Bernard Godden

Towards elucidation of the lignin degradation pathway in actinomycetes.

Six biodegradative actinomycete strains were grown on a dimeric model lignin compound of the β-aryl ether type. Although only two strains, Thermomonospora mesophila and Streptomyces badius, utilized the compound as a carbon and energy source and produced substantial amounts of monomeric products, all of the strains could demethylate the substrate and oxidize Cα on the phenylpropane side-chain. Streptomyces sp. EC1 produced small amounts of aromatic acids and unidentified lignin-derived products when grown on straw. This organism also produced cell-bound demethylase requiring H2O2 and Mn2+, protocatechuate 3,4-dioxygenase and β-carboxymuconate decarboxylase activity in response to growth on low-molecular-mass aromatic compounds but not lignocellulose or its polysaccharide components. Extracellular peroxidase and catalase activity were detected in all of the strains. These data are used to propose a scheme by which actinomycete attack of the lignin component of plant biomass can be envisaged.

Regulation of the production of hemicellulolytic and cellulolytic enzymes by a Streptomyces sp. growing on lignocellulose.

A Streptomyces sp. isolated from compost degraded the hemicellulose fraction of straw efficiently but apparently not native cellulose. Ball-milled straw induced endoglucanase, beta-glucosidase, beta-xylanase and beta-xylosidase. Carboxymethylcellulose, cellotetraose and cellotriose induced cellulolytic enzymes specifically whereas cellobiose acted as inducer for beta-glucosidase only. Cellotriose and cellotetraose induced beta-glucosidase, but only partially induced endoglucanase. Hemicellulose (in the form of xylan) and xylobiose induced only beta-xylanase and beta-xylosidase. Kraft lignin and syringic acid induced beta-xylanase and endoglucanase but not the other enzymes. 3,4-Dimethoxycinnamic acid slightly induced beta-xylanase whereas 3,5-dimethoxy-4-hydroxycinnamic acid specifically induced endoglucanase. Neither veratric acid nor vanillic and ferulic acids induced any of the cellulolytic or hemicellulolytic enzymes. Enzyme production was subject to a form of carbon catabolite repression. Endoglucanase and beta-xylanase were excreted into the culture medium. Four protein components, one acidic (pI 5.2) and three basic (pI 8.15, 8.45 and 8.65) exhibited beta-xylanase activity. Two acidic components (pI 3.55 and 3.75) displayed endoglucanase activity.

Factor analysis of the relationships between several physico-chemical and microbiological characteristics of some Belgian agricultural soils

Abstract Twenty Belgian agricultural soils, 16 of which had been organically cultivated, were examined for their biochemical and microbiological properties. In spite of the very different nature of the characteristics studied, close relationships were found between soil respiration and glucose mineralization rates, biomass-C as measured by the fumigation-incubation method, and several enzyme activities, namely FDA-hydrolase, alkaline phosphatase and dehydrogenase. Correlation coefficients between urease activity and other biological measurements were always found to be endowed with a negative sign. Moreover, factor analysis of the data showed that some physico-chemical characteristics such as soil organic C, total N, clay content and CEC were closely related to most of the biological measurements, while pH and sand content were not. Two procedures for the determination of dehydrogenase activity and two methods of calculation of biomass-C were also compared.

Identification and evolution of the cellulolytic microflora present during composting of cattle manure: on the role of Actinomycetes sp.

Population changes in cellulolytic microflora were studied during composting of cattle manure. Six bacterial and nine actinomycetes species were isolated. Among the isolates, two actinomycetes, Micromonospora chalcae and Pseudonocardia thermophila, were cellulolytic strains which were numerically dominant and might therefore play a notable role in the degradation of cellulose in cattle manure. Fungi were practically absent during the process, but two cellulose-degrading bacterial species, Sporocytophaga myxococcoides and Cytophaga hutchinsonii, appeared to coexist in equilibrium with actinomycetes during the maturation phase.

Mineralization of Composted 15N-Labelled Farmyard Manure During Soil Incubations

ABSTRACT Fresh farmyard manure (C-to-N ratio = 20.3) was composted in the presence of 15N-labelled (NH4)2SO4 using a bench-scale reactor under temperature conditions which reproduce the evolution of compost in a pile. C and N mineralization of composted farmyard manure (C-to-N ratio = 12.5) was monitored in two silty soils during an aerobic incubation at 28°C and 100% of WHC for 76 weeks. C mineralization of compost was assumed to come from a labile and a recalcitrant fraction which decomposed according to 1 and 0 order kinetic reactions, respectively[Cm = Clabile.(1-e−Klabile.t)+Kresistant.t]. The size of the labile fraction (Ciabiie) represented 31.3 and 19.9% of compost-C for the two soils, and its mineralization rate constant (kiabiie) ranged from 0.03 to 0.09 day−1. N-mineralization was assumed to come from only one labile fraction [Nm = Niabiie.(l-e−Klabile.t)]. This fraction ranged from 34 to 25% of compost-N for the two soils; its mineralization rate constant did not vary with soils (0.006 day−1)....

On the use of biological and chemical indexes for determining agricultural compost maturity: Extension to the field scale

Abstract A comparative study of a bench-scale and a pile composting showed that the C/N, ash percentage and alakaline phosphatase activity were potentially useful parameters for estimating the maturation of cattle manure compost. The values of these parameters were nearly constant during a simulated poor composting, whereas they changed significantly during an optimal process. Other parameters—decomposition degree, chemical oxygen demand, invertase and Rusch number—were less sensitive indicators of composting. The use of these data for agricultural compost samples has shown that high alkaline phosphatase activity and No3−/NH4+ ratio were correlated with compost maturity.

Changes in humus microbiological activity induced by the substitution of the natural beech forest by Norway spruce in the Belgian Ardennes

Abstract Different microbiological methods, including determination of enzymatic activity and potential nitrogen availability, and microbial biomass estimation were used to evaluate soil modifications induced by the massive planting of Norway spruce on acid soils of the climatic deciduous forest of high Belgium. Investigations were made on the surface humic layers (holorganic and hemiorganic horizons) of ochreous brown earths (Dystrochrepts) in two neighbouring forest stands, a natural beech high-forest (Fagus sylvatica L.) and a 92-year-old spruce plantation (Picea abies (L.) Karst.). Results show that spruce monoculture has a significant depressive effect on soil microbiological activity, clearly shown by the lowering of microbial biomass and the decrease of both FDA hydrolytic activity and nitrogen potential availability.

Growth and cellulase production of Micromonospora chalcae and Pseudonocardia thermophila.

Beta(1,4)glucosidases and carboxymethylcellulases were demonstrated in both strains when using carboxymethylcellulose as a carbon source for growth. Beta(1,4)Glucosidases appeared mainly as cell-bound activities, whereas carboxymethylcellulases were evenly distributed between the incubation fluids and the cellular fractions. In both microorganisms, glucose appeared to repress biosynthesis of the enzymes, and cellobiose and carboxymethylcellulose acted as inducers of the cellulase complex.

La croissance de microorganismes lignocellulolytiques sur les bodes activées: Application Potentielle

Summary A culture medium containing activated sludge and sawdust supports the growth of numerous lignocellulolytic microorganisms. One of them, Phanerochaete chrysosporium could be used in a composite feed for ruminants.