Biotechnological Production
Acetic acid is produced for beverage, food, and feed applications almost entirely
using the traditional vinegar process . First, ethanol is produced by fermentation
with Saccharomyces cerevisiae in the absence of oxygen. Then, acetic acid
is generated from ethanol by acetic acid bacteria, such as Acetobacter aceti,
Acetobacter pasteurianus, or Gluconacetobacter europaeus, under aerobic conditions. Different substrates, such as malt, fruits, and sugarcane, are used
for vinegar production . Today, processes with two stages (e.g. two-tank cycle
fermentation or two-stage submerged fermentation) are generally employed on an
industrial scale. In a first step, biomass is produced in parallel to the acetic acid
production. In the second part of the process, mainly acidification takes place.
Acetic acid concentrations up to 200 g.L-1 can be achieved .
The vinegar process has been well studied over many decades . However,
there are still attempts to enhance vinegar production, especially regarding productivity and cost minimization through alternative substrates, new
process concepts (e.g. immobilized cells or mixed cultures of yeasts and
acetic acid bacteria, and optimized acetic acid bacteria.
Acetic acid can be produced under anaerobic conditions by some microorganisms
such as Clostridium thermoaceticum . In free-cell batch fermentations,
acetate concentrations of 50 g.L-1 were reached in less than 192 h. Acetic
acid concentrations of 83–100 g.L-1, a yield of 0.74–0.80 g acetic acid per gram
glucose, and a productivity of 0.60–0.85 g.L-1.h-1 were observed under optimized
conditions in a cell-recovered fed-batch process with pH-control using
glucose as substrate.
Health Hazard
Recommended Personal Protective Equipment: Protective clothing should be worn when skin contact can occur. Respiratory protection is necessary when exposed to vapor. Complete eye protection is recommended; Symptoms Following Exposure: Breathing of vapors causes coughing, chest pains, and irritation of the nose and throat; may cause nausea and vomiting. Contact with skin and eyes causes burns; General Treatment for Exposure: INHALATION: Move the victim immediately to fresh air. If breathing becomes difficult, give oxygen and get medical attention immediately. INGESTION: If the victim is conscious, have him drink water or milk. Do not induce vomiting. SKIN OR EYE CONTACT: Flush immediately with lots of clean running water; wash eyes for at least 15 min. and get medical attention as quickly as possible; remove contaminated clothing; Toxicity by Inhalation (Threshold Limit Value): 10 ppm; Short-Term Exposure Limits: 40 ppm for 5 min.; Toxicity by Ingestion: LD50 0.5 to 5.0 g/kg (rat); Late Toxicity: No data; Vapor (Gas) Irritant Characteristics: Vapors cause moderate irritation such that workers will find high concentrations very unpleasant. Effects are temporary; Liquid or Solid Irritant Characteristics: This is a fairly severe skin irritant; may cause pain and secondary burns after a few minutes of contact; Odor Threshold: 1.0 ppm.
Chemical Reactivity
Reactivity with Water No reaction; Reactivity with Common Materials: Corrosive, particularly when diluted. Attacks most common metals including most stainless steels. Excellent solvent for many synthetic resins or rubber; Stability During Transport: Stable; Neutralizing Agents for Acids and Caustics: Dilute with water, rinse with sodium bicarbonate solution; Polymerization: Not pertinent; Inhibitor of Polymerization: Not pertinent.