Compost-mediated removal of polycyclic aromatic hydrocarbons from contaminated soil.

Compost-assisted remediation of a manufactured-gas plant soil contaminated with polycyclic aromatic hydrocarbons (PAHs) was performed in thermally insulated composting chamber using mushroom compost consisting wheat straw, chicken manure, and gypsum. The degradation of individual PAHs was in range of 20-60% at the end of 54 days of composting followed by further increase of PAH removal (37-80%) after another 100 days of maturation. Both chemical analysis of the contaminated soil for PAHs and ecotoxicity tests on bioluminescent bacteria, earthworms, and plant seeds were performed before and after the composting. After the composting, inhibition of bioluminescence decreased, whereas no significant change in toxicity was observed for earthworm survival and seed germination. Using bacterial culture of Escherichia coli K12 genotoxicity tests were performed on samples taken from different parts of the composting pile; after the composting the decrease in genotoxicity was observed only in the sample taken from upper part of the composted pile.

Natural cellulose fibers: heterogeneous acetylation kinetics and biodegradation behavior.

Steam-exploded fibers from flax (Linum usitatissimum) are heterogeneously acetylated using acetic anhydride and sulfuric acid as catalyst, with the aim to modify the surface properties without changing fiber structure and morphology. The acetylation reaction follows first-order kinetics up to a reaction time that depends on catalyst concentration (15 h when using 0.4 vol % of H(2)SO(4) or 50 h with 0.1 vol %). The fibers undergo no structural and/or morphological changes under either reaction condition. On the contrary, surface damage and structural modifications appear after longer reaction times, when the reaction kinetics change. The extent of biodegradation of acetylated fibers, evaluated from the weight percent remaining after 13 days of exposure to previously isolated cellulolytic bacteria Cellvibrio sp., decreases with increasing acetylation degree. After biodegradation the fibers show a higher acetyl content than before the experiment, indicating that the bacteria preferentially biodegrade unsubstituted cellulose, though also acetylated chains are cleaved. Biodegradable acetylated cellulose fibers with modified surface chemistry and unchanged structure are obtained for applications as polymer composite reinforcements.

Isolation and identification of cellulolytic bacteria involved in the degradation of natural cellulosic fibres.

In search for bacterial cultures that are able to rapidly degrade cellulosic plant fibres in vitro, 77 cellulolytic strains were isolated from Belgian and Czech soils after enrichment on flax or sisal fibres as sole sources of carbon. The strains were characterized using fatty acid analysis, and 74 strains were grouped into three major clusters by numerical analysis. The first major cluster contained Cellulomonas strains. Within this cluster three subclusters could be delineated by principal component analysis, that were recognized by their fatty acid compositions as Cellulomonas gelida, Cellulomonas biazotea and Cellulomonas cellulans, containing 9, 8 and 13 strains respectively. The second major cluster, with 9 strains, was assigned to Flavobacterium johnsoniae. The 34 strains of the third cluster could not be identified by commercial identification systems on the basis of their fatty acid profiles and API 20NE profiles. On the basis of their phenotypic characteristics they met the description of the genus Cellvibrio, their fatty acid profiles were similar to those of four authentic Cellvibrio mixtus strains, and the 16S rRNA genes from four representatives showed up to 97.8% sequence similarity to 16S rDNA from Cellvibrio mixtus ACM 2603. Three non-clustered strains were assigned to Curtobacterium flaccumfaciens, Achromobacter piechaudii and Pseudomonas mendocina. Two strains assigned to Cellvibrio were able to degrade several flax, broom and cotton fibres very rapidly in a standardized in vitro test, causing mass losses of 40 to 86% within 13 days of incubation, but not jute.