High yield synthesis of nigerooligosaccharides by transglycosylation catalyzed by α-glucosidase TaAglA from Thermoplasma acidophilum

Abstract

Nigerooligosaccharides (NOS) is a new functional oligosaccharide containing α-1,3 glucosidic bond with good anti-digestive properties and intestinal probiotics. Transglycosylation catalyzed by α-glucosidase is an effective method for the preparation of oligosaccharides. However, there are few reports on the enzymatic synthesis of nigerooligosaccharides by α-glucosidase at present. This study was aimed to investigate the transglycosylation property of the GH31 α-glucosidase from Thermoplasma acidophilum, TaAglA, and also evaluate its application performance in the preparation of NOS. It was found that TaAglA exhibited selectivity for α-1,3 and α-1,4 linkages when catalyzing hydrolysis, but for α-1,3 and α-1,6 linkages when catalyzing transglycosylation. Using 10% glucose and 20% maltose as substrates, TaAglA yielded 88.5 g/L NOS under the condition of pH 6.0, 80 °C and 1 U/mL enzyme addition, which was the highest level to our knowledge. In addition, components with higher polymerization degrees, i.e. nigerotriose and nigerosyl-glucose, occupied 53.6% proportion of the total NOS products, giving it better probiotic functions. Futhermore, after purification by glucoamylase digestion and yeast culture, the final yield of NOS was 26.1%, and the purity of the product was 93%. These findings on TaAglA were expected to provide a new candidate for large-scale enzymatic synthesis of NOS, and also have important theoretical significance for the study of GH31 α-glucosidase.