Conversion of β‐1,6‐Glucans to Gentiobiose using an endo‐β‐1,6‐Glucanase PsGly30A from Paenibacillus sp. GKG

Abstract

AbstractA plethora of di‐ and oligosaccharides isolated from the natural sources are used in food and pharmaceutical industry. An enzymatic hydrolysis of fungal cell wall β‐glucans is a good alternative to produce the desired oligosaccharides with different functionalities, such as the flavour enhancer gentiobiose. We have previously identified PsGly30A as a potential yeast cell wall degrading β‐1,6‐glycosidase. The aim of this study is to characterise the PsGly30A enzyme, a member of the GH30 family, and to evaluate its suitability for the production of gentiobiose from β‐1,6‐glucans. An endo‐β‐1,6‐glucanase PsGly30A encoding gene from Paenibacillus sp. GKG has been cloned and overexpressed in Escherichia coli. The recombinant enzyme has been active towards pustulan and yeast β‐glucan, but not on laminarin from the Laminaria digitata, confirming the endo‐β‐1,6‐glucanase mode of action. The PsGly30A shows the highest activity at pH 5.5 and 50 °C. The specific activity of PsGly30A on pustulan (1262±82 U/mg) is among the highest reported for GH30 β‐1,6‐glycosidases. Moreover, gentiobiose is the major reaction product when pustulan, yeast β‐glucan or yeast cell walls have been used as a substrate. Therefore, PsGly30A is a promising catalyst for valorisation of the yeast‐related by‐products.