| Lignin due to its intimate association with cellulose and hemicellulose forms a barrier to enzymatic attack. Bacterial lignin degradation has been reported to be more specific than with fungal systems, an advantage, leading to many industrial applications like vanillin, adhesives, binder for laminated or composite wood products, etc. Lignin is a complex biopolymer and small differences in its isolation techniques can result in significant changes in its molecular structure and configuration. Lignin conversion involves complex reactions of bond scission and functional group alteration. It is important to track and quantify these alterations.; An analytical method using high-performance size-exclusion chromatography (HPSEC) coupled with Multi-angle Laser Light Scattering (MALS), Quasi-elastic Light Scattering (QELS), Ultraviolet (UV) and Interferometric Refractometry (RI), detection was developed to characterize and monitor lignin. Shodex Asahipak GS-320 HQ column with 0.1M NaOH (pH 12.0) run at 0.5 ml/min gave the highest separation and most consistent recovery. Zimm, Debye and Berry formalisms were used to generated Zimm plots to evaluate the weight average molecular weight (MW), radius of gyration (rg), second virial coefficient (A2) and hydrodynamic radius (rh). This study also highlighted the differences between the unlyophilized and lyophilized lignin in terms of aggregation, pH dependence and stability over time. This aggregation has never been seen on a UV detector that has been used so far with SEC, reducing the reliability of depolymerization data obtained without light scattering.; Culture broths from Phanerochaete chrysosporium and Trametes cingulata, combined with cofactors such as hydrogen peroxide, dithiothreitol, copper, iron, and manganese ions were examined for the ability to modify lignin structure. Results showed changes in the molecular weight distribution of lignin components when treated with a combination 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. H2O2 and DTT showed the most significant changes in lignin molecular weight distribution.; Termites, beetles and other arthropods can digest living and decaying wood and other lignocellulosic plant litter. Microbial sources like other wood eating insect guts and waste water treatment sludge were screened for lignin depolymerization. NIR and AFM along with HP-SEC, were used to track changes in functional groups, size, shape and molecular weight of lignin molecules during incubations. Atomic Force Microscopy (AFM) and Near Infrared Spectroscopy (NIR) also proved effective for lignin characterization. Odontotaenius disjunctus (Betsy Beetle) guts dissected whole or separately as mid, fore 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 using Biolog and Gram Staining. |
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