BACTERIA INOCULUM SCREENING FROM PALM WINE TO IMPROVE THE FERMENTATION EFFICIENCY OF VINEGAR

Abstract

Bacteria found in spontaneously fermented palm wine derived from fresh sugar sap can undergo further fermentation to yield vinegar. Therefore, this research aims to isolate the inoculums from palm wine to increase the efficiency of vinegar fermentation to obtain more acid. A total of 20 isolates cultured on glucose yeast extract calcium carbonate agar medium were isolated from palm wine fermented for 30 days. The efficiency of the acid production was screened by the difference between the diameter of the colony and the clear zone on the medium. The morphological and biochemical properties were studied. It was found that the five isolates that had the widest clear zones were Ssv.14, Ssv.13, Ssv.17, Ssv.8, and Ssv.20, respectively. All isolates showed the similar basic characteristics of bacteria of the Acetobacter and Gluconobacter bacteria. These isolates were investigated for the potential to be vinegar inoculum based on the ability of acid production. The amount of acid was evaluated by titration of the cultures grown in the glucose ethanol yeast extract broth with 5% ethanol under aerobic conditions at room temperature for 30 days. It was found that the mixed inoculum of five isolates showed the most acidity (15.3±0.46% w/v), which was higher than the natural inoculum, palm wine (8.76±2.33% w/v), and distilled vinegar (5.00±0.54% w/v) with statistically significant (p ≤ 0.05), respectively. While the pure inoculum from each isolate produced acid in the range 0.06±0.08% w/v - 0.13±0.04% w/v. The mixed inoculum showed a pH value of 3, and the natural inoculum and the distilled vinegar gave a pH of 4. The pure inoculums gave a pH of 8. Therefore, the use of a selectively mixed inoculum with efficient acid production may be another approach that could enhance the production of vinegar in the future.