Aeration Effects on Vinegar Production from Coffee Pulp: Laboratory Fermentation and 100-L Scale-Up

Abstract

Aeration was tested as an operating variable in vinegar fermentation from coffee pulp. Acetobacter pasteurianus TISTR 102 was grown in a 10-L stirred-tank bioreactor supplied with air at 0.5, 1.0, or 1.5 vvm. The 1.0-vvm treatment reached 5.12% acetic acid after 144 h and an estimated viable cell concentration of 7.1467 log CFU/mL. It gave the highest acid concentration and shortest fermentation time among the three treatments. The logistic fit at this rate had R² = 0.9975, χ² = 0.3587, RMSE = 0.5821, and MBE = 0.3388. Oxygen limitation and adverse effects of greater aeration could explain the lower performance at the other rates, but their contributions were not established experimentally. When the 1.0-vvm condition was used in a 100-L fermenter, acetic acid reached 4.48%. Thus, this air supply rate performed best in the laboratory comparison and also supported fermentation in the larger vessel. Its transfer to another scale needs to account for vessel mixing, oxygen transfer, and temperature conditions.