Partial purification and characterization of an inducible extracellular β-Glucosidase of &lt;i&gt;Aspergillus niger&lt;/i&gt; IMI 502691

S A Adegoke,F J C Odibo

doi:10.4314/njb.v34i1.4

Abstract

β-Glucosidase (EC 3.2.1.21) was produced by Aspergillus niger IMI 502691 using solid state fermentation of cassava root fibre. The enzyme was partially purified and characterized. The enzyme extracted using 20mM phosphate buffer pH 6.8 was concentrated to 10ml with 5M sucrose solution using dialysis membrane. It was purified from the culture medium by ion exchange chromatography on Carboxymethyl Sepharose and gel filtration chromatography on Biogel P 4. β- Glucosidase was purified 3.17 fold to give 3.68% yield relative to the total activity in the crude extract and with over 300% increase in specific activity of 106.93Umg-1 proteins for the partially purified protein. The enzyme exhibited decrease in total protein and total activity of 86.1% and 27.16%, respectively and optimal activity at pH 5.0 and 80oC (1h) in the absence of calcium. The β- glucosidase showed a wide range of pH and temperature of 3.0 to 7.0 and 50oC to 90oC, respectively. The enzyme was most stable at 50oC but retained above 50% of its activity for 1h at 60oC. The β-glucosidase of Aspergillus niger IMI 502691 was significantly activated by Sr2+, Fe2+, Mn2+, Ni2+, Zn2+and Cu2+ tested except for Ca2+ which inhibited the enzyme.Keywords: Glucosidase, chromatography,extract,activity, inhibited

Highlights

Developing a bio-based economy is a world-wide strategy to address the global challenges of dwindling fossil energy reserve, environmental degradation and pollution associated with oil exploration, prospecting, spillage and climate change in the light of growing world population
In the time course for the production of βglucosidase by Aspergillus niger IMI 502691 growth was accompanied with rapid increase in microbial mass
In the time-course of β-glucosidase production from Aspergillus niger IMI 502691, reduced culture pH condition between day 3 and day 4 gave a corresponding increase in the β-glucosidase activity with optimal activity being observed at day 4 (Figure 1)

Summary

Introduction

Cellulosic biomass is essential in bio-based energy generation. Cellulase occupies a pivotal position in the success of energy generation from bio-based biomass (Arantes & Saddler, 2010). It is an enzyme complex made of exoglucanase (EC 3.2.1.91), endoglucanase (EC 3.2.1.4) and glucosidase Solid State Fermentation (SSF) is simple (Sreeja et al, 2006) with higher productivity (Machida, 2002). It requires less energy, less water output, less production cost and better product recovery (Priya et al, 2012). The method employed in the production of the enzyme would help to reduce the cost of enzyme production and reduce attendant problems associated with disposal of cassava root fibre, an agricultural waste, when implemented on large scale

Materials and Methods

Results

Discussion