Laccase-catalyzed oxidation of phenolic compounds in organic media

✍ Scribed by Hui-Ling Ma; Selim Kermasha; Jin-Ming Gao; Rogelio Morales Borges; Xiu-zhu Yu

• Publisher: Elsevier Science
• Year: 2009
• Tongue: English
• Weight: 646 KB
• Volume: 57
• Category: Article
• ISSN: 1381-1177
• DOI: 10.1016/j.molcatb.2008.07.006

✦ Synopsis

Rhus vernificera laccase-catalyzed oxidation of phenolic compounds, i.e., (+)-catechin, (-)-epicatechin and catechol, was carried out in selected organic solvents to search for the favorable reaction medium. The investigation on reaction parameters showed that optimal laccase activity was obtained in hexane at 30 • C, pH 7.75 for the oxidation of (+)-catechin as well as for (-)-epicatechin, and in toluene at 35 • C, pH 7.25 for the oxidation of catechol. E a and Q 10 values of the biocatalysis in the reaction media of the larger log p solvents like isooctane and hexane were relatively higher than those in the reaction media of lower log p solvents like toluene and dichloromethane. Maximum laccase activity in the organic media was found with 6.5% of buffer as co-solvent. A wider range of 0-28 g protein/ml in hexane than that of 0-16.7 g protein/ml in aqueous medium was observed for the linear increasing conversion of (+)-catechin. The kinetic studies revealed that in the presence of isooctane, hexane, toluene and dichloromethane, the K m values were 0.77, 0.97, 0.53 and 2.9 mmol/L for the substrate of (+)-catechin; 0.43, 0.34, 0.14 and 3.4 mmol/L for (-)-epicatechin; 2.9, 1.8, 0.61 and 1.1 mmol/L for catechol, respectively, while the corresponding V max values were 2.1 × 10 -2 , 2.3 × 10 -2 , 0.65 × 10 -2 and 0.71 × 10 -2 ␦A/g protein min); 1.8 × 10 -2 , 0.88 × 10 -2 , 0.19 × 10 -2 and 1.0 × 10 -2 ␦A/g protein min); 0.48 × 10 -2 , 0.59 × 10 -2 , 0.67 × 10 -2 and 0.54 × 10 -2 ␦A/g protein min), respectively. FT-IR indicated the formation of probable dimer from (+)catechin in organic solvent. These results suggest that this laccase has higher catalytic oxidation capacity of phenolic compounds in suitable organic media and favorite oligomers could be obtained.