Improving Ruminal Degradibility Of Oil Palm Fronds Using Enzyme Extracts From White Rot Fungi
Abstract Background: Oil palm fronds (OPF) when pretreated with white rot fungi (WRF) shows increased rumen degradability but with significant biomass loss. Thus, effects of pre-treated OPF with enzyme extracts from WRF on rumen degradability were studied in vitro. The enzyme extracts were prepared by inoculating OPF with three WRF, i.e Ceriporiopsis subvermispora, Lentinula edodes and Ganoderma lucidum, for 15, 30 and 45 days with either ammonium sulphate, (NH4)2SO4 and sodium nitrate, NaNO3 added to the culture media for each inoculation period. After preparation of enzyme extracts, the enzyme activities were determined. OPF was then pre-treated with enzyme extracts in a citrate buffer (pH 5.0) in a forced air oven at 40 oC during 5 days. Further, the in vitro rumen degradation of OPF pre-treated with enzyme extracts, with respect to the short chain fatty acid (SCFA) production, was determined after 24 h incubation. Activity of lignolytic (laccase and MnP), cellulolytic (CMCase and avicelase) and hemicellulolytic (xylanase) enzymes were measured in all of the extracts irrespective on the inoculation period. Results: Treatment of OPF with enzyme extracts from G. lucidum after 45 days of inoculation showed a numerical increase (13%) in total SCFA and apparently rumen degradable carbohydrates (ARDC) after 24 h in vitro incubation, without any loss of biomass. However, this increase was not clearly correlated to results of the enzyme assays. Conclusion: This study indicates pre-treatment of OPF with enzyme extracts from specific WRF to be promising to enhance the ruminal degradability of OPF without simultaneous loss of biomass.