Strain Improvement Acetobacter

Research on the causes of spontaneous mutation of strains of A. aceti and A. pasteurianus is under way to determine the nature of the genetic instability of ethanol oxidation during industrial vinegar production. Genetic analysis has implicated 

Comparison of acetic acid productivity between two transformants of Acetobacter aceti NBI2099 

Indicators of production and yield A. aceti NBI2099 (pMV24) A. aceti NBI2099 (pAL25)  

---

Immobilisation of an Acetobacter aceti strain in calcium alginate resulted in improvement of the operational stability, substrate tolerance and specific activity of the cells and 23 g phenylacetic acid was produced within 9 days of fed-batch cultivation in an airlift bioreactor [133]. Lyophilised mycelia of Aspergillus oryzae and Rhizopus oryzae have been shown to efficiently catalyse ester formation with phenylacetic acid and phenylpropanoic acid and different short-chain alkanols in organic solvent media owing to their carboxylesterase activities [134, 135] (Scheme 23.8). For instance, in n-heptane with 35 mM acid and 70 mM alcohol, the formation of ethyl acetate and propylphenyl acetate was less effective (60 and 65% conversion yield) than if alcohols with increased chain lengths were used (1-butanol 85%, 3-methyl-l-butanol 86%, 1-pentanol 91%, 1-hexanol 100%). This effect was explained by a higher chemical affinity of the longer-chain alcohols, which are more hydrophobic, to the solvent. 

Some strains of A. niger will oxidize D-mannose to mannonic acid and D-galactose to D-galactonic acid (281). Many species of Pseudomonas and also Acetobacter xylinum will oxidize pentoses to the corresponding pentonic acids (282). The yields are not always high but probably can be increased by improvements in the strains and in the cultural conditions. 

BC) depends on the strain type. Generally, the Acetobacter strains are most suitable for static (emers) cellulose biosynthesis. However, this method is not effective with respect to the yield of the final product. Therefore, the dynamic (submers fermentation) method has to be considered. The most important question of this method is to have stable bacteria strains because an unstable strain produces spontaneously inactive bacteria (Cel"). Therefore, the preparation of highly effective bacteria strains by mutagenisation and genetic manipulation improves the dynamic production of BC. The best pilot-scale world producer of BC is Weyerhauser Co., Tacoma, WA, USA in cooperation with Cetus Corp., Emerville, California, USA. 

Gossele F, Swings J, Kersters K, Pauwels P, De Ley J (1983b) Numerical analysis of phenotypic features and protein gel electrophoregrams of a wide variety of Acetobacter strains. Proposal for the improvement of the taxonomy of the genus Acetobacter Beijerinck 1898,215. Syst Appl Microbiol 4 338-368... 

---