title: Process optimization and kinetic evaluation for biosynthesis of D-isoascorbyl stearate.
abstract: The synthesis of D-isoascorbyl stearate from D-isoascorbic acid and stearic acid with immobilized lipase (Novozym(®)435) as catalyst was studied. Response surface methodology and Box-Behnken design with six variables and three levels were employed to evaluate the effects of processing conditions on the conversion of D-isoascorbic acid. The results confirmed that the response surface method and statistical analysis were proved to be useful in developing optimal conditions for D-isoascorbyl stearate synthesis. The optimum conditions were predicted as follows: reaction temperature 48 °C, reaction time 17.7 h, immobilized lipase amount 50.0 % (w/w, of D-isoascorbic acid), substrate molar ratio 9:1 (stearic acid to D-isoascorbic acid), D-isoascorbic acid concentration 0.14 mol/L (based on solvent), 4A molecular sieve addition 200 g/L (based on solvent), and the optimal conversion was 90.6 %. Through the kinetics model fitting of the esterification, it was considered that the esterification conformed to a Ping-Pong bi-bi kinetic model with D-isoascorbic acid inhibition, and the obtained kinetic constants showed that the inhibition of D-isoascorbic acid and the enzyme affinity to substrate were abate with the increase of the reaction temperature.
authors.affiliation: School of Chemical Engineering and Energy, Zhengzhou University, Zhengzhou, 450001, China, zhenfeng2083@163.com.
authors.forename: Zhenfeng
authors.initials: Z
authors.lastname: Liu
authors.forename: Yanmin
authors.initials: Y
authors.lastname: Shen
authors.forename: Weiwei
authors.initials: W
authors.lastname: Li
authors.forename: Wen
authors.initials: W
authors.lastname: Zhang
authors.forename: Tao
authors.initials: T
authors.lastname: Li
authors.forename: Baozeng
authors.initials: B
authors.lastname: Ren
mesh_terms: D001205:Ascorbic Acid / Q000096:biosynthesis*; D055162:Biocatalysis; D002175:Candida / Q000201:enzymology; D004800:Enzymes, Immobilized / Q000737:chemistry*; D004951:Esterification; D005656:Fungal Proteins; D007218:Industrial Microbiology; D007700:Kinetics; D008049:Lipase / Q000737:chemistry; D012997:Solvents / Q000737:chemistry; D013229:Stearic Acids / Q000737:chemistry*; D013499:Surface Properties; D013696:Temperature
chemical_list: D004800:Enzymes, Immobilized; D005656:Fungal Proteins; D012997:Solvents; D013229:Stearic Acids; C005056:isoascorbic acid; C031183:stearic acid; C093667:Novozyme 435; D008049:Lipase; D001205:Ascorbic Acid