Isolation, screening and identification of mannanase producer microorganisms

Palm kernel cake (PKC) is used widely in the animal feed industry but has limited use in poultry feed due to its high fibre and low protein contents. The major component of the fibre is mannan which is insoluble and difficult to digest. Therefore, isolation of local potential microbes capable of degrading mannan was explored from various sources such as peat soil, rotten oil palm trunks and raw PKC. The isolates were screened based on the clearing zone method on selective agar media containing Azo-carob-galactomannan as substrate. A total of 36 isolates were screened and only 13 had a clear zone ranging from 3.42 ± 0.02 mm to 5.44 ± 0.06 mm which were used for further analysis. These isolates were incubated in shake flasks at 35 °C for 48 h with 10 g/litre PKC as substrate. The best enzymes producer was isolate IBRL F16.A4 with specific mannanase enzyme acitivity of 17.82 ± 0.05 U/mg, production of glucosamine at 9.84 ± 0.11 mg/g and mannose at 9.54 ± 0.06 mg/g. The isolate IBRL F16.A4 was identified as Aspergillus niger IBRL F16.A4 using a scanning electron microscope