Fermentation and characterisation of potential kombucha cultures on papaya-based substrates

Abstract

The rising demands and increasing health-conscious population in global beverages consumptions promote the development of new variety of kombucha beverages using various plant and fruits. This study aimed to isolate, identify and characterise the microorganisms found in the kombucha starter. Isolated microorganisms showed high similarity (99%) towards an acetic acids bacterium, Komagataeibacter rhaeticus MFS1 and a yeast, Dekkera bruxellensis MFS1. Under low pH tolerance test, D. bruxellensis MFS1 was remained viable (log7 CFU/mL) but no viable cell was observed for K. rhaeticus MFS1 after 3 h exposure at pH 2. However, both strains retained viability when exposed to pH 3–4 for 3 h. When tested bile salt tolerance at different concentration (0.3–1%), D. bruxellensis MFS1 showed high tolerance with viability up to log7 CFU/mL after 4 h exposure at 1% concentration. In contrast, K. rhaeticus MFS1 only retained the viability up to 2 h under bile salt environment. The presence of 1.45–1.62% acetic acid with less than 0.5% ethanol was detected at the end of 4-days fermentation in both kombucha papaya samples. These preliminary results showed the potential of using these isolated strains as starter cultures for the production of novel functional fermented beverages from papaya pulp and leaves.