Luffa sponge offsets the negative effects of aeration on bacterial cellulose production.

AIMS: To offset the negative effects of aeration on bacterial cellulose (BC) production by acetic acid bacteria using enmeshed cellulose microfibrils (CM) on luffa sponge matrices (LSM). METHODS AND RESULTS: The CM were enmeshed on LSM (LSM-CM). The optimal amount of LSM-CM was determined for BC production under aerated conditions. Without LSM-CM, no BC was produced in seven out of nine production cycles at the highest aeration rate (9 l min-1 ). However, with 0·5% LSM-CM and an aeration rate of 3 l min-1 , a satisfactory oxygen transfer coefficient was achieved, and also a good yield of BC (5·24 g l-1 ). Moreover, the LSM-CM was able to be recycled through nine consecutive BC production cycles. The highest BC yields (from 5·8 ± 0·4 to 6·6 ± 0·4 g l-1 ) were associated with high bacterial biomass and this was confirmed by scanning electron microscopy. CONCLUSIONS: We confirm that LSM-CM works well as a starter. Microenvironments low in dissolved oxygen within the matrices of LSM-CM are important for BC production under aeration conditions. SIGNIFICANCE AND IMPACT OF THE STUDY: The LSM-CM provides a microenvironment which offsets the negative effects of aeration on BC production. A sustainable, economic process for mass BC production is described using recycled LSM-CM with aeration.

Influence of calcium chloride in the high temperature acetification by strain Acetobacter aceti WK for vinegar.

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.