Enzymatic degradation, antioxidant and rheological properties of a sphingan WL gum from Sphingomonas sp. WG

A molecular weight (Mw) controllable degradation strategy using the lyase WelR as the efficient tool was established, and the relationship between the Mw and the rheological properties and antioxidant activity of WL gum was systematically investigated. Four different WL samples WL1–WL4 with a gradient Mw change (from 4.70 × 106 to 1.45 × 106 Da) were obtained by controlling the enzymatic reaction conditions. As the Mw decreased, its apparent viscosity, intrinsic viscosity, viscous modulus (G″) and elastic modulus (G′) decreased. More interestingly, in contrast to the native WL, the G″ of the degraded WL became higher than G′. Besides, the biodegraded WL samples possessed much higher hydroxyl radicals scavenging activity than the original WL. WL4 with the lowest Mw showed the highest HO radical scavenging activity, about 94.65% at 1 mg/mL. This work provided a useful method to obtain a series of WL samples with controllable Mw and properties, which will broaden the application of sphingans. •A Mw controllable degradation strategy of WL gum by lyase WelR was established.•WL samples with a gradient Mw change (from 4.70 × 106 to 1.45 × 106 Da) were obtained.•As Mw decreased, WL gum solution changed from non-Newtonian fluid to Newtonian fluid.•In contrast to native WL, the G″ of the degraded WL gum became higher than G′.•The HO radicals scavenging activity of biodegraded WL gum enhanced significantly.