Secretome profile of Cellulomonas sp. B6 growing on lignocellulosic substrates.

AIMS: Lignocellulosic biomass deconstruction is a bottleneck for obtaining biofuels and value-added products. Our main goal was to characterize the secretome of a novel isolate, Cellulomonas sp. B6, when grown on residual biomass for the formulation of cost-efficient enzymatic cocktails. METHODS AND RESULTS: We identified 205 potential CAZymes in the genome of Cellulomonas sp. B6, 91 of which were glycoside hydrolases (GH). By secretome analysis of supernatants from cultures in either extruded wheat straw (EWS), grinded sugar cane straw (SCR) or carboxymethylcellulose (CMC), we identified which proteins played a role in lignocellulose deconstruction. Growth on CMC resulted in the secretion of two exoglucanases (GH6 and GH48) and two GH10 xylanases, while growth on SCR or EWS resulted in the identification of a diversity of CAZymes. From the 32 GHs predicted to be secreted, 22 were identified in supernatants from EWS and/or SCR cultures, including endo- and exoglucanases, xylanases, a xyloglucanase, an arabinofuranosidase/ß-xylosidase, a ß-glucosidase and an AA10. Surprisingly, among the xylanases, seven were GH10. CONCLUSIONS: Growth of Cellulomonas sp. B6 on lignocellulosic biomass induced the secretion of a diverse repertoire of CAZymes. SIGNIFICANCE AND IMPACT OF THE STUDY: Cellulomonas sp. B6 could serve as a source of lignocellulose-degrading enzymes applicable to bioprocessing and biotechnological industries.

Detection of the mosquitocidal toxin genes encoding Cry11 proteins from Bacillus thuringiensis using a novel PCR-RFLP method.

A polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method for detection of cry11 genes from Bacillus thuringiensis was established. Based on the analysis of conserved regions of the cry11 genes, 2 oligonucleotide primers were designed to amplify a 1459-bp fragment of the cry11Aa gene, and a 1471-bp of the cry11Ba and cry11Bb genes. The amplification products were digested with restriction endonuclease HinfI. Exotic B. thuringiensis strains and native isolates collected from soils, leaves and stored product dust of Argentina were analyzed to study the distribution of cry11 genes. The PCR-RFLP patterns revealed the detection of cry11 genes in 3 of 64 exotic strains and in 10 of 107 native B. thuringiensis isolates tested. Just the cry11Aa gene subclass was detected among these bacteria. Since the methodology was also developed to detect cry11Ba and cry11Bb genes, an experimental future confirmation will be required. Based on the results obtained, the PCR-RFLP method presented may be a valuable tool for specific detection of the mosquitocidal toxin genes encoding Cry11 proteins from B. thuringiensis.