Improvement of nutritional and bioactive properties of barley b-glucan-based food products using Bacillus subtilis 168 endo-b-1,3-1,4-glucanase

Abstract

The combination of b-oligosaccharides from enzymatically hydrolysed barley b-glucan has attracted interest recently due to its positive effects on human health. This study aimed to assess the impact of the endo-b-1,3-1,4-glucanase enzyme from Bacillus subtilis 168 on improving the nutritional and bioactive properties of barley b-glucan. A new procedure for the isolation of b-glucan was developed, at a lower temperature (45 °C), enabling purity from starch contamination, without affecting the yield (6 g b-glucan from 100 g of barley flour). The endo-b-1,3-1,4-glucanase is cloned into E. coli pQE_Ek enables the high production and purification (82% yield, 1.8 mg mL 1 and 440 U mg 1 ) of an enzyme identical to the natural one (25.5 kDa). The enzymatic reaction showed high efficiency of b-glucan degradation by recombinant enzyme, giving a mixture of products (of which 3-O-b-cellobiosyl-D-glucose and 3-O-b-cellotriosylD-glucose are the most abundant), the reduction of viscosity (17%) and increase in antioxidant capacities by 15.2%, 30.9% and 44.0% assessed by ABTS, DPPH and ORAC, respectively. These results indicate the possible application of endo-b-1,3-1,4-glucanase enzyme in improving the properties of barley bglucan used as functional foods.