Jurnal Kartika Kimia

Screening and Isolation of Thermophilic Amylase-Producing Bacteria from Ulubelu Hot Springs in Tanggamus Lampung

Fina Khaerunnisa Frima — 2025-11-07

Thermophilic bacteria generally thrive in hot springs and produce thermostable enzymes. These enzymes retain catalytic activity at high temperatures and play an important role in various industrial applications. This study aims to conduct screening, isolation, and characterization of thermophilic amylase-producing bacteria from the Ulubelu hot spring located in Tanggamus Regency, Lampung. Hot spring water samples from a location with a temperature of 60°C and pH 5 yielded eight bacterial isolates with amylolytic activity, as indicated by clear zones around the colonies. Among the isolates obtained, Ulb A3.7 exhibited the largest clear zone diameter and was therefore selected for further characterization. Morphological and physiological analyses revealed that Ulb A3.7 is a Gram-negative rod-shaped bacterium. The Ulb A3.7 isolate tested positive for oxidative-fermentative metabolism, oxidase activity, and glucose utilization. The crude α-amylase from Ulb A3.7 exhibited optimal activity at 80°C and demonstrated a broad activity range. The enzyme was able to retain its amylolytic activity for up to 300 minutes of incubation, indicating its potential for application in high-temperature industrial processes.

Evaluation of Ethyl Acetate Saponification Reaction: Comparison of the Accuracy of Conductometric and Titrimetric Methods

Hendriyana Hendriyana — 2025-11-27

This study evaluated the kinetic characteristics of the ethyl acetate saponification reaction using two analytical approaches, namely conductometry and titrimetry, in a stirred batch reactor system at various temperature conditions. Both methods showed that the reaction followed an overall second-order pattern, in line with the theory of saponification reaction kinetics. However, significant differences were found in the conversion values and activation energy obtained. The titrimetric method showed higher reproducibility and accuracy, with an estimated activation energy of 37.40 kJ/mol. This study also confirmed that increasing the reactant concentration accelerated the reaction rate by increasing the frequency of effective intermolecular collisions. Overall, the titrimetric method is recommended as a more reliable approach in the study of saponification kinetics in this experimental system.

Utilization of Freeze-Dried κ-Carrageenan for Methylene Blue Adsorption

Muhammad Iqbal — 2025-11-27

Methylene blue contamination in aquatic environments has become a global issue due to its widespread use in various industries. Methylene blue is a toxic, carcinogenic, and non-biodegradable dye. Adsorption can be employed as one method to mitigate this problem. The use of κ-carrageenan as an adsorbent offers an effective solution because κ-carrageenan is an abundant, easily obtainable, and economical biopolymer with promising adsorption performance. In this study, κ-carrageenan was cross-linked with K⁺ to form a hydrogel, which was then freeze-dried to produce a macroporous κ-carrageenan adsorbent. Characterization using FTIR confirmed the successful preparation of the adsorbent and the adsorption of methylene blue. SEM images showed changes in surface morphology, indicating successful adsorption. The adsorption process was optimum at pH 5, an adsorbent mass of 0.1 gram, and a contact time of 3 hours. Adsorption followed a pseudo-second-order kinetic model and the Langmuir isotherm model, with a maximum adsorption capacity, q_max of 128.7 mg/g at 328 K. Thermodynamic studies showed that the process was exothermic, became more disorder as a result of an increase in entropy, and occurred spontaneously. These results demonstrate that freeze-dried κ-carrageenan adsorbent has the potential for development in sustainable wastewater treatment technology.

New Modification of Natural Coagulants and Flocculants from Papaya Seeds (Carica Papaya L.) and Aloe Vera Gel in The Removal of Remazol Yellow Dye

Khalida Wijaya — 2025-12-07

A new modification of natural coagulant and flocculant from papaya seeds Carica papaya L. and aloe vera gel has been developed in this study to remove Remazol Yellow dye. The research parameters studied included the initial concentration of the test solution, pH, and stirring speed during the coagulation process. The initial concentration of the test solution varied from 10 to 50 mg/L, the pH ranged from 1 to 6, and the stirring speed was 650 to 1050 rpm during the coagulation phase. The coagulation and flocculation results were characterized using an FTIR spectrophotometer. The results showed that the optimum conditions were an initial concentration of 30 mg/L at pH 2 and a stirring speed of 950 rpm, resulting in the highest removal effectiveness of 97.55%. The results of FTIR spectrophotometry characterization showed that the sulfonate group -SO₃⁻ in Remazol Yellow had been removed, indicating that the protonated groups -NH₃⁺ and -COOH₂⁺ in papaya seeds and the anionic groups of the dye had electrostatic interactions. This study shows that the modification of papaya seeds and aloe vera gel as natural coagulants and flocculants shows sustainable potential for azo dye-based textile wastewater treatment.

Photoluminescent Carbon Dots for Intelligent Food Packaging: A Review on Sensing Mechanisms and Applications

Shobir Muntahal Maqsudi — 2025-11-30

Ensuring food safety and quality has become a global priority, demanding innovative solutions to detect early signs of spoilage or contamination. Intelligent food packaging systems offer a promising approach through real-time monitoring of food quality. Among various sensing materials, carbon dots have emerged as a novel class of fluorescent nanomaterials with exceptional optical properties, high water solubility, low toxicity, and tunable photoluminescence. This review discusses the synthesis strategies of CDs particularly focusing on green synthesis using biomass waste and their photoluminescence mechanisms including quantum confinement, surface state, carbon core state, and molecular state emissions. The application of CDs in smart packaging is highlighted, especially in detecting spoilage indicators such as ammonia, hydrogen sulfide, Total Volatile Basic Nitrogen, and pH changes. Various studies demonstrate the ability of CDs embedded in biopolymer matrices to produce distinct color changes in response to food spoilage, making them effective visual sensors. These findings support the development of eco-friendly, sensitive, and low-cost nano sensors for next-generation intelligent packaging technologies.