MIRANDA G. S. CHUA and MORRIS WAYMAN. Can. J. Chem. 57, 1141Chem. 57, (1979. Extractive-free aspen wood meal was subjected to autohydrolysis at 195'C for 5 min to 2 h, and the lignin extracted with 90% dioxane. Extracted autohydrolysis lignin was found to be higher in carbon but lower in hydrogen and oxygen content than aspen milled wood lignin. The methoxyl content was also lower than the reference lignin. These differences have been attributed to condensation and incorporation into the lignin of non-lignin components. A lignin extractability curve with a maximum delignification at autohydrolysis time of 30-40 min was found. From molecular weight distribution studies the ratio of high molecular weight to low molecular weight materials varied for the different extracted lignins and reached a maximum at autohydrolysis time of 40 min. A mechanism of depolymerization/repolymerization of the lignin via carbonium ions has been proposed. p-Hydroxybenzoic acid is postulated as contributing to the extractability of aspen lignin by acting as a blocking agent.MIRANDA G. S. CHUA et MORRIS WAYMAN. Can. J. Chem.,57, 1141Chem.,57, (1979. On a soumis de la sciure de bois de tremble (ne contenant plus de produits pouvant dtre extraits) a une autohydrolyse k 195'C pour des temps allant de 5 min k 2 h puis on en a extrait la lignine par du dioxanne a 90%. On a trouvk que la lignine extraite de l'autohydrolyse contient plus de carbone et moins d'hydrogkne et d'oxygene que la lignine provenant de bois de tremble broy6. La quantitk de methoxyle qui y est contenue est aussi plus faible que celle contenue dans la lignine de rkfkrence. On a attribuk ces diffkrences k la condensation et k I'incorporation dans la lignine de composants qui ne sont pas des lignines. On a dktermink une courbe permettant d'kvaluer la facilitk d'extraction de la lignine; elle prksente un maximum de dklignification a des temps d'autohydrolyse de 30 ti 40 min. En se basant sur des Btudes de distribution de masses moleculaires, on a determine que le rapport des produits de masses molkculaires klevBes/produits de masses molkculaires plus faibles varie suivant les diffkrentes lignines extraites et qu'il atteint un maximum k un temps d'autohydrolyse de 40 min. On propose un mkcanisme de dkpolymkrisation/repolymkrisation de la lignine par l'intermkdiaire de carbocations. On croit que I'acide p-hydroxybenzoi'que facilite l'extraction de la lignine de tremble en agissant cornrne agent bloqueur.[Traduit par le journal]

No abstract

Tot.ot~to, Otzt(irio M5S IA4Received November 21, 1973 M. WAYMAN and T. I. OBIAGA. Can. J. Chem. 52, 2102Chem. 52, (1974.A kinetic investigation of the polymerization of lignin-like polymers of coniferyl alcohol (DHP) using horseradish peroxidase as the phenol oxidase revealed the product to have a bimodal distribution of molecular weight. A peak representing material of low molecular weight M , 3000-4000 was first formed, followed by the formation of a second peak in the molecular weight range 80 000-100 000 whose growth appeared to proceed at the expense of the first.Alkaline degradation of lignins isolated from spruce and hemlock also gave products having a bimodal distribution of molecular weight, with peaks at the same values as found for the synthetic lignin. Lignin isolated during alkaline pulping of finely divided wood showed the presence of the same two components of high and low molecular weight.From these results, we have constructed models for the formation of lignin and for its degradation during an alkaline pulping of wood. The lignin macromolecule as it occurs in wood may well be material of narrow molecular weight distribution with d.p. about 500. It is proposed that this macromolecule is an assembly of subassemblies, or modules, each of d .~. about 20. Lignin formation is seen to proceed by enzyme dehydrogenation of the monomers first producing free radicals as described by Freudenberg, the free radicals reacting by a step condensation to form the modules, followed by intermodular addition polymerization to form the lignin macromolecules. Lignin degradation in pulping reactions involves first the nonrandom homolytic chain depolymerization of the n~acromolecule to yield free-radical carrying modules, which, after stabilization against recondensation by the pulping chemicals, break down to lower oligomers and monomers by a step depolymerization reaction.M. WAYMAN et T. I. OBIAGA. Can. J. Chem. 52, 2102Chem. 52, (1974. L'alcool coniferyle (DHP), sous I'influence de la peroxydase d u raifort agissant comme oxydase des phenols, se transforme en un polymere ressemblant a la lignine; ilne etude cinktique de cette polymerisation revele qile le produit a une distribution bimodale de la masse moleculaire. Un premier maximum correspondant a des produits de faibles poids moleculaires, M , 3000-4000 se forme en premier lieu ; un second sommet correspondant aux substances de poids rnoleculaires allant de 80 000-100 000 apparait ensuite et il semble que sa croissance se fait aux depends du premier.La digradation alcaline des lignines isolees du sapin et de la cigue donne aussi des produits ayant une distribution bimodale de la masse moleculaire, avec des maxima aux m&mes valeurs que celles trouvees pour la lignine synthttique. La lignine isolee lors de la pulpation alcaline du bois finement fractionne montre la presence des mCmes composantes de hauts et faibles poids moleculaires.A I'aide de ces resultats, nous avons construit des modeles pour la formation de la lignine et pour sa degradation lors d'une...

Infrared and ultraviolet studies of the lignins extracted from extractive-free aspen wood meal after autohydrolysis at 195 °C for periods varying from 5 min to 2 h indicated that these lignins were functionally modified and different from aspen milled wood lignin. The extracted lignins changed from a guaiacyl–syringyl type lignin to a syringyl-deficient type lignin with increasing autohydrolysis time. Extracted lignins were also observed to contain unconjugated β-ketone groups and conjugated carboxylic acid groups. It is proposed that the unconjugated β-ketone groups resulted from the depolymerization reactions of the lignin macromolecule under acidic conditions which formed monomeric, dimeric, and oligomeric/polymeric lignin fragments with Hibbert's ketone side chains. The conjugated carboxylic acid group observed to be present was attributed to p-hydroxybenzoic acid. p-Hydroxybenzoic acid has been postulated as contributing to the extractability of aspen lignin by acting as a blocking agent in the repolymerization of lignin fragments to form insoluble lignin.

Fifteen bacterial strains and four molds capable of growth on n-butane were isolated and partially classified. The bacteria were mostly Arthrobacter sp. and Brevibacterium sp.; among the molds, Penicillium nigricans, Allescheria boydii, and Graphium cumeiferum were identified, while the remaining mold had the appearance of Gliocladium, but was not firmly identified. Although able to grow on other alkanes and orthodox media, the bacterial isolates could not use methane. Growth rates on n-butane were unaffected by varying air or substrate partial pressures in the range of 10–90% atmosphere. High partial pressure of oxygen was inhibitory to most bacterial isolates, the degree of inhibition varying widely, however. Growth rates on n-butanol and on glucose were significantly higher than those on n-butane. Among the molds, only the Graphium would grow well in submerged, shaking culture.