Regioselective synthesis of 6’’-O-lauroyl-1-kestose and 6’’’-O-lauroylnystose by sequential enzymatic reactions of transfructosylation and acylation

Abstract

Fructan fatty acid esters are amphiphilic compounds with potential applications in the food industry due to their surface-active properties on the air/water interface. In this work, the regioselective synthesis of fatty acid esters of short-chain inulin-type fructooligosaccharides (FOS) was carried out in a two-step process comprising sequential enzymatic reactions of transfructosylation and acylation. In the first step, Schedonorus arundinaceus sucrose:sucrose 1-fructosyltransferase (1-SST, EC 2.4.1.99) converted sucrose (600 g/L) into the trisaccharide 1-kestose and the tetrasaccharide nystose in a ratio 9:1 with their sum accounting for 53% (w/w) of total carbohydrates. In the second step, the FOS mixture was transesterified with vinyl laurate in 2-methyl-2-butanol by immobilized Candida antarctica lipase B (CALB) (EC.3.1.1.3). NMR analysis of the synthesized monolaurate FOS esters revealed a regioselective acylation of the 6-OH of the terminal fructosyl moiety of both 1-kestose and nystose. The hydrophilic-lipophilic balance (HLB) values of 6’’-O-lauroyl-1-kestose and 6’’’-O-lauroylnystose were 14.7 and 15.7, respectively; which suggests their use as oil in water (O/W) emulsifiers. The main compound 6’’-O-lauroyl-1-kestose with critical micelle concentration (CMC) of 0.6 mM and surface tension of 45.8 mN/m proved to be a more efficient surfactant than 6’’’-O-lauroylnystose (CMC 5.38 mM) and surface tension 36.26 mN/m). We report a regioselective method for the synthesis of lauryl-FOS using the abundant and renewable resource sucrose as the starting substrate.

Keywords:

• Transfructosylation
• fructooligosaccharides
• acylation
• sequential enzymatic process
• sugar esters

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The present work was financially supported by LIBBA laboratory and Industrial Biotechnology Unit of CIATEJ. Amador Campos thanks the finantial support of CONACYT (Mexico) through the PhD scholarship 268290. CNPq [430922/2018-3 and 303352/2017-5], UFPR – Rede de Internacionalização em Bioprospecção, Biogeoquímica e Biotecnologia Ambiental [CAPES-PrInt 88887.311742/2018-00], FINEP, UFPR NMR Center, Project FODECIJAL-8975, and Project CB-237737.