolytic enzyme is synthesized as an inactive precursor which becomes active during translocation to the extracellular broth. Results obtained in immunolocalization experiments indicate the presence of the precursor in the outer part of cells. The export pathway of staphylolytic enzyme through the periplasmic space is proposed.