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Mycelial growth interactions and mannan-degrading enzyme activities from fungal mixed cultures grown on palm kernel cake
Abstract
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 mannandegrading 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 (bmannosidase) 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.
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 mannandegrading 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 (bmannosidase) 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.
