Microbial fuel cell (MFC) is one of promising fuel cell technologies. MFC utilizes biochemical activity of microorganism to convert the substrate to produce electricity through metabolism processes. Although the generation of the electricity is still in mW scale, MFCs has a great potential for the future application. The aim of this study was to investigate the performance of MFCs with and without the methylene blue (MB) as an electron mediator utilizing Saccharomyces cerevisiae as biocatalysts and glucose as substrate to generate electricity. Methods performed comprise of the S. cerevisiae yeast culture rejuvenation, preparation of the inoculum, preparation of the MFC reactor, preparation of MFC medium with 2% of glucose with and without MB mediator, periodical sampling, determination of growth curve, measurement of current, potential, calculation of power density, energy, glucose consumption, and production of bioethanol. MFC with mediator generated 5.5×10-5A of current, 0.886V of potential, 4.48×10-3 W/m2 of power density, 4.14×10-3 J of energy, 95.0% of glucose consumption and 0.74% (v/v) of bioethanol produced during the MFC process, while MFC without mediator generated 4.5×10-5 A of current, 0.689V of potential, 2.12×10-3 W/m2 of power density, 1.96×10-3 J of maximum energy, 96.3% of glucose consumption and 0.74% (v/v) of bioethanol produced. Power density yields from both type of MFC are still very low and not differ significantly. From the present study, it can be concluded that MB mediator only effected on potential yield in MFC using the condition applied in this study

Rice (Oryza sativa L.) is a primary food that is widely consumed throughout the world, especially in Asian countries. The two main subspecies of rice are japonica and indica which are different in physical characteristics. In general, both indica and japonica rice consist of three types of grain colors, namely white, red, and black. Furthermore, rice and rice by-products contain secondary metabolites such as phenolic compounds, flavonoids, and tocopherols that have bioactivities such as antioxidants, antimicrobial, cancer chemopreventive, antidiabetic, and hypolipidemic agents. The existence of health benefits in rice bran, especially as antioxidants, gives rice bran the opportunity to be used as a functional food. Most of the bioactive compounds in plants are found in bound form with cell wall components such as cellulose and lignin. The process of releasing bonds between bioactive components and cell wall components in rice bran can increase the antioxidant capacity. Fermentation and treatment with enzymes were able to increase the total phenolic content, total flavonoids, tocotrienols, tocopherols, and γ-oryzanol in rice bran.

Starch is a polymeric carbohydrate composed of glucose. As a source of energy, starch can be degraded by various amylolytic enzymes, including α-amylase. In a large-scale industry, starch processing cost is still expensive due to the requirement of high temperature during the gelatinization step. Therefore, α-amylase with raw starch digesting ability could decrease the energy cost by avoiding the high gelatinization temperature. It is known that the carbohydrate-binding module (CBM) and the surface-binding site (SBS) of α-amylase could facilitate the substrate binding to the enzyme’s active site to enhance the starch digestion. These sites are a noncatalytic module, which could interact with a lengthy substrate such as insoluble starch. The major interaction between these sites and the substrate is the CH/pi-stacking interaction with the glucose ring. Several mutation studies on the Halothermothrix orenii, SusG Bacteroides thetaiotamicron, Barley, Aspergillus niger, and Saccharomycopsis fibuligera α-amylases have revealed that the stacking interaction through the aromatic residues at the SBS is essential to the starch adsorption. In this review, the SBS in various α-amylases is also presented. Therefore, based on the structural point of view, SBS is suggested as an essential site in α-amylase to increase its catalytic activity, especially towards the insoluble starch.

Food preservation is one of the strategies taken to maintain the level of public health. Oxidation activity and microbial contamination are the primary causes of food spoilage. For health reasons, people prefer natural preservatives over synthetic ones. Syzygnium polyanthum is widely spread throughout Asia and is utilized as a spice by the community. S. polyanthum has been found to be rich in phenols, hydroquinones, tannins, and flavonoids, which are potential antioxidants and antimicrobial agents. Consequently, S. polyanthum presents a tremendous opportunity as a natural preservative. This paper reviews recent articles about S. polyanthum dating back to the year 2000. This review summarizes the findings of natural compounds presented in S. polyanthum and their functional properties as antioxidants, antimicrobial agents, and natural preservatives in various types of food.