Browsing by Author "AGOSIN, E"
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- ItemCATABOLISM OF 1,2-DIARYLETHANE LIGNIN MODEL COMPOUNDS BY 2 BROWN-ROT FUNGI(1990) ESPEJO, E; AGOSIN, E; VICUNA, RThe catabolism of dimethoxybenzil, anisoin and hydroanisoin in nitrogen-limited stationary cultures of the brown-rot fungi Wolfiporia cocos and Gloephyllum trabeum was analyzed. These three 1,2-diarylethane lignin model compounds, which differ in the degree of oxidation of the alkylic chain, gave rise to p-anisaldehyde in both cultures, suggesting that cleavage between the two aliphatic carbons had occurred. In turn, both strains reduced dimethoxybenzil and anisoin to hydroanisoin, whereas only Wolfiporia cocos was able to oxidize hydroanisoin to anisoin. On the other hand, chemically derived hydroxyl radical, but not superoxide radical, produced p-anisaldehyde plus other unidentified compounds from anisoin and hydroanisoin. Neither radical modified dimethoxybenzil significantly.
- ItemCATALYZED FLASH PRETREATMENTS IMPROVE SACCHARIFICATION OF PINE (PINUS-RADIATA) SAWDUST(1989) HOHLBERG, AI; AGUILERA, JM; AGOSIN, E; SANMARTIN, RPhysico-chemical pretreatments with steam explosion were used to improve digestion in vitro of pine sawdust. Maximum reducing sugar yields (g/100 g substrate) obtained after hydrolysis of pretreated samples were: 14 g for steam-exploded sawdust, 26 g for SO2 impregnated steam-exploded samples and 32.5 g for CO2 steam-exploded samples. Increase in digestibility is related to the catalytic effect of cooking at high temperatures with dissolved acids formed from the gases, as well as to the physical effect of the discharge during the explosion. Pretreatment with SO2 was the most efficient process for hydrolyzing hemicelluloses, as determined by the high content of soluble reducing sugars present in the washing liquor.
- ItemCHANGES IN MOLECULAR-SIZE DISTRIBUTION OF CELLULOSE DURING ATTACK BY WHITE ROT AND BROWN ROT FUNGI(AMER SOC MICROBIOLOGY, 1992) KLEMANLEYER, K; AGOSIN, E; CONNER, AH; KIRK, TKThe kinetics of cotton cellulose depolymerization by the brown rot fungus Postia placenta and the white rot fungus Phanerochaete chrysosporium were investigated with solid-state cultures. The degree of polymerization (DP; the average number of glucosyl residues per cellulose molecule) of cellulose removed from soil-block cultures during degradation by P. placenta was first determined viscosimetrically. Changes in molecular size distribution of cellulose attacked by either fungus were then determined by size exclusion chromatography as the tricarbanilate derivative. The first study with P. placenta revealed two phases of depolymerization: a rapid decrease to a DP of approximately 800 and then a slower decrease to a DP of approximately 250. Almost all depolymerization occurred before weight loss. Determination of the molecular size distribution of cellulose during attack by the brown rot fungus revealed single major peaks centered over progressively lower DPs. Cellulose attacked by P. chrysosporium was continuously consumed and showed a different pattern of change in molecular size distribution than cellulose attacked by P. placenta. At first, a broad peak which shifted at a slightly lower average DP appeared, but as attack progressed the peak narrowed and the average DP increased slightly. From these results, it is apparent that the mechanism of cellulose degradation differs fundamentally between brown and white rot fungi, as represented by the species studied here. We conclude that the brown rot fungus cleaved completely through the amorphous regions of the cellulose microfibrils, whereas the white rot fungus attacked the surfaces of the microfibrils, resulting in a progressive erosion.
- ItemCOMPARISON OF AERIAL AND SUBMERGED SPORE PROPERTIES FOR TRICHODERMA-HARZIANUM(ELSEVIER SCIENCE BV, 1995) MUNOZ, GA; AGOSIN, E; COTORAS, M; SANMARTIN, R; VOLPE, DSpores produced by aerial mycelium of Trichoderma harzianum P1, a potential biocontrol agent, showed both higher UV-resistance and longer viability after storage than those produced within liquid media ('submerged' spores). Aerial spores were produced in clusters, had a thick outer wall, and few organelles. Trehalose content was significantly lower than in submerged spores. Conversely, submerged spores were mostly collapsed, not clustered and larger than aerial spores. They had many cytoplasmic organelles and a thinner outer wall. These spores were hydrophilic, while aerial ones were highly hydrophobic. On analysis, the latter was related with the presence of a single major low molecular mass protein (< 14 kDa). This protein was nearly absent in extracts from walls of submerged spores but was found in the extracellular medium. An involvement of the outer wall layer in the resting state of T. harzianum spores is proposed.
- ItemFOOD, AGRICULTURAL AND MARINE BIOTECHNOLOGY IN CHILE(ELSEVIER SCIENCE BV, 1993) AGUILERA, JM; AGOSIN, E; MARTIN, RSEconomic segments with highest growth rates in Chile are those based on renewable resources like agriculture (fruits and vegetables), marine and forest products. Opportunities for biotechnology are based on a sound scientific base at universities, adequate funding and incipient industry-academia relationships. However, there is an urgent need to develop the engineering capabilities required to scale-up processes and to design, build and operate industrial biotechnology plants.
- ItemGLUTAMINE INVOLVEMENT IN NITROGEN CONTROL OF GIBBERELLIC-ACID PRODUCTION IN GIBBERELLA-FUJIKUROI(AMER SOC MICROBIOLOGY, 1993) MUNOZ, GA; AGOSIN, EWhen the fungus Gibberella fujikuroi ATCC 12616 was groWn in fermentor cultures, both intracellular kaurene biosynthetic activities and extracellular GA3 accumulation reached high levels when exogenous nitrogen was depleted in the culture. Similar patterns were exhibited by several nonrelated enzymatic activities, such as formamidase and urease, suggesting that all are subject to nitrogen regulation. The behavior of the enzymes involved in nitrogen assimilation (glutamine synthetase, glutamate dehydrogenase, and glutamate synthase) during fungal growth in different nitrogen sources suggests that glutamine is the final product of nitrogen assimilation in G. fujikuroi. When ammonium or glutamine was added to hormone-producing cultures, extracellular GA3 did not accumulate. However, when the conversion of ammonium into glutamine was inhibited by L-methionine-DL-sulfoximine, only glutamine maintained this effect. These results suggest that glutamine may well be the metabolite effector in nitrogen repression of GA3 synthesis, as well as in other nonrelated enzymatic activities in G. fujikuroi.
- ItemPRODUCTION AND DEGRADATION OF OXALIC-ACID BY BROWN ROT FUNGI(AMER SOC MICROBIOLOGY, 1991) ESPEJO, E; AGOSIN, EOur results show that all of the brown rot fungi tested produce oxalic acid in liquid as well as in semisolid cultures. Gloeophyllum trabeum, which accumulates the lowest amount of oxalic acid during decay of pine holocellulose, showed the highest polysaccharide-depolymerizing activity. Semisolid cultures inoculated with this fungus rapidly converted C-14-labeled oxalic acid to CO2 during cellulose depolymerization. The other brown rot fungi also oxidized C-14-labeled oxalic acid, although less rapidly. In contrast, semisolid cultures inoculated with the white rot fungus Coriolus versicolor did not significantly catabolize the acid and did not depolymerize the holocellulose during decay. Semisolid cultures of G. trabeum amended with desferrioxamine, a specific iron-chelating agent, were unable to lower the degree of polymerization of cellulose or to oxidize C-14-labeled oxalic acid to the extent or at the rate that control cultures did. These results suggest that both iron and oxalic acid are involved in cellulose depolymerization by brown rot fungi.
- ItemREGULATORY ASPECTS OF ENDOGLUCANASE PRODUCTION BY THE BROWN-ROT FUNGUS GLOEOPHYLLUM-TRABEUM(ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS, 1992) COTORAS, M; AGOSIN, E