High NaCl concentrations induce the resistance to thermal denaturation of an extremely halotolerant (salt-activated) β-mannanase from Bacillus velezensis H1

This study aims to report the first purification and characterization of ManH1, an extremely halotolerant β-mannanase from the halotolerantB. velezensis strain H1. Electrospray ionization quadrupole time-of-flight mass spectrometry (ESI-Q-TOF-MS) analysis revealed a single major peak with a molecular mass of 37.8  kDa demonstrating its purity. The purified enzyme showed a good thermostability as no activity was lost after a 48 h incubation under optimal conditions of 50 °C and pH 5.5. The enzyme’s salt activation nature was revealed when its maximum activity was obtained in the presence of 4 M NaCl,  it doubled compared to the no-salt condition. Moreover, NaCl strengthens its resistance to thermal denaturation, as its melting temperature (Tm) increased steadily with increasing NaCl concentrations reaching 75.5  °C in the presence of 2.5 M NaCl. TheKm andVmax values were 5.63  mg/mL and 333.33 µmol/min/mL, respectively, using carob galactomannan (CG) as a substrate. The enzyme showed a significant ability to produce manno-oligosaccharides (MOS) from lignocellulosic biomass releasing 13 mg/mL of reducing sugars from olive mill wastes (OMW) after 24 h incubation. The results revealed that this enzyme may have significant commercial values for agro-waste treatment, and other potential applications.
Source: World Journal of Microbiology and Biotechnology - Category: Microbiology Source Type: research