Aims: To improve the thermotolerant properties (TTP) of acetic acid bacteria (AAB) cells for high temperature acetification.
Methods and results: At high temperature (36 ± 1°C), the acetification rate (ETA) is usually lower than at 30 ± 1°C. The addition of 0·15% calcium chloride (CaCl2 ) may decrease the negative effect of the increase of temperature from 30 ± 1°C to 36 ± 1°C on the ETA. The effect of CaCl2 on the thermotolerant properties of acetic acid bacteria cells was investigated. The CaCl2 increased the content of phospholipids (phosphotidylcholine and phosphatidylglycerol), fatty acids (cis-vaccenic acid, palmitic acid and myristic acid) and the activities of membrane-bound enzymes involved in acetification, alcohol dehydrogenase and aldehyde dehydrogenase. Transmission electron microscope images revealed a more compact cell wall with CaCl2. Process consistency at 36 ± 1°C was tested in nine sequential acetification cycles using 0·15% (w/v) CaCl2. High ETAs (9·33 ± 0·6; 8·67 ± 0·8 and 9·67 ± 0·7 g l(-1) day(-1)) were obtained during the last three cycles.
Conclusions: The results confirm that changes of the content of lipid, activities of membrane-bound enzymes and cell-wall thickness occurred with added CaCl2.
Significance and impact of the study: High temperature acetification (HTA) with additions of CaCl2 was investigated. Significant reductions in the overall production costs result from lower cooling costs associated with HTA.
Keywords: calcium chloride; cell-wall thickness; cis-vaccenic acid; high temperature acetification; improved production economics; membrane-bound enzyme.
© 2015 The Society for Applied Microbiology.