Publications on Lignin
1. Determination of lignin by size exclusion chromatography using multi angle
laser light scattering by
Aarti V. Gidh; Stephen R. Decker; Todd B. Vinzant;
Michael E. Himmel; Clint Williford (pp. 102-110).
Published 17 April 2006 in J Chromatography, 1114(1):
102-10.
A method was developed using
high-performance size exclusion liquid chromatography (HPSEC) with multi-angle
laser light scattering (MALLS), quasi-elastic light scattering (QELS), interferometric refractometry
(RI) and UV detection to characterize and monitor lignin. The combination proved very
effective at tracking changes in molecular conformation of lignin
molecules over time; i.e. changes in molecular weight distribution, radius of gyration, and hydrodynamic radius. Until
this study, UV detection (280nm) had been the primary lignin determination
method for chromatography. Three different HPLC columns were used to study the
effects of pH, flow conditions, and
mobile phase compositions (dimethyl sulphoxide, water, 0.1M NaOH, and
lithium bromide) on the chromatography of
lignin. Since light scattering
accuracy is highly dependent on solute concentration, both the UV and RI
detectors were calibrated for use as concentration detectors. Shodex Asahipak GS-320 HQ column
with 0.1M NaOH (pH 12.0) run at 0.5ml/min was found
to give the highest separation and most consistent recovery. The study also
revealed that the lignin aggregated at
pH below 8.5. This aggregation was detected only by MALLS and was not observed
on UV or RI detectors. It is very important to take this loss in apparent
concentration due to aggregation into consideration before collecting reliable
depolymerization data.
Keywords: Lignin; Light scattering; Method development; HPLC; Aggregation
Culture broths from Phanerochaete
chrysosporium and Trametes cingulata ,
combined with co-factors such as hydrogen peroxide, dithiothreitol,
copper, iron, and manganese ions were examined for the ability to modify lignin
structure. High-performance size exclusion chromatography (HP-SEC) coupled to
multi-angle laser light scattering (MALLS) detection was used to determine the
effect of several white rot fungi, pH values, enzymes, and co-factors on the
molecular weight distribution of treated kraft
lignin. The analytical procedure tracked changes in molecular weight
distribution, radius of gyration, and hydrodynamic radius. Results showed
changes in the molecular weight distribution of lignin components when treated
with combinations of factors. The induced cultures showed more lignin
depolymerization for the specific lignin samples in which they were initially
grown. The distribution in the radius of gyration became narrower with time,
indicating that molecular conformation changed to a more uniform molecular
shape. H 2 O 2 and DTT showed the most significant changes in lignin molecular
weight distribution.
Keywords: Aggregation; Depolymerization; Fungi; Light-scattering; Lignin; Ligninase
3. Detailed Analysis of Modifications in Lignin After Treatment With Cultures Screened for Lignin Depolymerizing Agents by Aarti Gidh, Dinesh Talreja, Todd B. Vinzant, Clint Williford, and Alfred Mikell, in Applied Biochemistry and Biotechnology, Spring 2006, Volume 131, Issue 1-3, pps. 829-843, (ISSN:0273-2289)
Termites, beetles, and other arthropods can digest living and decaying wood plus other lignocellulosic plant litter. Microbial sources like other wood-eating insect guts and wastewater treatment sludge were screened for lignin depolymerization. Near infrared spectroscopy and atomic force microscopy (AFM) along with high-performance liquid chromatography (HPLC), were used to track changes in functional groups, size, shape, and molecular weight of lignin molecules during incubations. Odontotaenius disjunctus (Betsy beetle) guts dissected whole or separately as midgut, foregut, and hindgut, consumed corn stover but did not show lignin depolymerization. The sludge-treated lignin did show some reduction in molecular weight on the HPLC, particle size (350–650 nm initially to 135–220 nm by day 30) and particles per field on AFM. pH and the presence of nutrients had a substantial effect on the extent of depolymerization. Cultures in lignin and nutrients showed higher growth than cultures with lignin only. Colony characteristics within the beetle gut and the sludge were also evaluated.
Keywords: Lignin; beetles; NIR; HPLC;
AFM; depolymerization
4. Characterization of lignin using multi-angle
laser light scattering and atomic force microscopy by A.V.
Gidh , S.R.
Decker, C.H.
See, M.E.
Himmel , and C.W.
Williford, in
Analytica Chimica Acta., 555(2),
p. 250
Small differences in the
isolation techniques of lignin can result in significant changes in its
molecular structure and configuration. Light scattering (evaluated at 18
different angles in a plane), Atomic Force Microscopy (AFM) and Near Infrared
Spectroscopy (NIR) proved very effective for evaluating the characteristics of
lignin. Zimm plots were generated using Zimm,
Debye and