Effect of pH, temperature, and salt concentration on the growth of Bacillus subtilis T9-05 isolated from fish sauce

Abstract

Biogenic amines (BAs) are organic compounds found in fermented food products, such as sausage, fermented vegetables, wine, and fish sauce. Due to their potential to be harmful to human health and as markers of food quality, BAs content in food can be used as an indicator of food quality and food safety. Some bacteria have the ability to produce or degrade the BAs during fermentation. Environmental conditions can influence the growth of bacteria that produce biogenic amines. The aim of this study was to investigate the growth of Bacillus subtilis T9-05 isolated from fish sauce. Bacillus subtilis T9-05 was grown in tryptic soy broth with the treatment of pH (5, 6, 7, 8, and 9) and salt concentration (0, 1, 3, 6, 9, and 12% (w/v)) and the growing colonies were counted by the total plate count (TPC) method. Bacterial growth was also observed using different temperatures (25°C, 30°C, 35°C, 40°C, and 45°C). Differences in pH conditions and salt concentration significantly affected the growth of Bacillus subtilis T9-05. The highest growth of Bacillus subtilis T9-05 was achieved at pH 7-8 and a salt concentration of 0-1%. Bacillus subtilis T9-05 is classified as halotolerant bacteria. Bacillus subtilis T9-05 could be categorized as mesophilic bacteria based on its optimal growth rate of 35°C.