Complicated and strict protocols are followed to tune the size of gold nanoparticles (GNPs) in chemical synthesis methods. In this study, we address the polarity of solvents as a tool for tailoring the size of GNPs in the chemical reduction method. The effects of varying polarity index of the reaction medium on synthesizing gold nanoparticles by chemical reduction method have been investigated. Ethanol as a polar solvent, ethanol–water mixture as reaction medium, L-ascorbic acid as reducing agent, and polyvinylpyrrolidone as stabilizer were used to synthesize GNPs. The polarity index of the reaction medium was adjusted by changing the volume ratio of ethanol to water. UV–Vis, dynamic light scattering (DLS), and transmission electron microscopy (TEM) characterizations reveal that the growth of nanoparticles was gradually increased (~ 22 to 219 nm hydrodynamic diameter) with decreasing value of polarity index of the reaction medium (~ 8.2 to 5.2). Furthermore, the high polarity index of the reaction medium produced smaller and spherical nanoparticles, whereas lower polarity index of reaction medium results in bigger size of GNPs with different shapes. These results imply that the mechanistic of the growth, assembly, and aggregation phenomena of ligand or stabilizer-capped GNPs strongly rely on the polarity of solvent molecules. Using the proposed methodology, wide size range of GNPs with different morphology sizes can be synthesized by simply modulating the volume percentage of organic solvent in the reaction medium.

Immobilisation of cyclodextrin glucanotransferase (CGTase) on nanofibres was demonstrated. CGTase solution (1% v/v) and PVA (8 wt%) solution were mixed followed by electrospinning (-9 kV, 3 h). CGTase/PVA nanofibres with an average diameter of 176 ± 46 nm were successfully produced. The nanofibres that consist of immobilised CGTase were crosslinked with glutaraldehyde vapour. A CGTase/PVA film made up from the same mixture and treated the same way was used as a control experiment. The immobilised CGTase on nanofibres showed superior performance with nearly a 2.5 fold higher enzyme loading and 31% higher enzyme activity in comparison with the film.

The aim of this study is to evaluate microwave-assisted extraction at several microwave power and extraction time in extracting oil palm products, such as crude palm oil (CPO) and palm fatty acid (PFA) composition. The exposure time was shortened and overheating was avoided when sterilized mesocarp exposed to microwave prior to Soxhlet extraction in order to obtain good quality oil. The effects of CPO extraction and PFA composition on the distillate produced were investigated. Gas chromatography coupled with mass spectrometry (GC-MS) was used for the determination and quantification of PFA composition in the distilled products. Scanning electron microscopy (SEM) reveals that the microwave-assisted extraction technique had efficiently assisted in the release of oil by breaking down the mesocarp cell structure. To fill the research gap of microwave-assisted sterilization in the previous research, microwave-assisted extraction was introduced, in which two processes (i.e., extraction and drying) were conducted in one equipment. Oil yield and color, free fatty acids (FFA), Deterioration of Bleachability Index (DOBI), and carotene contents of the CPO were quantified. At 100 W, the extraction of CPO demonstrated 64% yield produced, with chemical properties of 0.301% FFA, 3.53 DOBI and 1132 ppm carotene with final temperature of 76.2°C during microwave-assisted extraction. The optimum condition for extracting PFA distillate was 300 W for 30 min of exposure time. Additionally, distillate obtained at the optimum condition using microwave-assisted extraction consisted of high palmitic acid (C16:0), caramel-like aroma, and possessed a sweet fragrance.