Abstract
Previous study by the authors showed that an alternative process to an airlift fermenter in the green vinegar production process could use a loofa sponge (a natural agricultural fibrous material) as the supporting material for Acetobacter aceti WK. Subsequently, aim of this study was production of green vinegar in a stirred tank reactor (STR). The filtered corn wine was supplied to the STR using fixation of A. aceti WK cells on the surface of a loofa sponge cut to a thickness of 2.5 cm. The loofa sponge was left in the STR until 60% of fermenting volume had been used. The charging rate of fresh, filtered corn wine for a semi-continuous production process was investigated. The highest acidification rate (ETA) was achieved at a charging rate of 30%. After 14 d of the adaptation period, the average acidity of 4.1±0.1% was produced during six cycles of fermentation at 30°C and 1vvm aeration supply within 40 d, while the ETA was in the range 0.0028%/h to 0.0067%/h. Scanning electron microscopy (SEM) showed that the surface of the loofa sponge acted as a good fibrous structure for cell fixation of A. aceti WK in the STR.
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