Weight loss indicates degradation of biomass caused by the fungi. When comparing the four fungal species, OL gave the highest loss, which averaged to 27.6%, followed by RV at 13.7% (Figure 2). Although CV was the slowest grower, it recorded a higher weight loss (12.2%) when compared with PC (8.0%). The results for the latter two species were similar to those reported by Halis (2011). OL caused nearly 30% weight loss when inoculated on kenaf biomass making it a desirable wood degrader.
Determination of weight loss gives a general idea on the performance of a fungus. The species with a better performance can be roughly identified from here. Weight loss indicates fungi with good degrading ability, supporting observation via naked eye, which can sometimes be misleading as what observed above between PC and CV. Both visual observation and weight loss determination showed general performance of the fungal species and can be used in selecting potential fungi for further analysis.
LIGNINASE ACTIVITY
Three types of enzyme assays were conducted to detect ligninase activity in the four fungal species. All species had high levels of lignin peroxidase (LiP) activity, with OL having the highest level (Figure 3). RV showed the highest activity for laccase, which was significantly different from OL and PC. CV had lower laccase activity compared with RV and PC showed only traces of it. Manganese peroxidase (MnP) activity detected was quite low in all four fungal species when compared with the other two enzymes. PC showed the highest activity but the difference with the other three species was insignificant.
White rot fungi can be classified into different groups based on their ability and characteristic in expressing enzyme activities. CV is one of the best-known fungus that produces all three lignolytic enzymes. Even though it is well-known that PC is an example of white rot fungus that does not produce laccase, there are evidences that low consistent amount of laccase has been detected in some strains (Srinivasan et al. 1995). Laccase activity was also detected here in OL but in low amounts. MnP activity was the lowest compared with the other enzymes and it stayed consistently low in all the four species tested. This might be due to the reason that in order for lignin to degrade, either LiP or MnP production is needed in association with