Experimental design of response surface methodology used for utilisation of palm kernel cake as solid substrate for optimised production of fungal mannanase

The results obtained from this work strongly indicate that the solid state fermentation (SSF) system using the palm kernel cake (PKC) as a substrate is an economical method for the production of β-mannanase at extremely low operational cost based on the fact that PKC is one of the cheap and abundant agro-waste by-products of the palm oil industry. Under initial conditions, i.e. 2 mm particle size of PKC, the moisture ratio of 1:1 of PKC:moistening agent and pH 7, Malbranchea cinnamomea NFCCI 3724 produced 109 U/gram distribution of the substrate (gds). The production of β-mannanase was optimised by the statistical approach response surface methodology (RSM) using independent variables, namely initial moisture (12.5), pH (9.0) and solka floc (100 mg). Noticeably, six fold enhancement of β-mannanase production (599 U/gds) was obtained under statistically optimised conditions. HPLC results revealed that β-mannanase is an endo-active enzyme that generated manno-oligosaccharides with a degree of polymerisation (DP) of 3 and 4. Semi-native PAGE analysis revealed that M. cinnamomea produced three isoforms of mannanase. Selective production of oligosaccharide makes M. cinnamomea β-mannanase an attractive enzyme for use in food and nutraceutical industries.