The structure and function of the N-linked carbohydrate chains in laccase III, one of the ligninolytic glycoenzymes from the white-rot fungus Coriolus versicolor, have been partially characterized using endoglycosidases (Endo F and Endo H) and the N-asparagine-specific inhibitor, tunicamycin. In the presence of 10 μg tunicamycin ml-1 laccase and proteinase activities in culture filtrates of C. versicolor were measured over 3 weeks. Laccase activity was slightly decreased by the addition of tunicamycin, whereas proteinase activity was increased. The N-linked carbohydrate chains were not necessary for laccase secretion and activity. Endo-glycosidase digestion showed that laccase III contained at least four N-linked carbohydrate chains, of which two were high-mannose type or hybrid type and two were complex type. Judging from the differences in the resistance of the native and the carbohydrate-depleted laccase to proteolytic digestion and high temperature, the four N-linked carbohydrate chains have important protective functions against proteolytic attack and elevated temperature.

The aim of this research was to evaluate the feasibility of aqueous saponin for the removal and biodegradation of polycyclic aromatic hydrocarbons (PAHs) from contaminated soil. Dissolution test confirmed the ability of saponin to increase the apparent solubility of the tested 3–5 rings PAH above the critical micelle concentration (approximately 1000 mg/L). Microbial test with pure culture of Sphingomonas sp. showed that saponin significantly enhanced the degradation of pyrene. For example, the percent degradation was 2.1 times higher in the presence of 2500 mg/L saponin than that of control without saponin after 60 hours incubation at around 10⁸ CFU/mL initial cell loading. These results suggest that the binding of pyrene with saponin does not pose a serious constraint to bacterial uptake. Contrary to pyrene, saponin was chemically stable against the PAHs degrader. It is also not toxic to the cell at least up to 2500 mg/L. Finally, using a spiked soil sample, extraction tests with 10,000 mg/L of saponin showed that around 52.7% and 0.3% of pyrene was removed from low and high organic spiked soils, respectively. The results from this study indicate that aqueous saponin is appropriate as a washing agent as well as biodegradation enhancer for the detoxification of PAHs-contaminated low organic carbon soil.