Isolation and characterisation of probiotic lactic acid bacteria from Malaysian fermented shrimp product pekasam senek

Lactic acid bacteria (LAB) from fermented foods have been proven as able to hinder the growth and activities of some foodborne pathogens. The present work thus aimed to isolate and characterise the potential LAB isolated from Malaysian fermented shrimp, pekasam senek (PS). Twelve isolates were obtained and molecularly identified via 16S rRNA gene sequencing, followed by acid and bile salt tolerance assessment, and cholesterol-lowering activity evaluation. The isolates showed satisfactory tolerance in a harsh acidic condition of pH 3.0; ten isolates (PS13, PS14, PS16, PS17, PS20, PS24, PS26, PS27, PS31, and PS33) exhibited over 90% of acid tolerance, while isolate PS22 exhibited 85.37% of acid tolerance, and isolate PS15 exhibited 75.73% of acid tolerance. For bile salts tolerance, nine isolates (PS13, PS14, PS15, PS16, PS17, PS24, PS27, PS31, and PS33) demonstrated survival rates ranging from 50 to 95% after 6 h of exposure to 0.3% bile salts. Despite showing a low tolerance to bile salt in comparison to the control, isolates PS20, PS22, and PS27 were still growing. The strains were identified as Lactiplantibacillus plantarum (PS13, PS15, PS17, PS20, PS24, PS31, and PS33), Bacillus cereus (PS14, and PS16), and Bacillus sp. (PS22, PS26, and PS27), using 16S rRNA gene sequencing. Lastly, PS24 and PS31 showed the highest cholesterol-lowering activity, with reductions of 80.50 and 80.19%, respectively. Meanwhile, PS13, PS14, PS16, PS17, PS20, PS26, PS27, and PS33 showed cholesterol-lowering activity of above 70%, and PS22 showed only 50.55% reduction. Each strain showed characteristics that influenced its ability to survive in acidic conditions, bile salts, and reduce cholesterol levels. These results proved that the isolates could have good properties as probiotics with positive cholesterol-lowering activity.