Synthesis of alkyl glucosides catalyzed by immobilized α-amylase from Thermotoga maritima

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Abstract The enzymatic production of alkyl glucosides is limited by the stability of the enzymes in the presence of alcohols. In the present study, we investigated three different supports: Sepharose 4B, crosslinked Sepharose (Fast Flow), and Eupergit C for the immobilization of α-amylase from Thermotoga maritima , AmyA, to increase its stability during the alcoholysis reaction. The enzyme immobilized on crosslinked Sepharose showed the best results, allowing its reutilization for at least five cycles while maintaining more than 50% residual activity. In addition, the immobilization of a previously reported H222Q variant resulted in a superior transglycosidic activity (> 50%) when compared to that of the wild-type (WT) AmyA. Moreover, both versions of the enzyme increased their residual activity after 24 h of incubation at 85°C upon immobilization. The alcoholysis with n -butanol, n -hexanol, and n -octanol was investigated to optimize the reaction conditions. Here, the addition of DMSO had a positive effect on the alcoholysis reactions with AmyA WT, achieving a total octyl glucoside title 1.75-fold higher than that obtained in the absence of DMSO. Importance Alkyl glucosides are valuable, non-toxic surfactants primarily synthesized chemically. The development of biocatalysts for their production has become a significant goal in the field of biocatalysis to avoid the disposal of toxic waste and environmentally harmful processes. To make these processes competitive, the use of low-cost raw materials and the recycling of biocatalysts are essential. The immobilization of Thermotoga maritima α-amylase has enabled its use in the presence of long-chain alcohols, achieving octyl glucoside production of 0.7 mg/mL—an unprecedented feat for an amylase. This study represents a breakthrough in the use of α-amylases for alkyl glucoside production.

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