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The pufferfish skin is a by-product that is underutilized. Skin tanning is the prospect way to enhance the economic value of pufferfish skin. The tanning process is a long one, including the process of curing the skin. Sodium chloride is commonly used for curing the skin. However, sodium chloride can increase the total dissolved solids (TDS) that will be problematic in the environment. Potassium chloride can be used instead of sodium chloride. This study aims to determine the influence of substituting sodium chloride with potassium chloride on the quality of tanned pufferfish skin. Sodium chloride and potassium chloride were used in the skin curing process, while the storage time was 0, 1, 2, and 3 weeks. The assays performed are salt concentration on the skin, scanning electron microscope (SEM), FTIR, and physical quality of tanned pufferfish skin. The results showed that the salt content of potassium chloride in the skin was more easily absorbed than the salt of sodium chloride. The SEM and FTIR tests, descriptively, show no significant difference. The physical quality of the pufferfish skin preserved using potassium chloride is better than that of sodium chloride. Potassium chloride deserves to be used as a substitute for sodium chloride.

Indonesia has large coastal areas. The fisheries are good for exploitation. In the previous studies, bacteria producing keratinase were isolated from fish market waste. Keratinase enzyme is able to degrade keratin on the skin. Enzyme activity is influenced by external conditions, such as pH, temperature, and incubation time. The study aimed to investigate the characteristics and the optimal conditions of the keratinase production. The materials used were keratinase from three Bacillus strains: Bacillus thuringensis BRAW_PT, Bacillus aerius BRAW_PB, and Bacillus subtilis BRAW_PI. The keratinase was investigated by sodium dodecyl sulfate (SDS PAGE) and nondenaturing polyacrylamide gel electrophoresis (Native PAGE). Conditions of the production were optimized by pH, temperature and incubation time on enzyme activity. The molecular weights of all keratinases from Bacillus species were 94.803 kDa and 70.115 kDa. The optimum activity of keratinase from B. thuringensis BRAW_PT and B. firmus BRAW_PI was obtained at pH 8, while keratinase from B. aerius BRAW_PB was optimal at pH 6-8. Keratinase from B. thuringensis BRAW_PT has maximum activity at 25°C, whereas keratinase from B. aerius BRAW_PB and B. firmus BRAW_PI at 29°C. All keratinases from Bacillus species are optimal at 90 minutes incubation. Based on the principal component analysis (PCA), B. thuringensis BRAW_PT was discriminated from the other enzymes.

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Indonesia possesses tremendous marine resources. Therefore, their marine products are appropriate for exploration. In the prior study, bacteria generating keratinase enzyme have isolated from local fish market trash. The keratinase may hydrolyze keratin on the skin. Surrounding parameters, such as temperature, pH, and incubation duration, are the factors affecting the activity of the enzyme. This study aims to isolate and characterize keratinase, and optimize its production. The enzyme from Bacillus cereus BRAW_KM was the main material utilized in this research. First, the keratinolytic bacterium was isolated and investigated the properties of keratinase using native polyacrylamide gel electrophoresis (PAGE) and sodium dodecyl sulfate (SDS)-PAGE. Then, the ideal conditions of keratinase synthesis were adjusted by temperature, pH, and incubation time on enzyme activity. Of 10 isolations discovered, one isolate shows the potential as a keratinolytic bacterium, which tends to behave like Bacillus sp. The molecular weights of keratinase were 130 kDa and 95 kDa. The optimum keratinase enzyme activity from B. cereus BRAW_KM was at 29 °C, pH 9, and 90 minutes of incubation.