Abstract

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Cost effective production of β-glucosidase which is of high value in most biotechnological processes requires an efficient microbial producer, technologies and biomass resources that are economical. This study aimed at evaluating the biochemical characteristics of β-glucosidase produced by Aspergillus niger under solid state fermentation using agro-industrial residues. Fungal isolates from spoilt yam were isolated and screened for the production of β-glucosidase. Study on the optimized conditions and industrial suitability of the produced β-glucosidase was carried out using the most potent fungal producer and the substrate that supported the highest yield of the enzyme. The β-glucosidase producer was identified culturally and morphologically as Aspergillus niger. The highest yield of β-glucosidase (161.4±3.2 U/g) was supported by bread fruit seed hull out of the four screened agro-waste. Optimal cultural conditions for the enhanced production of β-glucosidase ((210.1 U/g) were at pH 6.0, 35 oC, moisture level 75 %, inoculum size 2 % and incubation period of 72 hrs. The optimum activity of the crude enzyme was recorded at pH 6.0 and 60 oC. The pH stability of the enzyme was over a broad range of 4.0 – 8.0 with relative residual activity above 70 % recorded after incubation for 120 min. The β-glucosidase was thermostable as its half life was 4 hrs at 65 oC. This study showed that Aspergillus niger can effectively utilize a low cost substrate (breadfruit seed hull) for the production of β-glucosidase which might be suitable for diverse industrial processes as depicted by its biochemical characteristics.

Keywords: β-glucosidase; Aspergillus niger; solid state fermentation; breadfruit seed hull