Isolation and identification of the genera Acetobacter and Gluconobacter in coconut toddy (mnazi)

Abstract

This study investigated the occurrence and identified the dominant spoilage genera of acetic acid bacteria in coconut wine (mnazi), by plating the dilution series previously pre-enriched in a basalmedium onto GYP agar, followed by physiological and biochemical tests. Both Acetobacter and Gluconobacter strains were Gram variable, oxidase negative and catalase positive. All Acetobacterstrains over-oxidized ethanol to acetic acid and finally to CO2 and H2O, while Gluconobacter were unable to oxidize acetic acid to CO2 and H2O. Acetobacter and Gluconobacter alike showed positivegrowth at 25, 30 and 40°C and also at pH 7.0 and 4.5, while there was no growth at 45°C, pH 2.5 and 8.5. Acetobacter strains oxidized both lactate and acetate while Gluconobacter oxidized lactate only. Bothgenera were unable to liquefy gelatin. Acetobacter showed negative growth at 15°C and also in peptone medium, while Gluconobacter showed positive growth both in peptone medium and at 15°C. Bothgenera were able to ferment arabinose, xylose, ribose, glucose, galactose, mannose and melibiose and unable to ferment amylagdine, cellibiose, esculine, lactose, maltose, mannitol, melezitose, Nagluconate, raffinose, rhamnose and salicine. The Acetobacter and Gluconobacter strains isolated in this study were found to be responsible for the spoilage of mnazi

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