Filling the gap: Calibration of the low molar-mass range of cellulose in size exclusion chromatography with cello-oligomers.

Degraded celluloses are becoming increasingly important as part of product streams coming from various biorefinery scenarios. Analysis of the molar mass distribution of such fractions is a challenge, since neither established methods for mono- or disaccharides nor common methods for polysaccharide characterization cover the intermediate oligomer range appropriately. Size exclusion chromatography (SEC) with multi-angle laser light scattering (MALLS), the standard approach for celluloses, suffers from decreased scattering intensities in the lower-molar mass range. The limitation in the low-molecular range can, in principle, be overcome by calibration, but calibration standards for such "short" celluloses are either not readily available or structurally remote and thus questionable. In this paper, we present the calibration of a SEC system- for the first time - with monodisperse cellooligomer standards up to about 3400gmol-1. These cellooligomers are "short-chain celluloses" and can be seen as the "true" standard compounds, by contrast to commonly used standards that are chemically different from cellulose, such as pullulan, dextran, polystyrene, or poly(methyl methacrylate). The calibration is compared against those commercial standards and correction factors are calculated. Calibrations with non-cellulose standards can now be adjusted to yield better fitting results, and data already available can be corrected retrospectively.

Strain-specific detection of two Aureobasidium pullulans strains, fungal biocontrol agents of fire blight by new, developed multiplex-PCR.

AIM: The aim of this study was to develop a specific and sensitive identification method for two Aureobasidium pullulans biocontrol strains, CF10 and CF40, based on a sequence-characterized amplified region (SCAR) derived from RAPD - and multiplex-RAPD PCR analysis. METHODS AND RESULTS: The random amplified polymorphic DNA (RAPD) and multiplex RAPD-PCR techniques were used for a preliminary screening of A. pullulans genetic variability among 200 isolates. This approach allowed the selection of ten fragments present solely in strains CF10 and CF40. The RAPD fragments were cloned, sequenced and used to design two SCAR primers. Two primer pairs obtained from SCH3RAPD fragment of CF 40 and 6RAPD of CF10 were highly specific and sensitive. CONCLUSIONS: In this study, we developed strain-specific multiplex-PCR based on sequence-characterized amplified region (SCAR) markers to simultaneously detect both strains in a single PCR. SIGNIFICANCE AND IMPACT OF THE STUDY: This new multiplex-PCR provides a valuable tool for specific and sensitive identification of CF10 and CF40, and could be used in studies on the efficacy and persistence of introduced strains of A. pullulans for fire blight control.