Isolation and Characterization of Acetic acid Bacteria from Fruits and Fermented fruit juices for Vinegar Production

Abstract

Acetic acid bacteria are Gram negative aerobic bacteria capable of oxidizing ethanol to acetic acid. They are used in the industrial production of vinegar. The present study aims at isolation of acetic acid bacteria from various kinds of fruits and fermented fruit juices. Thirty varieties of fruits and 4 fermented fruit juices were collected from the northern and eastern areas in Thailand. Ninety-nine isolates of acetic acid bacteria were obtained from 18 varieties of fruits and 4 fermented fruit juices using sterile distilled water supplemented with 4.00% ethanol (v/v) as an enrichment medium. Eighty-nine isolates were identified to be in the genus Acetobacter and 10 isolates were in the genus Gluconobacter. Fifty-nine isolates were A.aceti as determined by biochemical tests. Nineteen isolates ; P1, P4, P6, P8, P12, K4, K5, K6, K7, K8, S1, S2, S3, S4, S5, S6, S7, S8 and S11 gave the widest yellow zone on bromocresol green ethanol agar. They were selected for acetic acid production and compared with A.aceti TISTR354 in ethanol-yeast extract medium supplemented with 6.00% (v/v) ethanol. It was found that P1, P4, P6, P12 and A. aceti TISTR354 gave the highest yield of acid 4.06%, 3.70%, 3.89%, 4.00% and 4.03%, respectively. All the isolates were tested for their tolerance to ethanol and acetic acid. It was found that they were able to grow at 4% and 6% ethanol. Moreover, isolates P1, P4, P6, P12, K6, K7, K8, S1, S2 and S11 were able to grow at 10.00% ethanol.