Full Length Research Paper

Mycelial growth interactions and mannan-degrading enzyme activities from fungal mixed cultures grown on palm kernel cake

F. B. Iluyemi¹ and M. M. Hanafi²*

¹Department of Land Management, Faculty of Agriculture, Universiti Putra Malaysia 43400-UPM, Serdang, Selangor, Malaysia.

²Institute of Tropical Agriculture, Universiti Putra Malaysia 43400-UPM, Serdang, Selangor, Malaysia.

*Corresponding author. E-mail: mmhanafi@agri.upm.edu.my. Tel: +603-89467842.

Accepted 23 April, 2009

Palm kernel cake (PKC), a by-product of the palm kernel oil extraction process contains mannan as its main polysaccharide. Mixed culture microbial degradation may enhance mannan-degrading enzymes production. Therefore, the objective of the study was to examine the nature of mycelial interactions and corresponding production of mannan-degrading enzymes of PKC. Fungal interactions was carried out using Sclerotium rolfsii and Aspergillus niger co-cultured with three Trichoderma strains (Trichoderma harzianum, Trichoderma longiobrachiatum and Trichoderma koningii) on potato dextrose agar (PDA) in disposable petri-dishes.  Measurements of growth diameters were taken on days 2 and 13. For mannan-degrading enzyme production, single and co-cultures of these fungi were carried out under submerged cultivation for 13 days with PKC as the carbon source. About 57% of observed interactions on PDA were deadlock, 29% replacement and 14% intermingling. In Trichoderma sp./A. niger mixed cultures, there was an overall significant enhancement of enzyme: 2 to 200 fold (b-D-mannanase), 8 to 25 fold (b-mannosidase) and from no change to 15 fold increase (a-galactosidase). There was no obvious relationship between enzyme production and protein yield. However, co-culturing of A. niger with the Trichoderma strains showed an enhancement of mannan-degrading enzyme activities without reducing biomass yield.

Key words: a-Galactosidase, b-D-mannanase, b-mannosidase, fungi, co-cultures, palm kernel cake.