Showing papers by "Andrew S. Ball published in 1992"
TL;DR: Six biodegradative actinomycete strains were grown on a dimeric model lignin compound andExtracellular peroxidase and catalase activity were detected in all of the strains and are used to propose a scheme by which actinologycete attack of the lign in component of plant biomass can be envisaged.
Abstract: 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.
107 citations
TL;DR: The activity of ten actinomycete strains against p-nitrophenyl β-d-cellobioside (pNPC) was investigated, finding that pNPC activity was optimal at 65° C and between pH 6.0 and pH 8.0, although this temperature value represented a compromise between increased reaction rate and thermal denaturation.
Abstract: The activity of ten actinomycete strains against p-nitrophenyl β-d-cellobioside (pNPC) was investigated. Intra- and extracellular activities were detected in all strains, although activities were found to vary between strains. Extracellular pNPC activity, detected in the thermophilic Streptomycete EC22 was six times greater than that of the next best strain. Culture supernatant studies on Streptomyces strain EC22 revealed that pNPC activity was optimal at 65° C and between pH 6.0 and pH 8.0, although this temperature value represented a compromise between increased reaction rate and thermal denaturation. At 65° C, the half-life of activity against pNPC was 150 min. The Km value of pNPC activity was found to be 3.33 mm. Enzyme activity was subject to competitive inhibition by both glucose and cellobiose with substrate inhibition constant (Ki) values of 2.2 mm and 1.4 mm respectively. Fast protein liquid chromatograph (FPLC) of culture supernatants from EC22 using anion exchange chromatography revealed the presence of two proteins with pNPC activity. This result was confirmed using gel-filtration chromatography which estimated the molecular mass of the two proteins to be approximately 48 and 33 kDa, with the specific activity of the 48 kDa enzyme being eight times greater than that of the 33 kDa protein.
4 citations