title: Lignocellulose-Adapted Endo-Cellulase Producing Streptomyces Strains for Bioconversion of Cellulose-Based Materials.
abstract: Twenty-fourActinobacteriastrains, isolated fromArundo donax, Eucalyptus camaldulensisandPopulus nigrabiomass during natural biodegradation and with potential enzymatic activities specific for the degradation of lignocellulosic materials, were identified by a polyphasic approach. All strains belonged to the genusStreptomyces(S.) and in particular, the most highly represented species wasStreptomyces argenteolusrepresenting 50% of strains, while 8 strains were identified asStreptomyces flavogriseus(synonymS. flavovirens) andStreptomyces fimicarius(synonymsStreptomyces acrimycini, Streptomyces baarnensis, Streptomyces caviscabies, andStreptomyces flavofuscus), and the other four strains belonged to the speciesStreptomyces drozdowiczii, Streptomyces rubrogriseus, Streptomyces albolongus, andStreptomyces ambofaciens. Moreover, allStreptomycesstrains, tested for endo and exo-cellulase, cellobiase, xylanase, pectinase, ligninase, peroxidase, and laccase activities using qualitative and semi-quantitative methods on solid growth medium, exhibited multiple enzymatic activities (from three to six). The 24 strains were further screened for endo-cellulase activity in liquid growth medium and the four best endo-cellulase producers (S. argenteolusAE58P,S. argenteolusAE710A,S. argenteolusAE82P, andS. argenteolusAP51A) were subjected to partial characterization and their enzymatic crude extracts adopted to perform saccharification experiments onA. donaxpretreated biomass. The degree of cellulose and xylan hydrolysis was evaluated by determining the kinetics of glucose and xylose release during 72 h incubation at 50°C from the pretreated biomass in the presence of cellulose degrading enzymes (cellulase and β-glucosidase) and xylan related activities (xylanase and β-xylosidase). The experiments were carried out utilizing the endo-cellulase activities from the selectedS. argenteolusstrains supplemented with commercial β-gucosidase and xylanase preparations from Genencore (Accellerase BG and Accellerase XY). Cellulose and xylan conversion, when conducted using commercial (hemi)cellulases, gave glucose and xylose yields of 30.17 and 68.9%, respectively. The replacement of the cellulolytic preparation from Genencor (Accellerase 1500), with the endo-cellulase fromS. argenteolusAE58P resulted in almost 76% of the glucose yield obtained in the presence of the commercial counterpart. Due to the promising results obtained by using the enzymatic crude extracts fromS. argenteolusAE58P in the pretreatedA. donaxsaccharification experiments, the proteins putatively responsible for endo-cellulase activity in this strain were identified by proteomics. Several proteins were confidently identified in differentStreptomycesspp., eight of which belong to the class of Carbohydrate active enzymes. Overall results highlighted the biotechnological potential ofS. argenteolusAE58P being an interesting candidate biocatalyst-producing bacterium for lignocellulose conversion and production of biochemicals and bioenergy.
authors.affiliation: Department of Agricultural Sciences, University of Naples Federico II Naples, Italy.
authors.forename: Valeria
authors.initials: V
authors.lastname: Ventorino
authors.affiliation: Institute of Biosciences and BioResources-National Research Council Naples, Italy.
authors.forename: Elena
authors.initials: E
authors.lastname: Ionata
authors.affiliation: Department of Chemical Sciences, University of Naples Federico II Naples, Italy.
authors.forename: Leila
authors.initials: L
authors.lastname: Birolo
authors.affiliation: Department of Chemical Sciences, University of Naples Federico II Naples, Italy.
authors.forename: Salvatore
authors.initials: S
authors.lastname: Montella
authors.affiliation: Institute of Biosciences and BioResources-National Research Council Naples, Italy.
authors.forename: Loredana
authors.initials: L
authors.lastname: Marcolongo
authors.affiliation: Institute of Biosciences and BioResources-National Research Council Naples, Italy.
authors.forename: Addolorata
authors.initials: A
authors.lastname: de Chiaro
authors.affiliation: Department of Agricultural Sciences, University of Naples Federico II Naples, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Espresso
authors.affiliation: Department of Chemical Sciences, University of Naples Federico II Naples, Italy.
authors.forename: Vincenza
authors.initials: V
authors.lastname: Faraco
authors.affiliation: Department of Agricultural Sciences, University of Naples Federico II Naples, Italy.
authors.forename: Olimpia
authors.initials: O
authors.lastname: Pepe
keywords: Arundo donax; Streptomyces spp.; biochemicals and bioenergy; endo-cellulase; saccharification