Purification and characterization of β-mannanase from Aspergillus terreus and its applicability in depolymerization of mannans and saccharification of lignocellulosic biomass.
Aspergillus terreus FBCC 1369 was grown in solid-state culture under statistically optimized conditions. β-Mannanase was purified to apparent homogeneity by ultrafiltration, anion exchange and gel filtration chromatography. A purification factor of 10.3-fold was achieved, with the purified enzyme exhibiting specific activity of 53 U/mg protein. The purified β-mannanase was optimally active at pH 7.0 and 70 °C and displayed stability over a broad pH range of 4.0-8.0 and a 30 min half-life at 80 °C. The molecular weight of β-mannanase was calculated as ~49 kDa by SDS-PAGE. The enzyme exhibited Kmand Vmaxvalues of 5.9 mg/ml and 39.42 µmol/ml/min, respectively. β-Mannanase activity was stimulated by β-mercaptoethanol and strongly inhibited by Hg2+. The β-Mannanase did not hydrolyze mannobiose and mannotriose, but only mannotetraose liberating mannose and mannotriose. This indicated that at least four mannose residues were required for catalytic activity. Oligosaccharide with a degree of polymerization (DP) three was the predominant product in the case of locust bean gum (16.5 %) and guar gum (15.8 %) hydrolysis. However, the enzyme liberated DP4 oligosaccharide (24 %) exclusively from konjac gum. This property can be exploited in oligosaccharides production with DP 3-4. β-Mannanase hydrolyzed pretreated lignocelluloses and liberated reducing sugars (% theoretical yield) from copra meal (30 %). This property is an important factor for the bioconversion of the biomass.
Enzyme Technology and Molecular Catalysis Laboratory, Department of Applied Microbiology, Dr. Harisingh Gour Vishwavidyalaya (A Central University), Sagar, MP, 470003, India.
Hemant
H
Soni
Enzyme Technology and Molecular Catalysis Laboratory, Department of Applied Microbiology, Dr. Harisingh Gour Vishwavidyalaya (A Central University), Sagar, MP, 470003, India.
Hemant Kumar
HK
Rawat
Enzyme Synergy Programme, Department of Biochemistry and Microbiology, Rhodes University, Grahamstown, Eastern Cape, 6140, South Africa.
Brett I
BI
Pletschke
Enzyme Technology and Molecular Catalysis Laboratory, Department of Applied Microbiology, Dr. Harisingh Gour Vishwavidyalaya (A Central University), Sagar, MP, 470003, India. nkango@gmail.com.
Naveen
N
Kango
Depolymerization; Lignocellulose; Oligosaccharides; Saccharification; β-Mannanase