Immobilized Candida rugosa lipase was used for the synthesis of citronellyl laurate from citronellol and lauric acid. Screening of different types of support (Amberlite MB-1 and Celite) for immobilization of lipase and solvent (n-hexane, n-heptane, and iso-octane) and optimization of reaction conditions, such as catalyst loading, effect of substrates molar ratio and temperature, have been studied. The maximum enzyme activity was obtained at 310 K. The immobilized C. rugosa lipase onto Amberlite MB-1 support was found to be the best support with a conversion of 89% of citronellyl laurate ester in iso-octane compared to Celite 545. Deactivation of C. rugosa lipase at 313, 318 and 323 K were observed. Ordered bi bi mechanism with dead end complex of lauric acid was found to fit the initial rate data and the kinetic parameters were obtained by non-linear regression analysis.
The enzymatic esterification of sugar-fatty acid ester to produce bio-based surfactants or emulsifiers has been recognized as an alternative way to the chemical synthesis due to its environmentally friendly reaction. Therefore, present study aimed to employ an optimal procedure for the continuous synthesis of fructose stearate by using immobilised Rhizomucor miehei lipase (RML) in a packed-bed reactor. Briefly, lipase immobilization on chicken eggshells was conducted and characterized using Transmission Electron Microscopy (TEM) and Brunauer-Emmett-Teller (BET) analysis. Subsequently, the screening of enzyme loading was performed. Response Surface Methodology (RSM) based on central composite design (CCD) was applied to optimize the temperature, flow rate and substrate molar ratio. The immobilisation efficiency on eggshells was 63.64%. After immobilization, the BET surface area, total pore volume and pore diameter of the eggshells were reduced to 1.0714 m2/g, 1.003 x 10−3 cm3/g and 3.7449 nm, respectively. Furthermore, both BET analysis before and after immobilization revealed that the pore structures of eggshells were classified as Type II isotherm. From preliminary study, enzyme loading of 1.5 g immobilized lipase was selected as the optimum enzyme loading. The quadratic model in RSM analysis was validated to predict the optimum conditions. A maximum of fructose stearate concentration as high as 7.252 x 10−1 mol/L obtained at a better condition of 37.47°C under a flow rate of 0.074 ml/min and 2.82:1 substrate molar ratio of fructose to stearic acid. This work has pronounced the eggshell is as a potential carrier for RML immobilization with ability to be used in packed bed reactor to synthesis fructose stearate.
A two-part study on pretreatment and fed-batch enzymatic hydrolysis of pretreated Tetraselmis suecica using a high initial biomass concentration was conducted. First, the effect of different pretreatment processes, i.e. microwave (MC), dilute alkaline (AK), and microwave-alkaline assisted (MAK) pretreatment, on enzymatic hydrolysis of T. suecica biomass was evaluated. Furthermore, high initial biomass concentration enzymatic hydrolysis improvement via a fed-batch strategy was performed. Among the pretreatments tested, the MAK pretreatment produced the highest sugar concentration at 9.83 ± 0.24 mg/mL, corresponding to a conversion yield of up to 85.58% of carbohydrate content available in the pretreated biomass. The solid fraction generated after pretreatment was characterized using Fourier transform infrared (FTIR) spectroscopy. The FTIR analysis revealed a significant change in the functional hydroxyl and acetyl groups of the biomass, which is favorable for enzymatic hydrolysis. Introducing an initial microalgal biomass concentration beyond 15% (w/v) exhibited a low enzymatic hydrolysis yield. The fed-batch enzymatic hydrolysis strategy of the MAK pretreated T. suecica was further investigated by adding the substrate at different time intervals. The findings indicate that the fed-batch operation system could enhance sugar production and enzymatic hydrolysis yield one-fold.
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