Production and characterization of manno-oligosaccharides from hydrolysis of mannan substrates by recombinant beta-mannanase from Bacillus licheniformis (Weigmann) Chester DSM 13

Abstract

Mannooligosaccharides (MOS) is a prebiotic produced by the hydrolysis of mannans and promotes gut health. One route in producing MOS is via enzymatic method, which employs microbial enzyme (e.g., β-mannanase) for mannan hydrolysis. In this work, we investigated the stability and propensity of β-mannanase from Bacillus licheniformis (BlManB) overexpressed in Lactiplantibacillus plantarum WCSF1 towards β-MOS production using several mannan sources. We also determined the fermentation conditions for optimal enzyme production in the food-grade system. Maximal crude enzyme yield was obtained (17.3 ± 1.2 kU per liter of fermentation broth with specific activity of 194 U/mg protein) by maintaining the pH at 6–6.5 at fermentation. Crude BlManB is stable at storage conditions of -20°C and 4°C. The crude overexpressed enzyme was also stable and active at conversion conditions (30 °C and 37 °C) in the presence of 2 mM dithiothreitol (DTT) . Analysis by high-performance anionexchange chromatography with pulsed amperometric detection (HPAEC-PAD) indicated that the crude enzyme produced known linear MOS of 235.88 mg/g using locust bean gum, 121.63 mg/g using copra meal, 71.71 mg/g using guar gum, 21.33 mg/g using spent coffee ground, and 86.76 mg/g using konjac glucomannan. The study has also shown that crude BlManB overexpressed in L. plantarum WCSF1 could be efficiently used to produce food-grade MOS.