Study of ultrasound-promoted,lipase-catalyzed synthesis of fructose ester

The effect of low energy ultrasound in biochemistry and biotechnology has attracted great attention in recent years.It can enhance substrate dissolution and improve mass transfer within and outside of a cell,both of which are beneficial to the synthesis of fructose ester.Here we describe the experimental study of the effect of ultrasounds of different intensity on the lipase-catalyzed synthesis of fructose ester in the solvent butanone.The results were compared with control reactions performed with no ultrasound.High performance liquid chromatography(HPLC)and thin layer chromatography(TLC)were used for qualitative and quantitative analyses.The results show the following:1)the concentration of monoester and diester increased with the reaction time,either with or without ultrasonic irradiation.Low energy ultrasound accelerated the reaction due to the effect of ultrasonic steady cavitations,and high energy ultrasound was not beneficial to the reaction.2)The application of ultrasound played an important role in our lipase-catalyzed reaction.It decreased reaction time as compared to a reaction without ultrasound that resulted in the same yield,increased reaction rate,and enhanced the amount of fructose ester produced.When the frequency was 10 kHz and sound intensity was 0.16W·m^(-2),the concentration of ester was twofold more than without ultrasonic irradiation after a reaction time of up to 12 h.With the proper ultrasonic parameters,the overall concentration of production appeared to increase exponentially with the reaction time.3)Ultrasound had little effect on the initial reaction rate,and continuous ultrasonic irradiation was favorable for the reaction.The longer the reaction continued,the more obvious the effects of the ultrasound became in our experiments.

Cloning, Expression and Characterization of a Lipase Gene from Marine Bacterium Pseudoalteromonas lipolytica SCSIO 04301

Absract A lipase gene, 1ip1233, isolated from Pseudoalteromonas lipolytica SCSIO 04301, was cloned and expressed in E. coli. The enzyme comprised 810 amino acid residues with a deduced molecular weight of 80kDa. Lip1233 was grouped into the lipase family X because it contained a highly conserved motif GHSLG. The recombinant enzyme was purified with Ni-NTA affinity chro- matography. The optimal temperature and pH value of Lip1233 were 45 ℃ and 8.0, respectively. It retained more than 70% of origi- nal activity after being incubated in pH ranging from 6.0 to 9.5 for 30min. It was stable when the temperature was below 45℃, but was unstable when the temperature was above 55℃. Most metal ions tested had no significant effect on the activity of Lip1233. Lip1233 remained more than original activity in some organic solvents at the concentration of 30% （v/v）. It retained more than 30% activity after incubated in pure organic solvents for 12 h, while in hexane the activity was nearly 100%. Additionally, Lip 1233 exhib- ited typical halotolerant characteristic as it was active under 4M NaC1. Lip1233 powder could catalyze efficiently the synthesis of fructose esters in hexane at 400C. These characteristics demonstrated that Lip1233 is applicable to elaborate food processing and organic synthesis.