Esters biotransformation by immobilized interfacial esterases from the Caribbean Sea anemone Stichodactyla helianthus

An immobilized biocatalyst (ShIE-Octyl) was obtained by interfacial adsorption on Octyl-Sepharose CL 4B support of all interfacial esterases from the aqueous extract of the sea anemone Stichodactyla helianthus. ShIE-Octyl, synthesized by this simple method, contains semipurified interfacial esterases, including the isotoxins StI and StII. The immobilized esterases are maximally stable at pH 7.0 for p-nitrophenylacetate hydrolysis (determined spectrophotometrically at 348 nm) during 6 days, although immobilization does not enhance the stability of the soluble enzymes toward pH. In contrast, immobilization appreciably increases the stability toward temperature and organic solvents. ShIE-Octyl shows 90 % residual activity after 6 days at 30 °C, and maintains at least 85 % initial activity in presence of 10 % methanol or acetonitrile. The immobilized derivative catalyzes the hydrolysis of the pharmacologically relevant esters: naproxen methyl ester, 2-oxyranylmethyl acetate (OMAc), methyl-prostaglandin A2 and ethyl-2-hydroxy-4-phenyl butanoate (HPBEt) (determined by RP-HPLC or HPTLC) with 95-100 % conversion in 6240 min, and tolerates 20 % organic solvents. The immobilized biocatalyst is selective for esters with simple alcoholic and complex acid structures, but showing the infrequent ability to hydrolyze esters with heteroatomic or aromatic alcoholic substituents, such as phenylethyl butyrate and 7-aminocephalosporanic acid. ShIE-Octyl is S-stereoselective in the bioconversion of chiral HPBEt and OMAc, and R-stereoselective in the hydrolysis of naproxen methyl ester in presence of 10 % methanol or acetonitrile. The selectivity by (S)-OMAc is favored at low temperature (4 °C) and buffer ionic strength (10 mM sodium phosphate). The enantioselectivities toward naproxen methyl ester and OMAc are unusual; then are particularly relevant.