Isolation of thermotolerant acetic acid bacteria from fruits for vinegar production

Abstract

Sixty thermotolerant acetic acid bacteria were isolated from 13 kinds of fruit using sterile distilled water supplemented with 4% ethanol (v/v) as an enrichment medium. Successful isolations were obtained from apple, Jamaican cherry, longan, mango, pineapple and rambutan. Morphological and biochemical examinations revealed that 43 isolates were members of the genus Acetobacter whereas the remaining 13 isolates were members of the genus Gluconobacter. Preliminary screening showed that isolates No. 13, 34, 36 and 37 gave the widest zone of acidity on overoxidation medium. These isolates were identified as A. aceti and selected for acetic acid production at 30 and 37°C by shaking culture for 14 days in ethanol-yeast extract medium. It was found that A. aceti isolate No. 37 from rambutan gave the highest acetic acid yield of 13.53 and 8.97 g L-1at 30 and 37°C, respectively after 7 days of fermentation. © 2008 Academic Journals Inc.