The foremost objective of this work is to prepare a novel electrochemical sensor-based screen-printed carbon electrode made of zinc oxide nanoparticles/molecularly imprinted polymer (SPCE–ZnONPs/MIP) and investigate its characteristics to detect sodium dodecyl sulfate (SDS).

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A rapid, simple, and sensitive voltammetric sensor has been fabricated to determine Rhodamine B (RhB), a textile coloring agent. Silver nanoparticles (AgNPs) were synthesized by the chemical reduction method of silver nitrate and sodium citrate. Graphene nanoplatelets (GPLs) and AgNPs were drop-casted on the surface of a working electrode of a screen-printed carbon electrode (SPCE), forming the SPCE-GPLs/AgNPs samples. Scanning electron microscopy−energy dispersive X-ray and cyclic voltammetry confirmed the altered surface of the SPCE. The square wave voltammetry was used for the electrochemical determination of RhB. The SPCE-GPLs/AgNPs demonstrated electrochemical responses to detect RhB with a linear range of 2−100 μM, and the limit of detection was 1.94 μM. The SPCE-GPLs/ AgNPs demonstrated a selective detection of RhB in the presence of common interfering compounds present in the food samples, including sucrose and monosodium glutamate. Furthermore, the sensor presented good reproducibility as well as repeatability in the detection of RhB. When the sensor was used to determine RhB in an actual food sample, similar results were shown as suggested by UV−vis spectroscopy analysis. Hence, the fabricated sensor can be applied for the detection of RhB in food samples.

Plastic wastes and petrochemical-based polymer materials have become a serious problem to the environment due to the characteristics of these materials that are difficult to degrade in nature. Polyhydroxyalkanoates (PHA) is one type of biodegradable plastics that have a great potential to replace the widely-used hydrocarbon plastics since it will decompose completely into carbon dioxide and water after burial for several months in the soil. PHA can be produced by microorganisms such as bacteria and algae through a fermentation process. The objective of this research is to obtain bacteria that can produce PHA. Screening was carried out by two sequential steps, qualitative and followed by quantitative methods. An amount of 29 bacteria strains isolated from Indonesians soil were screened for this purpose. The qualitative screening was conducted by growing the bacteria in a specific medium containing Nile red dye. The results showed that 19 strains were positive, generated pink to orange colonies under UV light at 235 nm. It was also confirmed by fluorescence microscope. The quantitative screening was performed by measuring the intracellular materials (predicted as PHA) of the bacterial cells by gravimetric method. The results indicated that the highest average of PHA content was 52.9%, 35.6% and 35.4 of dried cell weight, respectively for the Burkholderia sp B73, Bacillus sp B58, Bacillus toyonensis B50 and Staphylococcus cohni B66.

Electrochemical sensors based on ion-imprinting polymers have emerged as an effective analytical tool for heavy metal tracking.

In this study, antioxidant activities and identification of the bioactive substances in L. (Gg) seed hard shell were evaluated. The seed of L., an Indonesian native plant, is commonly consumed as a vegetable or further processed as cracker. Isolated substances from seed are mainly stilbenoid derivatives which show potent antioxidant, tyrosinase inhibitor, and antimicrobial activities. Nevertheless, the antioxidant activity of its crude extract is still considered weak. In this study, an effort was made to improve antioxidant potency by fractionation using macroporous adsorptive resin (MAR). This fractionation successfully enhanced antioxidant activity of red Gg seed hard shell extract with efficient adsorption contact time within 30 min. Antioxidant activity of fractions 25-75% v/v ethanol increased three- to sevenfold as compared to crude extract and more importantly resulted in dry product which was easier for further processes. Identification of bioactive compounds in Gg seed hard shell extract with different degrees of ripeness was also performed by HPLC and confirmed the presence of Gnetin C, resveratrol, and other stilbenoid derivatives. These other stilbenoid derivatives could be the main substances contributing in antioxidant action with lower IC as compared to both Gnetin C and resveratrol. In summary, fractionation process using MAR HPD-600 reduced unnecessary sugar molecules from red Gg seed hard shell extract hence resulting to fraction with strong antioxidant activity.

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